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  • Articles: DFG German National Licenses  (729)
  • Latest Papers from Table of Contents or Articles in Press  (433)
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  • 1
    Electronic Resource
    Electronic Resource
    A survey of dermatophytes from human patients in the United States from 1985 to 1987 (1991)
    Springer
    Mycopathologia 114 (1991), S. 117-126 
    Details
    ISSN: 1573-0832
    Keywords: dermatophytes ; survey ; United States ; humans ; 1985/87
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A survey of dermatophytes isolated from patients seeking medical advice was made from 1985 to 1987 in the United States. The survey included 54 locations with data from 45 cities and one state. Listing of the isolated dermatophytes and the frequency given by percentage of the total follows: Trichophyton rubrum 54.8%, T. tonsurans 31.3%, T. mentagrophytes 6.0%, Microsporum canis 4.0%, Epidermophyton floccosum 2.0%, M. gypseum 0.6%, and T. verrucosum 0.2%. Out of a total of 14,696 isolates M. audouinii was cultured 13 times, T. violaceum 12 times, M. nanum 6 times, T. terrestre 4 times, and T. soudanense twice. Single isolations were made of M.fulvum, M. ferrugineum and T. schoenleinii. Collection of dermatophyte data in Tucson, Arizona, began in 1966. In 1987, the first case of tinea capitis caused by T. tonsurans was observed. Other isolates of this organism as the cause of tinea capitis were made in this city during that year. These infections were in black children. With the recent growth of Tucson, the percentage of blacks in the population increased and this pathogen was introduced into the general population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00436431
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  • 2
    Electronic Resource
    Electronic Resource
    Are accessory nuclei involved in the establishment of developmental gradients in hymenopteran oocytes? (1991)
    Springer
    Development genes and evolution 199 (1991), S. 423-426 
    Details
    ISSN: 1432-041X
    Keywords: Oogenesis ; Accessory nuclei ; Developmental gradients ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the oocytes ofTenthredo olivacea, accessory nuclei (AN) are formed by budding from the nuclear envelope of the oocyte nucleus. Newly formed AN contain electron-dense material of nuclear origin and are surrounded by a double envelope devoid of pores. Such structures are subsequently transported to the peripheral ooplasm (periplasm), where they grow to reach a final diameter of 5 µm. In the envelopes of advanced AN nuclear pores arise. Through these pores “nuage” material is extruded into the surrounding periplasm. These findings are discussed with respect to a possible involvement of AN in the establishment of developmental gradients in hymenopteran oocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01705853
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  • 3
    Electronic Resource
    Electronic Resource
    The origin of the nascent blastocoele in preimplantation mouse embryos ultrastructural cytochemistry and effect of chloroquine (1991)
    Springer
    Development genes and evolution 200 (1991), S. 77-85 
    Details
    ISSN: 1432-041X
    Keywords: Lysosomes ; Ultrastructure ; Chloroquine ; Blastocyst ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mouse morulae are known to undergo cavitation as soon as some external cells have entered the sixth cell cycle (Garbutt et al. 1987). Since the early cytological features of cavitation are still unclear, we undertook a careful ultrastructural analysis of late morulae-nascent blastocysts. In addition, since maturation of lysosomes might be involved in the first step of cavity formation, we focused our attention on these organelles by means of the cytochemical localization of trimetaphosphatase activity and by the study of the effects of chloroquine on precavitation embryos. Our results suggest that cavitation starts in a few external cells (presumably competent cells entering the sixth cell cycle), by the chloroquine-sensitive formation of degradative autophagic vacuoles engulfing lipid droplets and vacuoles containing osmiophilic material. These complex structures enlarge (as a result of lipid metabolism?) and so transform into intrablastomeric cavities which, by means of a membrane fusion process, very rapidly become extracellular cavities that coalesce. The abembryonic pole of the blastocyst is determined in this way. Moreover, we suggest that the juxtacoelic cytoplasmic processes covering the inner cell mass (ICM) cells, which are known to restrict the expression of their totipotency during early cavitation (Fleming et al. 1984), are the latest remnants of the walls of the growing intrablastomeric cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637187
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  • 4
    Electronic Resource
    Electronic Resource
    Secretory tapetum of Brassica oleracea L.: polarity and ultrastructural features (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 28-35 
    Details
    ISSN: 1432-2145
    Keywords: Tapetal cells ; Brassica oleracea L ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the secretory, binucleate tapetum of Brassica oleracea in the micro spore mother cell (MMC) stage through to the mature pollen stage is reported. The tapetal cells differentiate as highly specialized cells whose development is involved in lipid accumulation in their final stage. They start breaking down just before anther dehiscence. Nuclei with dispersed chromatin, large nucleoli and many ribosomes in the cytoplasm characterize the tapetal cells. The wall-bearing tapetum phase ends at the tetrade stage. The dissolution of tapetal walls begins from the inner tangential wall oriented towards the loculus and proceeds gradually along the radial walls to the outer tangential one. The plasmodesmata transversing the radial walls between tapetal cells persist until the mature microspore, long after loss of the inner tangential wall. After wall dissolution, the tapetal protoplasts retain their integrity and position within the anther locule. The tapetal cell membrane is in direct contact with the exine of the microspores/pollen grains and forms tubular evaginations that increase its surface area and appear to be involved in the translocation of solutes from the tapetal cells to the microspores/ pollen grains. The tapetal cells exhibit a polarity expressed by spatial differentiation in the radial direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194568
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  • 5
    Electronic Resource
    Electronic Resource
    Brassica napus pollen development during generative cell and sperm cell formation (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 176-181 
    Details
    ISSN: 1432-2145
    Keywords: Pollen ; Brassica napus ; Mitoses ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190001
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 166-175 
    Details
    ISSN: 1432-2145
    Keywords: Helianthus annuus ; Ultrastructure ; Micropyle ; Pollen tube ; Synergid degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190000
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  • 7
    Electronic Resource
    Electronic Resource
    Sperm cells of the pollen tubes of Brassica: Ultrastructure and isolation (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 226-234 
    Details
    ISSN: 1432-2145
    Keywords: Male germ unit ; Sperm cells ; Isolation ; Pollen tubes ; Brassica napus ; Pollen-tube inner plasma membrane ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sperm cells of pollen tubes grown both in vivo and in vitro form a male germ unit. Extensions from both sperm cells of each pollen tube are closely associated with the tube nucleus. A high yield (2.7 × 104. 20 mg−1 pollen grains germinated) of intact sperm cells was obtained following release by osmotic shock from pollen tubes grown in vitro. Structural integrity of isolated sperm was maintained by isolation at low temperature in an osmotically balanced medium. At 4° C many isolated sperm pairs were still enclosed within the pollentube inner plasma membrane. Sperm cells not enclosed within this membrane no longer remained connected as a pair. During isolation vesicles formed on the sperm cell surface from disruption of the fibrillar components bridging the periplasmic space. Both in the pollen tube and after isolation the sperm nucleus is in close association with at least one region of the sperm plasma membrane. Sperm isolated at room temperature showed the presence of nucleopores, and nuclei were euchromatic, instead of heterochromatic as in intact sperm in the pollen tube.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190009
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  • 8
    Electronic Resource
    Electronic Resource
    Microsporogenesis and tapetal development in fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 215-225 
    Details
    ISSN: 1432-2145
    Keywords: Cytoplasmic male sterility ; Beta vulgaris ; Microsporogenesis ; Tapetum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of sporogenous and tapetal cells in the anthers of male-fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) plants was studied using light and transmission electron microscopy. In general, male-sterile anthers showed a much greater variability in developmental pattern than male-fertile anthers. The earliest deviation from normal anther development was observed to occur in sterile anthers at meiotic early prophase: there was a degeneration or irregular proliferation of the tapetal cells. Other early aberrant events were the occurrence of numerous small vesicles in the microspore mother cells (MMC) and a disorganized chromatin condensation. Deviations that occurred in sterile anthers at later developmental stages included: (1) less distinct inner structures in the mitochondria of both MMC and tapetal cells from middle prophase onwards. (2) dilated ER and nuclear membranes at MMC prophase, in some cases associated with the formation of protein bodies. (3) breakdown of cell walls in MMCs and tapetal cells at late meiotic prophase. (4) no massive increase in tapetal ER at the tetrad stage. (5) a general dissolution of membranes, first in the MMC, then in the tapetum. (6) abortion of microspores and the occurrence of a plasmodial tapetum in anthers reaching the microspore stage. (7) no distinct degeneration of tapetal cells after microspore formation. Thus, it seems that the factors that lead to abortive microsporogenesis are structurally expressed at widely different times during anther development. Aberrant patterns are not restricted to the tetrad stage but occur at early prophase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190008
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  • 9
    Electronic Resource
    Electronic Resource
    Fluoride effects on leaf cell ultrastructure of olive trees growing in the vicinity of the Aluminium Factory of Greece (1991)
    Springer
    Trees 5 (1991), S. 83-89 
    Details
    ISSN: 1432-2285
    Keywords: Air pollutants ; Chloroplasts ; Fluoride ; Olive tree leaves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227489
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  • 10
    Electronic Resource
    Electronic Resource
    Different epithelia in the distal human male urethra (1991)
    Springer
    Cell & tissue research 264 (1991), S. 23-32 
    Details
    ISSN: 1432-0878
    Keywords: Male urethra ; Urethral epithelium ; Immunocytochemistry ; Ultrastructure ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distal segment of the human male urethra, in particular the fossa navicularis, was studied with light- and electron microscopy as well as by means of histochemical and immunocytochemical methods. The fossa navicularis of the urethra contains a circumscribed zone of extremely thick, non-keratinized stratified squamous epithelium composed of cells containing a large amount of glycogen. These cells lack acid phosphatase activity and lysozyme-like immunoreactivity, both of which can be demonstrated to varying extents in the other zones of the distal male urethra. These glycogen-rich cells are considered to be the substrate for an endogenous flora of lactobacteria, whereas the acid-phosphatase activity and the lysozyme-like immunoreactivity indicate the presence of macrophages and the secretion of bactericidal agents at the epithelial surface. These observations suggest that the different zones with heterogeneous properties in the distal male urethra probably represent a defense system against the invasion of pathogenic microorganisms. Moreover, the glycogen-rich zone, which resembles the glycogen-rich epithelium of the vagina, is estrogen-dependent. This is demonstrated in cases of sex reversal in which after long-lasting estrogen treatment the glycogen-rich zone becomes extremely extended by displacement of the neighbouring epithelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305719
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  • 11
    Electronic Resource
    Electronic Resource
    Ultrastructure of melatonin-responsive cells in the ovine pars tuberalis (1991)
    Springer
    Cell & tissue research 263 (1991), S. 529-534 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin ; Pituitary gland, pars tuberalis ; Secretory cells ; Cyclic AMP ; Ultrastructure ; Cell culture ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Functional receptors for melatonin have been localized and characterized on the pars tuberalis (PT) of a number of mammalian species, but the cell-type responsive to melatonin is unknown. The ultrastructure of the ovine pars tuberalis has been examined and these findings correlated with the functional response of the gland to melatonin. This study revealed that two secretory cell types predominate in the ovine PT, which differ in the abundance of dense-core granules. The most abundant of the cells are either agranular or very sparsely granulated and represent 90% of the total population, with the remaining 10% being composed of cells with abundant dense-core vesicles. Few follicular cells were observed. This ratio of secretory cell-types persisted in primary culture, with the two types non-separable by Percoll gradient centrifugation. Using forskolin, as a non-specific stimulant of adenylate cyclase, melatonin was shown to inhibit the formation of cyclic AMP by 80–90% in cells both before and after Percoll centrifugation. The results demonstrate that the agranular secretory cells of the ovine pars tuberalis are the melatonin responsive cell-type of this gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327285
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  • 12
    Electronic Resource
    Electronic Resource
    Ultrastructure and distribution of somatostatin-like immunoreactive neurons and nerve fibres in the coeliac ganglion of cats (1991)
    Springer
    Cell & tissue research 263 (1991), S. 567-572 
    Details
    ISSN: 1432-0878
    Keywords: Somatostatin ; Coeliac ganglion ; Autonomic innervation ; Ultrastructure ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Somatostatin-like immunoreactivity was localized in nerve cell bodies and nerve terminals in the cat coeliac ganglion. Two types of somatostatin-immunoreactive cell bodies were revealed, the first being large (diameter 35 μm), numerous and weakly labelled, where—as the second was considerably smaller (diameter 10.4 μm), sparsely distributed and heavily stained. The immunoreactive nerve terminals were in synaptic contact with many immunonegative large neurons and dendrites. However, in a few cases, somatostatin-immunoreactive nerve terminals could also be observed on the surface of lightly stained neurons. Transection of vagal or mesenteric nerve failed to affect the distribution or density of somatostatin-like immunoreactive nerve terminals. These results demonstrate the existence of a synaptic input to the principal neurons of the coeliac ganglion of the cat by somatostatin-containing nerve terminals and suggest that this peptide may act as a neuromodulator or neurotransmitter. It is proposed that somatostatin-positive neurons provide intrinsic projections to other somatostatin-positive and to somatostatin-negative neurons throughout the coeliac ganglion, thereby creating a complex interneuronal system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327290
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  • 13
    Electronic Resource
    Electronic Resource
    Islets of preadipocytes highly committed to differentiation in cultures of adherent rat adipocytes (1991)
    Springer
    Cell & tissue research 264 (1991), S. 243-251 
    Details
    ISSN: 1432-0878
    Keywords: Preadipocytes ; Adipocyte precursor cells ; Adipose tissue ; Differentiation-cell cultures ; Ultrastructure ; Rat (Fischer 344)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cultures of adherent mature adipocytes, obtained from collagenase-digests of adipose tissue of the rat, invaribly contain rapidly proliferating, fibroblastlike cells despite the washing and centrifugation procedures empolyed during isolation of the fat cells. Such spindle-like cells originate from low-density structures, which we term “islets”, that are present, together with the mature adipocytes, in the floating layer of the digest of adipose tissue. Islets are found in preparations from adult (3–4 months old) as well as aging (17–24 months old) rats. By light-and electron microscopy, the islets appear as clusters of closely associated cells containing a variable amount of lipid-like material. Cells of endothelial or pericytic origin are also present in the islets. Within a few hours of culture, the islets give rise to those spindle-like cells that have been seen to proliferate in the cultures. By 36–48 hours, such cells begin to accumulate lipid droplets and, by 150 hours, assume the morphology of small mature adipocytes (diameter 20–35 μm) with a large central lipid droplet. The pattern of differentiation of these cells recalls that of preadipocytes derived from the stromal-vascular fraction of adipose tissue digests. Nonetheless, the extent and rapidity of their adipose conversion, as well as the culture conditions necessary for differentiation, are different and suggest that these cells are a substantially uniform subpopulation of adipocyte-precursor cells highly committed to differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313961
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  • 14
    Electronic Resource
    Electronic Resource
    Postnatal changes in the ultrastructure of the rat olfactory epithelium: the supranuclear region of the supporting cells (1991)
    Springer
    Cell & tissue research 265 (1991), S. 193-196 
    Details
    ISSN: 1432-0878
    Keywords: Postnatal development ; Olfactory epithelium ; Supporting cells ; Receptor cell dendrites ; Ultrastructure ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present electron-microscopical study reports ultrastructural changes occurring in the supranuclear region of the supporting cells of the rat olfactory epithelium during the first 16 days of postnatal life. These changes are concerned with the enclosure of receptor cell dendrites and an increase in the amount of smooth endoplasmic reticulum, which has a specific distribution in the supporting cell. An increase in microvillous projections at the free cell surface is also observed. Moreover, this report demonstrates that the cytoarchitecture of the apical portion of the olfactory epithelium at the 16th day of postnatal life is similar, with respect to the relationship between supporting cells and receptor cell dendrites, to that of adult animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318154
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  • 15
    Electronic Resource
    Electronic Resource
    Diversity of ultrastructure in different phenotypes of cultured microvessel endothelial cells isolated from bovine corpus luteum (1991)
    Springer
    Cell & tissue research 266 (1991), S. 37-49 
    Details
    ISSN: 1432-0878
    Keywords: Microvessel endothelial cells ; Cell culture ; Corpus luteum ; Ultrastructure ; Cow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Five different types of cultured microvessel endothelial cells defined by use of light microscopy and scanning electron microscopy in a preceding study were investigated by transmission electron microscopy. Type-1 cells displayed a deep invagination of the cell membrane or a single cilium. Granules of low electron density were abundant. A perinuclear ring of intermediate filaments occurred. Cultures of type-2 cells were subdivided into phenotype A, reminiscent of cell-type 1, and into phenotype B, assumed to be vascular smooth muscle cells. Many highly electron-dense granules appeared in late postconfluent cultures of both phenotypes. Cell-type 3 was conspicuous because of a large intracytoplasmic vacuole. Lysosomes with curvilinear bodies were found in cell-types 3 and 4. Both cell types developed a peripheral regular network of microfilaments. Cell-type 5 showed vesiculation of the rough endoplasmic reticulum, lipid droplets and a peripheral felt-like belt of microfilaments. Tubular forms seen in late postconfluent cultures of cell-types 1 to 3 displayed a core of extracellular matrix. Pseudotubular forms of cell-type 4 contained apoptotic bodies. Thus, as seen at the ultrastructural level, different features are maintained by cultured microvessel endothelial cells, suggesting that they have different inherent properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678709
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  • 16
    Electronic Resource
    Electronic Resource
    Effect of cytokines on thymic hematopoietic precursors (1991)
    Springer
    Cell & tissue research 264 (1991), S. 369-375 
    Details
    ISSN: 1432-0878
    Keywords: Thymus ; CD4- ; CD8- ; thymocyte ; Thymic hematopoietic precursors ; Cytokines ; Ultrastructure ; Mouse (DBA/2, H-2d)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We have previously shown that the interaction of thymocytes with thymic accessory cells (macrophages and/or interdigitating cells) is one of the factors required for thymocyte activation. Precursors of both thymic accessory cell and thymocytes are included in the CD4- CD8- Mac-1- Ia- subpopulation, and their respective maturation and/or activation may be modulated by granulocyte-macrophage colony-stimulating factor, interleukin 1 and interleukin 2. When CD4- CD8- thymic cells are activated with granulocyte-macrophage colony-stimulating factor plus interleukin 2, both macrophages and interdigitating-like cells are present, as shown by electron microscopy. When activated with interleukin 1 plus interleukin 2, the interdigitating-like cells is the only accessory cell present. In both culture conditions, large clusters are formed between interdigitating cells and lymphoid cells. These results have led us to propose two-step signals for thymocyte proliferation: first, the maturation of macrophages under granulocyte-macrophage colony-stimulating factor control and the production of interleukin 1, and secondly, the maturation of interdigitating cells under interleukin 1 control, their clustering with thymocytes which are then activated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313976
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  • 17
    Electronic Resource
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    The fine structure of lamellate cells in the brain of amphioxus (Branchiostoma lanceolatum, Cephalochordata) (1991)
    Springer
    Cell & tissue research 263 (1991), S. 597-600 
    Details
    ISSN: 1432-0878
    Keywords: Lamellate cell ; Ultrastructure ; Ciliary photoreceptors ; Nervous system, prochordates ; Branchiostoma lanceolatum (Acrania)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lamellate cells of amphioxus have round nuclei, and cytoplasm with many mitochondria and a large amount of glycogen. Each of these cells projects a highly modified, branched cilium into the central canal, where it characteristically forms lamellar structures. Primary branches and secondary lamellae often contain accessory microtubules that are not derived from the axonema. The functional and evolutionary significance of this cell type is discussed in relation to the ciliary photoreceptors found in other chordates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327295
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  • 18
    Electronic Resource
    Electronic Resource
    Cell types in the fetal pars tuberalis of the human adenohypophysis at mid-gestation (1991)
    Springer
    Cell & tissue research 264 (1991), S. 161-165 
    Details
    ISSN: 1432-0878
    Keywords: Adenohypophysis ; Pars tuberalis ; Ultrastructure ; Immunohistochemistry ; Fetal ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pars tuberalis of the adenohypophysis was investigated in three human fetuses at mid-gestation by electron microscopy or immunohistochemistry. In addition to gonadotrophs and thyrotrophs, identified by immunohistochemistry and ultrastructural morphology, electron microscopy revealed the existence of an additional differentiated cell type closely resembling “pars tuberalis-specific” cells known from other species. The role of this cell type in the human endocrine regulation remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305734
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    Effect of 1,10-phenanthroline on ultrastructure of pea leaves (1991)
    Springer
    Protoplasma 161 (1991), S. 23-30 
    Details
    ISSN: 1615-6102
    Keywords: 1,10-Phenanthroline ; Photodynamic herbicides ; Pisum sativum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have examined ultrastructural changes of mesophyll cells in pea leaves induced by the photodynamic herbicide 1,10-phenanthroline (Phe). Dark incubation of pea plants did not cause any damage in plants or changes in the ultrastructure of mesophyll cells. Two hours of illumination after pretreatment with Phe caused photooxidative damage in plant but was not sufficient to markedly change the ultrastructure, although dilation of endoplasmic reticulum (ER) cisternae occurred. Illumination for 12 h caused inhibition of grana formation in pretreated plants. These ultrastructural changes and the inhibition of chlorophyll (Chl) accumulation may be due to the inhibition of transport of certain proteins to the plastids, diminished accumulation of chlorophyll proteins (e.g., LHCP) and a decrease in activity of the chlorophyll synthetase.
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    URL: http://dx.doi.org/10.1007/BF01328894
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    Intercellular permeability inAbutilon nectary trichomes (1991)
    Springer
    Protoplasma 161 (1991), S. 150-159 
    Details
    ISSN: 1615-6102
    Keywords: Abutilon ; Lucifer Yellow ; Microinjection ; Nectary ; Transport ; Trichome ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Intercellular transport was examined in nectary hairs ofAbutilon slriatum var.thompsonii using dye-uptake and microinjection followed by fluorescence and electron microscopy. Dye-uptake experiments demonstrated that both Lucifer Yellow CH (LYCH) and diaminobenzidine (DAB) move centrifugally along an apoplastic pathway from the sepellary tissue towards the tip cell. Further, fluorescence of LYCH could also be detected inside the cells of the nectary trichome. When LYCH or LYCH/DAB were microinjected into the tip cell, the dye spread in a centripetal direction towards the stalk cell. Electron microscopical investigations of microinjected nectary hairs revealed numerous electron-opaque globules in the cytoplasm of the nectary hair cells. In addition, multivesicular bodies, nuclei with opaque regions and changes in the rough endoplasmic reticulum (RER) were seen in nectary hair cells even at very low concentrations of injected dye. Ultrastructural investigations provided evidence for cytological changes in microinjected nectary hairs.
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    URL: http://dx.doi.org/10.1007/BF01322727
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    Ultrastructure of the vegetative organisation and initial stages of silica plate deposition in the soil testate amoebaCorythion dubium (1991)
    Springer
    Protoplasma 163 (1991), S. 136-144 
    Details
    ISSN: 1615-6102
    Keywords: Corythion dubium ; Silica deposition ; Testate amoeba ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The siliceous body plates ofCorythion dubium are bound by a band of organic cement which is thickest at the lateral margins. The anterior vacuolar cytoplasm is separated by a pigment zone, which forms a dark band in the mid-body region, from the compact posterior region containing a typical vesicular nucleus surrounded by a region of dense endoplasmic reticulum. A pellicular basket of microtubules surrounds the posterior cytoplasm. The large Golgi complex lies between the nucleus and the fundus. Numerous coated and uncoated vesicles from the Golgi cisternae are seen in the peripheral cytoplasm alongside developing plates. These small siliceous plates are enclosed in silicon deposition vesicles lying in surface ruffles of the plasmalemma, often in association with a pair of microtubules. Observations are made on the formation of these vesicles and the early stages of silica deposition. A comparison is drawn between silica deposition inC. dubium and choanoflagellates where there is a similar association between silicon deposition vesicles and microtubules.
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  • 22
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    Effects of heat shock and thermoadaptation on the ultrastructure of cowpea (Vigna unguiculata) cells (1991)
    Springer
    Protoplasma 163 (1991), S. 125-135 
    Details
    ISSN: 1615-6102
    Keywords: Cowpea ; Heat shock ; Thermoadaptation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Suspension culture cells of cowpea (Vigna unguiculata) were examined using transmission electron microscopy to characterize morphological changes associated with hyperthermal stress. Cultures maintained at 26°C (unadapted cells) and 38°C (thermoadapted cells) were examined before and after exposure to elevated temperatures of 34°C and 45°C, respectively. Observations indicate that while there were significant ultrastructural differences between unadapted and thermoadapted cells, the following structural modifications in response to heat stress were observed in cells of both cultures: (a) almost a complete loss of polyribosomes, rough ER, and dictyosomes, (b) migration of intracellular waste material (presumably proteinaceous in composition) into the cell vacuole, (c) swelling of the nucleolus with assumed accumulation of preribosomal RNP granules, and (d) retraction of the tonoplast from the cytoplasm into the vacuoles of some cells. Heat shock granules (two size classes) were observed in the cytoplasm of stressed thermoadapted cells along with hollow-cored granules within the leucoplasts. Apart from a few minor differences, the morphological modifications that were made in apparent response to hyperthermal stress were remarkably similar in both cultures.
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    Ontogeny and ultrastructure of spontaneous nodules in alfalfa (Medicago sativa) (1991)
    Springer
    Protoplasma 162 (1991), S. 1-11 
    Details
    ISSN: 1615-6102
    Keywords: Rhizobium meliloti ; Development ; Symbiosis ; Nitrogen fixation ; Ultrastructure ; Spontaneous nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of spontaneous nodules, formed in the absence ofRhizobium and combined nitrogen, on alfalfa (Medicago sativa L. cv. Vernal) was investigated at the light and electron microscopic level and compared to that ofRhizobium-induced normal nodules. Spontaneous nodules were initiated from cortical cell divisions in the inner cortex next to the endodermis, i.e., the site of normal nodule development. These nodules, on uninoculated roots, were white multilobed structures, histologically composed of nodule meristems, cortex, endodermis, central zone and vascular strands. Nodules were devoid of intercellular or intracellular bacteria confirming microbiological tests. Early development of spontaneous nodules was initiated by series of anticlinal followed by periclinal divisions of dedifferentiated cells in the inner cortex of the root. These cells formed the nodular meristem from which the nodule developed. The cells in the nodule meristems divided unequally and differentiated into two distinct cell types, one larger type being filled with numerous membrane-bound starch grains, and the other smaller type with very few starch grains. There were no infection threads or bacteria in the spontaneous nodules at any stage of development. This size differentiation is suggestive of the different cell sizes seen inRhizobium-induced nodules, where the larger cell type harbours the invading bacteria and the smaller type is essential in supportive metabolic roles. The ontogenic studies further support the claim that these structures are nodules rather than aberrant lateral roots, and that plant possess all the genetic information needed to develop a nodule with distinct cell types. Our results suggest that bacteria and therefore theirnod genes are not necessarily involved in the ontogeny and morphogenesis of spontaneous and normal nodules in alfalfa.
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    URL: http://dx.doi.org/10.1007/BF01403895
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370101
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    Effects of carbon and oxygen limitations and calcium concentrations on biofilm removal processes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 17-25 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bacterial biofilm removal processes due to shear and catastrophic sloughing have been investigated in a turbulent flow system under conditions of carbon versus oxygen substrate limitations and varying aqueous phase calcium concentrations. Biofilm cellular and extracellular polymer carbon, total biofilm carbon and mass, and biofilm calcium concentrations are measured for pure culture biofilms of the facultative aerobe, Pseudomonas putida ATCC 11172. Results indicate oxygen-limited biofilms reach a higher steady-state biofilm organic carbon level than carbon-limited biofilms. Oxygen-limited biofilms also exhibit (1) a higher extracellular polymer-carbon: cell-carbon ratio throughout biofilm development and (2) a higher biofilm calcium content than carbon-limited biofilms. Increasing aqueous phase calcium concentrations increase the amount of biofilm calcium in both cases; the rate of calcium accumulation in oxygen-limited biofilms increases with increasing liquid phase calcium concentrations over the entire range studied while the rates of calcium accumulation in carbon-limited biofilms appear independent of aqueous phase calcium concentrations above 11.0 mg/L. Oxygen-limited biofilms with their higher extracellular polymer and calcium content exhibit shear removal rates that are 20-40% of those observed for carbon-limited biofilms. However, it is the oxygen-limited biofilms that experience catastrophic sloughing events. The carbon-limited biofilms studied here never sloughed even if subjected to intentional long-term deprivation of all nutrients. Reduced shear removal and the susceptibility to sloughing of the oxygen-limited biofilms are attributed to their more cohesive structure bought about by their relatively greater extracellular polymer production.
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    The effect of an applied potential on the activity of carbonic anhydrase immobilized on graphite rods (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 491-496 
    Details
    ISSN: 0006-3592
    Keywords: potentiostatic control of enzyme activity ; immobilized enzyme ; graphite ; conducting support ; specific anion inhibition ; carbonic anhydrase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of both a positive and a negative applied potential on the p-NPA hydrolysis activity of bovine carbonic anhydrase (BCA) immobilized on graphite rods has been investigated. Background experiments show that the pH-activity profile for BCA free in solution is not affected by either a negative or a positive potential applied to graphite rods placed in the same solution. However, the activity of BCA immobilized by covalent attachment to a graphite rod is influenced by a potential externally applied to the graphite rod. An overall increase in activity (as determined by the initial rate of the p-NPA hydrolysis reaction) is observed in the presence of a -0.2 V (Ag/AgCl) applied potential, while decreased activity is evident at +0.6 V (Ag/AgCl). This is indicative of an electrolyte anion effect rather than a local pH effect. In the presence of the specific anion inhibitors Cl- and SCN-, the relative BCA activity increases at -0.2 V (Ag/AgCl) and decreases at +0.6 V (Ag/AgCl) are consistent with the different BCA inhibition constants for Cl- and SCN-. Accelerated loss of immobilized BCA activity also accompanies the application of the external potentials, particularly at +0.6 V (Ag/AgCl). Results described here represent an early example of potentiostatic control of nonredox enzyme activity. Several possible mechanisms are discussed including specific anion inhibition, enzyme surface charge/charged support material interactions, and charged product inhibition. It is likely that a combination of such mechanisms is operational in this system. The implications of external potentials affecting the activity of immobilized enzymes in the design of stable immobilized enzyme electrodes are also discussed.
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    Growth and fermentation characteristics of new selected strains of Saccharomyces at high temperatures and high cell densities (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 528-536 
    Details
    ISSN: 0006-3592
    Keywords: yeast thermotolerance ; Saccharomyces ; invertase ; sugarcane juice fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Maintenance of high cell viability was the main characteristic of our new strains of thermotolerant Saccharomyces. Total sugar conversion to ethanol was observed for sugarcane juice fermentation at 38-40°C in less than 10 h and without continuous aeration of the culture. Invertase activity differed among the selected strains and increased during fermentation but was not dependent on cell viability. Invertase activity of the cells and optimum temperature for growth, as well as velocity of ethanol formation, were dependent on medium composition and the type of strain used. At high sugarcane syrup concentrations, the best temperature for ethanol formation by strain 781 was 35°C. Distinct differences among the velocities of ethanol production using selected strains were also observed in sugarcane syrup at 35-38°C.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370606
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370801
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  • 29
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    Strategies for reducing solvent toxicity in extractive fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 716-722 
    Details
    ISSN: 0006-3592
    Keywords: κ-carrageenan matrix ; Lactobacillus delbrueckii ; toxicity ; solvent diffusion ; extractive fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The toxicity of an Alamine 336/oleyl-alcohol extraction system on Lactobacillus delbrueckii was investigated. It was shown that the solvent affected the cells through the water-soluble portion and the immiscible portion of the solvent. While immobilization significantly protected the cells from the immiscible solvent phase, the water-soluble part of the solvent still caused toxicity to the microorganisms due to diffusion of the solvent into the matrix. Adding soybean oil to the κ-carrageenan matrix could trap the diffusing solvent molecules, and therefore reduce the toxic effect from the water soluble portion of the solvent. The protective ability of soybean oil was quantified through mathematical modeling and experimentation.
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    High-concentration cultivation of Lactococcus cremoris in a cell-recycle reactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 746-754 
    Details
    ISSN: 0006-3592
    Keywords: Lactococcus cremoris ; cell-recycle fermentor ; cross-flow filtration ; high cell concentration cultures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High-cell concentration cultivation of Lactococcus cremoris, a homofermentative lactic acid producer, in a cell-recycle fermentor is described. Cross-flow filtration allowing continuous removal of the inhibitory metabollte, the influence of dilution rate on growth was investigated in total or partial cell-recycle cultures. The dependence of growth characteristics on operating conditions was identified and quantified using lactose as the carbon source. Growth kinetics could be described by both lactate removal efficiency and nutrient availability. Based on physiological observations, biomass and lactic acid productivities were predicted in partial cell-recycle cultures.
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    URL: http://dx.doi.org/10.1002/bit.260370809
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    Observations of binary population biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 778-789 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biofilm research has focused on studies of undefined mixed microbial populations and, more recently, on investigations of monopopulation biofilms. In the first case, the biofilm is considered a homogeneous mass, ignoring the properties of individual species. The second case concentrates on the properties and processes of one microbial species in the biofilm. This article describes biofilm experiments conducted with monopopulations of Klebsiella pneumoniae and Pseudomonas aeruginosa and with binary populations of K. pneumoniae and P. aeruginosa. Process rates and stoichiometric coefficients were determined for the monopopulation and for the binary population biofilms and evaluated in light of the species distribution in the latter. Results indicate that neither the specific cellular product formation rate nor the glucose-oxygen stoichiometric ratio of K. pneumoniae or P. aeruginosa in the binary biofilm is affected by the presence of the other species. Consequently, species interaction was not observed. Although the specific cellular growth rate of K. pneumoniae is five times that of P. aeruginosa, the former species did not dominate the microbial population in the biofilm. Possible reasons for this unexpected behavior are discussed.
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    Modeling fermentations with recombinant microorganisms: Formulation of a structured model (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 802-808 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple structured model is described and compared with experimental data for fermentations with recombinant. Escherichia coli. The model is a so-called compartment, model, where the different biomass components are lumped together in a few intracellular variables. The model is able to describe, in a biologically reasonable fashion, a majority of the observations that have been made through fermentations with recombinant microorganisms. The model is especially suited for description of dynamic changes in plasmid copy number, e.g., runaway plasmid replication.
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    Absorption of CO2 in algal mass culture systems: A different characterization approach (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 834-842 
    Details
    ISSN: 0006-3592
    Keywords: microalgae ; bioreactor ; CO2 ; absorption ; KLa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the characterization of CO2 absorption in aerated microalgal culture systems, a different approach based on KLa(O2) determination and transformation was studied. To confirm the validity of this method, the influence of reactions between CO2 and compounds (OH-, H2O, and NH3) present in the culture medium upon the absorption mechanism was evaluated under different physical and chemical culture conditions. Under these conditions, knowledge of the relative magnitudes of the diffusion and reaction kinetics permitted the evaluation of their relative importance. For the determination of the parameters required for the calculation of the CO2 absorption constant, empirical correlations for KL0 and a were used that had been previously verified with experimental data for O2 absorption. Since, for the conditions studied, the absorption rate was shown to be independent of the chemical reactions taking place in the liquid phase, the KLa for CO2 could be directly related to the KLa for O2 by a simple factor that took into account the difference in aqueous diffusivity of the two gases. Thus, using methods developed for determining O2 absorption in gas-liquid contactors, it is possible to adequately characterize CO2 absorption for laboratory and pilot scale algal production systems.
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    Enzymatic syntheses of alkyds. II: Lipase-catalyzed polytransesterification of dichloroethyl fumarate with aliphatic and aromatic diols (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 883-888 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260371001
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    Photosynthetic activity of plant cells solubilized in water-in-oil microemulsions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 918-921 
    Details
    ISSN: 0006-3592
    Keywords: plant cells ; photosynthesis ; microemulsion ; organic solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With the aim of possibly extending plant microbiology and photosynthesis beyond the usual applicability in aqueous solution, we investigated the solubilization of plant cells inorganic media with the help of water-in-oil microemulsions. Cells isolated from leaves of Rumex obtusifolius were solubilized in a water/2-ethyl-hexyl-sodiumsulfosuccinate/isooctane system, containing 20% water (v:v) and 240 mM surfactant, and the oxygen evolution/consumption was measured polarographically. Although no oxygen evolution was detectable in the organic medium, the cells were able to carry out photosynthetic oxygen consumption at the expense of ascorbate. To a lesser extent, photosynthetic oxygen consumption was measured using N, N, N′, N′-tetramethyl-p-phenylenediamine as electron donor. The rate of ascorbate photooxidation was linearly related to the concentration of cells.
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    A study of the energetics and economics of microalgal mass culture with the marine chlorophyte Tetraselmis suecica: Implications for use of power plant stack gasesHawaii Institute of Marine Biology Contribution No. 819. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 936-947 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The marine phytoplankter Tetraselmis suecica was grown in shallow outdoor flumes for a period of approximately 6 months at the Natural Energy Laboratory of Hawaii. In full sunlight, gross production rates were 15-20 g C m-2 d-1. The corresponding photosynthetic efficiencies (PE's) were 9-10%. Respiration losses removed about half the gross production. The CO2 utilization efficiencies of 96 ± 11% were achieved by bubbling CO2 into the culture with the use of a counterflow sump system. Adding the CO2 in the form of carbonated water resulted in utilization efficiencies of 81 ± 11%. Archimedes screws proved superior to both paddle wheels and propellers as a means of circulating the water in the flumes. Insertion of foil arrays into the flumes to effect systematic mixing of the culture significantly enhanced production. The enhancement was greater when the foils were oriented at a small angle relative to the horizontal than when they were oriented at the same angle relative to the vertical. Light modulation effects are implicated as the probable cause of most of the enhancement. Substitution of electric power plant stack gases for pure CO2 resulted in no significant change in the production of T. suecica grown in chemostat culture.
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    Papain kinetics in the presence of a water-miscible organic solvent (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 967-972 
    Details
    ISSN: 0006-3592
    Keywords: papain ; organic solvent ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of various concentrations of a water-miscible organic solvent [a 7:3 (v/v) mixture of N, N dimethylformamide and dimethylsulfoxide] on the kinetics of papain have been investigated. The parameters kcat and Km for the amidase and esterase activity of papain using N-α-benzoyl-DL-arginine-p-nitroanilide (BAPNA) and N-α-benzoyl-L-arginine ethyl ester (BAEE) as substrates were determined. For both types of activity, kcat initially increased (up to about 15% solvent), and then decreased with increasing concentrations of organic solvent. In contrast, Km increased sharply with the organic solvent concentration. Active site titration at 0 and 50% solvent indicated no change in the amount of active enzyme. Fluorometric measurements of the emission spectrum of papain did not indicate any major conformational changes with increasing concentrations of organic solvent.
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    URL: http://dx.doi.org/10.1002/bit.260371011
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    Analysis of polymer synthesis rates during steady-state growth of X. campestris (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 383-385 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370413
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    Effect of continued exposition to ethanol on activity of the ammonium and fructose transport systems in Saccharomyces cerevisiae var. ellipsoideus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 389-391 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ethanol and cycloheximide inhibited the function of the ammonium transport system in growing cultures of Saccharomyces cerevisiae var. ellipsoideus measured as methylamine uptake. The effect was reversible with ethanol and irreversible with the antibiotic. The kinetic data are consistent with a reduction of the number of active carrier molecules located in the plasma membrane. In contrast, neither ethanol nor cycloheximide affected the specific rate of fructose uptake.
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    Plant cell bioreactor for the production of protoberberine alkaloids from immobilized Thalictrum rugosum cultures (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 397-403 
    Details
    ISSN: 0006-3592
    Keywords: immobilized Plant cells ; plant cells bioreactor ; Protoberberine Alkaloids ; Thalictrum rugosum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cultured Thalictrum rugosum cells were immobilized using a glass fiber substratum previously shown to provide optimum immobilization efficiency based on spontaneous adhesion mechanisms. When cultivated in shake flasks, immobilized cells exhibited decreased growth and protoberberine alkaloid production rates in comparison to freely suspended cells. Since alkaloid production is growth associated in T. rugosum, the decreased specific production rate was a function of the slower growth rate. Cells immobilized on glass fiber mats appear to be amenable for extended culture periods. Maximum biomass and protoberberine alkaloid levels were maintained for at least 14 days in immobilized cultures. In contrast, fresh weight, dry weight, and total alkaloid content decreased in suspension cultures following the linear growth phase.Glass fiber mats were incorporated in to a 4.5-L plant cell bioreactor as horizontal disks supported on a central rod. Mixing in the reactor was provided by the combined actions of a magnetic impeller and a cylindrical sparging colum. fThe magnetic impeller and a cylindrical sparging column. The entire inoculum biomass of T. rougosum, introduced as suspension, was spontaneously immobilized with in 8h. During liner phase, the growth rate of bioreactor cultivated immobilized cells (μ = 0.06 day-1) was 50% that immobilized cell viability in both systems was determined to be similar. The increase in specific production of protoberberine alklodis was initially similar in bioreactor-and culture period. The increase in specific production of protoberberine alkaloids was initially similar in bioreactor-and shake-flask-cultivated immobilized cells. However, the maximum specific production of bioreactor grown cultures was lower. The scale up potential of an immobilization strategy based on the spontaneous adhesion of immobilization strategy based on the spontaneous adhesion of cultured plant cells to glass fiber is demonstrated.
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    Quantitative evaluation of the pH profile in organic acid fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 190-195 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No Abstrct.
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    Mass transfer characterization of an airlift probe for oxygenating and mixing cell suspensions in an NMR spectrometer (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 205-209 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen transfer characteristics of a 20-mm O.D. airlift contactor fitted with an oxygen microelectrode were determined by steady-state sulfite oxidation measurements. The volumetric mass transfer coefficient kLa was proportional to sparging power input per unit volume raised to a power which varied from 0.41 in water (coalescing bubbles) to 0.76 in NaCl solutions (noncoalescing bubbles). The highest observed kLa value was 0.012 s-1 which is sufficient to aerate Escherichia coli in an NMR spectrometer at moderate to high cell densities, depending on the physiological state of the cells.
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    A parametric study ot protease production in batch and fed-batch cultures of Bacillus firmus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 467-483 
    Details
    ISSN: 0006-3592
    Keywords: alkaline protease ; Bacillus firmus ; extracellular enzymes ; nitrogen/oxygen/phosphorous limitation ; acetic acid ; ethanol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Proteolytic enzymes produced by Bacillus species find a wide variety of applications in brewing, detergent, food, and leather industries. Owing to significant differences normally observed in culture conditions promoting cell growth and those promoting production of metabolites such as enzymes, for increased efficacy of bioreactor operations it is essential to identify these sets of conditions (including medium formulation). This study is focused on formulation of a semidefined medium that substantially enhances synthesis and secretion of an alkaline protease in batch cultures of Bacillus firmus NRS 783, a known superior producer of this enzyme. The series of experiments conducted to identify culture conditions that lead to improved protease production also enables investigation of the regulatory effects of important culture parameters including pH, dissolved oxygen, and concentrations of nitrogen and phosphorous sources and yeast extract in the medium on cell growth, synthesis and secretion of protease, and production of two major nonbiomass products, viz., acetic acid and ethanol. Cell growth and formation of the three nonbiomass products are hampered significantly under nitrogen, phosphorous, or oxygen limitation, with the cells being unable to grow in an oxygen-free environment. Improvement in protease production is achieved with respect to each culture parameter, leading in the process to 80% enhancement in protease activity over that attained using media reported in the literature. Results of a few fed-batch experiments with constant feed rate, conducted to examine possible enhancement in protease production and to further investigate repression of protease synthesis by excess of the principal carbon and nitrogen sources, are also discussed. The detailed investigation of stimulatory and repressory effects of simple and complex nutrients on protease production and metabolism of Bacillus firmus conducted in this study will provide useful guidelines for design of bioreactors for production of protease and bulk chemicals by this bacterium.
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    Development of pure culture biofilms of P. putida on solid supports (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 512-518 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas putida biofilms were developed on and biofilm accumulation rate data were obtained for the following two classes of support materials: charged surfaces and noncharged hydrophobic and hydrophilic surfaces. The effects of surface roughness and porosity on the rate of microbial attachment were also examined.Materials bearing a net positive or negative surface charge supported the greatest biofilm accumulation and the highest biofilm accumulation rate. Uncharged hydrophobic materials achieved the next greatest biofilm accumulation, averaging approximately 50% of the total biomass which was accumulated on the charged surface materials after 16 days. Uncharged hydrophilic materials supported very little biofilm development. In general, biofilm accumulation increased with decreased surface roughness. The effect of pore size on biofilm accumulation was not conclusive.The biofilm accumulation kinetics showed an exponential accumulation rate for the charged surfaces and an approximately linear accumulation rate for the hydrophobic materials. This difference in accumulation kinetics is consistent with proposed differences in the physicochemical mechanism governing attachment to these two types of surface materials.
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    Kinetics of loss of a recombinant plasmid in Bacillus subtilis (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 927-935 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus subtilis ; recombinant plasmid ; deletion rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant plasmid pCEDS is structurally unstable in Bacillus subtilis cultures. We have previously shown that stability can be independently increased by changing from a complex medium supporting high growth rates to a chemically-defined medium supporting a lower growth rate and removal of a 4.77-kb EcoRI fragment from pCED3 to give plasmid YS1. Further stabilization was achieved by combining the two approaches. In the present work, we show that the stabilization of the plasmid-encoded LacZ+ phenotype can be explained solely by the effect on the growth rate ratio between cells containing modified and parental plasmids. By using modified stability experiments (where a single cell rather than a suspended colony was used to initiate growth), independent growth rate measurements, and a simple mathematical model, we can describe the kinetics of the loss of the LacZ+ phenotype in terms of two variables, α and p (where α is the ratio of growth rates between modified and parental cells, and p is the probability of obtaining modified cells from parental cells). Under the conditions tested, the average values of α were 1.52 for cultures growing in complex medium, 1.28 for cultures growing in defined medium, and 1.18 for cultures containing the modified plasmid pYS1 growing in complex medium. The calculated p values ranged between 10-8 and 10-10 under all conditions. Plasmid (pYS137) was used to directly estimate plasmid deletion rates in B. subtilis and it showed a rate between 5 × 10-8 and 1.1 × 10-9 deletions/cell/generation. In contrast to B. subtilis, there were no detectable differences in growth rates between Escherichia coli strains harboring plasmid pCEDS and plasmid-free cells. These results explain the observed stability of pCEDS in E. coli cultures and indicate that readily detected instability in B. subtilis cultures can be the result of rare deletion events.
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    Oxygen transfer in slurry bioreactors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 960-966 
    Details
    ISSN: 0006-3592
    Keywords: bioreactors ; oxygen transfer ; fermentation ; mycelial fermentation ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen transfer in bioreactors with slurries having a yield stress was investigated. The volumetric mass transfer coefficients in a 40-L bubble column with simulated fermentation broths, the Theological properties of which were represented by the Casson model, were measured. Experimental data were compared with a theoretical correlation developed on the basis of a combination of Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence. Comparisons between the proposed correlation and data for the simulated broths show good agreement. The mass transfer data for actual mycelial fermentation broths reported previously by the authors were re-examined. Their Theological data was correlated by the Bingham plastic model. The oxygen transfer rate data in the mycelial fermentation broths fit the predictions of the proposed theoretical correlation.
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    Effect of medium osmolarity on hybridoma growth, metabolism, and antibody production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 989-993 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Ultrasound-enhanced bioprocess. II: Dehydrogenation of hydrocortisone by Arthrobacter simplex (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 998-1003 
    Details
    ISSN: 0006-3592
    Keywords: Arthrobacter simplex ; controlled ultrasonic irradiation ; microbial conversion ; ultrasound facilitated diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dehydrogenation of hydrocortisone by agitated suspensions of free and immobilized cells of Arthrobacter simplex ATCC 6946 was investigated under controlled ultrasonic irradiation at a frequency of 20 kHz. The microbial conversion was optimized first with respect to mechanical agitation and subsequently with respect to an additionally superimposed sonication. The optimization of ultrasound intensity and its mode of application were established at a level which maintained the structural integrity of the cells as well as their biocatalytic activity. Various regimes of ultrasound at power densities of 0.030-0.120 W/mL were applied in systems of soluble (0.4 g/L) and excess (1 g/L) hydrocortisone and only a moderate enhancement of the bioconversion by free cells was observed. This result was explained by a better ultrasound-induced dispersal of microscopic clumps of cells and self-adhering clusters of the steroids. However, a quite significant enhancement effect was obtained in bioconversion systems of soluble substrate by gel-entrapped cells. This enhancement was explained by a phonophoretic effect associated with ultrasound-facilitated diffusion of the substrates - oxygen and hydrocortisone - within the gel beads.
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    The biodegradation of mixtures of organic solvents by mixed and monocultures of bacteria (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1037-1042 
    Details
    ISSN: 0006-3592
    Keywords: biodegradation ; organic solvents ; biooxidation ; bacteria ; competition interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Much more information concerning the biodegradation kinetics of mixtures of common industrial chemicals, such as organic solvents, needs to be gathered before wastewater biotreatment process performance can become a matter of design. Here, the biooxidation of a solvent mixture comprizing methanol, acetone, isopropanol, and methylene chloride is examined. The fact that the enrichment culture obtained comprized only two solvent-utilizing strains, together with only minor percentages of nonsolvent utilizing satellite strains, was contrary to the theory of microbial competition. In addition, the complex relationship between the two solvent-utilizing strains indicates that further work is necessary on the pathways involved in isopropanol and acetone biooxidation and on the effects of operating conditions on the fluxes along such pathways.
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    A molecular model for singlet/singlet energy transfer of monovalent ligand/receptor interactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1066-1075 
    Details
    ISSN: 0006-3592
    Keywords: Resonance energy transfer ; papain ; concanavalin A ; molecular model ; monovalent ligand and receptor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A stochastic model is described that predicts the degree of singlet/singlet energy transfer in complexes formed between monovalent ligands and monovalent receptors. The modeling approach is intended to serve as an analytical tool for approximating the level of fluorescence quenching that can be expected to occur in fluorescently labeled monovalent ligands and receptors that are bound together in complexes. This approach has utility in areas such as modeling protein/protein interactions and designing fluorescence energy transfer assays.Using the crystallographic data for papain (monovalent ligand ) and concanavalin A (monovalent receptor ) along with a molecular graphics computational package the ligand and receptor were docked together to form a ligand/receptor complex. The intermolecular distances between the lysine resides of the ligand and receptor were then estimated, receptor complex was calculated assuming a value for the characteristic length R0 of the donor/acceptor pair. Results from the stochastic model were used to calculate the level of fluorescence quenching one would expect for a resonance energy transfer competition assay based on the monovalent ligand/pair.Three key assumptions were made during the model development. First, all lysine resides for the ligand and receptor were equally reactive with the dye molecules so the stoichiometry of the donor and acceptor chromophores was governed by a binomial distribution. Second, the dye molecules were located at the α-carbon position for each reactive lysine residue. Finally, in the energy transfer competition assay, it was assumed that equilibrium existed between the ligand, receptor, and competing hapten at all times. Based on these assumptions, results are presented that indicate the maximum energy transfer for the monovalent papain/concanavalin. A complex is strongly dependent on the number of acceptor chromophores and on the value of R0. Results are also presented on the approximate level of fluorescence quenching that may occur in a competition assay based on the papin/pConA complex. Lastly, a strategy is discussed for maximizing the dynamic range and linearity of energy transfer assays by optimizing several key design variables.
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    Optimization of L-malic acid production by Aspergillus flavus in a stirred fermentor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1108-1116 
    Details
    ISSN: 0006-3592
    Keywords: organic acids ; Aspergillus flavus ; molar yield ; stirred fermentor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of various nutritional and environmental factors on the accumulation of organic acids (mainly L-malic acid) by the filamentous fungus Aspergillus flavus were studied in a 16-L stirred fermentor. Improvement of the molar yield (moles acid produced per moles glucose consumed) of L-malic acid was obtained mainly by increasing the agitation rate (to 350 rpm) and the Fez+ ion concentration (to 12 mg/L) and by lowering the nitrogen (to 271 mg/L) and phosphate concentrations (to 1.5 mM) in the medium. These changes resulted in molar yields for L-malic acid and total C4 acids (L-malic, succinic, and fumaric acids) of 128 and 155%, respectively. The high molar yields obtained (above 100%) are additional evidence for the operation of part of the reductive branch of the tricarboxylic acid cycle in L-malic acid accumulation by A. flavus. The fermentation conditions developed using the above mentioned factors and 9% CaCO3 in the medium resulted in a high concentration (113 g/L L-malic acid from 120 g/L glucose utilized) and a high overall productivity (0.59 g/L h) of L-malic acid. These changes in acid accumulation coincide with increases in the activities of NAD+-malate dehydrogenase, fumarase, and citrate synthase.
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    Lipase-catalyzed hydrolysis of 2-naphtyl esters in biphasic system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 30-36 
    Details
    ISSN: 0006-3592
    Keywords: lipase-catalyzed hydrolysis ; 2-naphtyl ester ; biphasic system ; interfacial reaction ; two-film model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The authors measured the rate of hydrolysis of the homologs of 2-naphtyl ester by using a Lewis cell with constant interfacial area to elucidate the kinetic mechanism of the lipase-catalyzed hydrolysis in biphasic system. On the basis of the two-film model, it was found from the analysis of experimental results that the hydrolysis of these substrates proceeds at the interface between the aqueous and organic phases. The interfacial reaction rate could be correlated by Michaelis-Menten mechanism. The values of the rate constant and the Michaelis constant were almost independent of the kinds of 2-naphtyl ester. The values of the interfacial kinetic parameters for 2-naphtyl ester were much greater than those for the hydrolysis in the aqueous phase.
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    Modeling growth and succinoglucan production by Agrobacterium radiobacter NCIB 9042 in batch cultures (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 65-74 
    Details
    ISSN: 0006-3592
    Keywords: Succinoglucan ; Agrobacterium radiobacter ; Structured model ; ATP ; cofactors balances ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wild-type Agrobacterium radiobacter NCIB 9042 has been cultivated in batch cultures on a synthetic medium which was adapted for growth and succinoglucan production. Experiments were carried out in a 4-L stirred-tank aerated reactor. Glucose, biomass, polysaccharide, protein, and inorganic- and organic-nitrogen concentrations were measured, and oxygen consumption and CO2 production rates were obtained by a gas-balance technique. Nitrogen balance shows that inorganic nitrogen is entirely recovered into proteins. The carbon balance is satisfied with in ±5%. Stoichiometric equations for biomass growth and succinoglucan synthesis were established. The biosyntheticpolymer pathways including ATP and cofactor consumption were investigated. From previous studies, a (P/O) value of 1.66 is selected for oxygen sufficient cultures. The actual ATP requirements of 25.4 mmol ATP/g succinoglucan (38.5 mol ATP/mol succinoglucan), determined by a metabolic analysis, is 2.39 times the stoichiometric value. Experimental results were modeled by a system of differential equations. The exponential growth phase was described by a nitrogen-limited Monod equation. Subsequent succinoglucan synthesis followed a slightly modified Luedeking-Piret relation partitioning internal and external polysaccharide. Experimentally determined coefficients are compared with published results for continuous culture of A. radiobacter NCIB 11883.
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    Development of biosensors for the simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 99-103 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sensors for the simultaneous determinations of sucrose and glucose, lactose and glucose, and starch and glucose were prepared by a combination of the enzyme system shown below and an oxygen electrode: The mechanism for separating the substrates with the proposed sensors is based on the time lag arising from reaction and diffusion. Invertase, β-galactosidase, amyloglucosidase, mutarotase, and glucose oxidase were covalently immobilized on triacetyl cellulose membranes containing 1,8-diamino-4-aminomethyloctane. A glucose oxidase membrane, mutarotase membrane, three sheets of triacetyl cellulose membranes, and invertase, or β-galactosidase or amyloglucosidase membrane were placed in that order on the tip of the oxygen electrode. Calibration curves for sucrose, lactose, and starch were linear up to 40 mM, 60-180 mM, and 10%, respectively. The simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose was possible when the amount of glucose coexised was in the range of 2-16% sucrose, 2.8-8.3% lactose, or 0.1-1% starch. The relative errors were ±4% for sucrose and ±3% for lactose in 100 assays. The starch sensor was reused only five times. Each enzyme membrane was fairly stable for more than 10 days.
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    α-Amylase adsorption on starch crystallites (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 127-134 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus subtillis ; binding free energy ; Adsorption isotherm ; monolayer adsorption process ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The goal of this work was to characterize the adsorption of Bacillus subtills α-amylase onto crystalline starchy materials of the B-type polymorph. Monodisperse spherulitic particles (R ż6; 5.0 μm), essentially resistant to α-amylolysis at 25°C were prepared from short amylose chains (DPn ≈ 15). The α-amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 μg/cm2 at 25°C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was ΔG ≈ -20.7 kJ/mol. This is smaller than published values for the binding of α-amylase to soluble amylosic chains (ΔG 〈 -30 kJ/mol).
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260371101
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    Enzymatic synthesis of esters using an immobilized lipase (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1004-1009 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; immobilized enzymes ; enzymes in organic solvents ; enzyme activity and stability ; continuous enzymatic synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various esters were synthesized in nearly anhydrous hexane from alcohols and carboxylic acids using a lipase from Candida cylindracea. The enzyme was immobilized on a nylon support and protein loadings as high as 10 mg/g were obtained. The activity of the immobilized enzyme was maximum in a range of temperatures from 25 to 37°C. Ethylpropionate was formed from ethanol and propionic acid at a rate of 0.017 mol/h g immobilized protein. Different esters were formed at comparable rates and equilibrium conversions could generally be approached in less than 10 h in a batch reaction system. The immobilized lipase catalyst was quite stable and retained about one third of the initial activity after repeated experiments during the course of 72 days. A stirred tank continuous flow reactor was used successfully for the continuous production of esters.
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    Increased protein productivity from immobilized recombinant yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1029-1036 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; protein production ; continuous culture Saccharomyces cerevisiae ; plasmid stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Saccharomyces cerevisiae strain Mc16/p520 has an unstable plasmid, p520, which directs production of a wheat α-amylase. The effects of immobilizing this microorganism on the plasmid stability and the specific productivity of the secreted α-amylase were investigated. Small gelatin beads were used as the support in both fluidized and packed bed configurations, and the yeast cells were attached by covalent cross-linking with glutaraldehyde. These data were then compared to those for nonimmobilized, suspension cells.Plasmid stability was increased for the immobilized cells during continuous culture at dilution rates both above and below washout. Continuous suspension cultures were not stable and rapidly lost the plasmid. Immobilization caused an increase in specific and volumetric productivity during continuous culture, with a packed bed design resulting in the highest specific productivity.
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    Oxygen uptake by entrapped hybridoma cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1050-1053 
    Details
    ISSN: 0006-3592
    Keywords: hybridomas ; immobilization ; oxygen ; respiration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen consumption by hybridoma cells immobilized in 1- and 3.9-mm-diameter calcium alginate beads was measured. The entrapped cells consumed oxygen at about 10 μmol/min per 109 cells, regardless of the bead size and cell loading. In contrast, the same cells in suspension culture respire at specific rates of 3-8 μmol/min per 109 cells (depending on the cell density). The growth rate of the immobilized cells was significantly reduced, while specific antibody production was comparable to that of free cells.
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    A novel technique for the measurement of disruption in high-pressure homogenization: Studies on E. coli containing recombinant inclusion bodies (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 363-370 
    Details
    ISSN: 0006-3592
    Keywords: homogenization, high-pressure ; cell disruption ; inclusion bodies ; size distribution ; centrifuge, analytical ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The high-pressure homogenization of Escherichia coli, strain JM101, containing inclusion bodies of recombinant porcine somatotropin was investigated. A novel technique employing an analytical disc centrifuge was used to monitor the disruption. This a direct technique which measures cell disintegration rather than soluble protein release. The technique is particularly suited to measurements where the disruption approaches 100%. The disk centrifuge provides a size distribution of the homogenate, and furnishes evidence for the preferential disruption of larger cells. For E. coli containing inclusion bodies, and increase in the cell feed concentration from 145 g/L (wet weight) to 330 g/L resulted is poorer homogenization. Poorer disruption was also obtained by lowering the feed temperature from 20°C to 5°C. Only slight variations in performance were obtained by increasing the feed pH from 7.5 to 9.0 or by storing the feed at 4°C for 24 h prior to disruption. Comparison with uninduced E. coli strain JM101, showed that the disruption obtained is higher for bacteria containing a recombinant inclusion body.
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    Characteristics of batch culture of a recombinant bacillus brevis excreting a foreign esterase (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1247-1252 
    Details
    ISSN: 0006-3592
    Keywords: batch culture ; Bacillus brevis ; esterase ; host-vector system ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The productivity of extracellular enzyme was evaluated in batch culture using a protein hyperexcreting host, Bacillus brevis HPD315 harboring pHSC131, which carried a gene (est) encoding esterase activity from Bacillus stearother mophilus. Optimum temperature and pH for the bacterial growth and the production of extracellular esterase were found to be 35°C and pH 6.5, by using the standard medium (GPY) containing neomycin as a selective pressure, Under the cultivation condition employed, cell growth reached 5 g dry cell weight/L, while the extracellular esterase activity amounted to 4.5 U/mL. Most (79%-92%) of the esterase produced was excreted into the medium. pHSC131 was stably retained in the host cell during cultivation in the presence of neomycin. However, in the absence of neomycin, the plasmid was completely lost from the host after 12-h cultivation accompanied by decreases in both esterase activity and production of total extracellular protein. The copy number of the plasmid was estimated to be approximately 7 throughout the cultivation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the excreted proteins showed the presence of a protein having an apparent molecular weight of 32,000, which equals to the value predicted from the DNA sequence of the est gene.
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    Cellulase production by Trichoderma reesei when cultured on xylose-based media supplemented with sorbose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 12-16 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ability of L-sorbose to stimulate cellulase production In shake flask culture of Trichoderma reesei was examined in mineral salts media (initial pH 5.0) containing either 1.0% D-xylose, 1.0% cellulose, and/or 0.1, 0.3, or 0.5% L-sorbose. When sorbose was the only carbon source, growth was limited, little substrate was utilized, pH increased, and cellulase activity was not apparent. The other carbon sources promoted good growth, pH dropped sharply to 2.5-3.0, substrate was utilized rapidly, and cellulase activity was detected. After three weeks of fermentation, twice as much cellulase activity was detected in the medium containing only cellulose as the carbon source, as compared to xylose as the carbon source. Cellulase activity was higher when media contained xylose supplemented with sorbose compared to xylose as the only carbon source. At 0.3 and 0.5% levels of sorbose supplementation of xylose-based media, cellulase activity was similar to that in cellulose-based media.
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    Physiological changes during the adaptation of hybridoma cells to low serum and serum-free media (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 35-46 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two murine hybridoma cell lines (167.4G5.3 and S3H5/γ2bA2) were adapted to grow in low-serum and serum-free media by a weaning procedure. The changes in cell growth, metabolic, and antibody production rates with adaptation were examined using biochemical and flow cytometric analyses. After adaptation to a particular serum level, the short-term serum response of the cells was experimentally determined. Specific growth rates, glucose and glutamine uptake and lactate and ammonia production rates, and specific antibody production rates were evaluated from the data. For both cell lines, an improvement in cell growth was observed after adaptation, and both higher growth rates and higher cell concentrations were obtained. The specific glucose and glutamine uptake rates and the lactate and ammonia production rates changed insignificantly with adaptation. Conversely, changes in the specific antibody production rate of the two cell lines differed. Cell line 167.4G5.3 showed a loss in antibody productivity at low serum levels, while the S3H5/γ2bA2 kept its original productivity in low-serum-containing media. The intracellular antibody content for S3H5/γ2bA2 cells remained unaltered by adaptation, but a low antibody containing cell population appeared in the 167.4G5.3 culture. The loss of specific antibody productivity in this cell line was due to the appearance of this population.
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    Model of oxygen transport limitations in hollow fiber bioreactors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 80-92 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Axial and radial oxygen depletion are believed to be critical scale-limiting factors in the design of cell culture hollow fiber bioreactors. A mathematical analysis of oxygen depletion has been performed in order to develop effectiveness factor plots to aid in the scaling of hollow fiber bioreactors with cells immobilized in the shell-side. Considerations of the lumen mass transport resistances and the axial gradients were added to previous analyses of this immobilization geometry. An order of magnitude analysis was used to evaluate the impact of the shell-side convective fluxes on the oxygen transport. A modified Thiele modulus and a lumen and membrane resistance factor have been derived from the model. Use of these terms in the effectiveness factor plots results in a considerable simplification of the presentation and use of the model. Design criteria such as fiber dimensions and spacing, reactor lengths, and recycle flow rates can be selected using these plots. Model predictions of the oxygen limitations were compared to experimental measurements of the axial cell distributions in a severely oxygen limited hollow fiber bioreactor. Despite considerable uncertainty in our parameters and nonidealities in hollow fiber geometry, the cell distribution correlated well with the modeling results.
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    Reaction kinetics in biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 877-882 
    Details
    ISSN: 0006-3592
    Keywords: microtechnique ; microprobe ; biofilm ; dissolved oxygen concentration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel in situ microtechnique allows evaluating parameters of diffusion-controlled reactions in biofilms. A microprobe, 15 μm in diameter, was used to simultaneously measure the dissolved oxygen concentration and the optical density at different depths in a submerged biofilm. Based on the results, the biofilm diffusion coefficient for dissolved oxygen, Df the dissolved oxygen flux through the biofilm surface, J02, and the half velocity coefficient, Ks, have been calculated.
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    Fluorescence modeling in a multicomponent system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 907-922 
    Details
    ISSN: 0006-3592
    Keywords: fluorescene monitoring ; inner-filter effect ; biosensor ; tryptophan ; tyrosine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extensive fluorescence database for binary tyrosinetryptophan mixtures utilizing 280 nm excitation was collected. The database spanned three orders of magnitude (10-6M-10-3M) and covered all compositions within this range. A generalized model for describing the multicomponent fluorescence signals as a function of emission wavelength, excitation wavelength, and sample composition was derived. A geometric integral that contained all the geometric factors affecting fluorescence was introduced; thus the model was applicable to various configurations, including the three used in this study: an NADH probe, a backscatter laser-induced fluorescence setup, and a commercial spectroflurometer. A correction factor was proposed that allowed linearization of the fluorescence signals with respect to fluorophore concentrations. The effect of the water Raman on fluorescence spectra was also modeled. The model contains only two wavelength-dependent parameters for each of the components present in a sample, one specifying absorption of the excitation energy and the other specifying the species' fluorescence tendency. These wavelength-dependent parameters were correlated with polynomials. The average prediction error at each wavelength was 10-20%, a major portion of which was attributed to experimental uncertainties.
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    Protein immobilization to polystyrene via long poly(ethylene lycol) chains (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 952-955 
    Details
    ISSN: 0006-3592
    Keywords: human albumin ; Protein conjugate ; caionic polymer ; PEG chains ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Human albumin has been attached to 24-hole polystyrene plates via branched poly(ethylene lycol) (PEG) spacer arms. A tetraepoxude of PEG of molecular weight (1.4-1.5) × 104 g/mol was reacted with the protein in solution allowing approximately one-third of the oxirane rings to react. The protein conjugate was then coupled to the long, cationic polymer poly(ethylene imine) (PEI), and the protein-PEG-PEI adduct was subsequently adsorption to unmodified polystyrene. Since the protein is linked to the surface via long, hydrophilic and nonchargedchains, interactions between the biomolecule and the surface is minimized.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380901
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    Differential product release (DPR) of proteins from yeast: A new technique for selective product recovery from microbial cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 977-985 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel method has been developed for the separation of bioproducts from yeast cells. The method uses a combination of physical, chemical, and biological agents such as lytic enzymes, osmotic supports, and spheroplast stabilizers. Using this technique, products (proteins and enzymes) can be released from specific cell locations at different process states; it has thus been celled differential product release (DPR). The wall-associated proteins are released first and the lytic enzyme is removed together with the wall proteins at this stage. Secondly, the cytosol products are released by a mild procedure during which the organelles remained intact. Finally, the organelle proteins are solubilized. In each stage, specific proteins are released while others are kept inside the different cell compartments. This method can be used with relatively high yeast concentrations (up to 145 g dry wt/L) and gives higher product recoveries and much higher selectivity than mechanical disruption.
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    Long-term perfusion culture of hybridoma: A “grow or die” cell cycle system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 781-787 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; continuous culture ; cell cycle ; tangential filtration ; cell separation ; nuclepore membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/109 cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar “grow or die” life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.
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    Kinetic parameters of a mixed culture oxidizing sulfide and sulfur with oxygen (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 813-820 
    Details
    ISSN: 0006-3592
    Keywords: loading rate ; growth yield ; oxidation rate ; free-cell suspensions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic parameters of biological sulfide oxidation are described. The influence of the sulfide loading rate on growth yield and specific oxidation rate were investigated with free-cell suspensions. It is concluded that at least two types of bacteria were present, namely, sulfate producers (type A) that grow at higher loading rates. Type A bacteria have a growth yield of 04 g dry S/mol S, while type B bacteria have a growth yield of 04 g dry S/mol S. Type A has a high affinity for sulfide and is inhibited by sulfide at sulfide concentrations exceeding 10 mg/L. Type B has a low affinity for sulfide and is not inhibited by sulfide, but by oxygen.
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    Use of a lipase immobilized in a membrane reactor to hydrolyze the glycerides of butteroil (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 853-868 
    Details
    ISSN: 0006-3592
    Keywords: A spergillus niger ; continuous hydrolysis ; membrane reactor ; butteroil ; immobilized lipase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lipase from A spergillus niger, immobilized by adsorption on a microporous, polypropylene flat-sheet membrane, was used to effect the continous hydrolysis of the glycerides of melted butterfat at 35°C. For the reaction conditions used in this research, a pseudo-zero order rate expression can be used to model the kinetics of the overall hydrolysis of butterfat. Multiresponse nonlinear regression methods were employed to determine the kinetic parameters of a multisubstrate rate expression derived fro ma mechanism based on the general Michaëlis-Menten approach. For the multiresponse data taken at pH 7.0, the dependence of the maximum rate of release of each fatty acid residue of butterfat on its carbon chain length is accurately described by a skewed, bell-shaped (or Γ-type) distribution. Data taken at five different pH values were fit assuming a Dixon-Webb diprotic model for the pH dependence of the reaction rate. The thermal deactivation of the immobilized lipase obeyed first-order kinetics with a half-life of 19.9 days at 35°C. The multisubstrate model is useful for the prediction of the free fatty acid profile of lipolyzed butterfat, whereas the lumped-substrate model provides an estimate of the overall degree of hydrolysis as a function of the reactor space time.
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    Xylanase production by Aspergillus awamori. Development of a medium and optimization of the fermentation parameters for the production of extracellular xylanase and β-xylosidase while maintaining low protease production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 883-890 
    Details
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; low protease production ; dinitrosalicylic method ; xylanase ; β-xylosidase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A growth medium was developed for maximal production in batch culture of extracellular xylanase and β-xylosidase by Aspergillus awamori CMI 142717 and a mutant (AANTG 43) derived from the wild-type strain. The optimum pH for the production of xylanase and β-xylosidase was 4.0. The best temperature of xylanase production was 30°C; 35°C was optimal for β-xylosidase. Protease production was never completely suppressed under any of the conditions tested. However, protease titre was 3.5-fold less than the control in medium in which proteose peptone and yeast extract were omitted: the level of xylanase was not affected (8.6 U mL-1) but β-xylosidase titre was increased 4.7-fold to 1.5 U mL-1. When corn steep liquor was used as the sole nitrogen source, xylanse and β-xylosidase titres were further increased by 1.5- and 1.9-fold, respectively. Of the carbon sources investigated, ball-milled oat straw or oat spelt xylan produced the highest titres of xylanse and β-xylosidase. None of the soluble carbon sources investigated produced the high titres of xylanase or β-xylosidase induced by either oat straw for xylanse and β-xylosidase was 2% and the optimum spore inoculum was between 106 and 107 spores/mL-1 final concentration. The level of xylanse activity obtained in the culture filtrates of the mutant was a remarkable 820 U mL-1 when the reducing sugar released was measured by the dinitrosalicylic acid method. This enzyme titre would appear to be the highest reported so far. The xylanases system contained the correct balance of enzymes to effect extensive hydrolysis of oat spelt xylan. The protease titre was very low.
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    Kinetic analysis of cephalosporin biosynthesis in Streptomyces clavuligerus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 941-947 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces clavuligerus ; cephalosporin ; rate-limiting enzyme ; kinetic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model describing the cephalosporin biosynthesis in Streptomyces clavuligerus was developed. Using previously reported kinetic data of biosynthetic enzymes, we examined the kinetics of cephalosporin production. The predicted time profile of the specific production rate during a batch culture parallels that of experimental observation. Sensitivity analysis reveals that δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine (ACV) synthetase is the rate-limiting enzyme. The effect of amplifying ACV synthetase on the specific production rate was analyzed theoretically. Increasing ACV synthetase enhances the production rate initially until ACV synthetase enhances the production rate initially until deacetocycephalosporin C hydroxylase becomes rate-limiting. Such kinetic analysis can provide a rational basis for modifying the biosynthetic machinery of cephalosporin through gene cloning.
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    Effect of agitational shear on growth and protease production by Thermomonospora fusca (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 371-374 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Minimizing the errors associated with the determination of effective diffusion coefficients when using spherical cell immobilization matrices (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 386-388 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gel materials are often used to entrap biological catalysts. Several experimental methods have been proposed to estimate the diffusion coefficient of important chemical species within these materials. An error analysis for the bead method was performed and, contrary to previously reported results, when proper experimental conditions were employed, the error associated with the bead method was similar to that obtained using the other common methods.
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    Determination of kinetic parameters related to the piasmid instability: For the recombinant fermentation under repressed condition (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 404-414 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The plasmid stability under the repressed state of cloned gene was studied theoretically as well as experimentally using recombinant E. coli K12ΔH1Δtrp/pPLc23trpA1 as a “host-vector” model system. The important kinetic parameters studied were the plasmid loss rate (θ) describing the rate at which the plasrnid-harboring cells lose plas-mids and the plasmid-free cells are generated per unit time and the difference in growth rates (Δ) between the two genotypes. These parameters were carefully defined, studied, and compared with other key kinetic parameters involved in the recombinant fermentation to further our understanding of metabolism of recombinants. The ratio of the concentration of plasmid-free cells to plasmid-harboring cells (Ω) was introduced, and the mathematical model was derived and used for the determination of the kinetic parameters associated with plasmid instability. These methods developed based on the theoretical considerations were tested experimentally. The results of these methods were compared, and the best method was selected and recommended. The effect of temperature and dilution rate on kinetic parameters θ and Δ were also studied in continuous culture, in order to provide some practical information related to the operation and control of recombinant fermentation processes.
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    Uptake of cadmium and zinc by the alga Chlorella vulgaris: II. Multi-ion situation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 445-455 
    Details
    ISSN: 0006-3592
    Keywords: synergism antagonism ; metal uptake ; Chlorella vulgaris ; cadmium ; zinc ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many microorganisms are capable of sequestering and concentrating heavy metals from their aqueous environment. While much research has beep carried out on the uptake of single species of metal ions, little attention seems to have been given to the study of multimetal ion systems. A mathematical model has previously been developed to describe the uptake of individual metal species by a microorganism. The model proposes two sequential processes: an initial rapid uptake due to cellular surface adsorption and a subsequent slow uptake due to membrane transport of the metal into the cells. This article extends the treatment by considering the uptake of two metal species together, cadmium and zinc, under different experimental conditions. The results are discussed in terms of possible mechanistic interactions.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370601
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    Large-Scale, High-density freezing of hybridomas and its application to high-density culture (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1110-1113 
    Details
    ISSN: 0006-3592
    Keywords: high-density freezing ; high-density culture ; hybridoma ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large-scale, high-density freezing of hybridomas was studied to apply frozen cells to start high-density culture. We showed here that hybridomas can be frozen at 1.5 × 108 cells/mL, without decrement in viability and proliferating activity. Blood transporting bags were used for large-scale freezing to store 25 mL of cell suspension with a cell density, 1.5 × 108/mL. The number of cells stored in a bag (3.0 × 109 cells) was enough to start a high-density culture at a 10 times higher cell density (6.0 × 106 cells/mL) than normal inoculation, and the cells proliferated to 107 cells/mL within 2 days. These results indicate that the large-scale freezing method is useful for large-scale culture of mammalian cells.
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    Catalytic action of L-2-halo acid dehalogenase on long-chain L-2-haloalkanoic acids in organic solvents (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1114-1117 
    Details
    ISSN: 0006-3592
    Keywords: L-2-halo acid dehalogenase ; dehalogenation ; in dimethyl sulfoxide ; 2-hydroxy acids ; stereospecific production of substrate specificity ; change in organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Lyophilized preparation of L-2-halo acid dehalogenase was not only stable but also catalytically active in anhydrous dimethyl sulfoxide, toluene, and other organic solvents. 2-Halo acids with long alkyl (C5-C16) or aromatic (phenyl and benzyl) side chains were inert in water but dehalogenated effectively in anhydrous dimethyl sulfoxide by the lyophilized enzyme. Long chain 2-haloalkanoic acids such as 2-bromohexadecanoic acids were better as substrate than short-chain halo acids (e.g., 2-chloropropanoic acid). The dehalogenation proceed with inversion of C2 configuration to produce the corresponding (2R)-2-hydroxy acids in anhydrous dimethyl sulfoxide in the same way as found in water.
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    Immobilization-stabilization of α-chymotrypsin by covalent attachment to aldehyde-agarose gels (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1144-1152 
    Details
    ISSN: 0006-3592
    Keywords: stabilization of chymotrypsin ; enzyme-support multipoint attachment ; effect of denaturing agents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed a strategy for immobilization-stabilization of α-chymotrypsin by multipoint covalent attachment of the enzyme, through its amino groups, to agarosealdehyde gels. We have studied the role of the main variables that control the intensity of these enzyme-support multi-interaction processes (surface density of aldehyde groups in the activated gel, contact time between the immobilized enzyme and the activated support prior to borohydride reduction of the derivatives, etc.). In this way, we have prepared a number of very different chymotrypsinagarose derivatives. Our best derivatives, with the most intense multipoint attachment, were more stable than one-point attached derivatives and were more than 60,000-fold more stable than soluble enzyme in the absence of autolysis phenomena. In spite of the dramatic stabilization, the catalytic activity of these derivatives is little changed (they only lose 35% of intrinsic activity after this intense enzyme-support multi-interaction process). In addition, we have also demonstrated the very high capacity of 6% aldehyde-agarose gels to immobilize pure chymotrypsin (40 mg enzyme/mL catalyst). Furthermore, we have been able to establish a clear correlation between enzyme-support multipoint covalent attachment, stabilization against very different denaturing agents (heat, urea, organic cosolvents), and insensitivity of those immobilized chymotrypsin molecules to some activating agents.
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    Continuous production of Ammonium lactate by Streptococccus cremoris in a three-stage reactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1173-1181 
    Details
    ISSN: 0006-3592
    Keywords: Streptococcus cremoris ; continuous three stage fermentation ; ammonium lactate ; whey permeate ; FACWP ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch and continuous fermentation studies were performed to optimize the production of ammonium lactate from whey to optimize the production of ammonium lactate from whey permeate. The product known as fermented ammoniated condensed whey permeate (FACWP) is a very promising animal feed. After an initial screening of four strains which produce predominantly L(+)- lactic acid, the desired isomer [D(-)-lactic acid is toxic], Streptococcus cremoris 2487 was chosen for further study. In batch mode, pH between 6.0 and 6.5 and 35°C provided optimum incubation conditions. To stimulate a plug flow reactor, three CSTRs (continuous stirred tank reactors) were connected in tandem. For a 7.5-h retention time, 1.6-fold and 1.3-fold higher productivities were obtained for three-stage than for the single- and two-stage reactors, respectively. Various retentions times were examined (5, 7.5, and 10 h; 5g/L yeast extract). Although maximum lactate productivity occurred at a 5-h residence time (5.38 g/L H. 75% lactose utilization), lactose utilization was more complete at 7.5 h (4.38 g/L h productivity, 91% lactose utilization and a productivity, 91% lactose utilization). Retention time was increased to 15 h to obtain 95.9% lactose utilization and a productivity of 2.42g/L h for 2g/L yeast extract. Based on this lower yeast extract concentration, it was determined that ammonium lactate production and subsequent concentration by 11-fold would yield a product (FACWP) 17% more than soybean meal (crude protein contents are equivalent, 44%) at current market prices.
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    Steroid bioconversion in a microemulsion system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1210-1217 
    Details
    ISSN: 0006-3592
    Keywords: Δ1,2-dehydrogenation of high steroid concentrations ; microemulsion system ; enzyme kinetics ; biphasic system ; stability in ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Δ1,2-dehydrogenation of high concentrations of the steroid -methyl-Reichstein's compound S-21-acetate (16MRSA) in a microemulsion system was studied using heat-dried and thawed Arthrobacter simplex cells as biocatalyst. The microemulsion system consists of an organic phase [75-95% (v/v)] with steroid (1-60 g/Ltot), an aqueous phase [5-25% (v/v)] containing the cells (5-30 g/Ltot), and a neutral surfactant (5-20 g/L organic solvent). Benzene derivatives, which solubilize 16MRSA up to 94 g/L, and phospholipids were used as organic solvents and surfactants, respectively, and menadione was added as an external electron acceptor. Factors affecting the dehydrogenation rate in the microemulsion system were studied. The influences of the 16MRSA and the menadione concentration on the dehydrogenation rate were described by Michaelis-Menten kinetics, apparent V′max and K′m values of 2.06 g/g dry weight h and 18.9 g/L for 16MRSA and 4.97 g/g dry weight h and 1.91 g/L for menadione being obtained. Optimal menadione concentration was dependent on the steroid concentration was dependent on the steroid concentration used. The reaction was strongly inhibited by high product concentrations. Much higher activities were obtained with the thawed cells than with the dried cells, conversions of 98% being reached within 14-16 h. for 16MRSA and cell dry weight concentrations of 40 and 10 g/L, respectively. Activity retention in a batch stirred tank reactor remained constant during the first 16-24 h of operation and then decreased, depending on the stirring rate; 22 to 65% of the initial reaction rate was obtained after 48 h at stirring rates of 650 and 2000 rpm, respectively.
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    Effects of Carbon dioxide on the Rheological behavior and oxygen transfer in submerged penicillin fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1223-1232 
    Details
    ISSN: 0006-3592
    Keywords: penicillin fermentation ; carbon dioxide effect ; oxygen transfer ; oxygen diffusion ; rheological behavior ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fermentations of Penicillium chrysogenum have been made with different CO2 contents in the influent gas streams. The rheological behavior of the culture broth was found to be significantly changed by exposure to high levels of CO2. This is attributed to the wide variation in the morphology of P. chrysogenum, from normal mycelia with long hyphae to roughly spherical pellets when subjected to high levels of CO2. A correlation has been developed relating volumetric O2 transfer coefficients, kLa, with the effective O2 diffusion coefficients, De, and the apparent viscosities, μapp, based on the results obtained in this study. The use of CO2 as a potent means for altering the rheological properties of culture broths and consequently improving the O2 transfer capabilities in penicillin fermentations was clearly demonstrated.
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    Protein extraction by reverse micelles: A study of the factors affecting the forward and backward transfer of α-chymotrypsin and its activity (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1239-1246 
    Details
    ISSN: 0006-3592
    Keywords: protein extraction ; α-chymotrypsin ; micelles ; reverse ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: α-chymotrypsin is taken as a model protein to investigate three aspects of the protein extraction by reverse micelles: (1) the comparison between the two forward transfer techniques, i.e., the liquid-liquid and the solid state-liquid transfer; (2)the back-transfer, i.e., the capability of the protein to be recovered from the micellar solution; and (3) the maintainance of the enzyme activity at the end of the extraction cycle. Concerning the forward transfer from the liquid phase, we study first the effect of salt initially present in the aqueous phase on the equilibrium concentration of the extracted species; further, we study the forward protein extraction from the solid state, and the effect of pH, salt, and protein concentration on the transfer efficiency. Concerning the back transfer, we find the somewhat surprising result, that the percentage of protein back-extraction depends on the type and concentration of salt used for the forward transfer. Preliminary data concerning an alternative method for the back-transfer using silica gel to liberate the protein from the micellar environment, are presented. Finally, it is found that the enzyme activity depends again on the type and concentration of salt used for the forward transfer.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260381101
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    Calcium and phosphate effects on growth and alkaloid production in Coffea arabica: Experimental results and mathematical model (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 859-868 
    Details
    ISSN: 0006-3592
    Keywords: Coffea arabica ; calcium ; phosphate ; cell growth ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plant, mammalian, and microbial cells are commonly immobilized in calcium alginate gels for the production of valuable secondary metabolites. However, calcium ions are known to inhibit growth in various types of cells, and calcium is an integral part of such gels. Therefore, an investigation was conducted to evaluate the effect of calcium on the growth and alkaloid production of a model cell-line, Coffea arabica, in suspension culture before, attempting to immobilize such cells in alginate. A kinetic model was then developed from the results to describe cell growth and alkaloid production and the mechanism by which calcium influences these variables. In addition, it was observed that there was a characteristic relationship between the concentration of calcium in the external medium and the concentration of extra cellular and intracellular phosphate. The intracellular phosphate level was, in turn, related to the production of alkaloids. Using these results, a dynamic mathematical model of cell growth and alkaloid production was developed based on the proposed roles of calcium and phosphate. The model showed satisfactory agreement with three sets of experiments at different calcium concentrations. A possible linkage between the calcium and phosphate results is postulated based on the limited solubility of calcium phosphate.
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    URL: http://dx.doi.org/10.1002/bit.260370910
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    Measuring kLa with randomly pulsed dynamic method (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 889-893 
    Details
    ISSN: 0006-3592
    Keywords: oxygen transfer coefficient ; kLa ; pulsed dynamic method ; mechanically agitated vessels ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This reports on the determination of the overall oxygen transfer coefficient in a mechanically agitated vessel using a randomly pulsed dynamic method. This method consists in exciting the system by randomly switching the inlet gas stream with air or nitrogen with an identical volumetric flow rate. A pseudo-random binary sequence was used. This procedure is routinely used in process control for the identification of system's transfer function. The pulsed dynamic method gives good reliability (as compared with the traditional gassing-out method) and reproducibility in water. However, further improvement is needed before it can be used to monitor on-line the kLa during a fermentation.
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    URL: http://dx.doi.org/10.1002/bit.260370914
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    Transient response method for evaluating the rate constants of reactions over immobilized enzymes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 922-926 
    Details
    ISSN: 0006-3592
    Keywords: transient response method ; rate constants ; immobilized enzyme ; glucose oxidation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient response method was utilized to evaluate the rate constants of reaction over immobilized enzyme. Glucose oxidation catalyzed by the immobilized glucose oxidase in a fixed-bed reactor was selected as an example. A theoretical model including the effects of axial dispersion, film diffusion, and intraparticle diffusion was established for the reactor. The individual rate constant of each elementary step of this enzymatic reaction was determined through direct fitting of the experimental response data to the model.
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    Semicontinuous enzymatic hydrolysis of lignocelluloses (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 948-954 
    Details
    ISSN: 0006-3592
    Keywords: cellulase ; cellulose hydrolysis ; steam treatment ; ultrafiltration ; enzyme adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lignocelluloses (steamed hardwood and hardwood kraft pulp) were semicontinuously hydrolyzed on a large scale [2-2. 5 kg of substrate vs. 20, 000 IU filter paperase (FPase)] using a 10-L hydrolysis reactor with an ultrafiltration unit for the recovery and reuse of cellulases. The substrate was added to the reactor at appropriate intervals to keep a concentration of approximately 5% (w/v). All of the enzyme was added at the beginning and no further addition was done. The ultrafiltration unit was operated intermittently rather than continuously due to its enough capacity (dilution rate of 2.5 h-1) and making the enzyme durable. The enzyme required to produce one gram of reducing sugar in this reactor was 27.3 FPase IU/g RS for steamed hardwood and 7.4 FPase IU/g RS for hardwood kraft pulp. The sugar composition of hydrolyzate was unaltered virtually from beginning to end of the hydrolysis in spite of the progressive loss of enzyme activities. The analysis of the enzyme composition in the hydrolyzate during hydrolysis revealed that an exo-β-D-glucanase component was adsorbed selectively at the stages of advanced hydrolysis extent.
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    Growth, death, and oxygen uptake kinetics of Pichia stipitis on xylose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 973-980 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pichia stipitis NRRL Y-7124 has potential application in the fermentation of xylose-rich waste streams, produced by wood hydrolysis. Kinetic models of cell growth, death, and oxygen uptake were investigated in batch and oxygen-limited continuous cultures fed a rich synthetic medium. Variables included rates of dilution (D) and oxygen transfer (K1a) and concentrations of xylose (X), ethanol (E), and dissolved oxygen (Cox). Sustained cell growth required the presence of oxygen. Given excess xylose, specific growth rate (μ) was a Monod function of Cox. Specific oxygen uptake rate was proportional to μ by a yield coefficient relating biomass production to oxygen consumption; but oxygen uptake for maintenance was negligible. Thus steady-state COX depended only on D, while steady-state biomass concentration was controlled by both D and K1a. Given excess oxygen, cells grew subject to Monod limitation by xylose, which became inhibitory above 40 g/L. Ethanol inhibition was consistent with Luong's model, and 64. 3 g/L was the maximum ethanol concentration allowing growth. Actively growing cells died at a rate that was 20% of μ. The dying portion increased with E and X.
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    Elmer L. Gaden, Jr., father of biochemical engineering (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 995-997 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260371102
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    Tubular bioreactors: Case study of bioreactor performance for industrial production and scientific researchThe experimental work of this article granted by the Austrain Ministry of Science and Research together with the MF Andritz AG in Graz (1987-1990) and 1991-1992 (FFWF project No. 7695). (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1054-1065 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Application of bioreactors is dominated by industrial production with the consequence that bioreactors also for scientific purposes are mainly used following an empiric pragmatic approach. For the sake of a breakthrough in biotechnology in general, and especially for advanced process development, a more systematic approach is emphasized here. This methodology in bioreactor performance studies is explained and the meaning clarified in a case study of a new type of tubular bioreactor. The central role of so-called “model bioreactors” in bench-scale applications is illustrated as a powerful contribution to the optimal design of bioreactors in technical scale. Pilot plant data in case of a tubular reactor for the production of ethanol with Zymomonas and biopesticides with Bacillus thuringiensis are presented.
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    Kinetic study of hybridoma cell growth in continuous culture. I. A model for non-producing cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 55-64 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetic behavior of a nonproducing hybridoma clone AFP-27-NP was investigated in continuous culture under glucose-limited conditions. A total of more than 21, 000 h of cultures were operated at dilution rates ranging from 0.01 to 0.06 h-1. The viable cell concentrations, dead cell concentrations, and cell volumes all varied with the dilution rate. A steady-state model was developed based on the biomass concentration and the glucose concentration. The specific growth rate as a function of glucose concentration is described by a model similar to the Monod model with a threshold glucose concentration and a minimum specific growth rate incorporated; the model is meaningful only at glucose concentrations and specific growth rates above these levels. A death rate is included in the model which is described by an inverted Monod-type function of glucose concentration. The yield coefficient based on glucose is constant in the lower range of specific growth rates and changes to a new constant value in the upper region of specific growth rates. No maintenance term for glucose consumption was needed; in the plot of specific glucose consumption rate vs. specific growth rate, the line intercepted the specific growth rate axis at a value close to the minimum growth rate. The values for the model parameters were determined from regression analysis of the steady-state data. The model predictions and experimental results fit very well.
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    Simultaneous saccharification and fermentation of cellulose to lactic acid (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 93-96 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent interest in the industrial manufacture of ethanol and other organic chemicals from biomass has led to the utilization of surplus grain and cane juice as a fermentation feedstock. Since those starting materials are also foods, they are expensive. As an alternative, cellulosic substances - the most abundant renewable resources on earth1 - have long been considered for conversion to readily utilizable hydrolyzates.2, 3For the production of ethanol from cellulose, we have proposed the simultaneous saccharification and fermentation (SSF) process.4 In SSF, enzymatic cellulose hydrolysis and glucose fermentation to ethanol by yeast proceed simultaneously within one vessel. The process advantages - reduced reactor volume and faster saccharification rates - have been confirmed by many researchers.5-8 During SSF, the faster saccharification rates result because the glucose product is immediately removed, considerably diminishing its inhibitory effect on the cellulase system.9To effectively apply the SSF method to produce substances fermented from glucose, several conditions should be satisfied. One is coincident enzymatic hydrolysis and fermentation conditions, such as pH and temperature. The other is that cellulase inhibition by the final product is less than that by glucose and/or cellobiose. One of us has reported that acetic acid, citric acid, itaconic acid, α-ketoglutaric acid, lactic acid, and succinic acid scarcely inhibit cellulase.10 This suggests that if the microorganisms which produce these organic acids were compatible with cellulase reaction conditions, the organic acids could be produced efficiently from cellulosic substrates by SSF.In this article, the successful application of SSF to lactic acid production from cellulose is reported. Though there have been several reports of direct cellulose conversion to organic acids by anaerobes such as Clostridium, only trace amounts of lactic acid were detected in the fermentation medium among the low-molecular-weight fatty acid components.11-13 Lactic acid is one of the most important organic acids and has a wide range of food-related and industrial applications.
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    Lewis cell studies to determine reactor design data for two-liquid-phase bacterial and enzymic reactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 133-140 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Substrate transfer rates from organic to aqueous phases were measured in the presence and absence of biocatalyst in the reaction medium, using modified Lewis cells. These measurements, in combination with intrinsic aqueous phase biocatalytic reaction kinetics, were used to confirm that benzyl acetate hydrolysis by pig liver esterase and toluene oxidation by a strain of Pseudomonas putida occur uniformly throughout the bulk of the aqueous phase. Such data may be used to provide a basis for two-liquid-phase biocatalytic reactor design.
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    Modeling of enzyme-potentiometric sensors involving acid- or base-forming reactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 160-176 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzyme-potentiometric sensors in which the chemical conversion of the analyte leads to the formation of an acid and/or a base can often display complex response characteristics. In these sensors, the, electrochemically monitored species is usually the H+ ion (pH-based sensors). However, in some cases the conjugate-ion of the H+ (or OH-) ion of the acid (or base) produced-can also be monitored - a specific example being the urease-NH4+ sensor. The response of both types of sensors is strongly affected by: (1) the degree of dissociation of the products and their transport properties in the enzymic film, (2) the amounts of pH-buffers present in the test solution, (3) the test solution's pH, and (4) the diffusion coefficients of the various species. In this article, a previously developed theoretical model for pH-based sensors - in which the differences in diffusivities of the various species were ignored - is generalized to accommodate for such differences, and extended to the latter of the above two types of sensors. It is shown that when the sensor operates under analyte diffusion-controlled conditions, the response of either type of sensor can be predicted by a simple algebraic equation which is independent of the actual kinetics of the enzymic reaction.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370209
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370301
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