ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Summary The fermentation of cellobiose, glucose and cellulose MN 300 by Cellulomonas fermentans was studied. The molar growth yields (i.e. grams of cells per mole of hexose equivalent) were similar on cellobiose and cellulose at low sugar consumption levels (47.8 and 46.5 respectively), but was lower on glucose (38.0). The occurrence of cellobiose phosphorylase activity, detected in cellobiose- and cellulose-grown cells, might explain this result. The specific growth rates measured in cultures on cellobiose, glucose and cellulose were 0.055 h-1, 0.040 h-1 and 0.013 h-1 respectively. Growth inhibition was observed, and a drop in YH occurred after relatively low but different quantities of hexose were consumed (2.2 mM, 5 mM and 8 mM hexose equivalent with cellulose, glucose and cellobiose respectively), which coincided with a change in the fermentative metabolism from a typical mixed acid metabolism (1 ethanol, 1 acetate and 2 formate synthesized by consumed hexose) to a more ethanolic fermentation. When growth ceased in cellulose cultures, consumption of cellulose continued, as did production of ethanol. Molar growth yields of C. fermentans were similar in anaerobic and aerobic cellobiose cultures (47.8 g/mol and 42.2 g/mol respectively). Specific growth rates were also quite similar under both culture conditions (0.055±0.013 h-1 and 0.070±0.007 h-1 respectively). Aerobic metabolism was studied using 14C glucose. During the exponential growth phase, acetate, succinate and nonidentified compound(s) accumulated in the supernatant, but no 14CO2 was produced. During the stationary phase, acetate was oxidized and 14CO2 produced, but without any further biomass synthesis. It seems that a blocking of metabolite oxidation may have occurred in C. fermentans except in the case of acetate, but acetate oxidation was apparently not coupled with production of energy utilizable in biosynthesis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00253904
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