ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract All strains of Comamonas testosteroni investigated here, produced quinohaemoprotein ethanol dehydrogenase (QH-EDH) when grown on ethanol or butanol, but one strain of C. acidovorans and of C. terrigena did not. Hybridization experiments showed that the gene for QH-EDH is absent in the latter two strains. Induction and properties of the QH-EDHs seem to be similar: all C. testosteroni strains produced the enzyme in its apo-form [without pyrroloquinoline quinone (PQQ)] and the levels were higher at growth at low temperature; preference for the R-enentiomer and similar selectivity was shown in the oxidation of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by cells (supplemented with PQQ); the fragment of the qhedh gene gave high hybridization with the DNA of the C. testosteroni strains. Experiments with C. testosteroni LMD 26.36 revealed that the organism is well suited for production of (S)-solketal: it shows an adequate enantioselectivity (E value of 49) for the oxidation of racemic solketal; the conversion rate of (R)-solketal is only 3.5 times lower than that of ethanol; the optimal pH for conversion (7.6) is in a region where solketal has sufficient chemical stability; separation of the remaining (S)-solketal from the acid formed is simple; induction of QH-EDH, the sole enzyme responsible for the oxidation of (R)-solketal, occurs during growth on ethanol or butanol so that the presence of solketal (inhibitory for growth) is not required; production of active cells and the conversion step can be integrated into one process, provided that PQQ and solketal addition occur at the appropriate moment; the conversion seems environmentally feasible. However, since high concentrations of solketal inhibit respiration via QH-EDH, further investigations on the mechanism of inhibition and the stability of the enzyme might be rewarding as it could lead to application of higher substrate concentrations with consequently lower down-stream processing costs.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00170216
