Fermentation of d-xylose by Clostridium butyricum LMG 1213t 1 in chemostats

Abstract

Clostridium butyricum LMG 1213t 1 was able to grow on d-xylose and l-arabinose in a minimal medium. In a chemostat in carbon limitation, the same fermentation balance (when corrected for the difference in carbon atoms) was obtained on d-xylose as on glucose in the pH range 5.5–7.0. Per mole d-xylose consumed, 1.74 mol H 2 was produced, which was equal to the H 2 production on glucose previously reported. By varying the dilution rate, the molar growth yields remained less than half these on glucose. From a critical literature survey, we propose that this was caused by an additional ATP expenditure for the active transport of d-xylose across the cell membrane. From our data we calculated that 1 mol ATP was required for the transport of d-xylose. With higher d-xylose concentrations, the butyrate production and molar growth yield Y xylose gradually decreased, but the H 2 production remained constant. On glucose-xylose mixtures (10 g l -1 total sugar), the fermentation of d-xylose was not inhibited by glucose under the conditions tested. The molar growth yields increased linearly with the weight percentage of glucose in the carbon source, while the H 2 production was not affected.