Fermentation of D-Xylose to Ethanol by Bacillus macerans

In the absence of oxygen Bacillus macerans is able to ferment xylose. The principal products are ethanol, formate, C02, acetone and H2. The yield of ethanol was 61% based on the theoretical value of 0.51 g per g xylose consumed. The cells could grow in the presence of up to 4% (v/v) of added ethanol but the growth rate was already reduced to about 50% by 1% (v/v) of alcohol. Glucose and the pentoses arabinose and xylose were sequentially utilized when initially present as a mixed substrate. Enzymatic studies indicate that xylose was metabolized via the pentosephosphate and Embden-Meyerhof pathways. At an oxygen concentration of 1—2% air saturation 42 g/1 xylose were completely fermented within 160 h and 10 g/1 ethanol were produced.