Selection Of New Strain Enterobacter Cloacae AFB4-4 Able To Produce Ethanol

Xylose is the most abundant monosaccharide in lignocellulose hydrolysate atfer glucose. Consequently,efficient utilization of xylose is of key concern of converting lignocellulosic hydrolysates to ethanol. Thereofre, to obtain a bacterial strain that can largely convert xylose to ethanol is very important to ethanol production. This research works on strains screening,identifing and optimizing,the main content is as follows.1. Five strains which can convert xylose to ethanol efficiently was isolated by TTC method from natural environment with xylose as sole carbon substrate.And then,a bacteria strain named AFB4-4 which can convert xylose to ethanol was obtained by ethanol fermentation.2. AFB4-4 was identified by analyzing its physiological biochemical characteristics and applying the molecule biological means 16S rDNA.It is classfied as Enterobacter cloacae.This bacteria can use many pentoses and hexoses to ethanol fermentation.3. The parameters in the process of converting xylose to ethanol were optimized. When temperature amounted to 35℃, inoculum solution was 6×107/mL, initial pH was 6.5 and fermented in microaerophilic condition for 48h, the yield of ethanol was 4.95 g/L and 53.8%(vs theory data)when xylose(20g/L)was sole carbon substrate, the yield of ethanol was 2.44 g/L and 23.9%(vs theory data)when glucose(20 g/L)was sole carbon substrate.The ability of this bacteria converting xylose to ethanol is better than glucose. In the presence of a mixture of glucose (10 g/L) and xylose (20g/L), microaerophilic cultures of the strain produced 6.28 g/L ethanol. The results showed that the strain can effectively co-ferment both glucose and xylose simultaneously to ethanol.