An enterobacter was isolated from a wild carp intestinal in Xinjiang and identified as Enterobacter sp.on the basis of both 16S rDNA gene sequencing and examination of its physiological and biochemical properties.This strain was found to be able to produce biohydrogen by fermentation of glucose,xylose and the mixture of the two reducing sugars,particularly,this bacterium owned strong capacity to metabolize xylose,which enabled the hydrogen yield using xylose as substrate 3 times of that using glucose as substrate.This strain was further used for hydrogen production by fermentation of cotton stalk hydrolysate,the results showed that the highest daily hydrogen concentration could reach 1.06±0.22 molH2/mol RS(reducing sugar),and the cumulative hydrogen yield could reach 2.09 molH2/mol RS,as well as the utilization rates of xylose and glucose in cotton stalk hydrolysate achieved to higher than 90%after 120 h fermentation.In addition,using the genome DNA as template,an open reading frame gene segment of Fe-hydrogenase hydA gene with a size of about 450 bp was cloned through design of conservative sequence of Fe-hydrogenase,the gene sequence was found to have 97%similarity with the corresponding sequence in Enterobacter cloacae IIT-BT 08 through sequence blast.