Isolation of cellulose-hydrolytic bacteria and applications of the cellulolytic enzymes for cellulosic biohydrogen production

Nine cellulolytic bacterial strains were isolated from soil sample taken in southern Taiwan. Through 16S rRNA sequence matching; eight of those isolates belong to Cellulomonas sp., while the other one belongs to Cellulosimicrobium cellulans. The activity of cellulolytic enzymes (cellulases and xylanase) produced from those strains was mainly present extracellularly and the enzyme production was dependent on cellulosic substrates (xylan, rice husk and rice straw) used for growth. HPLC analysis confirmed the bacterial hydrolysis of these cellulosic substrates for soluble sugars production. The efficiency of fermentative H2 production from the enzymatically hydrolyzed rice husk was examined with seven H2-producing pure bacterial isolates. With an initial reducing sugar concentration of 0.36 g l−1, only Clostridium butyricum CGS5 exhibited efficient H2 production from the rice husk hydrolysates with a cumulative H2 production and H2 yield of 88.1 ml l−1 and 19.15 mmol H2 (g reducing sugar)−1 (or 17.24 mmol H2 (g cellulose)−1), respectively.