Biohydrogen production from cellulosic hydrolysate produced via temperature-shift-enhanced bacterial cellulose hydrolysis.

A "temperature-shift" strategy was developed to improve reducing sugar production from bacterial hydrolysis of cellulosic materials. In this strategy, production of cellulolytic enzymes with Cellulomonas uda E3-01 was promoted at a preferable temperature (35 degrees C), while more efficient enzymatic cellulose hydrolysis was achieved under an elevated culture temperature (45 degrees C), at which cell growth was inhibited to avoid consumption of reducing sugar. This temperature-shift strategy was shown to markedly increase the reducing sugar (especially, monosaccharide and disaccharide) concentration in the hydrolysate while hydrolyzing pure (carboxymethyl-cellulose, xylan, avicel and cellobiose) and natural (rice husk, rice straw, bagasse and Napier-grass) cellulosic materials. The cellulosic hydrolysates from CMC and xylan were successfully converted to H(2) via dark fermentation with Clostridium butyricum CGS5, attaining a maximum hydrogen yield of 4.79 mmol H(2)/g reducing sugar.