Catalytic hydrolysis of starch for biohydrogen production by using a newly identified amylase from a marine bacterium Catenovulum sp. X3.

An identified cold-adaptive, organic solvents-tolerant alkaline α-amylase (HP664) from Catenovulum sp. strain X3 was heterologously expressed and characterized in E. coli , and it was further applied to starch saccharification for biohydrogen production. The recombinant HP664 belongs to a member of glycoside hydrolase family 13 (GH13), with a molecular weight of 69.6 kDa without signal peptides, and also shares a relatively low similarity (49%) to other reported amylases. Biochemical characterization demonstrated that the maximal enzymatic activity of HP664 was observed at 35 °C and pH 9.0. Most metal ions inhibited its activity; however, low polar organic solvents (e.g., benzene and n -hexane) could enhance the activity by 35–50%. Additionally, HP664 also exhibited the catalytic capability on various polysaccharides, including potato starch, amylopectin, dextrin and agar. In order to increase the bioavailability of starch for H 2 production, HP664 was utilized to elevate fermentable oligosaccharide level, and the results revealed that the maximal hydrolytic percentage of starch was up to 44% with 12 h of hydrolysis using 5.63 U of HP664. Biohydrogen fermentation of the starch hydrolysate by Clostridium sp. strain G1 yielded 297.7 mL of H 2 after 84 h of fermentation, which is 3.73-fold higher than the control without enzymatic treatment of HP664. [ABSTRACT FROM AUTHOR]