초록
<P><B>Abstract</B></P> <P>An identified cold-adaptive, organic solvents-tolerant alkaline α-amylase (HP664) from <I>Catenovulum</I> sp. strain X3 was heterologously expressed and characterized in <I>E. coli</I>, 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 69.6kDa 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 <I>n</I>-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<SUB>2</SUB> 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 12h of hydrolysis using 5.63U of HP664. Biohydrogen fermentation of the starch hydrolysate by <I>Clostridium</I> sp. strain G1 yielded 297.7mL of H<SUB>2</SUB> after 84h of fermentation, which is 3.73-fold higher than the control without enzymatic treatment of HP664.</P>