A cold-adapted and detergent-stable α-amylase from marine bacterium Photobacterium gaetbulicola Gung47^T

A novel cold-adapted and halotolerant α-amylase gene (AmyPG2) was cloned and expressed from the marine bacterium Photobacterium gaetbulicola Gung47^T. The highest activity of AmyPG2 was displayed at 25 °C and pH 8.0. In addition, the residual activity of AmyPG2 remained at approximately 12-30% at low temperatures (0-5 °C). It can remain 50% activity after 1.6 and 1.0 h at 35 and 40 °C, respectively, demonstrating remarkable thermal stability among cold-adapted enzymes. AmyPG2 was strongly stimulated by NaCl, with its specific activity towards various substrates increasing more than 100-fold. In particular, the specific activity towards mung starch reached 1352.2 ± 45.7 U/mg. The catalytic efficiency was further improved approximately 2.5-fold by site-directed mutagenesis near the putative binding sites. AmyPG2 and its mutant I236V were able to efficiently saccharify starch at low temperature (25 °C), achieving the final hydrolysis rates of 51.2 ± 1.8 and 62.5 ± 2.4% for 8% mung starch, respectively. In addition, AmyPG2 and I236V showed good tolerance to all commercial detergents tested, significantly improving the detergent removal efficiency. This study demonstrated the potential of the cold-adapted α-amylase AmyPG2 and its mutant for industrial applications, particularly in food processing and detergent formulation. KEY POINTS: A novel α-amylase (AmyPG2) from a marine bacterium was cold-adapted and halotolerant. The I236V mutant (2.5-fold higher activity) was obtained by site-directed mutagenesis. The enzyme has potential applications in starch saccharification and detergent formulation.