A novel cold-active type I pullulanase from a hot-spring metagenome for effective debranching and production of resistant starch

Pullulanase is a potent enzyme for starch debranching. In this study, a novel type I pullulanase (PulM) was identified from the metagenome of a thermal aquatic habitat that exhibits optimal activity of debranching at 40 degrees C temperature and pH 6.0 to 7.0. More than 50% enzymatic activity was detected at the low temperature of 4 degrees C, determining it a cold-active type I pullulanase. It was able to efficiently catalyze the hydrolysis of alpha-1,6-glycosidic linkages in pullulan, with a specific activity of 177 U mg(-1). The results determined PulM to be a potential starch debranching biocatalyst, causing a significant increase of about 80% in the apparent amylose content of potato starch. Retrogradation of the debranched starch resulted in the formation of resistant starch 3. The yield of resistant starch was estimated to be about 45%. The resistant starch exhibited higher crystallinity, enhanced heat-stability, and resistance to alpha-amylase digestion, as compared to native starch.

Automated summary

A novel type I pullulanase (PulM) with optimal debranching activity at 40 degrees C and pH 6.0 to 7.0 was identified in this study. PulM showed cold-active properties with over 50% enzymatic activity detected at 4 degrees C. The enzyme efficiently catalyzed the hydrolysis of alpha-1,6-glycosidic linkages in pullulan and increased the apparent amylose content of potato starch by about 80%. The debranched starch led to the formation of resistant starch 3, which exhibited higher crystallinity, enhanced heat-stability, and resistance to alpha-amylase digestion compared to native starch.