A Novel <scp>d</scp> -Allulose 3-Epimerase Gene from the Metagenome of a Thermal Aquatic Habitat and <scp>d</scp> -Allulose Production by Bacillus subtilis Whole-Cell Catalysis

Abstract

d -Allulose is a noncaloric sugar substitute with antidiabetes and antiobesity potential. With several characteristics of physiological significance, d -allulose has wide-ranging applications in the food and pharmacology industries. The development of a thermostable biocatalyst is an objective of mainstream research aimed at achieving industrial acceptability of the enzyme. Aquatic habitats of extreme temperatures are considered a potential metagenomic resource of heat-tolerant biocatalysts of industrial importance. The present study explored the thermal-spring metagenome of the Tattapani geothermal region, Chhattisgarh, India, discovering a novel d -allulose 3-epimerase gene, daeM , encoding an enzyme of high-level heat stability. The daeM gene was expressed in the microbial cells of a nonpathogenic and safe-grade species, B. subtilis , which was found to be capable of performing d -fructose to d -allulose interconversion via a whole-cell catalysis reaction. The results indicate that DaeM is a potential biocatalyst for commercial production of the rare sugar d -allulose. The study established that extreme environmental niches represent a genomic resource of functional sugar-related biocatalysts.