Characterization of a novel amylosucrase gene from the metagenome of a thermal aquatic habitat, and its use in turanose production from sucrose biomass

Turanose is a natural isomer of sucrose. It is an emerging functional sweetener of the next generation. Turanose is catalytically synthesized from the sucrose biomass by employing amylosucrase enzyme. In this study, a novel gene encoding amylosucrase (As-met) has been identified from the metagenome of a thermal aquatic habitat. As-met exhibits 37-55% identity at the protein level with the known amylosucrases characterized till date. As-met was cloned and expressed in Escherichia coli, followed by protein purification, and characterization. As-met protein exhibited the maximum total activity at 9.0 pH and 60 degrees C temperature, whereas, 8.0 pH and 50 degrees C temperature were found optimum for transglycosylation activity. As-met showed fairly high thermal tolerance at 50 degrees C. The conjugation of As-met protein with functionalized iron nanoparticles significantly improved its thermal tolerance, showing hardly any loss in the enzymes activity even after 72 h of heat (50 degrees C) exposure. The turanose yield of about 47% was achieved from 1.5 M sucrose, containing 0.5 M fructose in the reaction. Turanose was purified ((similar to)95%) via a bio-physical process, and characterized by TLC, HPLC, and NMR. The novel amylosucrase gene was demonstrated to be a potential candidate for turanose production, utilizing various sucrose containing feed-stocks.