Thermal stabilization of D psicose 3 epimerase enzyme and its recruitment in D allulose synthesis using agro industrial residues as feedstock

Abstract

D-psicose or D-allulose is an epimer of D-fructose. It is an ultra-low calorie sweet sugar biomolecule of GRAS status. It is a functional sugar of rare occurrence that exerts anti-obesity and anti-diabetic effects. The present doctoral study was aimed at the development of novel biocatalyst systems, with significantly improved thermal activity and stability, for the catalytic transformation of D-fructose to D-allulose. This study, for the first time, established that N-terminal fusion of Smt3, a yeast homolog of SUMO protein, could confer improvement in the optimal catalytic activity and thermal stability of the enzyme, as compared the native counterpart. Further enhancement in thermal activity and stability was experienced after the covalent immobilization of the enzyme molecules onto the magnetic nanoparticles. During the journey of development of novel biocatalyst systems, this study reported discovery of a novel highly thermotolerant D-allulose 3-epimerase by exploring thermal spring metagenomic resource. Another novel D-allulose 3-epimerase was identified from the genomic information of a probiotic strain of Bacillus sp. To the best of our information, these novel genes encode for proteins that display the highest thermal tolerance reported to date for a D-allulose 3-epimerase. The above described D-allulose 3-epimerase biocatalyst systems were employed for the enzymatic treatment of a variety of fruit pomace generated after the fruit juice processing. Further, the foliage residual biomass of cabbage, and banana pseudostem were also utilized a low-cost feedstock for the biosynthesis of D-allulose. In this study, the catalytic conversion yield of 25-30% D-allulose has been achieved. newline