Abstract: A strain capable of producing α-glucosidase inhibitor as a potential antidiabetic agent from mulberry leaf was isolated. Subsequently, atmospheric and room temperature plasma (ARTP) was applied to mutagenize the isolated strain for improved production of α-glucosidase inhibitors. At the same time, the physicochemical properties and stability were investigated preliminarily. Out of the 188 isolated strains, a bacterial strain named XuW-LB-188 was selected after examination of α-glucosidase inhibitory activity using 4-nitrophenyl-α-D-glucopyranoside (PNPG) as a substrate, giving an inhibition percentage of 52.67% in the fermentation supernatant. On the basis of its morphological characteristics and 16S rDNA gene sequence, the strain was preliminarily identified as Bacillus atrophaeus. After ARTP mutation breeding and subsequent high-throughput screening, T-690 was selected out of 880 mutant strains, whose inhibition rate (73.25%) against α-glucosidase was increased by 40.61% compared with that of the original strain. The experiment results indicated that the α-glucosidase inhibitor mainly existed in the fermentation broth. Consequently, the inhibitor was an extracellular product. Moreover, it had high polarity and good thermostability.

Key words: α-glucosidase inhibitor, mulberry leaf, endophytes, screening, atmospheric and room temperature plasma (ARTP), Bacillus atrophaeus