In vitro probiotic screening and evaluation of space-induced mutant .

Space mutation is an efficient tool in microbial breeding. The aim of the present study was to screen out space-induced mutants of with potent probiotic properties. The wild-type GS18 was subjected to 31 days and 18.5 hr of space flight, in which 13 isolates were selected for analysis. These mutants were assayed for milk fermentation performance, low pH resistance, bile salt tolerance, hydrophobicity, and antimicrobial activity. The 16S rDNA sequencing was applied to identify the stain and compare it with the wild type. Results showed that the isolate SS18-50 had the strongest probiotic properties with no mutation in 16S rRNA sequence compared to the wild type. Specifically, SS18-50 had good milk fermentation performance. The viscosity of fermented milk, acid tolerance, and bile salt tolerance were increased by approximately 10%, 8%, and 9%, respectively ( < .05). The antibacterial activity () was also increased significantly compared to the wild type ( < .05). This study indicates that SS18-50 has the great potential to serve as a probiotic for dairy products.