Adaptive laboratory evolution of Lactobacillus gasseri-01 toward a safe probiotic for enhanced sulforaphane transformation.

Sulforaphane is a potent isothiocyanate with significant physiological activity. Its bioavailability from dietary sources is relatively low and relies on biotransformation by the gut microbiota from glucoraphanin. Lactobacillus gasseri (L. gasseri) is a promising candidate for enhancing sulforaphane transformation because of its probiotic safety and inherent myrosinase-like activity. However, the natural transformation efficiency of the wild-type strain is limited, necessitating enhancement of its transformation capability. This research employed adaptive laboratory evolution (ALE) to enhance the sulforaphane transformation capability of L. gasseri-01 under selective pressure with glucoraphanin as the carbon source. Comprehensive safety assessments and genomic and phenotypic analyses were conducted on the enhanced strain. The results showed that the sulforaphane production rate of the enhanced L. gasseri increased from 2.49 × 10-4 mg h-1 logCFU-1 to 4.52 × 10-4 mg h-1 logCFU-1. Meanwhile, the enhanced L. gasseri exhibited antibiotic susceptibility to tetracyclines, macrolides and penicillins antibiotics. Importantly, whole genome sequencing showed that the genome of the enhanced strain had been streamlined. Genes related to carbohydrate metabolism, particularly glycoside hydrolase genes, had been enriched, which correlated with the improved utilization rate of glucoraphanin. Consistently, in vivo research confirmed that oral administration of the enhanced L. gasseri could increase the levels of sulforaphane in the cecum and serum, modulate the gut microbiota composition, and increase beneficial bacterial genera such as Akkermansia. Therefore, ALE can generate a functionally enhanced L. gasseri-01 with safety features. This research can provide a viable strategy for enhancing the bioavailability of sulforaphane.