Evaluation of novel isolates of Lacticaseibacillus rhamnosus Probio-M9 derived through space mutagenesis

This study evaluated the growth and probiotic properties of Probio-M9 after exposure to the environment of space. Probio-M9 has excellent probiotic properties. As a rapidly developed new cutting-edge technology, space mutagenesis can confer potentially desirable properties to novel isolates. In this study, three novel isolates (HA-R7970-29, HG-R7970-18, HG-R7970-29) mutated from Probio-M9 in space, had significantly higher growth characteristics than the original Probio-M9. Antibacterial properties, auto aggregation ability, cell surface hydrophobicity and antioxidant activity of the three mutagenic isolates were evaluated. The results showed that Probio-M9 remained stable after mutagenesis, and the mutant strains could effectively inhibit the growth of six common pathogenic bacteria. The mutated isolates showed strong auto aggregation ability (49.3%–76.5%, 24h) and cell surface hydrophobicity (25.7%–43.0%); HA-R7970-29 showed significantly higher auto aggregation ability and cell surface hydrophobicity than HG-R7970-18 and HG-R7970-29 (P < 0.05). In addition, the supernatants and bacterial suspensions of the three mutated isolates had strong antioxidant activities. Genomic analysis identified genes associated with bacteriocin, adhesion properties and antioxidant activity and probiotic features at the genetic level. Mutated isolates not only had good growth characteristics but also exhibited excellent probiotic properties indicating their potential as probiotics.