Enhancement of exopolysaccharides production in L. bulgaricus by intense pulse light mutagenesis

In order to explore the feasibility of intense pulse light (IPL) technology used in microbial mutant breeding and obtain mutant strains with high yield of polysaccharides, the wild strain of L. bulgaricus IMAU40160 was mutated by IPL. Fourier transform infrared and scanning electron microscopy were used to analyze the primary structure of polysaccharides. Based on superoxide polysaccharide (O₂^-) and hydroxyl radical (·OH) scavenging ability, the antioxidant capacity of polysaccharides was studied. The mutagenic mechanism of IPL was explored using SDS-PAGE. Results showed that mutant strain L27 could be obtained by IPL mutant breeding and the yield of polysaccharide was (490.98±12.26) mg/L, which increased by 98% compared with that of the wild strain. IPL treatment would not influence the chemical bonds of polysaccharides. After the mutagenesis, polysaccharides showed irregular porous surface morphology and exhibited stronger antioxidant activities. IPL could cause the change of strain protein expression. This result would provide a theoretical basis for further research on the application of IPL in breeding superior strains. In conclusion, IPL could be applied in mutant breeding of mutants with high yield polysaccharide of L. bulgaricus IMAU40160.