A High-throughput Strategy For Screening High-L-lactic Acid-productivity Lactobacillus Paracasei

A novel high-throughput strategy for screening high-lactic acid-productivity Lactobacillus paracasei strains was developed. The strategy typically relies upon the visual color change of bromocresol green in liquor medium due to the release of the lactic acid produced by microorganism. Adding of bromocresol green into the screening media allows real-time observation of the color change during fermentation processes, which can be used to distinguish of high-lactic acid-productivity mutant from low one. Mutant UV16with improved L-lactic acid productivity and high-sugar-resistant characteristics was singled out by the combination of above strategy with ultraviolet (UV) mutagenesis and KMnO4-KBr plate isolation method.. After culturing40hours, mutant UV16produced112.5g/L L-lactic acid in the fermentation medium containing150g/L glucose. It’s L-lactic acid productivity increased by34.49%, and the specific production of lactic acid by20.19%. The combined strategy with atmospheric and room temperature plasma (ARTP) mutagenesis and KMnO4-KBr plate isolation was established, too, resulting in mutant A6with significantly enhanced L-lactic acid productivity. Compared with the original strain, mutant A6grew better with a shorter lag phase. After culturing30hours in the fermentation medium containing126g/L glucose, mutant A6produced120.0g/L L-lactic acid with95%yield and4.00g/L-h L-lactic acid productivity was observed. In comparison with the original strain, the productivity increased by42.35%and the specific production increased by14.12%.