Breeding Of High-yield Phenyllactic Acid Strains And Optimization Of Fermentation Conditions

Phenyllactic acid (Phenyllactic Acid, PLA), also known as β-phenyllactic acid or3-phenyllactic acid, Is anew type of natural preservatives in recent years found. This topic through mutation breeding method.Optimum mutagenic condition, and then through the single factor test, orthogonal test, rotation test designcombined with the optimization of medium and fermentation conditions by response surface method. Breedingof phenyl lactic acid producing strain, providing excellent strains for the production of phenyl lactic acidfermentation. The research contents of this paper include the following three aspects:1. Screening of Lactobacillus Plantarum LY-78strain by Ultraviolet radiation mutationThe purpose of this study was to obtain high-yield mutant strains by ultraviolet irradiation of independentseparable lactobacillus Plantarum LY-78,The experiment adopted the double-layer plate antagonistic methodand the Oxford cup diffusion method for the determination of antibacterial circle diameter,throughreverse-phase high performance liquid chromatography assay for quantification of content of phenyllactic acid,Selecting mutant strains with antibacterial circle diameter larger and phenyl lactic acid yield higher as the beststrain. The results showed that the ultraviolet (20W,30cm) time was90s the obtained mutant strain UY-26having a higher production of phenyllactic acid, up to0.591g/L, the production was improved by2.4timescompared to that of original strain(0.246g/L).2. Screening of Lactobacillus Plantarum LY-78strain by NTG mutagenesisThis research used independent separable lactobacillus Plantarum LY-78as the original strain,throughnitrosoguanidine mutagenesis, inhibited titer for detection indicators, using double-plate antagonistic methodand the Oxford Cup agar diffusion method to screen mutant strains. taking fermentation test to screeningmutant strains high performance liquid chromatography assay for quantification of content of phenyllactic acid,determining the best strains by the production of phenyllactic acid in accordance.The test results show thatnitrosoguanidine mutagenesis concentration of1.0g/L,the mutagenesis time is40min,the obtained mutantstrain NY-34having a higher production of phenyllactic acid, phenyllactic acid production up to0.648g/L,The production was improved by2.63times compared to that of original strain(0.246g/L).3. Optimization of mutant strain NY-34fermentation medium and fermentation conditionsThe mutant strain NY-34as production strain,By single factor experiment,Box-Benhnken centralcomposite design combined with response surface methodology to optimize the fermentation conditions.Theoptimized conditions are as follows:fermentation time75h,fermentation temperature33℃,9%of theinoculum size, Strains of age17h, the liquid volume to0.15L/0.25L.the initial pH7.0, Shaker150r/min, Thefermentation medium was optimized by orthogonal test,optimization of the fermentation medium componentsusing response surface method.The optimized medium composition is as follows:beef extract16.58g/L,magnesium sulfate0.84g/L, dipotassium hydrogen phosphate1.41g/L, peptone12.52g/L, sodium acetate3.81g/L, the addition of glucose20.00g/L, the addition of Calcium carbonate15.00g/L, and thephenylalanine add30.00g/L, the addition of Tween-809.00mL/L, yeast extract5.00g/L,hydrogendiammonium citrate2.00g/L, manganese sulfate0.25g/L, Media and culture conditions optimized,phenyllactic acid yield of3.17g/L and optimization of0.648g/L, compared to the yield increased by4.89times. Through UV and nitrosoguanidine mutagenesis on Lactobacillus Plantarum LY-78strains, screening themutagenesis mutant NY-34which its character was improved, the optimization of fermentation medium andfermentation conditions, mutant of phenyllactic acid-producing ability was greatly improved, providingexcellent strains and technical support for the industrial production of phenyl lactic acid.