Improvement Of Performance And Application Of Lactococcus Lactis Subsp. Lactis 11454 Lactinocedin,and Lactic Acid By Genome Shuffling

Nisin is a polypeptide with bacteriostatic effect produced by Lactococcus lactis,which can be hydrolyzed by proteases in the human body,so it will not cause harm to the human body.Lactococcus lactis subsp.Lactis 11454 is one of the lactococcus lactis strains that produce Nisin.In this paper,in order to increase the production of Nisin and lactic acid,Lactococcus lactis subsp.lactis 11454 was used as the starting strain,and genome shuffling technology was used to obtain a strain with high yield of Nisin and lactic acid after multiple rounds of evolution.After that,the batch fermentation conditions of high-yield strains were optimized,and batch fermentation was carried out under optimal conditions,and Nisin and lactic acid were produced by synchronous saccharification fermentation using straw,and finally degradable mulch film was prepared from the remaining residue of synchronous saccharification fermentation.The main research contents of the paper are as follows:(1)Lactococcus lactis subsp.lactis 11454 was used as the original strain,and the parental library was constructed by using ultraviolet mutagenesis.Genome rearrangement by protoplast fusion yielded a well-characterized strain Lactococcus lactis subsp.lactis F41,which had a Nisin yield of 2798 IU/m L,which was 2.32 times that of the original strain,and its lactic acid yield of 14.82 g/L,which was 2.40 times that of the original strain.(2)Single-factor experiments were used to optimize the fermentation conditions of Lactococcus lactis subsp.lactis F41 in batches.Nisin and lactic acid were produced in batches using straw for synchronous saccharification fermentation feeding under optimal conditions,with a Nisin yield of 2822 IU/m L and a lactic acid yield of 18.0g/L.(3)Degradable mulch film was prepared from synchronous saccharification fermentation residue,polyvinyl alcohol and citric acid as raw materials.