Screening And Breeding Strains Producing L-serine And Constructing Gene-engineering Strains

L-serine is applied for medicine,food and cosmetic widely,but usage of L-serine is limited of its high price.A majority of product is imported in China.Nowadays,L-serine is produced through chemosynthesis.However,DL-style product is difficult to be splitten and environment is polluted by the technics.The way to microorganism fermentation has the virtue of low price,little pollution and high pure product.So high yield strains is key to produce L-serine.In the experiment,we screened strains deficient in L-serine decomposing activity and which feedback inhibition by L-serine is desensitized from Brevibacterium flavum.On the base,we further screened high yield strains producing L-serine by flask fermentation.The mutants produce L-serine increasing to 18/Lfrom 10g/L.Then D-3-phosophoglycerate dehydrogenase(D-3-PGDH)gene is cloned through the mutants template and cloned into shuttle vector pEC7.The reconstructive plasmid is transformed in the mutant Brevibacterium flavum and gene-engineering strains are obtained.Two high yield strains producing L-serine are screened by fermentation.The average production of L-serine by the mutant strains reach to 28g/l . The production hold prominent increase comparing start strains with the gene-engineering strains.Constructing gene-engineering strains successfully will depreciate the price of L-serine and enlarge application in many field.This will lay the groud of industrialization of L-serine by direct fermentation.