Breeding Of L-Serine Producing Mutant And Study Of Conditions In Fermentation

This paper is about L-Serine production by fermentation method which mainly investigated contents were breeding of L-Serine producing mutant and optimization of medium composition and fermentation conditions on L-Serine production in flask.The concentrations of L-Serine and glycine in broth were qualitatively and quantitatively determined with paper chromatography and spectrophotometer. The determination conditions of L-Serine and glycine were established. The relationship between the content of L-Serine in broth and the absorbency could be described by an expression. It was showed that the method has a high accuracy and precision in the determination of L-Serine and glycine. The method was also easy to operate and suitable for the screening of strains producing L-Serine.The L-Serine producing mutant ZC-8(D-SerR,GlyHR,MthR,SGR,Met-)was derived from Pseudomonas flava LJW-01(D-SerR,GlyR,MthR) seprated from the preserved mutant of the lab by combination treatment with diethylsulfate(DES) and N-methyl-N'-nitro- N-nitrosoguanidine (NTG). It could accumulate 6.2 g/L L-Serine.Compared with the original strain. ZC-8 has an improvement about 100% in the ability of accumulating L-Serine. It has a good stability of descendiblity of L-Serine producing.The effects of medium composition and fermentation conditions on L-Serine production in flask were considered. The seed medium compositions were optimized as follows(g/L): glucose 20, corn steep liquor 20, (NH4)2SO4 20, KH2PO4 1, MgSO4·7H2O 0.2. The optimal fermentation medium compositions were selected as follows(g/L):glycine 35, glucose 5, corn steep liquor 14, (NH4)2SO4 22, KH2PO4 1, MgSO4·7H2O 0.8, CaCO3 20. The optimum fermentation conditions were 250mL contains 25mL broth, original pH8.0~8.5, culturing at 30±1℃on reciprocating shaker, shaking speed 100r/min, seed volume 10%, fermentation time 72h. After optimization, the produc- tion of L-Serine was up to 9.82g/L.