Study On The Over-producing Phosphatidylserine In Corynebacterium Glutamicum

Phosphatidylserine(Phosphatidylserine,PS)is one of the phospholipids which regulates the key protein function of the membrane.Due to its function of improving the brain capability,repairing brain damage,and enhancing memory,PS is widely used in the treatment of Alzheimer’s disease,depression,and ADHD,etc.In this study,the key genes of PS biosynthetic pathway in C.glutamicum were modified to direct more carbon flux into the PS biosynthetic pathway.We also evaluated the growth of recombinant strains and PS production.This study lays a foundation for the study of the synthesis of PS in the C.glutamicum.(1)In order to increase the pool of the precursor L-serine of PS in Corynebacterium glutamicum ATCC13032(Abbreviated as Cgl),the serine deaminase gene sdaA which can decompose L-serine into pyruvate was knocked out,resulting in the recombinant strains Cgl-1.In Cgl-1.The PS precentage in total phospholipid was increased by 10.43%and PS content in dry cells was 0.46-fold more than that in Cgl,reaching 0.79 mg/g dry cells,and the cell growth of the recombinan strains was not affected.(2)In order to increase the content of the precursor L-serine and CDP-diacylglycerol of PS in Cgl,four strains overexpressing serAΔ591,serC,serB,and cdsA,were constructed and designated Cgl-2,Cgl-3,Cgl-4 and Cgl-5.PS percentage in total phospholipid increased by 24.34%,8.69%,7.83%and 16.52%,respectively.Meanwhile,PS content in dry cells was improved to 1.08 mg/g.Furthermore,the cell growth of recombinant strains was not affected.(3)To further enhance PS accumulation,six recombinant strains Cgl-6,Cgl-7,Cgl-8,Cgl-9,C gl-10,Cgl-11,which overexpress serAΔ591,serC,serB,cdsA,pssA and cars were constructed in Cgl-1 respectively.PS content in total phospholipid of recombinant strains increased by 35.65%,13.04%,11.30%,27.82%and 30.43%,respectively in Cgl-6,Cgl-7,Cgl-8,Cgl-9 and Cgl-10.PS content was notably increased in Cgl-6,Cgl-9 and Cgl-10.In Cgl-6 PS content in dry cells reached 1.34 mg/g dry cells,PS content has not been improved in Cgl-11.The growth of recombinant strains was not affected.(4)Strain Cgl-12 that overexpresses serAΔ591,cdsA,and pssA was constructed.The content of PS was improved by 45.22%compared with the native bacteria Cgl with a yield of 1.98 mg/g dry cells,which indicated the PS yield was improved by gene overexpression and knockout.The growth of recombinant strains was not affected.