The Biosynthesis Of L-2,3-Diaminopropionic Acid

Escherichia coli is widely used in various biotechnology because of its many advantages,such as clear genetic background,biological structure,technical operation and culture conditions.In the industrial bio-fermentation,amino acid production has attracted much attention in the biological field due to its wide medicinal value.This paper describes the construction and optimization of the first biosynthesis of L-2,3-diaminopropionic acid using microbial Escherichia coli as a host.The specific steps of the whole process are as follows:The biosynthesis of L-DAP in E.coli was successfully achieved after transferring the foreign gene sbnA and sbnB into the wild-type strain BW25113.Through the metabolic optimization methods of endogenous gene overexpression,competitive pathway knockout and module optimization,the yield of L-DAP in the shake flask was increased from the initial 123.2 mg/L to 347.9 mg/L.In the previous experiment,no matter whether the growth of the strain or the production of the product required sufficient substrate:glutamic acid,2g/L of glutamate sodium was added to the previous shake flask fermentation process.In the subsequent industrial development and the necessity of step simplification,this topic aims to achieve the independent accumulation of glutamate in vivo by enhancing glutamate dehydrogenase and modifying the TCA cycle to accumulate precursors.After the transformation,the yield of L-DAP in the shake flask reached 554.7 mg/L.During the experiment,it was found that with the continuous transformation of BW25113 strain,the increasing production of L-DAP caused the cell growth to be more and more inhibited。In the process of solving,try to interpret the gene by knocking out or over-expressing the pathway.The mechanism by which this inhibition process occurs.At the end of the study,the expansion culture was carried out through the fermenter.The main work of this section is:due to the difference of each fermenter and under different process conditions,the growth of the fermentation target and the production level of related products are not the same.Therefore,the research focuses on optimizing the fermentation conditions to obtain higher yields of the target product,and testing for possible industrialization.