Biosynthesis Of Gallic Acid

Gallic acid(GA),also known as 3,4,5-trihydroxybenzoic acid,is a polyphenol that is widely found in nature,mainly in plants,and it has many biological activities,including anti-inflammatory and antibacterial,antioxidant,anti-tumor,etc.It has high application value in the fields of food,medicine and chemical industry.However,at present,this substance is mostly prepared by chemical method,which not only has limited raw materials,but also has harsh reaction conditions.The environment of strong acid and alkali will also cause great damage to the equipment,and its synthesis amount is insufficient,which has a large market gap,Biosynthesis,as an emerging production method,has mild reaction conditions,and the raw material is glucose,which is easier to obtain,so the production potential is huge.This subject also aims to explore how mass production of GA can be achieved.In this subject,a high-efficiency pathway for the synthesis of GA was first obtained through literature search,and 3-dehydroshikimate(3-DHS)was synthesized through the endogenous shikimate pathway of Escherichia coli,and the precursor was catalyzed by two-step exogenous enzymes to synthesize GA.The two enzymes are 3-dehydroshikimate dehydratase Qui C from Pseudomonas putida and p-hydroxybenzoate hydroxylase Pob A** from Pseudomonas aeruginosa(two amino acid site mutations in this enzyme),constructing a pathway for de novo synthesis of gallic acid.On this basis,we improved the supply of precursors,reduced the carbon flow of competing pathways,explored the supply of cofactors,modified the PTS system,etc.,and achieved high yield of GA,with a shake flask yield of 4.36 g/L and the conversion rate of glucose is 17.4 g/g.On this basis,the related exploration of fed-batch experiment was carried out,and a strain with stable yield in shake flask fermentation was taken as the key research object,and related fermentation conditions were studied,including culture medium,yeast powder,p H etc.,the optimized yield reached 12.5 g/L.At the same time,we obtained another strain that performed better in shake flask fermentation and was transformed with PTS.On the basis of previous research,we tried and explored the fed-batch experiment,and the yield reached 15.1 g/L,the conversion rate of glucose is 0.21 g/g.This subject provides ideas for the biosynthesis of gallic acid,and the mass production of GA can be further realized on this basis.