Production Of Betalains In Engineered Escherichia Coli

Betalains is a kind of botanical water-soluble natural nitrogen-containing pigments,which used as food additives and cosmetics.Betalains and anthocyanin pigments do not coexist in a same plant,and their metabolic pathway is an important phytochemical classification index.Betalains have potential pharmacological effects of anti-tumor,anti-oxidation,anti-malaria and liver protective,which have promoted the further study of them.In this paper,the biosynthesis genes BvDODA MjDODA and YgiD,from L-??to betalamic acid,which is the key intermediate product of betalains,were screened and therefore expressed to produce betalamic acid in vivo successfully.The genes of cytochrome P450 enzymes and tyrosine hydroxylase,CYP76AD1,BvCPR and HpaBC were introduced to extend the biosynthesis pathway from L-tyrosine to betalamic acid.By studying the addition of precursor and reductant,adjusting the concentration of IPTG and optimizing the fermentation pattern to search the optimum condition for the production of betalamic acid,which established the basis for the biosynthesis of different kinds of betalains.To search the formation efficiency of different kinds of betaxanthins,adding different amino acids at the stage of the maximum amount of betalamic acid produced.Only 12 amino acids could combine with betalamic acid to form betaxanthins through the experiment of 20 kinds of amino acids.Among them,the production of histidinebetaxanthin was dominant absolutely,which was determined as the final target product.The content of histidine-betaxanthin was determined indirectly by quantifying the stable histidine hydrochloride in this paper.The production of histidine-betaxanthin was 445.84mg/L when 6mM L-DOPA,1mM ascorbic acid and 6mM histidine hydrochloric were added.