Biosynthesis of anthocyanin in metabolically engineered Escherichia coli
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Anthocyanins are water-soluble colored pigments found in terrestrial plants. They are responsible for the red, blue and purple coloration of many flowers, fruits and other plant parts. Anthocyanins have been known to possess various health benefits such as cardioprotective, anti-inflammatory, antioxidant, and anti-aging properties. However, minute quantities of these polyphenols produced in plants complicate the effort to assess their full potential. Thus, the overall goal of our project is to engineer a recombinant Escherichia coli strain capable of high anthocyanin production. In our previous work, the capacity of synthesizing anthocyanin from recombinant E. coli was initially low, so we aimed to improve the production further. First, to accelerate the in vivo reaction rate, fluxes toward the UPD-glucose backbone were increased via gene deletions and overexpressions. Second, we altered various E. coli transporter genes to improve substrate uptake and product excretion. However, high-level synthesis was only achieved through altering the expression system. Third, we optimized the fermentation protocol specifically for the anthocyanin-producing E. coli strain. Through these strategies, an extracellular anthocyanin titer of 353 mg/L was achieved. This result demonstrates the feasibility of E. coli as a host for high-yield anthocyanin production for pharmaceutical applications.