9 Correspondingly, research has increasingly focused on a diverse range of chemicals with the potential to be produced by microbial fermentation. Compared with the traditional process, the microbial production of natural chemicals has the potential for a shorter production cycle and higher productivity. 7,8 In recent years, with the rapid development of genetic engineering and metabolic engineering, microbial platforms have shown increasing potential to produce plant-derived metabolites on an industrial scale. 6 Industrial and natural green production of caffeine is still dependent on whole plant extraction, which is limited by the limited low caffeine in plants and the long growing cycle. However, despite the growing demand for healthy green caffeine production, this valuable chemical is mainly manufactured by chemical synthesis, which is associated with environmental pollution. 3–5Ĭaffeine is currently the most routinely ingested bioactive compound, and exists in a variety of caffeine-containing beverages include tea, coffee, soft drinks, and energy drinks, as well as in caffeinated food products. A moderate amount of caffeine intake is beneficial for human health, as strong evidence reveals that caffeine is associated with a reduced risk of many diseases such as Parkinson's disease, Alzheimer's disease, type 2 diabetes, depression, and cancer of the liver and endometrium. Caffeine has a desirable stimulatory effect on the central nervous system. 1,2 In addition to these physiological functions, caffeine has many valuable pharmacological effects. Previous studies have shown that caffeine plays an important role in chemical defense and allelopathy during plant growth. Introduction As one of the most popular purine alkaloids, caffeine (1,3,7-trimethylxanthine) represents a characteristic secondary metabolite derived from purine nucleotides in many higher plants. This novel microbial conversion also represents an innovative approach to produce value-added methylxanthine chemicals from cheap carbon sources. ![]() The final strain ( BL21/pRSF-eCS1-SAM2-vgb-eGUD1) produced up to 21.46 ± 1.03 mg L −1 caffeine from 20 g L −1 of glucose in shake flask culture, yielding caffeine up to 2.96 mg g −1 glucose, which represents the highest titer of caffeine produced by fermentation reported to date. Caffeine accumulation was then increased using two metabolic strategies: higher-level expression of the target enzymes, and enhancement of xanthine and S-adenosyl- L-methionine biosynthesis. ![]() Xanthine-to-caffeine conversion was first achieved by the expression of a plant-derived gene encoding tea caffeine synthase (TCS1). In this study, we developed a novel approach for de novo caffeine production in metabolically engineered Escherichia coli. Currently, this valuable chemical is mainly manufactured by chemical synthesis. Caffeine (Cf, 1,3,7-trimethylxanthine), a major secondary metabolite of many higher plants, is widely used in popular non-alcoholic beverages, and in the pharmaceutical and health industries.
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