Abstract
Pterostilbene is a derivative of resveratrol with a higher bioavailability and biological activity, which shows antioxidant, anti-inflammatory, antitumor, and antiaging activities. Here, directed evolution and host strain engineering were used to improve the production of pterostilbene in Escherichia coli. First, the heterologous biosynthetic pathway enzymes of pterostilbene, including tyrosine ammonia lyase, p-coumarate: CoA ligase, stilbene synthase, and resveratrol O-methyltransferase, were successively directly evolved through error-prone polymerase chain reaction (PCR). Four mutant enzymes with higher activities of in vivo and in vitro were obtained. The directed evolution of the pathway enzymes increased the pterostilbene production by 13.7-fold. Then, a biosensor-guided genome shuffling strategy was used to improve the availability of the precursor L-tyrosine of the host strain E. coli TYR-30 used for the production of pterostilbene. A shuffled E. coli strain with higher L-tyrosine production was obtained. The shuffled strain harboring the evolved pathway produced 80.04 ± 5.58 mg/l pterostilbene, which is about 2.3-fold the highest titer reported in literatures.
Highlights
Stilbenes are a small category of the secondary metabolites of plants derived from the general phenylpropanoid pathway
In our previous study (Niu et al, 2020b), we developed a strain improvement strategy of biosensor-guided genome shuffling and applied this strategy to improve the production of shikimic acid in E. coli
Wang et al (2015) reported that the highest conversion efficiency of resveratrol to pterostilbene was obtained using the resveratrol O-methyltransferase (ROMT) from V. vinifera
Summary
Stilbenes are a small category of the secondary metabolites of plants derived from the general phenylpropanoid pathway. Occurring stilbenes are found primarily in grapes, peanuts, blueberries, and some medical plants (Tsai et al, 2017). Stilbenes play a major role in the defense response of plants; their abundance is expected to increase when the plants are exposed to some harsh environmental conditions, such as UV irradiation and fungal infection (Wang et al, 2010). Numerous scientific studies have revealed the broad range of health-improving activities of stilbenes including antioxidant activity, anti-inflammatory activity, antitumor activity, and antiaging activity (Burns et al, 2002; Ulrich et al, 2005; Baur et al, 2006; Campagna and Rivas, 2010). Pterostilbene is a structural analogy of the well-studied stilbene resveratrol. Because of the substitution of hydroxyl with methoxy groups, the lipophilicity of pterostilbene is enhanced substantially, enhancing the increased bioavailability and biological activity of pterostilbene in comparison with that of resveratrol (Shao et al, 2010; Kosuru et al, 2016)
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