De novo biosynthesis of tyrosol acetate and hydroxytyrosol acetate from glucose in engineered Escherichia coli
Introduction
Plant phenolic compounds have antioxidant and other beneficial biological activities, so they have wide applications both as functional food components and as nutraceuticals [1]. Among these phenolic compounds, tyrosol and hydroxytyrosol derived from virgin olive oil and olives extract, have attracted extensive attention [2]. Tyrosol and hydroxytyrosol are widely recognized as an antioxidant, anti-inflammatory molecule that inhibits platelet aggregation and plays a protective role in the heart [3,4]. However, they have low bioavailability due to their low absorption and high metabolism in human liver and small intestine [5].
Acetylation of phenolic compounds has been reported to enhance lipophilicity as well as absorption and cell permeability, thus improving their bioavailability [6]. Tyrosol acetate derivatives showed better antimicrobial and antileismaniac activities than tyrosol. This effect can be attributed to its increased lipophilicity [7,8]. Tyrosol acetate also showed a higher cytotoxic effect on cancer lines than tyrosol [9]. On the other hand, hydroxytyrosol acylation can improve antioxidant activity, decrease tumor necrosis factor (TNF) and interleukin (IL) 1B plasma levels, decrease IL1B and chemokine ligand 2 levels of adipose tissue and showed greater anti-inflammatory effects than hydroxytyrosol [[10], [11], [12]]. This acetylation can be explored by reaction with acid chlorides or acid anhydrides, but these chemical routes do not meet the requirements necessary for food applications. Several enzymatic methods have been reported for the preparation of tyrosol acetate or hydroxytyrosol acetate [13]. However, there are some drawbacks by using enzymes in bioprocesses such as the need of expensive enzymes and substrates. Thus, it is of great significance to develop microbial cell factories for achieving tyrosol acetate or hydroxytyrosol acetate biosynthesis. In this study, a de novo biosynthetic pathway for the production of tyrosol acetate and hydroxytyrosol acetate was constructed in E. coli (Fig. 1).
Section snippets
Plasmids and strains
Plasmid pDG11 for expression of the feedback resistant mutant of 3-deoxy-d-arabinoheptulosonate-7-phosphate synthase AroGfbr (D146 N) was constructed in our previous study [14]. The feedback resistant mutant of chorismate mutase/prephenate dehydrogenase TyrAfbr (GenBank CP032679.1) was synthesized by Genewiz Biotech Co. Ltd., amplified by PCR using primers TyrAfbr-XbaI and TyrAfbr-SpeI-SalI. The XbaI-SalI fragment of TyrAfbr was inserted into SpeI and SalI sites of pDG11 to give pDG20. The
Screening aldehyde reductase for biosynthesis of tyrosol
Recently, several research groups have reported the biosynthesis of tyrosol in E. coli using the intrinsic aldehyde reductase of E. coli [[16], [17], [18]]. However, which aldehyde reductase is primarily responsible for catalyzing the reduction of 4-hydroxyphenylacetaldehyde to tyrosol has not been identified. Aldehyde reductase is a superfamily enzyme which catalyze the reduction of a large variety of aldehydes. There are multiple aldehyde reductases in E. coli, such as YahK, YeaE, DkgB and
Discussion
Acetylated tyrosol and hydroxytyrosol can effectively improve their lipophilicity and thus promote their absorption and cell permeability [12,25,26]. This acetylation can be accomplished by acid-base catalysis, but these chemical methods do not meet the requirements necessary for food applications. In recent years, a number of pioneering studies have demonstrated the application of lipase for the bioproduction of tyrosol acetate and hydroxytyrosol acetate [13]. Aissa et al. reported that
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (31960216) and National Science Foundation of Jiangxi Province (220192BBG70007 and 20192BCBL23012).
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