Engineering Escherichia coli to convert acetic acid to β-caryophyllene

Abstract

BackgroundUnder aerobic conditions, acetic acid is the major byproduct produced by E. coli during the fermentation. And acetic acid is detrimental to cell growth as it destroys transmembrane pH gradients. Hence, how to reduce the production of acetic acid and how to utilize it as a feedstock are of intriguing interest. In this study, we provided an evidence to produce β-caryophyllene by the engineered E. coli using acetic acid as the only carbon source.ResultsFirstly, to construct the robust acetate-utilizing strain, acetyl-CoA synthases from three different sources were introduced and screened in the E. coli. Secondly, to establish the engineered strains converting acetic acid to β-caryophyllene, acetyl-CoA synthase (ACS), β-caryophyllene synthase (QHS1) and geranyl diphosphate synthase (GPPS2) were co-expressed in the E. coli cells. Thirdly, to further enhance β-caryophyllene production from acetic acid, the heterologous MVA pathway was introduced into the cells. What’s more, acetoacetyl-CoA synthase (AACS) was also expressed in the cells to increase the precursor acetoacetyl-CoA and accordingly resulted in the increase of β-caryophyllene. The final genetically modified strain, YJM67, could accumulate the production of biomass and β-caryophyllene up to 12.6 and 1.05 g/L during 72 h, respectively, with a specific productivity of 1.15 mg h−1 g−1 dry cells, and the conversion efficiency of acetic acid to β-caryophyllene (gram to gram) reached 2.1 %. The yield of β-caryophyllene on acetic acid of this strain also reached approximately 5.6 % of the theoretical yield.ConclusionsIn the present study, a novel biosynthetic pathway for β-caryophyllene has been investigated by means of conversion of acetic acid to β-caryophyllene using an engineered Escherichia coli. This was the first successful attempt in β-caryophyllene production by E. coli using acetic acid as the only carbon source. Therefore, we have provided a new metabolic engineering tool for β-caryophyllene synthesis.

Central pathway engineering for enhanced succinate biosynthesis from acetate in Escherichia coli

“…In previous studies, it has proven that overexpressing the single acs gene enhanced the acetate assimilation in E. coli (Lin, Castro, Bennett, & San, 2006;Zha, Rubin-Pitel, Shao, & Zhao, 2009). In this study, we selected the ACS from Acetobacter pasteurianus, whose ability of conversion of acetate into acetyl-CoA was more efficient than that of E. coli (Yang & Nie, 2016). However, the overexpression of acs AP impaired the growth of the recombinant strain on acetate ( Figure S7) and inhibited the production of succinate, which were similar to the results of the overexpression of acs from E. coli (Li, Huang, et al, 2016).…”

“…Photosynthesis of acetate from CO 2 was achieved by introduction of the self‐photosensitization into a nonphotosynthetic M. thermoacetica ( M. thermoacetica ‐CdS system) with nearly 90% maximum yield (Sakimoto, Wong, & Yang, ). Recently, acetate had been used as alternative carbon source to produce free fatty acids (Xiao et al, ), lipids (Hu et al, ), β‐caryophyllene (Yang & Nie, ) and succinate (Li, Huang, et al, ).…”

“…Recently, acetate had been used as alternative carbon source to produce free fatty acids (Xiao et al, 2013), lipids (Hu et al, 2016), β-caryophyllene (Yang & Nie, 2016) and succinate (Li, Huang, et al, 2016).…”

Plant-Derived Terpenes: A Feedstock for Specialty Biofuels

“…Zhang et al demonstrated through metabolic engineering of the terpene mevalonate (MVA) precursor pathway in E. coli, in combination with optimization of growth and culturing conditions, that sabinene could be synthesized at a concentration of 2.65 g l -1 [21]. Two recent reports demonstrated that the plasticity of the terpene biosynthetic pathway could be exploited for production of β-caryophyllene at high levels (1.05 g l -1 and 1.52 g l -1 ) in engineered E. coli [22,23]. With the application of systems biology and synthetic biology, metabolic engineering in microbial systems has further potential for commercializing biofuels, including lower cost and high product yield [24,25].…”

An in vitro synthetic biosystem based on acetate for production of phloroglucinol

“…Acetate could be derived from a variety of cheap sources, such as (i) products during syngas fermentation [ 10 ], hydrolysis under acid or alkali pretreatment [ 11 ] and pyrolysis of lignocellulosic biomass [ 12 ], (ii) intermediates from anaerobic digestion of organic wastes [ 13 ], (iii) production by methanol carbonylation [ 14 ], (iv) methane conversion from natural gas or biogas [ 15 ]. It has been demonstrated that Cryptococcus curvatus could be able to produce lipid using acetate as a major carbon source [ 16 ] and engineered E. coli could convert acetate to succinic acid, fatty acids and β-caryophyllene [ 17 – 19 ]. The utilization of acetate as a nontraditional carbon source is becoming one of the most interesting direction in industry biotechnology due to obviously lower cost, sufficient source, no direct competition for food supplies with people, and price stability.…”