Abstract
Microorganisms can utilize biomass to produce valuable chemicals, showing sustainable, renewable and economic advantages compared with traditional chemical synthesis. As a potential five-carbon platform polymer monomer, 5-aminovalerate has been widely used in industrial fields such as clothes and disposable goods. Here we establish an efficient whole-cell catalysis for 5-aminovalerate production with ethanol pretreatment. In this study, the metabolic pathway from L-lysine to 5-aminovalerate was constructed at the cellular level by introducing L-lysine α-oxidase. The newly produced H2O2 and added ethanol both are toxic to the cells, obviously inhibiting their growth. Here, a promising strategy of whole-cell catalysis with ethanol pretreatment is proposed, which greatly improves the yield of 5-aminovalerate. Subsequently, the effects of ethanol pretreatment, substrate concentration, reaction temperature, pH value, metal ion additions and hydrogen peroxide addition on the whole-cell biocatalytic efficiency were investigated. Using 100 g/L of L-lysine hydrochloride as raw material, 50.62 g/L of 5-aminovalerate could be excellently produced via fed-batch bioconversion with the yield of 0.84 mol/mol. The results show that a fast, environmentally friendly and efficient production of 5-aminovalerate was established after introducing the engineered whole-cell biocatalysts. This strategy, combined with ethanol pretreatment, can not only greatly enhance the yield of 5-aminovalerate but also be applied to the biosynthesis of other valuable chemicals.
Highlights
The 5AVA production is closely related to the biological metabolism of L-lysine7. 5AVA is mainly synthetized through the coupled system of L-lys 2-monooxygenase (DavB) and 5-aminovaleramide amidohydrolase (DavA)[8]
Our previous studies have demonstrated that L-lys HCl is a better substrate to produce 5AVA10 and L-pipecolic acid (L-PA) than L-lys[29], respectively increasing the titer of 5AVA10 by 24% and L-PA29 by 21%
A green whole-cell biocatalytic production for the 5AVA was established in this work
Summary
The 5AVA production is closely related to the biological metabolism of L-lysine7. 5AVA is mainly synthetized through the coupled system of L-lys 2-monooxygenase (DavB) and 5-aminovaleramide amidohydrolase (DavA)[8]. Cheng et al reported that L-lys hydrochloride (L-lys HCl) could be oxidative decarboxylated by L-lys α-oxidase (RaiP) from Scomber japonicas to produce 5AVA in Escherichia coli (E. coli)[10] Based on these three basic synthetic routes converting L-lys to 5AVA, the three related bioproduction processes (i.e., microbial fermentation, enzymatic catalysis, and whole-cell methods) have been widely explored. In Cheng’s research, the addition of 4% (v/v) ethanol effectively enhanced the level of RaiP protein expression, which could increase the titer of 5AVA to 29.12 g/L10. Effective strategies for improving expression level of proteins were developed, include the optimization of the host strains, vector, culture medium and gene sequences, as well as the addition of ethanol[25]. Whole-cell biocatalysts CJ02RaiP exhibiting a better catalytic activity was achieved
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