Abstract:Succinic acid, a dicarboxylic acid produced as an intermediate of the tricarboxylic acid (TCA) cycle, is one of the most important platform chemicals for the production of various high value-added derivatives. As traditional chemical synthesis processes suffer from nonrenewable resources and environment pollution, succinic acid biosynthesis has drawn increasing attention as a viable, more environmentally friendly alternative. To date, several metabolic engineering approaches have been utilized for constructing… Show more
“…For example, citric acid is used as the second carbon source by lactobacillus and can be converted into acetic acid and oxaloacetic acid by a citrate lyase, while the oxaloacetic acid can be further translated into pyruvic acid which is eventually reduced to lactic acid by the lactate dehydrogenase ( 42 ). In addition, in the oxidative branch pathway of the TCA cycle, oxaloacetate can also be converted into succinic acid through a serious of enzymes like aconitase, isocitrate dehydrogenase, and succinic acid can be further converted to fumarate by succinate dehydrogenase ( 43 ). The changes of total polyphenols as well as citric acid, succinic acid, lactic acid and oxalic acid contents were similar to our previous study ( 17 ), in which the contents of polyphenols and lactic acid increased, citric acid and succinic acid decreased, and oxalic acid showed no obvious changes after the Moringa oleifera leaves were fermented with Lactobacillus plantarum S35 .…”
IntroductionGamma-aminobutyric acid (GABA), one of the main active components in Moringa oleifera leaves, can be widely used to treat multiple diseases including inflammation.MethodsIn this study, the anti-inflammatory activity and the underlying anti-inflammatory mechanism of the GABA-enriched Moringa oleifera leaves fermentation broth (MLFB) were investigated on lipopolysaccharide (LPS)-induced RAW 264.7 cells model. The key active components changes like total flavonoids, total polyphenols and organic acid in the fermentation broth after fermentation was also analyzed.ResultsELISA, RT-qPCR and Western blot results indicated that MLFB could dose-dependently inhibit the secretions and intracellular expression levels of pro-inflammatory cytokines like 1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α). Furthermore, MLFB also suppressed the expressions of prostaglandin E2 (PGE2) and inducible nitric oxide synthase (iNOS). Moreover, the mRNA expressions of the key molecules like Toll-like receptor 4 (TLR-4) and nuclear factor (NF)-κB in the NF-κB signaling pathway were also restrained by MLFB in a dose-dependent manner. Besides, the key active components analysis result showed that the GABA, total polyphenols, and most organic acids like pyruvic acid, lactic acid as well as acetic acid were increased obviously after fermentation. The total flavonoids content in MLFB was still remained to be 32 mg/L though a downtrend was presented after fermentation.DiscussionOur results indicated that the MLFB could effectively alleviate LPS-induced inflammatory response by inhibiting the secretions of pro-inflammatory cytokines and its underlying mechanism might be associated with the inhibition of TLR-4/NF-κB inflammatory signaling pathway activation. The anti-inflammatory activity of MLFB might related to the relative high contents of GABA as well as other active constituents such as flavonoids, phenolics and organic acids in MLFB. Our study provides the theoretical basis for applying GABA-enriched Moringa oleifera leaves as a functional food ingredient in the precaution and treatment of chronic inflammatory diseases.
“…For example, citric acid is used as the second carbon source by lactobacillus and can be converted into acetic acid and oxaloacetic acid by a citrate lyase, while the oxaloacetic acid can be further translated into pyruvic acid which is eventually reduced to lactic acid by the lactate dehydrogenase ( 42 ). In addition, in the oxidative branch pathway of the TCA cycle, oxaloacetate can also be converted into succinic acid through a serious of enzymes like aconitase, isocitrate dehydrogenase, and succinic acid can be further converted to fumarate by succinate dehydrogenase ( 43 ). The changes of total polyphenols as well as citric acid, succinic acid, lactic acid and oxalic acid contents were similar to our previous study ( 17 ), in which the contents of polyphenols and lactic acid increased, citric acid and succinic acid decreased, and oxalic acid showed no obvious changes after the Moringa oleifera leaves were fermented with Lactobacillus plantarum S35 .…”
IntroductionGamma-aminobutyric acid (GABA), one of the main active components in Moringa oleifera leaves, can be widely used to treat multiple diseases including inflammation.MethodsIn this study, the anti-inflammatory activity and the underlying anti-inflammatory mechanism of the GABA-enriched Moringa oleifera leaves fermentation broth (MLFB) were investigated on lipopolysaccharide (LPS)-induced RAW 264.7 cells model. The key active components changes like total flavonoids, total polyphenols and organic acid in the fermentation broth after fermentation was also analyzed.ResultsELISA, RT-qPCR and Western blot results indicated that MLFB could dose-dependently inhibit the secretions and intracellular expression levels of pro-inflammatory cytokines like 1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α). Furthermore, MLFB also suppressed the expressions of prostaglandin E2 (PGE2) and inducible nitric oxide synthase (iNOS). Moreover, the mRNA expressions of the key molecules like Toll-like receptor 4 (TLR-4) and nuclear factor (NF)-κB in the NF-κB signaling pathway were also restrained by MLFB in a dose-dependent manner. Besides, the key active components analysis result showed that the GABA, total polyphenols, and most organic acids like pyruvic acid, lactic acid as well as acetic acid were increased obviously after fermentation. The total flavonoids content in MLFB was still remained to be 32 mg/L though a downtrend was presented after fermentation.DiscussionOur results indicated that the MLFB could effectively alleviate LPS-induced inflammatory response by inhibiting the secretions of pro-inflammatory cytokines and its underlying mechanism might be associated with the inhibition of TLR-4/NF-κB inflammatory signaling pathway activation. The anti-inflammatory activity of MLFB might related to the relative high contents of GABA as well as other active constituents such as flavonoids, phenolics and organic acids in MLFB. Our study provides the theoretical basis for applying GABA-enriched Moringa oleifera leaves as a functional food ingredient in the precaution and treatment of chronic inflammatory diseases.
With growing concerns about environmental issues and sustainable economy, bioproduction of chemicals utilizing microbial cell factories provides an eco-friendly alternative to current petro-based processes. Creating high-performance strains (with high titer, yield, and productivity) through metabolic engineering strategies is critical for cost-competitive production. Commonly, it is inevitable to fine-tuning or rewire the endogenous or heterologous pathways in such processes. As an important pathway involved in the synthesis of many kinds of chemicals, the potential of the glyoxylate cycle in metabolic engineering has been studied extensively these years. Here, we review the metabolic regulation of the glyoxylate cycle and summarize recent achievements in microbial production of chemicals through tuning of the glyoxylate cycle, with a focus on studies implemented in model microorganisms. Also, future prospects for bioproduction of glyoxylate cycle-related chemicals are discussed.
“…Therefore, much attention has been paid to the biosynthesis of SA and a lot of relevant studies have been conducted [ 10 ]. Compared to chemical processing, biosynthesis has a wider range of raw materials and lower costs [ 11 ]. Fig.…”
Succinic acid (SA) is an intermediate product of the tricarboxylic acid cycle (TCA) and is one of the most significant platform chemicals for the production of various derivatives with high added value. Due to the depletion of fossil raw materials and the demand for eco-friendly energy sources, SA biosynthesis from renewable energy sources is gaining attention for its environmental friendliness. This review comprehensively analyzes strategies for the bioconversion of lignocellulose to SA based on the lignocellulose pretreatment processes and cellulose hydrolysis and fermentation principles and highlights the research progress on acid production and SA utilization under different microbial culture conditions. In addition, the fermentation efficiency of different microbial strains for the production of SA and the main challenges were analyzed. The future application directions of SA derivatives were pointed out. It is expected that this research will provide a reference for the optimization of SA production from lignocellulose.
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