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1.
Microb Cell Fact ; 19(1): 102, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32398078

RESUMO

BACKGROUND: Acetoin, especially the optically pure (3S)- or (3R)-enantiomer, is a high-value-added bio-based platform chemical and important potential pharmaceutical intermediate. Over the past decades, intense efforts have been devoted to the production of acetoin through green biotechniques. However, efficient and economical methods for the production of optically pure acetoin enantiomers are rarely reported. Previously, we systematically engineered the GRAS microorganism Corynebacterium glutamicum to efficiently produce (3R)-acetoin from glucose. Nevertheless, its yield and average productivity were still unsatisfactory for industrial bioprocesses. RESULTS: In this study, cellular carbon fluxes in the acetoin producer CGR6 were further redirected toward acetoin synthesis using several metabolic engineering strategies, including blocking anaplerotic pathways, attenuating key genes of the TCA cycle and integrating additional copies of the alsSD operon into the genome. Among them, the combination of attenuation of citrate synthase and inactivation of phosphoenolpyruvate carboxylase showed a significant synergistic effect on acetoin production. Finally, the optimal engineered strain CGS11 produced a titer of 102.45 g/L acetoin with a yield of 0.419 g/g glucose at a rate of 1.86 g/L/h in a 5 L fermenter. The optical purity of the resulting (3R)-acetoin surpassed 95%. CONCLUSION: To the best of our knowledge, this is the highest titer of highly enantiomerically enriched (3R)-acetoin, together with a competitive product yield and productivity, achieved in a simple, green processes without expensive additives or substrates. This process therefore opens the possibility to achieve easy, efficient, economical and environmentally-friendly production of (3R)-acetoin via microbial fermentation in the near future.


Assuntos
Acetoína/metabolismo , Corynebacterium glutamicum/metabolismo , Engenharia Metabólica/métodos , Técnicas de Cultura Celular por Lotes , Reatores Biológicos , Corynebacterium glutamicum/genética , Fermentação , Glucose/metabolismo , Redes e Vias Metabólicas , Óperon
2.
J Biotechnol ; 322: 29-32, 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-32653638

RESUMO

Over the past decade, 5-aminolevulinic acid (5-ALA) has been highlighted as a promising functional feed additive and immunomodulator for improving the general health, immune response, and resistance to disease of livestock and poultry. However, it is very costly to produce 5-ALA using conventional chemical synthesis methods. Classical microbial fermentation fulfills the criteria of environmental friendliness, but the unsatisfactory titers still hinder actual industrial production. This study aimed to develop a solid-state fermentation (SSF) process that can be used to efficiently enrich feed with 5-ALA at a low cost. First, the endogenous 5-ALA synthase was overexpressed in Saccharomyces cerevisiae via integrating a copy of HEM1 gene into the chromosome and introducing a multi-copy plasmid pRS416-HEM1 which constitutively overexpresses HEM1 gene. The resulting strain ScA3 was able to produce 63.82 mg/L 5-ALA in shake-flask fermentation. After process optimization, a titer of 225.63 mg/kg dry materials, exceeding the usual effective dosage reported in animal trials, was achieved within 48 h through SSF of 20 kg feed in a 90-L steel drum. To our knowledge, this is the first report on combining microbial 5-ALA production with SSF in feed processing, which will hopefully promote the application and popularization of 5-ALA in the feed industry.


Assuntos
Ácido Aminolevulínico/metabolismo , Ração Animal , Fermentação/genética , Saccharomyces cerevisiae , 5-Aminolevulinato Sintetase/genética , 5-Aminolevulinato Sintetase/metabolismo , Microbiologia Industrial/métodos , Plasmídeos/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
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