Impact of the cultivation strategy on resveratrol production from glucose in engineered Corynebacterium glutamicum

The health benefits of polyphenols such as stilbenes and flavonoids for humans are increasingly attracting attention. Resveratrol is awell-characterized naturally-occurring stilbeneandpotentanti-oxidant, which isused as food supplement and cosmetic ingredient. Several microorganisms including Corynebacterium glutamicum were engineered for resveratrol production from glucose. Based on the cultivation of a resveratrol-producing C. glutamicum strain in shake flasks, different strategies for improving production under controlled conditions at bioreactor scale were tested. To this end, different cultivation parameters including substrate concentration and operation modes (batch and fed-batch) were evaluated. Whereas the highest biomass concentration was observed during fed-batch fermentation, the maximum resveratrol production was achieved in batch mode. The maximal titer obtained was 12 mg L−1 of resveratrol without the addition of the fatty acid synthase inhibitor cerulenin, which was previously shown to be crucial for production with C. glutamicum. The specific growth rate duringproductionseemstohaveasignificanteffectinresveratrolproductionandapparentlylowspecificgrowth rates may redirect the metabolic bottleneck from p-coumaric acid formation to malonyl-CoA or ATP availability. We also show that high oxygen concentrations in the bioreactor negatively affected the obtained resveratrol titerswithC.glutamicum,whichismost likelydueto thestrongtendency ofresveratrol tooxidizeoroligomerize. Thus, up-scaling of the resveratrol production process is technically challenging and individual process parameters have to be optimized cautiously.We would like to thank the European Union Framework Program 7 "BacHBerry" (www.bachberry.eu), Project No. FP7- 613793 for financial support, the PortugueseFoundation forScience andTechnology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 − Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Engineering Corynebacterium glutamicum as a designer-bug for the bio-based production of chemical building blocks and biofuel

The restriction of fossil raw materials, as well as the impact of their use on the environment heads to a global social and economic crisis. Therefore, a strong political and technical interest arises for the replacement of petroleum-derived chemicals and fuels by such derived from biomass. The well-known amino acid producer Corynebacterium glutamicum was used in the last decade for the bio-based production of building block chemicals, as well as for biofuels. In this work, C. glutamicum was engineered for efficient aerobic production of pyruvate from glucose leading to both significantly decreased by-product formation, and extensively increased pyruvate accumulation. Since pyruvate is a central precursor for the 1,4-dicarboxylic acids malate, fumarate and succinate, C. glutamicum ELB P was further used as a basis for the production of these compounds. At first, a fermentation system was established leading to succinate formation as major product of C. glutamicum ELB P under oxygen deprivation conditions. To investigate long-term succinate production, a tri-phasic fed-batch fermentation system was established, including an aerobic growth phase on acetate for biomass formation. This was followed by a self-induced microaerobic phase at the end of growth, using minimal aeration. At last an anaerobic production phase on glucose was established in the same bioreactor by gassing with CO2. Inactivation of succinate dehydrogenase (SDH) or fumarase (Fum) in C. glutamicum ELB P should interrupt the reductive branch of tricarboxylic acid cycle for the anaerobic production of fumarate and malate, respectively. However, deletion of the corresponding genes did not lead to satisfying production of fumarate or malate. Last, based on an aerobic 2-ketoisovalerate producing strain, a C. glutamicum mutant was successfully engineered for the production of isobutanol from glucose under oxygen deprivation conditions. Weitere Artikel, die für diese Dissertation verwendet wurden, sind erschienen in: Applied microbiology and biotechnology, 2012, Vol. 94, Heft 2, S. 449-459 (DOI 10.1007/s00253-011-3843-9) URL: http://link.springer.com/article/10.1007%2Fs00253-011-3843-9; Microbial Biotechnology, 2012, (DOI: 10.1111/1751-7915.12013) URL: http://onlinelibrary.wiley.com/doi/10.1111/1751-7915.12013/abstrac

Bio-based production of organic acids with Corynebacterium glutamicum

The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, l-and d-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers. Funding Information Work in the laboratories of the authors was supported by the Fachagentur Nachwachsende Rohstoffe (FNR) of the Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV; FNR Grants 220-095-08A and 220-095-08D; Bio-ProChemBB project, ERA-IB programme), by the Deutsche Bundesstiftung Umwelt (DBU Grant AZ13040/05) and the Evonik Degussa AG

Corynebacterium glutamicum Tailored for Efficient Isobutanol Production ▿ †

We recently engineered Corynebacterium glutamicum for aerobic production of 2-ketoisovalerate by inactivation of the pyruvate dehydrogenase complex, pyruvate:quinone oxidoreductase, transaminase B, and additional overexpression of the ilvBNCD genes, encoding acetohydroxyacid synthase, acetohydroxyacid isomeroreductase, and dihydroxyacid dehydratase. Based on this strain, we engineered C. glutamicum for the production of isobutanol from glucose under oxygen deprivation conditions by inactivation of l-lactate and malate dehydrogenases, implementation of ketoacid decarboxylase from Lactococcus lactis, alcohol dehydrogenase 2 (ADH2) from Saccharomyces cerevisiae, and expression of the pntAB transhydrogenase genes from Escherichia coli. The resulting strain produced isobutanol with a substrate-specific yield (YP/S) of 0.60 ± 0.02 mol per mol of glucose. Interestingly, a chromosomally encoded alcohol dehydrogenase rather than the plasmid-encoded ADH2 from S. cerevisiae was involved in isobutanol formation with C. glutamicum, and overexpression of the corresponding adhA gene increased the YP/S to 0.77 ± 0.01 mol of isobutanol per mol of glucose. Inactivation of the malic enzyme significantly reduced the YP/S, indicating that the metabolic cycle consisting of pyruvate and/or phosphoenolpyruvate carboxylase, malate dehydrogenase, and malic enzyme is responsible for the conversion of NADH+H+ to NADPH+H+. In fed-batch fermentations with an aerobic growth phase and an oxygen-depleted production phase, the most promising strain, C. glutamicum ΔaceE Δpqo ΔilvE ΔldhA Δmdh(pJC4ilvBNCD-pntAB)(pBB1kivd-adhA), produced about 175 mM isobutanol, with a volumetric productivity of 4.4 mM h−1, and showed an overall YP/S of about 0.48 mol per mol of glucose in the production phase

A Novel Efficient L-Lysine Exporter Identified by Functional Metagenomics

Lack of active export system often limits the industrial bio-based production processes accumulating the intracellular product and hence complexing the purification steps. L-lysine, an essential amino acid, is produced biologically in quantities exceeding two million tons per year; yet, L-lysine production is challenged by efficient export system at high titers during fermentation. To address this issue, new exporter candidates for efficient efflux of L-lysine are needed. Using metagenomic functional selection, we identified 58 genes encoded on 28 unique metagenomic fragments from cow gut microbiome library that improved L-lysine tolerance. These genes include a novel L-lysine transporter, belonging to a previously uncharacterized EamA superfamily, which is further in vivo characterized as L-lysine exporter using Xenopus oocyte expression system as well as Escherichia coli host. This novel exporter improved L-lysine tolerance in E. coli by 40% and enhanced yield, titer, and the specific production of L-lysine in an industrial Corynebacterium glutamicum strain by 7.8%, 9.5%, and 12%, respectively. Our approach allows the sequence-independent discovery of novel exporters and can be deployed to increase titers and productivity of toxicity-limited bioprocesses