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Metabolic Engineering Communications

Hery Rabeharindranto, Sara Castaño-Cerezo, Thomas Lautier, Luis F Garcia-Alles, Christian Treitz, Andreas Tholey, Gilles Truan
Spatial clustering of enzymes has proven an elegant approach to optimize metabolite transfer between enzymes in synthetic metabolic pathways. Among the multiple methods used to promote colocalisation, enzyme fusion is probably the simplest. Inspired by natural systems, we have explored the metabolic consequences of spatial reorganizations of the catalytic domains of Xanthophyllomyces dendrorhous carotenoid enzymes produced in Saccharomyces cerevisiae . Synthetic genes encoding bidomain enzymes composed of CrtI and CrtB domains from the natural CrtYB fusion were connected in the two possible orientations, using natural and synthetic linkers...
June 2019: Metabolic Engineering Communications
Yunchang Xie, Qinglian Li, Xiangjing Qin, Jianhua Ju, Junying Ma
Three atypical regulatory genes, hmtABD have been discovered within the himastatin biosynthetic gene cluster (BGC) in Streptomyces hygroscopicus ATCC 53653 and the roles of their products have been identified. HmtA and HmtD do not show any structurally distinct features characteristic of regulatory function yet were shown to play important repressive and stimulatory roles, respectively, related to himastatin biosynthesis. HmtB encodes a conserved acetylglutamate kinase; new member of this family serves as repressor of secondary metabolism...
June 2019: Metabolic Engineering Communications
Jie Zhu, Cory Schwartz, Ian Wheeldon
In metabolic engineering, most available pathway engineering strategies aim to control enzyme expression by making changes at the transcriptional level with an underlying assumption that translation and functional expression follow suit. In this work, we engineer expression of a key reaction step in medium chain ester biosynthesis that does not follow this common assumption. The native Saccharomyces cerevisiae alcohol acyltransferses Eeb1 and Eht1 condense acyl-CoAs with ethanol to produce the corresponding ester, a reaction that is rate limiting in engineering ester biosynthesis pathways...
June 2019: Metabolic Engineering Communications
Wei Niu, Levi Kramer, Joshua Mueller, Kun Liu, Jiantao Guo
1,2-propanediol (1,2-PDO) is an industrial chemical with a broad range of applications, such as the production of alkyd and unsaturated polyester resins. It is currently produced as a racemic mixture from nonrenewable petroleum-based feedstocks. We have reported a novel artificial pathway for the biosynthesis of 1,2-PDO via lactic acid isomers as the intermediates. The pathway circumvents the cytotoxicity issue caused by methylglyoxal intermediate in the naturally existing pathway. Successful E. coli bioconversion of lactic acid to 1,2-PDO was shown in previous report...
June 2019: Metabolic Engineering Communications
Inese Strazdina, Elina Balodite, Zane Lasa, Reinis Rutkis, Nina Galinina, Uldis Kalnenieks
Ability to ferment in the presence of oxygen increases the robustness of bioprocesses and opens opportunity for novel industrial setups. The ethanologenic bacterium Zymomonas mobilis performs rapid and efficient anaerobic ethanol fermentation, yet its respiratory NADH dehydrogenase (Ndh)-deficient strain ( ndh- ) is known to produce ethanol with high yield also under oxic conditions. Compared to the wild type, it has a lower rate of oxygen consumption, and an increased expression of the respiratory lactate dehydrogenase (Ldh)...
December 2018: Metabolic Engineering Communications
Hoang V Dinh, Zachary A King, Bernhard O Palsson, Adam M Feist
Conversion of renewable biomass to useful molecules in microbial cell factories can be approached in a rational and systematic manner using constraint-based reconstruction and analysis. Filtering for high confidence in silico designs is critical because in vivo construction and testing of strains is expensive and time consuming. As such, a workflow was devised to analyze the robustness of growth-coupled production when considering the biosynthetic costs of the proteome and variability in enzyme kinetic parameters using a genome-scale model of metabolism and gene expression (ME-model)...
December 2018: Metabolic Engineering Communications
Mara Reifenrath, Maren Bauer, Mislav Oreb, Eckhard Boles
Mandelic acid is an important aromatic fine chemical and is currently mainly produced via chemical synthesis. Recently, mandelic acid production was achieved by microbial fermentations using engineered Escherichia coli and Saccharomyces cerevisiae expressing heterologous hydroxymandelate synthases ( hmaS ). The best-performing strains carried a deletion of the gene encoding the first enzyme of the tyrosine biosynthetic pathway and therefore were auxotrophic for tyrosine. This was necessary to avoid formation of the competing intermediate hydroxyphenylpyruvate, the preferred substrate for HmaS, which would have resulted in the predominant production of hydroxymandelic acid...
December 2018: Metabolic Engineering Communications
Suvi Santala, Elena Efimova, Ville Santala
For improving the microbial production of fuels and chemicals, gene knock-outs and overexpression are routinely applied to intensify the carbon flow from substrate to product. However, their possibilities in dynamic control of the flux between the biomass and product synthesis are limited, whereas dynamic metabolic switches can be used for optimizing the distribution of carbon and resources. The production of single cell oils is especially challenging, as the synthesis is strictly regulated, competes directly with biomass, and requires defined conditions, such as nitrogen limitation...
December 2018: Metabolic Engineering Communications
Sandra Moser, Gernot A Strohmeier, Erich Leitner, Thomas J Plocek, Koenraad Vanhessche, Harald Pichler
The triterpenoid (+)-ambrein is a natural precursor for (-)-ambrox, which constitutes one of the most sought-after fragrances and fixatives for the perfume industry. (+)-Ambrein is a major component of ambergris, an intestinal excretion of sperm whales that is found only serendipitously. Thus, the demand for (-)-ambrox is currently mainly met by chemical synthesis. A recent study described for the first time the applicability of an enzyme cascade consisting of two terpene cyclases, namely squalene-hopene cyclase from Alicyclobacillus acidocaldarius ( Aa SHC D377C) and tetraprenyl-β-curcumene cyclase from Bacillus megaterium ( Bme TC) for in vitro (+)-ambrein production starting from squalene...
December 2018: Metabolic Engineering Communications
Jong-Won Lee, Narayan P Niraula, Cong T Trinh
Alkenes are industrially important platform chemicals with broad applications. In this study, we report a direct microbial biosynthesis of terminal alkenes from fermentable sugars by harnessing a P450 fatty acid (FA) decarboxylase from Macrococcus caseolyticus (OleTMC ). We first characterized OleTMC and demonstrated its in vitro H2 O2 -independent activities towards linear C10:0-C18:0 FAs, with higher activity for C16:0-C18:0 FAs. Next, we engineered a de novo alkene biosynthesis pathway, consisting of OleTMC and an engineered E...
December 2018: Metabolic Engineering Communications
Ulf W Liebal, Lars M Blank, Birgitta E Ebert
Microbial carbon dioxide assimilation and conversion to chemical platform molecules has the potential to be developed as economic, sustainable processes. The carbon dioxide assimilation can proceed by a variety of natural pathways and recently even synthetic CO2 fixation routes have been designed. Early assessment of the performance of the different carbon fixation alternatives within biotechnological processes is desirable to evaluate their potential. Here we applied stoichiometric metabolic modeling based on physiological and process data to evaluate different process variants for the conversion of C1 carbon compounds to the industrial relevant platform chemical succinic acid...
December 2018: Metabolic Engineering Communications
Xiaojing Jia, Robert M Kelly, Yejun Han
( R )-acetoin is a four-carbon platform compound used as the precursor for synthesizing novel optically active materials. Ethylene glycol (EG) is a large-volume two-carbon commodity chemical used as the anti-freezing agent and building-block molecule for various polymers. Currently established microbial fermentation processes for converting monosaccharides to either ( R )-acetoin or EG are plagued by the formation of undesirable by-products. We show here that a cell-free bioreaction scheme can generate enantiomerically pure acetoin and EG as co-products from biomass-derived D-xylose...
December 2018: Metabolic Engineering Communications
Amanda M Williams-Rhaesa, Gabriel M Rubinstein, Israel M Scott, Gina L Lipscomb, Farris L Poole Ii, Robert M Kelly, Michael W W Adams
Caldicellulosiruptor bescii is an extremely thermophilic cellulolytic bacterium with great potential for consolidated bioprocessing of renewable plant biomass. Since it does not natively produce ethanol, metabolic engineering is required to create strains with this capability. Previous efforts involved the heterologous expression of the gene encoding a bifunctional alcohol dehydrogenase, AdhE, which uses NADH as the electron donor to reduce acetyl-CoA to ethanol. Acetyl-CoA produced from sugar oxidation also generates reduced ferredoxin but there is no known pathway for the transfer of electrons from reduced ferredoxin to NAD in C...
December 2018: Metabolic Engineering Communications
Robert F Standaert, Richard J Giannone, Joshua K Michener
Metabolic pathway assembly typically involves the expression of enzymes from multiple organisms in a single heterologous host. Ensuring that each enzyme functions effectively can be challenging, since many potential factors can disrupt proper pathway flux. Here, we compared the performance of two enzyme homologs in a pathway engineered to allow Escherichia coli to grow on 4-hydroxybenzoate (4-HB), a byproduct of lignocellulosic biomass deconstruction. Single chromosomal copies of the 4-HB 3-monooxygenase genes pobA and praI , from Pseudomonas putida KT2440 and Paenibacillus sp...
June 2018: Metabolic Engineering Communications
Johan O Westman, Jonas Nyman, Richard M A Manara, Valeria Mapelli, Carl Johan Franzén
Yeast flocculation is the reversible formation of multicellular complexes mediated by lectin-like cell wall proteins binding to neighbouring cells. Strong flocculation can improve the inhibitor tolerance and fermentation performance of yeast cells in second generation bioethanol production. The strength of flocculation increases with the size of the flocculation protein and is strain dependent. However, the large number of internal repeats in the sequence of FLO1 from Saccharomyces cerevisiae S288c makes it difficult to recombinantly express the gene to its full length...
June 2018: Metabolic Engineering Communications
Sai Zhang, Yaodong He, Biswarup Sen, Xiaohong Chen, Yunxuan Xie, Jay D Keasling, Guangyi Wang
The unicellular heterotrophic thraustochytrids are attractive candidates for commercial polyunsaturated fatty acids (PUFA) production. However, the reactive oxygen species (ROS) generated in their aerobic fermentation process often limits their PUFA titer. Yet, the specific mechanisms of ROS involvement in the crosstalk between oxidative stress and intracellular lipid synthesis remain poorly described. Metabolic engineering to improve the PUFA yield in thraustochytrids without compromising growth is an important aspect of economic feasibility...
June 2018: Metabolic Engineering Communications
Raphael Ferreira, Paulo Gonçalves Teixeira, Michael Gossing, Florian David, Verena Siewers, Jens Nielsen
Triacylglycerols (TAGs) are valuable versatile compounds that can be used as metabolites for nutrition and health, as well as feedstocks for biofuel production. Although Saccharomyces cerevisiae is the favored microbial cell factory for industrial production of biochemicals, it does not produce large amounts of lipids and TAGs comprise only ~1% of its cell dry weight. Here, we engineered S. cerevisiae to reorient its metabolism for overproduction of TAGs, by regulating lipid droplet associated-proteins involved in TAG synthesis and hydrolysis...
June 2018: Metabolic Engineering Communications
Ramesh K Jha, Jeremy M Bingen, Christopher W Johnson, Theresa L Kern, Payal Khanna, Daniel S Trettel, Charlie E M Strauss, Gregg T Beckham, Taraka Dale
Robust fluorescence-based biosensors are emerging as critical tools for high-throughput strain improvement in synthetic biology. Many biosensors are developed in model organisms where sophisticated synthetic biology tools are also well established. However, industrial biochemical production often employs microbes with phenotypes that are advantageous for a target process, and biosensors may fail to directly transition outside the host in which they are developed. In particular, losses in sensitivity and dynamic range of sensing often occur, limiting the application of a biosensor across hosts...
June 2018: Metabolic Engineering Communications
Kaushik Raj, Siavash Partow, Kevin Correia, Anna N Khusnutdinova, Alexander F Yakunin, Radhakrishnan Mahadevan
Adipic acid is an important industrial chemical used in the synthesis of nylon-6,6. The commercial synthesis of adipic acid uses petroleum-derived benzene and releases significant quantities of greenhouse gases. Biocatalytic production of adipic acid from renewable feedstocks could potentially reduce the environmental damage and eliminate the need for fossil fuel precursors. Recently, we have demonstrated the first enzymatic hydrogenation of muconic acid to adipic acid using microbial enoate reductases (ERs) - complex iron-sulfur and flavin containing enzymes...
June 2018: Metabolic Engineering Communications
Weihua Wu, Fang Liu, Ryan W Davis
Recent studies have revealed that caryophyllene and its stereoisomers not only exhibit multiple biological activities but also have desired properties as renewable candidates for ground transportation and jet fuel applications. This study presents the first significant production of caryophyllene and caryolan-1-ol by an engineered E. coli with heterologous expression of mevalonate pathway genes with a caryophyllene synthase and a caryolan-1-ol synthase. By optimizing metabolic flux and fermentation parameters, the engineered strains yielded 449 mg/L of total terpene, including 406 mg/L sesquiterpene with 100 mg/L caryophyllene and 10 mg/L caryolan-1-ol...
June 2018: Metabolic Engineering Communications
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