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Metabolic Engineering

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https://www.readbyqxmd.com/read/28438645/releasing-the-potential-power-of-terpene-synthases-by-a-robust-precursor-supply-platform
#1
Guangkai Bian, Yichao Han, Anwei Hou, Yujie Yuan, Xinhua Liu, Zixin Deng, Tiangang Liu
Terpenoids represent the largest family of natural products. Their structural diversity is largely due to variable skeletons generated by terpene synthases. However, terpene skeletons found in nature are much more than those generated from known terpene synthases. Most promiscuous terpene synthases (i.e. those that can generate more than one product) have not been comprehensively characterised. Here, we first demonstrated that the promiscuous terpene synthases can produce more variable terpenoids in vivo by converting precursor polyisoprenoid diphosphates of different lengths (C10, C15, C20, C25)...
April 21, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28433737/exploring-biochemical-pathways-for-mono-ethylene-glycol-meg-synthesis-from-synthesis-gas
#2
M Ahsanul Islam, Noushin Hadadi, Meric Ataman, Vassily Hatzimanikatis, Gregory Stephanopoulos
Mono-ethylene glycol (MEG) is an important petrochemical with widespread use in numerous consumer products. The current industrial MEG-production process relies on non-renewable fossil fuel-based feedstocks, such as petroleum, natural gas, and naphtha; hence, it is useful to explore alternative routes of MEG-synthesis from gases as they might provide a greener and more sustainable alternative to the current production methods. Technologies of synthetic biology and metabolic engineering of microorganisms can be deployed for the expression of new biochemical pathways for MEG-synthesis from gases, provided that such promising alternative routes are first identified...
April 19, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28414174/iterative-integration-of-multiple-copy-pathway-genes-in-yarrowia-lipolytica-for-heterologous-%C3%AE-carotene-production
#3
Shuliang Gao, Yangyang Tong, Li Zhu, Mei Ge, Yian Zhang, Daijie Chen, Yu Jiang, Sheng Yang
β-Carotene is a terpenoid molecule with high hydrophobicity that is often used as an additive in foods and feed. Previous work has demonstrated the heterologous biosynthesis of β-carotene from an intrinsic high flux of acetyl-CoA in 12 steps through 11 genes in Yarrowia lipolytica. Here, an efficient biosynthetic pathway capable of producing 100-fold more β-carotene than the baseline construct was generated using strong promoters and multiple gene copies for each of the 12 steps. Using fed-batch fermentation with an optimized medium, the engineered pathway could produce 4g/L β-carotene, which was stored in lipid droplets within engineered Y...
April 13, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28400330/metabolomics-driven-approach-to-solving-a-coa-imbalance-for-improved-1-butanol-production-in-escherichia-coli
#4
Toshiyuki Ohtake, Sammy Pontrelli, Walter A Laviña, James C Liao, Sastia P Putri, Eiichiro Fukusaki
High titer 1-butanol production in Escherichia coli has previously been achieved by overexpression of a modified clostridial 1-butanol production pathway and subsequent deletion of native fermentation pathways. This strategy couples growth with production as 1-butanol pathway offers the only available terminal electron acceptors required for growth in anaerobic conditions. With further inclusion of other well-established metabolic engineering principles, a titer of 15g/L has been obtained. In achieving this titer, many currently existing strategies have been exhausted, and 1-butanol toxicity level has been surpassed...
April 8, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28400329/deletion-of-type-i-glutamine-synthetase-deregulates-nitrogen-metabolism-and-increases-ethanol-production-in-clostridium-thermocellum
#5
Thomas Rydzak, David Garcia, David M Stevenson, Margaret Sladek, Dawn M Klingeman, Evert K Holwerda, Daniel Amador-Noguez, Steven D Brown, Adam M Guss
Clostridium thermocellum rapidly deconstructs cellulose and ferments resulting hydrolysis products into ethanol and other products, and is thus a promising platform organism for the development of cellulosic biofuel production via consolidated bioprocessing. While recent metabolic engineering strategies have targeted eliminating canonical fermentation products (acetate, lactate, formate, and H2), C. thermocellum also secretes amino acids, which has limited ethanol yields in engineered strains to approximately 70% of the theoretical maximum...
April 8, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28396036/coordination-of-metabolic-pathways-enhanced-carbon-conservation-in-1-3-propanediol-production-by-coupling-with-optically-pure-lactate-biosynthesis
#6
Bo Xin, Fei Tao, Yu Wang, Hongyu Liu, Cuiqing Ma, Ping Xu
Metabolic engineering has emerged as a powerful tool for bioproduction of both fine and bulk chemicals. The natural coordination among different metabolic pathways contributes to the complexity of metabolic modification, which hampers the development of biorefineries. Herein, the coordination between the oxidative and reductive branches of glycerol metabolism was rearranged in Klebsiella oxytoca to improve the 1,3-propanediol production. After deliberating on the product value, carbon conservation, redox balance, biological compatibility and downstream processing, the lactate-producing pathway was chosen for coupling with the 1,3-propanediol-producing pathway...
April 7, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28392294/a-systematic-optimization-of-medium-chain-fatty-acid-biosynthesis-via-the-reverse-beta-oxidation-cycle-in-escherichia-coli
#7
Junjun Wu, Xia Zhang, Xiudong Xia, Mingsheng Dong
Medium-chain fatty acids (MCFAs, 6-10 carbons) are valuable precursors to many industrial biofuels and chemicals, recently engineered reversal of the β-oxidation (r-BOX) cycle has been proposed as a potential platform for efficient synthesis of MCFAs. Previous studies have made many exciting achievements on functionally characterizing four core enzymes of this r-BOX cycle. However, the information about bottleneck nodes in this cycle is elusive. Here, a quantitative assessment of the inherent limitations of this cycle was conducted to capitalize on its potential...
April 7, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28390749/metabolic-engineering-of-escherichia-coli-for-the-production-of-four-five-and-six-carbon-lactams
#8
Tong Un Chae, Yoo-Sung Ko, Kyu-Sang Hwang, Sang Yup Lee
Microbial production of chemicals and materials from renewable sources is becoming increasingly important for sustainable chemical industry. Here, we report construction of a new and efficient platform metabolic pathway for the production of four-carbon (butyrolactam), five-carbon (valerolactam) and six-carbon (caprolactam) lactams. This pathway uses ω-amino acids as precursors and comprises two steps. Activation of ω-amino acids catalyzed by the Clostridium propionicum β-alanine CoA transferase (Act) followed by spontaneous cyclization...
April 5, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28389395/high-throughput-enzyme-screening-platform-for-the-ipp-bypass-mevalonate-pathway-for-isopentenol-production
#9
Aram Kang, Corey W Meadows, Nicolas Canu, Jay D Keasling, Taek Soon Lee
Isopentenol (or isoprenol, 3-methyl-3-buten-1-ol) is a drop-in biofuel and a precursor for commodity chemicals such as isoprene. Biological production of isopentenol via the mevalonate pathway has been optimized extensively in Escherichia coli, yielding 70% of its theoretical maximum. However, high ATP requirements and isopentenyl diphosphate (IPP) toxicity pose immediate challenges for engineering bacterial strains to overproduce commodities utilizing IPP as an intermediate. To overcome these limitations, we developed an "IPP-bypass" isopentenol pathway using the promiscuous activity of a mevalonate diphosphate decarboxylase (PMD) and demonstrated improved performance under aeration-limited conditions...
April 5, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28389394/kinetically-accessible-yield-kay-for-redirection-of-metabolism-to-produce-exo-metabolites
#10
Jimmy G Lafontaine Rivera, Matthew K Theisen, Po-Wei Chen, James C Liao
The product formation yield (product formed per unit substrate consumed) is often the most important performance indicator in metabolic engineering. Until now, the actual yield cannot be predicted, but it can be bounded by its maximum theoretical value. The maximum theoretical yield is calculated by considering the stoichiometry of the pathways and cofactor regeneration involved. Here we found that in many cases, dynamic stability becomes an issue when excessive pathway flux is drawn to a product. This constraint reduces the yield and renders the maximal theoretical yield too loose to be predictive...
April 5, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28389396/robust-identification-of-metabolic-control-for-microbial-l-methionine-production-following-an-easy-to-use-puristic-approach
#11
A Teleki, M Rahnert, O Bungart, B Gann, I Ochrombel, R Takors
The identification of promising metabolic engineering targets is a key issue in metabolic control analysis (MCA). Conventional approaches make intensive use of model-based studies, such as exploiting post-pulse metabolic dynamics after proper perturbation of the microbial system. Here, we present an easy-to-use, purely data-driven approach, defining pool efflux capacities (PEC) for identifying reactions that exert the highest flux control in linear pathways. Comparisons with linlog-based MCA and data-driven substrate elasticities (DDSE) showed that similar key control steps were identified using PEC...
April 4, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28377275/phosphoketolase-overexpression-increases-biomass-and-lipid-yield-from-methane-in-an-obligate-methanotrophic-biocatalyst
#12
Calvin A Henard, Holly K Smith, Michael T Guarnieri
Microbial conversion of methane to high-value bio-based fuels, chemicals, and materials offers a path to mitigate GHG emissions and valorize this abundant-yet -underutilized carbon source. In addition to fermentation optimization strategies, rational methanotrophic bacterial strain engineering offers a means to reach industrially relevant titers, carbon yields, and productivities of target products. The phosphoketolase pathway functions in heterofermentative bacteria where carbon flux through two sugar catabolic pathways to mixed acids (lactic acid and acetic acid) increases cellular ATP production...
April 2, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28363762/an-integrated-network-analysis-reveals-that-nitric-oxide-reductase-prevents-metabolic-cycling-of-nitric-oxide-by-pseudomonas-aeruginosa
#13
Jonathan L Robinson, Jacob M Jaslove, Allison M Murawski, Christopher H Fazen, Mark P Brynildsen
Nitric oxide (NO) is a chemical weapon within the arsenal of immune cells, but is also generated endogenously by different bacteria. Pseudomonas aeruginosa are pathogens that contain an NO-generating nitrite (NO2(-)) reductase (NirS), and NO has been shown to influence their virulence. Interestingly, P. aeruginosa also contain NO dioxygenase (Fhp) and nitrate (NO3(-)) reductases, which together with NirS provide the potential for NO to be metabolically cycled (NO→NO3(-)→NO2(-)→NO). Deeper understanding of NO metabolism in P...
March 29, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28359705/manipulation-of-ges-and-erg20-for-geraniol-overproduction-in-saccharomyces-cerevisiae
#14
Guo-Zhen Jiang, Ming-Dong Yao, Ying Wang, Liang Zhou, Tian-Qing Song, Hong Liu, Wen-Hai Xiao, Ying-Jin Yuan
Manipulation of monoterpene synthases to maximize flux towards targeted products from GPP (geranyl diphosphate) is the main challenge for heterologous monoterpene overproduction, in addition to cell toxicity from compounds themselves. In our study, by manipulation of the key enzymes geraniol synthase (GES) and farnesyl diphosphate synthase (Erg20), geraniol (a valuable acyclic monoterpene alcohol) overproduction was achieved in Saccharomyces cerevisiae with truncated 3-hydroxy-3-methylglutaryl-coenzyme reductase (tHMGR) and isopentenyl diphosphate isomerase (IDI1) overexpressed...
March 27, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28356220/ethyl-acetate-production-by-the-elusive-alcohol-acetyltransferase-from-yeast
#15
Aleksander J Kruis, Mark Levisson, Astrid E Mars, Max van der Ploeg, Fernando Garcés Daza, Valeria Ellena, Servé W M Kengen, John van der Oost, Ruud A Weusthuis
Ethyl acetate is an industrially relevant ester that is currently produced exclusively through unsustainable processes. Many yeasts are able to produce ethyl acetate, but the main responsible enzyme has remained elusive, hampering the engineering of novel production strains. Here we describe the discovery of a new enzyme (Eat1) from the yeast Wickerhamomyces anomalus that resulted in high ethyl acetate production when expressed in Saccharomyces cerevisiae and Escherichia coli. Purified Eat1 showed alcohol acetyltransferase activity with ethanol and acetyl-CoA...
March 27, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28342964/establishing-a-novel-biosynthetic-pathway-for-the-production-of-3-4-dihydroxybutyric-acid-from-xylose-in-escherichia-coli
#16
Jia Wang, Xiaolin Shen, Rachit Jain, Jian Wang, Qipeng Yuan, Yajun Yan
3-Hydroxy-γ-butyrolactone (3HBL) is an attractive building block owing to its broad applications in pharmaceutical industry. Currently, 3HBL is commercially produced by chemical routes using petro-derived carbohydrates, which involves hazardous materials and harsh processing conditions. Only one biosynthetic pathway has been reported for synthesis of 3HBL and its hydrolyzed form 3,4-dihydroxybutyric acid (3,4-DHBA) using glucose and glycolic acid as the substrates and coenzyme A as the activator, which involves multiple steps (>10 steps) and suffers from low productivity and yield...
March 23, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28323063/lipid-engineering-reveals-regulatory-roles-for-membrane-fluidity-in-yeast-flocculation-and-oxygen-limited-growth
#17
Daniel Degreif, Tristan de Rond, Adam Bertl, Jay D Keasling, Itay Budin
Cells modulate lipid metabolism in order to maintain membrane homeostasis. Here we use a metabolic engineering approach to manipulate the stoichiometry of fatty acid unsaturation, a regulator of cell membrane fluidity, in Saccharomyces cerevisiae. Unexpectedly, reduced lipid unsaturation triggered cell-cell adhesion (flocculation), a phenomenon characteristic of industrial yeast but uncommon in laboratory strains. We find that ER lipid saturation sensors induce expression of FLO1 - encoding a cell wall polysaccharide binding protein - independently of its canonical regulator...
March 18, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28286292/metabolic-engineering-of-escherichia-coli-for-the-production-of-2-fucosyllactose-and-3-fucosyllactose-through-modular-pathway-enhancement
#18
Di Huang, Kexin Yang, Jia Liu, Yingying Xu, Yuanyuan Wang, Ru Wang, Bin Liu, Lu Feng
Fucosyllactoses, including 2'-fucosyllactose (2'-FL) and 3-fucosyllactose (3-FL), are important oligosaccharides in human milk that are commonly used as nutritional additives in infant formula due to their biological functions, such as the promotion of bifidobacteria growth, inhibition of pathogen infection, and improvement of immune response. In this study, we developed a synthetic biology approach to promote the efficient biosynthesis of 2'-FL and 3-FL in engineered Escherichia coli. To boost the production of 2'-FL and 3-FL, multiple modular optimization strategies were applied in a plug-and-play manner...
March 9, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28238759/in-vitro-metabolic-engineering-for-the-production-of-%C3%AE-ketoglutarate
#19
Barbara Beer, André Pick, Volker Sieber
α-Ketoglutarate (aKG) represents a central intermediate of cell metabolism. It is used for medical treatments and as a chemical building block. Enzymatic cascade reactions have the potential to sustainably synthesize this natural product. Here we report a systems biocatalysis approach for an in vitro reaction set-up to produce aKG from glucuronate using the oxidative pathway of uronic acids. Because of two dehydrations, a decarboxylation, and reaction conditions favoring oxidation, the pathway is driven thermodynamically towards complete product formation...
February 22, 2017: Metabolic Engineering
https://www.readbyqxmd.com/read/28232235/estimation-of-flux-ratios-without-uptake-or-release-data-application-to-serine-and-methionine-metabolism
#20
Roland Nilsson, Irena Roci, Jeramie Watrous, Mohit Jain
Model-based metabolic flux analysis (MFA) using isotope-labeled substrates has provided great insight into intracellular metabolic activities across a host of organisms. One challenge with applying MFA in mammalian systems, however, is the need for absolute quantification of nutrient uptake, biomass composition, and byproduct release fluxes. Such measurements are often not feasible in complex culture systems or in vivo. One way to address this issue is to estimate flux ratios, the fractional contribution of a flux to a metabolite pool, which are independent of absolute measurements and yet informative for cellular metabolism...
February 20, 2017: Metabolic Engineering
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