Single-Cell Biorefinery

Qi, Qingsheng; Liang, Quanfeng

doi:10.1016/b978-0-444-63453-5.00011-2

Cited by 5 publications

(4 citation statements)

References 91 publications

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“…glucose and 30%-40% xylose. [41] Nonetheless, the results presented here serve as a general proof-of-concept and it is reasonable to expect that the trends we observed here will be maintained regardless of the medium sugar concentrations and ratio.…”

Section: Discussionsupporting

confidence: 62%

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae

Lane

Turner

Jin

2023

Biotechnology Journal

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Engineered Saccharomyces cerevisiae expressing a lactic acid dehydrogenase can metabolize pyruvate into lactic acid. However, three pyruvate decarboxylase (PDC) isozymes drive most carbon flux toward ethanol rather than lactic acid. Deletion of endogenous PDCs will eliminate ethanol production, but the resulting strain suffers from C2 auxotrophy and struggles to complete a fermentation. Engineered yeast assimilating xylose or cellobiose produce lactic acid rather than ethanol as a major product without the deletion of any PDC genes. We report here that sugar flux, but not sensing, contributes to the partition of flux at the pyruvate branch point in S. cerevisiae expressing the Rhizopus oryzae lactic acid dehydrogenase (LdhA). While the membrane glucose sensors Snf3 and Rgt2 did not play any direct role in the option of predominant product, the sugar assimilation rate was strongly correlated to the partition of flux at pyruvate: fast sugar assimilation favors ethanol production while slow sugar assimilation favors lactic acid. Applying this knowledge, we created an engineered yeast capable of simultaneously converting glucose and xylose into lactic acid, increasing lactic acid production to approximately 17 g L−1 from the 12 g L−1 observed during sequential consumption of sugars. This work elucidates the carbon source‐dependent effects on product selection in engineered yeast.

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Section: Discussionsupporting

confidence: 62%

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae

Lane

Turner

Jin

2023

Biotechnology Journal

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“…However, a more economically attractive conversion would be to transform commonly available monomeric sugars (glucose, xylose, galactose, arabinose, and mannose) into rare sugars or sugar derivatives which are parts of drug components. Typically, lignocellulosic hydrolysates consist of glucose and xylose as the major monosaccharide components in which glucose makes up approximately 30–50% and xylose approximately 20% of feedstock dry weight. − Galactose, arabinose, and mannose can be obtained in much lower quantities (1–10% of dry weight). Sugar derivatives have various biological activities because they contain a variety of stereospecific structures which can interact with different target receptors or enzymes and trigger biological reaction cascades .…”

Section: Production Of Lignocellulosic Biomass-derived Productsmentioning

confidence: 99%

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

et al. 2021

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Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO 2 and CH 4 ) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

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“…Lignocellulosic material is comprised of cellulose, hemicellulose, and lignin, and it is often a waste stream for many processes, making it an ideal feedstock because it is inexpensive and renewable [18]. The hydrolysis of lignocellulosic biomass breaks down the polysaccharides into the monosaccharide units, of which glucose and xylose are the two predominant sugars [19,20].…”

Section: Introductionmentioning

confidence: 99%

“…Glucose has been a favourite of the fermentation industry since it is easily utilised by numerous microbes and is a widely available feedstock [20]. Glucose is consumed through the glycolytic pathway, which is common in many organisms, unlike the pentose phosphate pathway that is required for the fermentation of xylose [18].…”

Section: Introductionmentioning

confidence: 99%

Rhizopus oryzae for Fumaric Acid Production: Optimising the Use of a Synthetic Lignocellulosic Hydrolysate

2022

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The hydrolysis of lignocellulosic biomass opens an array of bioconversion possibilities for producing fuels and chemicals. Microbial fermentation is particularly suited to the conversion of sugar-rich hydrolysates into biochemicals. Rhizopus oryzae ATCC 20344 was employed to produce fumaric acid from glucose, xylose, and a synthetic lignocellulosic hydrolysate (glucose–xylose mixture) in batch and continuous fermentations. A novel immobilised biomass reactor was used to investigate the co-fermentation of xylose and glucose. Ideal medium conditions and a substrate feed strategy were then employed to optimise the production of fumaric acid. The batch fermentation of the synthetic hydrolysate at optimal conditions (urea feed rate 0.625mgL−1h−1 and pH 4) produced a fumaric acid yield of 0.439gg−1. A specific substrate feed rate (0.164gL−1h−1) that negated ethanol production and selected for fumaric acid was determined. Using this feed rate in a continuous fermentation, a fumaric acid yield of 0.735gg−1 was achieved; this was a 67.4% improvement. A metabolic analysis helped to determine a continuous synthetic lignocellulosic hydrolysate feed rate that selected for fumaric acid production while achieving the co-fermentation of glucose and xylose, thus avoiding the undesirable carbon catabolite repression. This work demonstrates the viability of fumaric acid production from lignocellulosic hydrolysate; the process developments discovered will pave the way for an industrially viable process.

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Single-Cell Biorefinery

Cited by 5 publications

References 91 publications

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Rhizopus oryzae for Fumaric Acid Production: Optimising the Use of a Synthetic Lignocellulosic Hydrolysate

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