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Exploring the Potential of Cyanobacterial Biomass for Bioethanol Production
Published in Jitendra Kumar Saini, Surender Singh, Lata Nain, Sustainable Microbial Technologies for Valorization of Agro-Industrial Wastes, 2023
Nirmal Renuka, Sachitra Kumar Ratha, Virthie Bhola, V. Kokila, Lata Nain, Faizal Bux, Radha Prasanna
Among the important reactions targeted in cyanobacteria is the diversion of pyruvate through metabolic engineering into useful industrial products, including ethanol. A key enzyme catalyzing the decarboxylation of pyruvate to acetaldehyde in alcohol fermentation is pyruvate decarboxylase (PDC, EC 4.1.1.1), present in fungi, plants, and yeasts, but absent in humans and rare and found only in very few bacterial species. The PDC of Zymomonas mobilis has been extensively explored in ethanol production; however, the spotlight has shifted to a number of other bacterial PDCs, which have pH optimum or lower Km, such as Gluconacetobacter diazotrophicus, Zymobacter species, etc. The Zymomonas mobilis PDC enzyme with an optimum pH of 6.0 is a homotetramer of 240 kDa that has been utilized the most; however, as a majority of cyanobacteria have optimal pH in the range of 7.5–8.0, exploring other PDCs is in progress. Preference is always for organisms with a lower Km, which can increase the flux from pyruvate and catalyze the coupling of acetaldehyde with ADH better.
Hemicellulose Conversion to Ethanol
Published in Charles E. Wyman, Handbook on Bioethanol, 2018
Ethanol and Coproduct Formation. Doelle [50] and Gottschalk [51] provide excellent discussions of microbial metabolism associated with product formation. Yeasts and a few bacteria, most notably Z. mobilis and Erwinia amylovora, contain pyruvate decarboxylase (PDC) and are able to directly decarboxylate pyruvate to acetaldehyde, the immediate precursor of ethanol. Microorganisms such as Z. mobilis and S. cerevisiae that express PDC can ferment hexoses to ethanol at yields approaching the theoretical value of 2 mol ethanol/mol hexose or 0.51 g ethanol/g hexose (1.67 mol/mol pentose or 0.51 g/g pentose). As discussed previously, however, in their wild-type form these microorganisms are not capable of fermenting pentoses.
Bioethanol production
Published in Ozcan Konur, Bioenergy and Biofuels, 2017
Carlos Ariel Cardona Alzate, Carlos Andrés García, Sebastián Serna Loaiza
The production of ethanol via fermentation necessarily starts with sugar. For example, when glucose is used as the main sugar, it is converted to pyruvate by glycolysis enzymes and it also produces adenosine triphosphate (ATP) and nicotinamide adenine dinucleotides (NADHs). Then, pyruvate is decarboxylated by pyruvate decarboxylase to acetaldehyde, which is later reduced to ethanol by alcohol dehydrogenase using the NADH previously generated (Jarboe et al., 2009). This is the metabolic route applied by S. cerevisiae, and it is very common in yeasts and fungi. S. cerevisiae is the most used yeast at the industrial scale and it is able to ferment six-carbon sugars, but hardly ferments five-carbon sugars (pentoses) because it cannot express the xylanase enzyme to convert xylose to xylulose (Tian et al., 2008).
Effect of nickel oxide nanoparticles on bioethanol production by Pichia kudriavzveii IFM 53048 using banana peel waste substrate
Published in Environmental Technology, 2023
Florence Obiageli Nduka, Ikechukwu Noel Emmanuel Onwurah, Chikodili Joseph Obeta, Ekene John Nweze, Chinelo Chinenye Nkwocha, Favor Ntite Ujowundu, Ozoemena Emmanuel Eje, Juliet Onyinye Nwigwe
Micronutrients like nickel play a vital role in bioethanol production. They are required for catalytic action where they act as cofactors/activators that bind to enzyme active sites such as alcohol dehydrogenase, consequently activating and improving anaerobic production of bioethanol. The redox potential of NiO NPs triggers metabolic shifts within the cell that lead to the formation of ethanol [6]. Furthermore, the transfer NiO NPs across the cell enhances glycolysis beyond the pyruvate dehydrogenase catalytic reaction, thus resulting in an influx and overflow of substrate towards pyruvate decarboxylase, thereby raising Pichia kudriavzevii IFM 53048 affinity for glucose and consistently enhancing the rate of bioethanol production. The enzymatic activities of pyruvate decarboxylase and alcohol dehydrogenase enzymes play the role of transforming its substrate, pyruvate into ethanol and carbon dioxide causing the reoxidation of two NADH resulting from glycolysis in the absence of oxygen [52].
Effects of pyruvate decarboxylase (pdc1, pdc5) gene knockout on the production of metabolites in two haploid Saccharomyces cerevisiae strains
Published in Preparative Biochemistry & Biotechnology, 2022
Wen Zhang, Jie Kang, Changli Wang, Wenxiang Ping, Jingping Ge
Ethanol is the main metabolite of S. cerevisiae, and pyruvate decarboxylase is the cytoplasmic enzyme at the fulcrum between fermentation and sugar catabolism.[20] Therefore, the Pyruvate decarboxylase 1 (pdc1) and Pyruvate decarboxylase 5 (pdc5) genes were knocked out by the Cre/loxP system to observe the changes in growth metabolism and the difference in growth metabolism between the MATa and MATα types of haploid S. cerevisiae. To obtain haploid strains with a high yield of 2,3-butanediol, the selection of strains for the industrial production of 2,3-butanediol was expanded. At the same time, this method lays a theoretical foundation for obtaining excellent haploid strain hybridization and provides valuable resources for breeding planning and quantitative genetic research.[21]