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Bioconversion of Waste Biomass to Bioethanol
Published in Prakash Kumar Sarangi, Sonil Nanda, Bioprocessing of Biofuels, 2020
Prakash Kumar Sarangi, Sonil Nanda
Several microorganisms including fungi (e.g. Aspergillus, Candida shehatae, Fusarium sp., Kluyveromyces sp., Neurospora sp., Phanerochaete sp., Penicillium sp., Pichia kudriavzevii, Saccharomyces cerevisiae, Schizophyllum sp., Sclerotium sp., Trichoderma sp., etc.) and bacteria (e.g. Acetovibrio sp., Bacillus sp., Clostridium thermocellum, Erwinia sp., Escherichia coli, Klebsiella oxytoca, Ruminococcus sp., Zymomonas mobilis, etc.) accomplish fermentation of biomass hydrolysates to produce ethanol (Nanda et al. 2014b). S. cerevisiae is a model microorganism for ethanol fermentation because of its high efficiency, stability, a faster rate of sugar conversion and high solvent (alcohol) tolerance. Moreover, it is also considered as GRAS (generally regarded as safe). S. cerevisiae is also a potential producer of zymase, an enzyme complex that manifests the biocatalysis of sugar fermentation into ethanol and CO2 (Lin and Tanaka 2006).
The Other Energy Markets
Published in Anco S. Blazev, Global Energy Market Trends, 2021
The fructose and glucose are produced in the presence of invertase (a catalyst). These sugars then react with another enzyme called zymase, which is also contained in the yeast to produce ethanol and carbon dioxide.
Bioethanol production from sugarcane molasses with supplemented nutrients by industrial yeast
Published in Biofuels, 2023
Hasan Shahriar Raby, Md Anowar Saadat, Ahmed Nazmus Sakib, Fatema Moni Chowdhury, Abu Yousuf
Bioalcohol is produced from sugar by the presence of the zymase enzyme. The most used sources of sugar are sweet fruits, sugarcane, barley, corn, wheat, and potatoes. The secretion of zymase takes place when yeast is added to the sugar medium. It should be noted that all sugar cannot be fermented by zymase. Cane sugar (sucrose), beet sugar, or malt sugar is not fermentable with zymase directly. Outside of its cell wall, yeast must develop the enzyme invertase to disintegrate sucrose into glucose and fructose. Upon the decomposition of glucose and fructose, microbes can metabolize them directly, followed by fermentation. The fermentation process of molasses to bioethanol using yeast is a well-established practice worldwide, involving the dilution of molasses, inoculation with yeast, fermentation, and distillation. Bangladesh’s only state-owned profit-making distillery corporation is Carew & Company (Bangladesh) Ltd. Molasses, a by-product of the sugar industry is used as a raw material in the distillery business. Molasses contains approximately 42%–50% fermentable sugar that is not further processable for sugar production [10]. Alcohol fermentation is an aerobic type, but yeast propagation is both anaerobic and aerobic type. While S. cerevisiae (yeast) has already been recommended as the most suitable yeast for bioethanol production, Carew & Co.'s present strain is not thermotolerant [11–13]. For the past few years, the distillery unit has been experiencing declining spirit yields, which had a significant impact on revenue. The super-critical factor is the high temperature resulting from exothermic fermentation as well as seasonal temperature which leads to a significant death rate of cells when it goes more than 40 °C.