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Ethanol Production and Alcoholic Beverages
Published in Debabrata Das, Soumya Pandit, Industrial Biotechnology, 2021
Ethanol fermentation is known as alcoholic fermentation which converts sugars such as glucose, fructose, and sucrose into ethanol and carbon dioxide as the main products. Because yeasts perform this conversion in the absence of oxygen, alcoholic fermentation is considered an anaerobic process. The alcohol can be classified as taxable and non-taxable alcohol. Taxable alcohol is used in its pure form, mainly for human consumption as different alcoholic beverages. In addition, it is used in the pharmaceutical industry, the perfume industry etc. Non-taxable alcohol is utilized as chemical feedstock e.g. acetic acid, the polythene industry, the rubber industry etc. These are unfit for human consumption (due to addition of certain chemicals). This type of denatured ethanol contains additives to make it poisonous, foul smelling or nauseating.
Industrial Fermentation Processes
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
Ethanol fermentation, also called alcoholic fermentation, is a biological process that converts sugars such as glucose, fructose, sucrose, etc. into cellular energy, producing ethanol and carbon dioxide as products. Because yeasts perform this conversion in the absence of oxygen, alcoholic fermentation is carried out under anaerobic condition.
Sustainable Production of Biofuels—A Green Spark: Technology, Economics, and Environmental Issues
Published in V. Sivasubramanian, Bioprocess Engineering for a Green Environment, 2018
Rajarathinam Ravikumar, Muthuvelu Kirupa Sankar, Manickam Nareshkumar, Moorthy Ranjithkumar
Ethanol fermentation is an intensified recovery process in which fermentable sugars (hexose and pentose) are converted to ethanol by microorganisms. A vast number of microorganisms that can obtain ethanol from C6 and C5 in the fermentation process have been presented in the literature. Regardless of the microbial species, native microorganisms remain insufficient in conventional ethanol production due to the lack of availability of sugar-rich input and low ethanol yields (Aydemir et al., 2014). Therefore, while ethanol production from lignocellulosic materials is racing ahead, conventional processes are not economical; hence, researchers with an eye toward efficient, cost-effective, high-yield ethanol production have been looking for advanced methods that use microbial strains (Kondo et al., 2002). Effective recovery of ethanol from hydrolysate requires GMOs that convert both hexose and pentose sugars in a single step. Microbes were genetically modified to enhance ethanol tolerance, enable co-fermentation of hexose and pentose sugars, secrete extracellular hydrolytic enzymes, and reduce by-product formation. Table 9.3 shows genetic modifications made in Saccharomyces cerevisiae to enhance ethanol productivity.
Multiobjective optimization and nonlinear model predictive control of the continuous fermentation process involving Saccharomyces Cerevisiae
Published in Biofuels, 2022
One of the most common organisms used for ethanol fermentation is the yeast, Saccharomyces cerevisiae. The advantages of using S. cerevisiae for fermentation are that it ferments glucose to ethanol as the sole product, it has a high ethanol tolerance, and industrial scale-up of the process is well understood [2]. Also, S. cerevisiae is highly favored because of its common use in ethanol production, its GRAS (Generally Regarded as Safe) status, and its use as nutrient enhancers in animal feeds [3]. While continuous fermentations involving S. cerevisiae are more attractive because of higher potential efficiency than batch or fed batch operations, it involves more theoretical and experimental challenges because of complex nonlinear behavior. Oscillations and multiple steady-states of biomass, substrate, and product (ethanol) concentrations were observed by several workers in continuous cultures of S.cerevisiae [4–11].
Microbial fuel cells: a sustainable solution for bioelectricity generation and wastewater treatment
Published in Biofuels, 2019
Har Mohan Singh, Atin K. Pathak, Kapil Chopra, V.V. Tyagi, Sanjeev Anand, Richa Kothari
Different scientists have utilized different substrates in various MFC designs. Kim et al. [97] designed an MFC with carbon as a source of energy and Proteus vulgaris as a catalytic source. Catalet al. [98] utilized for the first time an ethanol fermentation process as the substrate in an MFC. The ethanol fermentation process produces polyalcohols as byproducts, such as xylitol, arabitol, ribitol, galactitol, mannitol and sorbitol. The substrate was used and treated in three different MFC designs, single-chambered, mediator-less, and air-cathode, with mixed culture inoculum extracted from domestic wastewater. The systems show high pollutant removal efficiency, of 71–92% COD removal. Catal et al. [99] in another experiment utilized six different hexose-rich waters, three pentoses and three sugar derivatives,and found that when the substrate was used in a single-chambered air-cathode MFC with mixed bacterial culture for carbohydrate-rich wastewater treatment, 80% COD removal efficiency was achieved by the system. Rikameet al. [100] utilized acidogenic food wastewater with 5000 mg COD L−1 and obtained 90% removal, whereas Li et al. [101] utilized food waste leachate as substrate in an MFC, resulting in 87% removal of COD. The work of different researchers on removal of pollutants from different wastewaters is summarized in Table 4.
Waste into energy conversion technologies and conversion of food wastes into the potential products: a review
Published in International Journal of Ambient Energy, 2021
Jeya Jeevahan, A. Anderson, V. Sriram, R. B. Durairaj, G. Britto Joseph, G. Mageshwaran
Any material that contains sugar can be converted into ethanol by ethanol fermentation process. The feedstocks used for producing ethanol through fermentation are catagorized into three major types, namely (a) sugar, (b) starch and (c) cellulose. While sugars can directly be converted into ethanol by fermentation, starches and celluloses must be converted into the fermentable sugars. The sugars can be obtained from sugarcane, sugar beets, molasses and fruits. Molasses (about 50 wt% of sugar) is the widely used sugar for ethanol fermentation and is thick syrup produced during the refinement process of sugar. Molasses is first sterilised and then taken to the fermentation plant. Since high concentration of sugar results in incomplete sugar conversion and prolonged fermentation time, molasses is diluted with water. Once yeast or bacteria is added, fermentation is initiated and the process is continued at 20–32°C for about 1–3 days. Starch cannot be directly fermented by yeast or bacteria. So, it must be broken down into fermentable sugars. Starch is first hydrolysed and cooked at a high temperature by adding α-amylase. α-amylase breaks down the starch polymer thereby avoiding gelatinisation. The high temperature (140–180°C) produces mechanical shear necessary to rupture and cleave starch molecules and the resulting mixture flows into a flash tank it is cooled and liquefied by adding additional α-amylase. The pH value is adjusted to 4–5 with mineral acids, and glucoamylase enzyme is added to the liquefied starch, which converts liquefied starch into glucose. The resulting dextrose is fermented further to produce ethanol. Among the three types of feedstocks, cellulose is the most abundant source and is largely unutilised. Cellulose is a mixture of carbohydrates (cellulose and hemicellulose) and lignin in which the carbohydrates are tightly bound to lignin because of strong hydrogen bonds. The following biological processes are required for converting the cellulose into ethanol: delignification (breaking of complex binding between lignin and carbohydrates), depolymerisation of the carbohydrates to produce (to form fermentable sugars), and fermentation of sugars to produce ethanol (Bothast and Schlicher 2005; Kim, Lee, and Pak 2011).