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The Corn Ethanol Industry
Published in Shelley Minteer, Alcoholic Fuels, 2016
Nancy N. Nichols, Bruce S. Dien, Rodney J. Bothast, Michael A. Cotta
Starch is washed to remove residual protein and is converted to a glucose syrup. First, the starch is jet-cooked and held for liquefaction at 90°C with alpha-amylase. In contrast to the dry-grind process, all of the alpha-amylase is added prior to jet cooking. Then glucoamylase and pullulanase, a α-1⟶6 debranching enzyme, are added to convert dextrin polymers to sugars. Addition of pullulanase ensures good conversion of dextrins to glucose by decreasing formation of isomaltose, a glucose dimer. Isomaltose is present at starch polymer branching points and can also be formed by “reversion” of glucose to isomaltose in a reaction catalyzed by glucoamylase. After saccharification, glucose is fermented to ethanol by an industrial strain of S. cerevisiae. In wet mills, the fermentation is often run using a series of fermenters in a semi-continuous process. Approximately 2.5 gallons of ethanol are produced from a bushel of corn in the wet-milling process.
Modeling and evaluation of the sucrose-degrading activity of recombinantly produced oligo-1,6-glucosidase from A. gonensis
Published in Preparative Biochemistry & Biotechnology, 2023
Hakan Karaoglu, Zeynep Dengız Balta
To determine the kinetic parameters of rAgoSuc2, a series of reactions were carried out with sucrose in the range of 0-500 mM. It was revealed that rAgoSuc2 showed simple Michaelis-Menten kinetics. In the analyses performed by OriginPro 2021 program, the values of Km, Vmax, kcat, and kcat/Km were determined as 44.69 ± 1.27 mM, 6.28 ± 0.05 µmoL/min/mg protein, 6.70 1/s and 0.15 1/mM−1, respectively. The O-1-6-glucosidases are also commonly referred to as isomaltase and maltase. In these oligosaccharides, the enzyme shows activity on various substrates, such as isomaltohexaose, isomaltose, and maltose, and especially hydrolyzes 1-6 glycosidic bonds. In addition to these activities, the enzyme is also capable of hydrolyzing 1-2 glyosidic bonds present in sucrose.[30] In this study about the sucrase-degrading activity of the enzyme, sucrose was used as the substrate. Similarly, there have been several studies about the activity of O-1-6-glucosidases against sucrose. Deng et al.[31] reported that the values of Km and kcat/Km of O-1-6-glucosidase from Saccharomyces cerevisiae were 147 mM and 351/mMs−1, respectively. Schonert et al.[32] determined the Km value of O-1-6-glucosidase obtained from Bacillus subtilis as 10.2 mM.