Native or Raw Starch Digestion:  A Key Step in Energy Efficient Biorefining of Grain

• Published in: Journal of agricultural and food chemistry Vol. 54; no. 2; pp. 353 - 365
• Main Authors: Robertson, George H, Wong, Dominic W. S, Lee, Charles C, Wagschal, Kurt, Smith, Michael R, Orts, William J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 25.01.2006
• Subjects: alcoholic fermentation; alpha-amylase; Amylases - metabolism; biofuels; Biological and medical sciences; Conservation of Energy Resources; Edible Grain - chemistry; Energy; Energy-Generating Resources; enzymatic hydrolysis; ethanol; Ethanol - metabolism; ethanol production; Fermentation; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; glucan 1,4-alpha-glucosidase; glucose; Glucose - metabolism; Glucosidases - metabolism; heat treatment; Hydrolysis; Kinetics; saccharification; small cereal grains; starch; Starch - chemistry; Starch - metabolism; Starch and starchy product industries; Substrate Specificity; Temperature; solid starch; Cold; Starch; Enzyme; Liquefaction; Environmental factor; Saccharification; enzymes; Digestion; Fermentation; Solid; Hydrolysis; starch structure; Energy; cold cook; Cereal; cold hydrolysis; Carbohydrate; Raw starch; Structure; Polysaccharide
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf051883m

Improved molecular disassembly and depolymerization of grain starch to glucose are key to reducing energy use in the bioconversion of glucose to chemicals, ingredients, and fuels. In fuel ethanol production, these biorefining steps use 10−20% of the energy content of the fuel ethanol. The need to minimize energy use and to raise the net yield of energy can be met by replacing high-temperature, liquid-phase, enzymatic digestion with low temperature, solid-phase, enzymatic digestion. Also called cold hydrolysis, the approach is a step toward a “green” method for the production of fuel ethanol. There has been substantial prior and increased recent interest in this approach that is presented in this first review of the subject. We include incentives, developmental research, fundamental factors of raw starch digestion, and novel approaches in enzymology and processing. The discussion draws on resources found in enzymology, engineering, plant physiology, cereal chemistry, and kinetics. Keywords: Raw starch; solid starch; digestion; enzymes; starch structure; cold cook; cold hydrolysis; liquefaction; saccharification; fermentation