title: Identification of crucial yeast inhibitors in bio-ethanol and improvement of fermentation at high pH and high total solids.
abstract: Compounds inhibitory to enzymatic hydrolysis and fermentation are generated from neutral steam exploded corn stover in the process of producing bio-ethanol. In this study, weak acids were identified as main yeast inhibitors, while phenols and aldehyde contribute to the inhibition to a lower degree. Main weak acids in hydrolysates are acetic acid and formic acid, for which critical levels for yeast inhibition are 6 and 4g/L, respectively. The inhibitory effect of these compounds can be greatly overcome by increasing pH of hydrolysates to 6.0-9.0, but there is a risk of bacterial contamination when fermenting at high pH. The relationship of pH, total solids of hydrolysates, fermentation and contamination was studied in detail. Results indicate that the contamination by bacteria when fermenting at high pH can be prevented effectively using hydrolysates with total solids of more than 20%. Meanwhile, ethanol yield is improved significantly.
authors.affiliation: Bioenergy Department of R&D China, Novozymes (China) Investment Co. Ltd., Beijing 100085, China.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Huang
authors.forename: Xinyan
authors.initials: X
authors.lastname: Guo
authors.forename: Dongmin
authors.initials: D
authors.lastname: Li
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Liu
authors.forename: Jiafang
authors.initials: J
authors.lastname: Wu
authors.forename: Haiyu
authors.initials: H
authors.lastname: Ren
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D001419:Bacteria / Q000254:growth & development; D056804:Biofuels; D018533:Biomass; D000431:Ethanol / Q000737:chemistry / Q000378:metabolism*; D005285:Fermentation; D005561:Formates / Q000737:chemistry; D005662:Furaldehyde / Q000031:analogs & derivatives / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008031:Lignin / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D003313:Zea mays / Q000737:chemistry
chemical_list: D056804:Biofuels; D005561:Formates; D010636:Phenols; C030544:formic acid; C036909:lignocellulose; D000431:Ethanol; C008046:5-hydroxymethylfurfural; D008031:Lignin; D005662:Furaldehyde; D019342:Acetic Acid