title: Inhibitory activity of carbonyl compounds on alcoholic fermentation by Saccharomyces cerevisiae.
abstract: Aldehydes and acids play important roles in the fermentation inhibition of biomass hydrolysates. A series of carbonyl compounds (vanillin, syringaldehyde, 4-hydroxybenzaldehyde, pyrogallol aldehyde, and o-phthalaldehyde) were used to examine the quantitative structure-inhibitory activity relationship of carbonyl compounds on alcoholic fermentation, based on the glucose consumption rate and the final ethanol yield. It was observed that pyrogallol aldehyde and o-phthalaldehyde (5.0 mM) reduced the initial glucose consumption rate by 60 and 89%, respectively, and also decreased the final ethanol yield by 60 and 99%, respectively. Correlating the molecular descriptors to inhibition efficiency in yeast fermentation revealed a strong relationship between the energy of the lowest unoccupied molecular orbital (ELUMO) of aldehydes and their inhibitory efficiency in fermentation. On the other hand, vanillin, syringaldehyde, and 4-hydroxybenzaldehyde (5.0 mM) increased the final ethanol yields by 11, 4, and 1%, respectively. Addition of vanillin appeared to favor ethanol formation over glycerol formation and decreased the glycerol yield in yeast fermentation. Furthermore, alcohol dehydrogenase (ADH) activity dropped significantly from 3.85 to 2.72, 1.83, 0.46, and 0.11 U/mg at 6 h of fermentation at vanillin concentrations of 0, 2.5, 5.0, 10.0, and 25.0 mM correspondingly. In addition, fermentation inhibition by acetic acid and benzoic acid was pH-dependent. Addition of acetate, benzoate, and potassium chloride increased the glucose consumption rate, likely because the salts enhanced membrane permeability, thus increasing glucose consumption.
authors.affiliation: Forest Products Laboratory and Center for Bioenergy and Bioproducts, Auburn University , 520 Devall Drive, Auburn, Alabama 36849, United States.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Cao
authors.forename: Maobing
authors.initials: M
authors.lastname: Tu
authors.forename: Rui
authors.initials: R
authors.lastname: Xie
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Yonnie
authors.initials: Y
authors.lastname: Wu
authors.forename: Sushil
authors.initials: S
authors.lastname: Adhikari
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism; D000447:Aldehydes / Q000737:chemistry / Q000494:pharmacology*; D001547:Benzaldehydes / Q000737:chemistry / Q000494:pharmacology; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects*; D005947:Glucose / Q000378:metabolism; D021281:Quantitative Structure-Activity Relationship; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009764:o-Phthalaldehyde / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000447:Aldehydes; D001547:Benzaldehydes; C069665:syringaldehyde; D000431:Ethanol; D009764:o-Phthalaldehyde; C100058:vanillin; D000426:Alcohol Dehydrogenase; D005947:Glucose; C011483:4-hydroxybenzaldehyde