title: Identification of Small Aliphatic Aldehydes in Pretreated Lignocellulosic Feedstocks and Evaluation of Their Inhibitory Effects on Yeast.
abstract: Six lignocellulosic hydrolysates produced through acid pretreatment were analyzed for the occurrence of formaldehyde, acetaldehyde, and glycolaldehyde. Acetaldehyde was found in all six (0.3-1.6 mM) and formaldehyde in four (≤ 4.4 mM), whereas glycolaldehyde was not detected. To assess the relevance of these findings, fermentations with yeast and formaldehyde or acetaldehyde were performed in the concentration interval 0.5-10 mM. Formaldehyde already inhibited at 1.0 mM, whereas 5.0 mM acetaldehyde was needed to obtain a clear inhibitory effect. After 24 h of fermentation, 1.5 mM formaldehyde reduced the glucose consumption by 85%, the balanced ethanol yield by 92%, and the volumetric productivity by 91%. The results show that formaldehyde and acetaldehyde are prevalent in pretreated lignocellulose and that formaldehyde in some cases could explain a large part of the inhibitory effects on yeast by lignocellulosic hydrolysates, as three of six hydrolysates contained ≥ 1.9 mM formaldehyde, which was shown to be strongly inhibitory.
authors.affiliation: Department of Chemistry, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Adnan
authors.initials: A
authors.lastname: Cavka
authors.affiliation: Department of Chemistry, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Stagge
authors.affiliation: Department of Chemistry, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Leif J
authors.initials: LJ
authors.lastname: Jönsson
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000494:pharmacology*; D001709:Biotechnology; D005285:Fermentation; D006868:Hydrolysis; D008031:Lignin / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000447:Aldehydes; C036909:lignocellulose; D008031:Lignin
keywords: acetaldehyde; fermentation inhibition; formaldehyde; glycolaldehyde; lignocellulose; mass spectrometry; pretreatment