Identification of Small Aliphatic Aldehydes in Pretreated Lignocellulosic Feedstocks and Evaluation of Their Inhibitory Effects on Yeast

• Published in: Journal of agricultural and food chemistry 2015-11, Vol.63 (44), p.9747-9754
• Main Authors: Cavka, Adnan, Stagge, Stefan, Jönsson, Leif J
• Format: Article
• Language: English
• Subjects: acetaldehyde; Aldehydes - chemistry; Aldehydes - pharmacology; Biotechnology; Fermentation; fermentation inhibition; formaldehyde; glycolaldehyde; Hydrolysis; Lignin - chemistry; Lignin - metabolism; lignocellulose; mass spectrometry; pretreatment; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - metabolism
• ISSN: 0021-8561; 1520-5118; 1520-5118
• DOI: 10.1021/acs.jafc.5b04803

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.