Characterization and Fermentation of Dilute-Acid Hydrolyzates from Wood

Abstract

Dilute-acid hydrolyzates from alder, aspen, birch, willow, pine, and spruce were fermented without prior detoxification. The hydrolyzates were prepared by a one-stage hydrolysis process using sulfuric acid (5 g/L) at temperatures between 188 and 234 °C and with a holding time of 7 min. The fermentations were carried out anaerobically by Saccharomyces cerevisiae (10 g of d.w./L) at a temperature of 30 °C and an initial pH of 5.5. The fermentabilities were quite different for the different wood species, and only hydrolyzates of spruce produced at 188 and 198 °C, hydrolyzates of pine produced at 188 °C, and hydrolyzates of willow produced at 198 °C could be completely fermented within 24 h. From the sum of the concentrations of the known inhibitors furfural and 5-(hydroxymethyl)furfural (HMF), a good prediction of the maximum ethanol production rate could be obtained, regardless of the origin of the hydrolyzate. Furthermore, in hydrolyzates that fermented well, furfural and HMF were found to be taken up and converted by the yeast, concomitant with the uptake of glucose.

Innovative pretreatment strategies for biogas production

“…This method breaks the intramolecular bonds between the lignin, hemicellulose, and cellulose in the cell wall and hydrolyzes the hemicellulose (Taherzadeh & Jeihanipour, 2012). However, at a high temperature and acid concentration, undesirable dehydration occurs resulting in the hemicellulose and cellulose being degraded into different types of inhibitory compounds, such as furfural (Taherzadeh et al, 1997). Hence, it is necessary to carry out the pretreatment at mild conditions to prevent excessive sugar degradation.…”

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status

“…For example, poor fermentability of dilute acid-wood hydrolysates was primarily correlated to high levels of furfural, 5-hydroxymethylfurfural (5-HMF) and acetic acid (Taherzadeh et al 1997). Therefore, these categories will be the major focus of review.…”

“…The predominant furan derivatives, furfural and 5-HMF, which are mainly derived from dehydration of pentose and hexose sugars during hydrolysis, are among the strongest inhibitors in lignocellulosic hydrolysates (Taherzadeh et al 1997). Although furfural is more toxic than 5-HMF, both compounds act synergistically to suppress yeast growth (Liu et al 2004).…”

Thermotolerant Zymomonas mobilis: Comparison of Ethanol Fermentation Capability with that of an Efficient Type Strain

“…mobilis strains, TISTR 405, TISTR 548, TISTR 550 and TISTR 551, were obtained from the TISTR Culture Collection Bangkok MIRCEN, and ZM4 (NRRL B-14023) was provided by E. Yanase. These strains were cultivated in YPD medium consisting of 0.3% (w/v) yeast extract, 0.5% (w/v) peptone and 3% (w/v) glucose [13] at the temperature indicated with a shaking speed of 100 rpm [14]. Cells were harvested and suspended in 10 mM phosphate buffer (pH 7.0) and then passed twice through a French press at 16,000 psi, followed by a low-speed centrifugation for removing unbroken cells, then centrifuged at 86,000 g for 90 min.…”