Inhibitory Compounds in Lignocellulosic Biomass Hydrolysates during Hydrolysate Fermentation Processes

Abstract

To compare the composition and performance of various lignocellulosic biomass hydrolysates as fermentation media, 8 hydrolysates were generated from a grass-like and a wood biomass. The hydrolysate preparation methods used were 1) dilute acid, 2) mild alkaline, 3) alkaline/peracetic acid, and 4) concentrated acid. These hydrolysates were fermented at 30°C, pH 5.0 using Saccharomyces cerevisiae CEN.PK113-7D as model strain. The growth in different hydrolysates varied in the aspects of lag-phase, growth rate, glucose consumption rate and ethanol production rate. Subsequently, 11 potential inhibitory compounds as described in literature were selected for further analysis. The concentrations of these compounds were determined in the time-samples of the 8 fermentations, using a novel analytical method, ethyl-chloroformate derivatization-GC-MS. Some of these compounds, e.g. furfural, decreased during the fermentation process, while others, such as formic and benzoic acid, remained almost constant. Inhibitory effect analysis of individual compound revealed that most of these compounds exhibit little effect at the concentrations detected in hydrolysates. Only furfural and benzoic acid clearly affected the growth of the model yeast: furfural elongated the lag-phase, while benzoic acid reduced the growth rate and biomass yield.

Comparison of Ethanol Yield Between Separate and Simultaneous Hydrolysis and Ethanol Fermentation of Formic- Fractionated Sugarcane Bagasse

“…Our result seemed higher than reported by both Zha et al (2012) and Zhao (2012). In Zha report, the highest fermentation yields of 86 % can be obtained after 60 hours of fermentation of hydrolysate of bagasse pretreated by four techniques (2 % H 2 SO 4 , 3 % Ca(OH) 2 ), alkaline/paracetic acid and 72 % H 2 SO 4 ) [16]. The detoxification was needed to improve the fermentation yield; treatment of the hydrolysate with Ca(OH) 2 at pH 10 for 1h helped improving the fermentation yield to 92 % while that of the undetoxified hydrolysate achieved only 62% [15].…”

“…The performance of the SGB fermentation showed the hydrolysate of the fractionated bagasse could be easily fermented, gave high fermentation yield of 91.08 ± 2.02 % theoretical yield. Our result seemed higher than reported by both Zha et al (2012) and Zhao (2012). In Zha report, the highest fermentation yields of 86 % can be obtained after 60 hours of fermentation of hydrolysate of bagasse pretreated by four techniques (2 % H 2 SO 4 , 3 % Ca(OH) 2 ), alkaline/paracetic acid and 72 % H 2 SO 4 ) [16].…”

Optimization of Saccharification Conditions of Lignocellulosic Biomass under Alkaline Pre-Treatment and Enzymatic Hydrolysis

“…The influences of temperature (140 • C and 160 • C) and the concentration of sulfuric acid (5-20 g/dm 3 ) on the formation of inhibitors were examined. It turned out that the higher the temperature and the higher the concentration of sulfuric acid, the higher the concentration of acetic and formic acids, HMF and furfural, with the highest concentration observed for formic acid [69,73]. Some of the inhibitory compounds may be adsorbed on the surface of the wood sediments.…”

“…The effect of using sludge water on the effectiveness of inhibitor removal was investigated. It turned out that six rinsing cycles allows to remove the total content of 87% formic acid, 64% acetic acid, 86% furfural and 87% HMF [73].…”

Produção de polímeros biodegradáveis por Escherichia coli recombinante a partir de açúcares derivados do hidrolisado do bagaço de cana-de-açúcar.

“…Enquanto este último processo depende de enzimas comerciais, que representam um custo significante para o processo, a hidrólise mediada por ácidos gera uma mistura complexa de substâncias tóxicas aos microrganismos, na qual se incluem acetatos, furanos, ácidos alifáticos, compostos fenólicos e aromáticos (CARVALHO LIMA, 2001;FELIPE et al, 1997;ZHA et al, 2012).…”