Inhibition of fermentative H2 production by hydrolysis byproducts of lignocellulosic substrates

Abstract

a b s t r a c tLignocellulosic materials are potential renewable substrates for fermentative H 2 production; however, most of the methods available to hydrolyze these materials produce fermentation inhibitors. This study assessed the effect of three different groups of inhibitors on fermentative H 2 production by a mixed culture: (1) acetic acid; (2) furan derivatives, such as furfural and 5-hydroxymethylfurfural (HMF); and (3) phenolic monomers, such as vanillin, syringaldehyde, and 4-hydroxybenzoic acid (HBA). Conduction of batch assays in the presence of glucose and different concentrations of inhibitors helped to assess how the inhibitors affected the kinetic parameters of the modified Gompertz model (R m , H max , and l). The concentrations of inhibitors that reduced 50% of the maximum H 2 production rate (IC50) were estimated. In terms of IC50, HBA provided the largest inhibition, 0.38 g L À1 , which is a novel result in the literature. HBA was followed by HMF and furfural, 0.48 and 0.62 g L À1 , respectively. Vanillin, syringaldehyde, and acetic acid at 0.71; 1.05; and 5.14 g L À1 provided the same inhibition level, respectively. Knowledge about the degree of inhibition of these compounds shall contribute to sustainable H 2 production from lignocellulosic substrates.

Comparative autohydrolysis study of two mixtures of forest and marginal land resources for co-production of biofuels and value-added compounds

“…As previously reported, at T MAX ¼ 206 C, high percentages of hemicellulose were removed but also primary degradation products (F and HMF) were kept at relatively low levels, which could be achieved by applying pretreatment conditions of moderate severity. Although pretreatment improves enzymatic access to cellulose for further fermentation, it generates byproducts decomposition which may affect negatively fermentation [35].…”

Inhibitory effects of furan derivatives and phenolic compounds on dark hydrogen fermentation

“…These inhibitors negatively affect the cell membrane function, growth and glycolysis of fermentative bacteria (Behera et al, 2014). Several studies investigated the inhibitory effects of fermentative inhibitors on biohydrogen fermentation (Cao et al, 2010;Kongjan et al, 2010;Liu et al, 2014;Park et al, 2011;Quéméneur et al, 2012;Siqueira and Reginatto, 2015). Cao et al demonstrated the inhibition effect of furfural, 5-HMF and phenolic compounds from acid-pretreated cornstalk on thermophilic hydrogen fermentation by using Thermoanaerobacterium thermosaccharolyticum W16 (Cao et al, 2010).…”

Enzymatically and/or thermally treated Macroalgae biomass as feedstock for fermentative H2 production

“…We analyzed all the samples treated in this study, to detect HMF at 0.1, 0.5, 1.1, 1.9, 2.8, and 7.6 mg/L after autoclave treatment of the sample for 1, 2, 3, 4, 5, and 6 h, respectively. Such concentrations were very low as compared to fermentation inhibitory concentrations described for H 2producing Clostridium in the literature: above 1.0 g/L [18,30,31].…”

“…Apart from different carbohydrate types, algae biomass hydrolysates may contain significant levels of non-sugar components, such as 5-HMF, a product of hexose degradation that is toxic to microbes used to convert biomass to biofuels [18,30,31]. Therefore, it is desirable that hydrolysates contain fermentable sugars but low inhibitor concentration.…”