Ethanol production using concentrated oak wood hydrolysates and methods to detoxify.
ABSTRACT Ethanol production from concentrated oak wood hydrolysate was carried out to obtain a high ethanol concentration and a high ethanol yield. The effect of added inhibitory compounds, which are typically produced in the pretreatment step of steam-explosion on ethanol fermentation, was also examined. p-Hydroxybenzoic aldehyde, a lignin-degradation product, was the most inhibitory compound tested in this study. Compounds with additional methyl groups had reduced toxicity and the aromatic acids were less toxic than the corresponding aldehydes. The lignin-degradation products were more inhibitory than the sugar-derived products, such as furfural and 5-hydroxymethylfurfural (HMF). Adaptation of yeast cells to the wood hydrolysate and detoxification methods, such as using charcoal and overlime, had some beneficial effects on ethanol production using the concentrated wood hydrolysate. After treatment with charcoal and low-temperature sterilization, the yeast cells could utilize the concentrated wood hydrolysate with 170 as well as 140 g/L glucose, and produce 69.9 and 74.2 g/L ethanol, respectively, with a yield of 0.46-0.48 g ethanol/g glucose. In contrast, the cells could not completely utilize untreated wood hydrolysate with 100 g/L glucose. Low-temperature sterilization, with or without charcoal treatment, was very effective for ethanol production when highly concentrated wood hydrolysates were used. Low-temperature sterilization has advantages over traditional detoxification methods, such as using overlime, ion exchange, and charcoal, because of the reduction in the total cost of ethanol production.
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ABSTRACT: O hidrolisado hemicelulósico de palha de arroz foi tratado com cinco tipos de carvão ativo (pó e granulado) com o objetivo de remover, por adsorção, compostos tóxicos que podem agir como inibidores no processo de bioconversão de xilose em xilitol, por Candida guilliermondii. Os valores máximos de fator de rendimento em xilitol (YP/S = 0,67g g-1) e produtividade volumétrica (QP = 0,61g L-1 h-1) foram atingidos quando o hidrolisado foi tratado com carvão ativo em pó de partículas de tamanho pequeno (0,043mm), baixa granulometria (32% retidos em peneira de 325mesh) e grande área superficial (860m2 g-1), características as quais favoreceram a adsorção dos compostos tóxicos.Ciência e Tecnologia de Alimentos 03/2004; 24(1):94-100. · 0.33 Impact Factor
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ABSTRACT: The demand for renewable energy is increasing due to increasing energy consumption and global warming associated with increasing use of fossil fuels. Hydrogen gas is considered as a good energy carrier due to its high energy content. Biomass (e.g. agricultural and forestry residues, food industry wastes, and energy crops) is amenable to dark fermentative hydrogen production. However, lignocellulosic materials require pretreatment and/or hydrolysis prior to dark fermentation. This paper reviews potential biomass sources for hydrogen fermentation as well as the effects of different pretreatment and hydrolysis methods on sugar yields as well as hydrogen yields from hydrolyzates. The effects of process parameters on dark fermentative hydrogen production from lignocellulosic hydrolyzates are also discussed.Biomass and Bioenergy 08/2014; 67:145–159. · 2.98 Impact Factor
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ABSTRACT: A new xylose fermenting yeast was isolated from over-ripe banana by enrichment in xylose-containing medium. The phylogenetic analysis of ITS1-5.8S-ITS2 region sequences of ribosomal RNA of isolate BY2 revealed that it shows affiliation to genus Pichia and clades with Pichia caribbica. In batch fermentation, Pichia strain BY2 fermented xylose, producing 15 g l−1 ethanol from 30 g l−1 xylose under shaking conditions at 28°C, with ethanol yield of 0.5 g g−1 and volumetric productivity of 0.31 g l−1 h−1. The optimum pH range for ethanol production from xylose by Pichia strain BY2 was 5–7. Pichia strain BY2 also produced 6.08 g l−1 ethanol from 30 g l−1 arabinose. Pichia strain BY2 can utilize sugarcane bagasse hemicellulose acid hydrolysate for alcohol production, efficiency of fermentation was improved by neutralization, and sequential use of activated charcoal adsorption method. Percent total sugar utilized and ethanol yield for the untreated hydrolysate was 17.14% w/v and 0.33 g g−1, respectively, compared with 66.79% w/v and 0.45 g g−1, respectively, for treated hemicellulose acid hydrolysate. This new yeast isolate showed ethanol yield of 0.45 g g−1 and volumetric productivity of 0.33 g l−1 h−1 from sugarcane bagasse hemicellulose hydrolysate detoxified by neutralization and activated charcoal treatment, and has potential application in practical process of ethanol production from lignocellulosic hydrolysate.Annals of Microbiology 63(1). · 1.55 Impact Factor