Comparison of the fermentability of enzymatic hydrolyzates of sugarcane bagasse pretreated by steam explosion using different impregnating agents

Sugarcane bagasse is a potential lignocellulosic feedstock for ethanol production, since it is cheap, readily available, and has a high carbohydrate content. In this work, bagasse was subjected to steam explosion pretreatment with different impregnation conditions. Three parallel pretreatments were carried out, one without any impregnation, a second with sulfur dioxide, and a third with sulfuric acid as the impregnating agent. The pretreatments were performed at 205°C for 10 min. The pretreated material was then hydrolyzed using celluloytic enzymes. The chemical composition of the hydrolyzates was analyzed. The highest yields of xylose (16.2 g/100 g dry bagasse), arabinose (1.5 g/100 g), and total sugar (52.9 g/100 g) were obtained in the hydrolysis of the SO2-impregnated bagasse. The H2SO4-impregnated bagasse gave the highest glucose yield (35.9 g/100 g) but the lowest total sugar yield (42.3 g/100 g) among the three methods. The low total sugar yield from the H2SO4-impregnated bagasse was largely due to by-product formation, as the dehydration of xylose to furfural. Sulfuric acid impregnation led to a three-fold increase in the concentration of the fermentation inhibitors furfural and 5-hydroxymethylfurfural (HMF) and a two-fold increase in the concentration of inhibitory aliphatic acids (formic, acetic, and levulinic acids) compared to the other two pretreatment methods. The total content of phenolic compounds was not strongly affected by the different pretreatment methods, but the quantities of separate phenolic compounds were widely different in the hydrolyzate from the H2SO4-impregnated bagasse compared with the other two hydrolyzates. No major differences in the content of inhibitors were observed in the hydrolyzates obtained from SO2-impregnated and non-impregnated bagasse. The fermentability of all three hydrolyzates was tested with a xylose-utilizing Saccharomyces cerevisiae strain with and without nutrient supplementation. The hydrolyzates of SO2-impregnated and nonimpregnated bagasse showed similar fermentability, whereas the hydrolyzate of H2SO4-impregnated bagasse fermented considerably poorer.

[1]  L. Gustafsson,et al.  Physiological effects of 5-hydroxymethylfurfural on Saccharomyces cerevisiae , 2000, Applied Microbiology and Biotechnology.

[2]  Jean-Philippe Delgenès,et al.  Effects of lignocellulose degradation products on ethanol fermentations of glucose and xylose by Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, and Candida shehatae , 1996 .

[3]  R. Lamuela-Raventós,et al.  Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent , 1999 .

[4]  C. M. Kinoshita,et al.  Steam explosion of sugarcane bagasse as a pretreatment for conversion to ethanol. , 1998 .

[5]  E. Sjöström,et al.  Wood Chemistry: Fundamentals and Applications , 1981 .

[6]  James C. Linden,et al.  Optimizing peracetic acid pretreatment conditions for improved simultaneous saccharification and co-fermentation (SSCF) of sugar cane bagasse to ethanol fuel , 1999 .

[7]  Bärbel Hahn-Hägerdal,et al.  Fermentation of lignocellulosic hydrolysates. I: inhibition and detoxification , 2000 .

[8]  Lonnie O. Ingram,et al.  Effect of organic acids on the growth and fermentation of ethanologenic Escherichia coli LY01. , 1999 .

[9]  Mats Galbe,et al.  The effect of water-soluble inhibitors from steam-pretreated willow on enzymatic hydrolysis and ethanol fermentation , 1996 .

[10]  E. Hägglund.  Chemistry of wood , 1951 .

[11]  L. Gustafsson,et al.  Characterization and fermentation of dilute-acid hydrolyzates from wood , 1997 .

[12]  Leif J. Jönsson,et al.  Comparison of different methods for the detoxification of lignocellulose hydrolyzates of spruce , 1999 .

[13]  J. Weiner,et al.  Fundamentals and applications , 2003 .

[14]  W. A. Scheffers,et al.  Effect of benzoic acid on metabolic fluxes in yeasts: A continuous‐culture study on the regulation of respiration and alcoholic fermentation , 1992, Yeast.

[15]  Mats Galbe,et al.  Optimisation of steam pretreatment of SO2-impregnated mixed softwoods for ethanol production , 1998 .

[16]  B. Hahn-Hägerdal,et al.  Detoxification of wood hydrolysates with laccase and peroxidase from the white-rot fungus Trametes versicolor , 1998, Applied Microbiology and Biotechnology.

[17]  B. Hahn-Hägerdal,et al.  Anaerobic Xylose Fermentation by Recombinant Saccharomyces cerevisiae Carrying XYL1, XYL2, andXKS1 in Mineral Medium Chemostat Cultures , 2000, Applied and Environmental Microbiology.

[18]  J. Bautista,et al.  Effects of furfural and 5-hydroxymethylfurfural on the fermentation of Saccharomyces cerevisiae and biomass production from Candida guilliermondii , 1988 .

[19]  Mats Galbe,et al.  Comparison of SO2 and H2SO4 impregnation of softwood prior to steam pretreatment on ethanol production , 1998 .

[20]  P. Gray,et al.  Optimization of steam explosion as a method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification , 1987, Biotechnology and bioengineering.

[21]  Leif J. Jönsson,et al.  Influence of lignocellulose-derived aromatic compounds on oxygen-limited growth and ethanolic fermentation by Saccharomyces cerevisiae , 2000, Applied biochemistry and biotechnology.

[22]  Pettersson Lg,et al.  The mechanism of enzymatic cellulose degradation. Isolation and some properties of a beta-glucosidase from Trichoderma viride. , 1974 .

[23]  L. Gustafsson,et al.  Conversion of furfural in aerobic and anaerobic batch fermentation of glucose by Saccharomyces cerevisiae. , 1999, Journal of bioscience and bioengineering.

[24]  G. Zacchi,et al.  The generation of fermentation inhibitors during dilute acid hydrolysis of softwood , 1999 .

[25]  D. Gregg,et al.  A techno-economic assessment of the pretreatment and fractionation steps of a biomass-to-ethanol process , 1996 .