Acid‐catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol

Utilization of ethanol produced from biomass has the potential to offset the use of gasoline and reduce CO2 emissions. This could reduce the effects of global warming, one of which is the current outbreak of epidemic proportions of the mountain pine beetle (MPB) in British Columbia (BC), Canada. The result of this is increasing volumes of dead lodgepole pine with increasingly limited commercial uses. Bioconversion of lodgepole pine to ethanol using SO2‐catalyzed steam explosion was investigated. The optimum pretreatment condition for this feedstock was determined to be 200°C, 5 min, and 4% SO2 (w/w). Simultaneous saccharification and fermentation (SSF) of this material provided an overall ethanol yield of 77% of the theoretical yield from raw material based on starting glucan, mannan, and galactan, which corresponds to 244 g ethanol/kg raw material within 30 h. Three conditions representing low (L), medium (M), and high (H) severity were also applied to healthy lodgepole pine. Although the M severity conditions of 200°C, 5 min, and 4% SO2 were sufficiently robust to pretreat healthy wood, the substrate produced from beetle‐killed (BK) wood provided consistently higher ethanol yields after SSF than the other substrates tested. BK lodgepole pine appears to be an excellent candidate for efficient and productive bioconversion to ethanol. Biotechnol. Bioeng. 2007;98: 737–746. © 2007 Wiley Periodicals, Inc.

[1]  G. Zacchi,et al.  Simultaneous saccharification and fermentation of steam-pretreated spruce to ethanol , 2000, Applied biochemistry and biotechnology.

[2]  T. Clark,et al.  Steam Explosion of the Softwood Pinus Radiata with Sulphur Dioxide Addition. I. Process Optimisation , 1987 .

[3]  M. Galbe,et al.  Effect of substrate and cellulase concentration on simultaneous saccharification and fermentation of steam-pretreated softwood for ethanol production. , 2000, Biotechnology and bioengineering.

[4]  R. Overend,et al.  Fractionation of lignocellulosics by steam-aqueous pretreatments , 1987, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[5]  C. Breuil,et al.  Ophiostomatoid and basidiomycetous fungi associated with green, red, and grey lodgepole pines after mountain pine beetle (Dendroctonus ponderosae) infestation , 2005 .

[6]  T. Clark,et al.  The relationship between fiber‐porosity and cellulose digestibility in steam‐exploded Pinus radiata , 1988, Biotechnology and bioengineering.

[7]  Jamie Robinson.  Pretreatment and fermentation of Douglas-fir whitewood and bark feedstocks for ethanol production , 2003 .

[8]  J. Petty,et al.  The effects of drying on the structure and permeability of the wood of Abies grandis , 1970, Wood Science and Technology.

[9]  H. Jeppsson,et al.  An interlaboratory comparison of the performance of ethanol-producing micro-organisms in a xylose-rich acid hydroysate , 1994, Applied Microbiology and Biotechnology.

[10]  C. W. Dence,et al.  The Determination of Lignin , 1992 .

[11]  M. Galbe,et al.  Reduced inhibition of enzymatic hydrolysis of steam-pretreated softwood. , 2001, Enzyme and microbial technology.

[12]  Mark T. Holtzapple,et al.  Lime pretreatment of crop residues bagasse and wheat straw , 1998 .

[13]  Warren Mabee,et al.  Biorefining of softwoods using ethanol organosolv pulping: preliminary evaluation of process streams for manufacture of fuel-grade ethanol and co-products. , 2005, Biotechnology and bioengineering.

[14]  Bruce E. Dale,et al.  Hydrolysis of lignocellulosics at low enzyme levels: Application of the AFEX process , 1996 .

[15]  Bin Yang,et al.  Fast and efficient alkaline peroxide treatment to enhance the enzymatic digestibility of steam-exploded softwood substrates. , 2002, Biotechnology and bioengineering.

[16]  C. Breuil,et al.  Nutrient Consumption and Pigmentation of Deep and Surface Colonizing Sapstaining Fungi in Pinus contorta , 2001 .

[17]  J. Saddler,et al.  Ethanol fermentation of enzymatically hydrolysed pretreated wood fractions using Trichoderma cellulases, Zymomonas mobilis, and Saccharomyces cerevisiae , 1982 .

[18]  M. Galbe,et al.  Influence of Enzyme Loading and Physical Parameters on the Enzymatic Hydrolysis of Steam‐Pretreated Softwood , 2001, Biotechnology progress.

[19]  W. Cǒté,et al.  Factors affecting permeability and pit aspiration in coniferous sapwood , 1968, Wood Science and Technology.

[20]  M. Galbe,et al.  Effect of reduction in yeast and enzyme concentrations in a simultaneous-saccharification-and-fermentation-based bioethanol process , 2005 .

[21]  Michael M. Wu,et al.  Optimization of steam explosion to enhance hemicellulose recovery and enzymatic hydrolysis of cellulose in softwoods , 1999 .

[22]  M. Galbe,et al.  The influence of lactic acid formation on the simultaneous saccharification and fermentation (SSF) of softwood to ethanol , 2000 .

[23]  L. Safranyik,et al.  Characteristics and utilization of post-mountain pine beetle wood in solid wood products. , 2006 .

[24]  Steam Pretreatment of Douglas-Fir Wood Chips , 2000 .

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

[26]  S. Mansfield,et al.  Tolerance and adaptation of ethanologenic yeasts to lignocellulosic inhibitory compounds , 2006, Biotechnology and bioengineering.

[27]  Robinson,et al.  Fermentability of the hemicellulose-derived sugars from steam-exploded softwood (douglas fir) , 1999, Biotechnology and bioengineering.

[28]  John N. Saddler,et al.  SO2-catalyzed steam explosion of corn fiber for ethanol production , 2002 .

[29]  John N. Saddler,et al.  Steam pretreatment of douglas-fir wood chips , 2000, Applied biochemistry and biotechnology.

[30]  Mark Holtzapple,et al.  Inhibition of Trichoderma reesei cellulase by sugars and solvents , 1990, Biotechnology and bioengineering.

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

[32]  G. Zacchi,et al.  A comparison between batch and fed-batch simultaneous saccharification and fermentation of steam pretreated spruce , 2005 .

[33]  J N Saddler,et al.  Steam‐explosion pretreatment of wood: Effect of chip size, acid, moisture content and pressure drop , 1986, Biotechnology and bioengineering.

[34]  M. Cotta,et al.  An ethanologenic yeast exhibiting unusual metabolism in the fermentation of lignocellulosic hexose sugars , 2004, Journal of Industrial Microbiology and Biotechnology.

[35]  J. Régnière,et al.  Effect of climate change on range expansion by the mountain pine beetle in British Columbia , 2003 .

[36]  A. Kurabi,et al.  Enzymatic hydrolysis of steam-exploded and ethanol organosolv-pretreated douglas-fir by novel and commercial fungal cellulases , 2005, Applied biochemistry and biotechnology.

[37]  B. Ahring,et al.  Inhibition of ethanol-producing yeast and bacteria by degradation products produced during pre-treatment of biomass , 2004, Applied Microbiology and Biotechnology.

[38]  F. P. Eddy,et al.  Two-stage dilute-acid pretreatment of softwoods , 2000, Applied biochemistry and biotechnology.

[39]  J. Saddler,et al.  Enzymatic hydrolysis of various pretreated lignocellulosic substrates and the fermentation of the liberated sugars to ethanol and butanediol , 1983 .

[40]  M. Galbe,et al.  Combined use of H2SO4 and SO2 impregnation for steam pretreatment of spruce in ethanol production , 2003, Applied biochemistry and biotechnology.