Integrated analysis of hydrothermal flow through pretreatment

Biotechnology for Biofuels

Veronique Archambault-Leger²  Xiongjun Shao²  Lee R Lynd¹ 

[1] Mascoma Corporation, NH, 03766, Lebanon, USA

[2] Dartmouth College, Hanover, NH, 03755, USA

关键词: Clostridium thermocellum;    Consolidated bioprocessing;    SSF;    Xylan;    Cellulosic;    Biofuel;    Hydrothermal pretreatment;    Flowthrough pretreatment;   

Others  :  798263
DOI  :  10.1186/1754-6834-5-49

 received in 2012-03-25, accepted in 2012-07-02,  发布年份 2012

【 摘 要 】

Background

The impact of hydrothermal flowthrough (FT) pretreatment severity on pretreatment and solubilization performance metrics was evaluated for three milled feedstocks (corn stover, bagasse, and poplar) and two conversion systems (simultaneous saccharification and fermentation using yeast and fungal cellulase, and fermentation by Clostridium thermocellum).

Results

Compared to batch pretreatment, FT pretreatment consistently resulted in higher XMG recovery, higher removal of non-carbohydrate carbon and higher glucan solubilization by simultaneous saccharification and fermentation (SSF). XMG recovery was above 90% for FT pretreatment below 4.1 severity but decreased at higher severities, particularly for bagasse. Removal of non-carbohydrate carbon during FT pretreatment increased from 65% at low severity to 80% at high severity for corn stover, and from 40% to 70% for bagasse and poplar.

Solids obtained by FT pretreatment were amenable to high conversion for all of the feedstocks and conversion systems examined. The optimal time and temperature for FT pretreatment on poplar were found to be 16 min and 210°C. At these conditions, SSF glucan conversion was about 85%, 94% of the XMG was removed, and 62% of the non carbohydrate mass was solubilized. Solubilization of FT-pretreated poplar was compared for C. thermocellum fermentation (10% inoculum), and for yeast-fungal cellulase SSF (5% inoculum, cellulase loading of 5 and 10 FPU/g glucan supplemented with β-glucosidase at 15 and 30 U/g glucan). Under the conditions tested, which featured low solids concentration, C. thermocellum fermentation achieved faster rates and more complete conversion of FT-pretreated poplar than did SSF. Compared to SSF, solubilization by C. thermocellum was 30% higher after 4 days, and was over twice as fast on ball-milled FT-pretreated poplar.

Conclusions

XMG removal trends were similar between feedstocks whereas glucan conversion trends were significantly different, suggesting that factors in addition to XMG removal impact amenability of glucan to enzymatic attack. Corn stover exhibited higher hydrolysis yields than bagasse or poplar, which could be due to higher removal of non-carbohydrate carbon. XMG in bagasse is more easily degraded than XMG in corn stover and poplar. Conversion of FT-pretreated substrates at low concentration was faster and more complete for C. thermocellum than for SSF.

【 授权许可】

   
2012 Archambault-Leger et al.; licensee BioMed Central Ltd.

【 图 表 】

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【 参考文献 】

• [1]Lynd L, Cruz CHB: Make way for ethanol. Science 2010, 330:1176-1177.
• [2]Nathanael G, Celik FE, Dale B, Jackson M, Jayawardhana K, Jin H, Larson ED, Laser MS, Lynd LR, MacKenzie D, Mark J, McBride J, McLaughlin S, Saccardi D: Growing energy: how biofuels can help end America’s oil dependence. Natural Resources Defense Council 2004. http://www.nrdc.org/air/energy/biofuels/biofuels.pdf webcite
• [3]Farrell A, Plevin RJ, Turner BT, Jones AD, O'Hare M, Kammen DM: Ethanol can contribute to energy and environmental goals. Science 2006, 311:506-508.
• [4]Lynd L, Laser MS, Bransby D, Dale BE, Davison B, Hamilton R, Himmel M, Keller M, McMillan JD, Sheehan J, Wyman CE: How biotech can transform biofuels. Nat Biotechnol 2008, 26:169-172.
• [5]Alvira P, Tomás-Pejó E, Ballesteros E, Negro MJ: Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review. Bioresour Technol 2010, 101:4851-4861.
• [6]Himmel M, Ding SY, Johnson DK, Adney WS, Nimlos MR, Brady JW, Foust TD: Biomass Recalcitrance: Engineering Plants and Enzymes for Biofuels Production. Science 2007, 315:804-807.
• [7]McMillan J, Himmel ME, Baker JO, Overend RP: Pretreatment of lignocellulosic biomass. Washington, DC; 1994.
• [8]Wyman C, Dale B, Elander RT, Holtzapple M, Ladisch MR, Lee YY: Coordinated development of leading biomass pretreatment technologies. Bioresour Technol 2005, 96:1959-1966.
• [9]Yang B, Wyman CE: Pretreatment: the key to unlocking low-cost cellulosic ethanol. Biofuels, Bioprod Biorefin 2008, 2:26-40.
• [10]Mosier N, Wyman CE, Dale BE, Elander R, Lee YY, Holtzapple M, Ladisch M: Features of promising technologies for pretreatment of lignocellulosic biomass. Bioresour Technol 2005, 96:673-686.
• [11]Olson D, McBride JE, Shaw AJ, Lynd LR: Recent progress in consolidated bioprocessing. Curr Opin Biotechnol 2011, 23:396-405.
• [12]Zhang Y-H, Himmel ME, Mielenz JR: Outlook for cellulase improvement: screening and selection strategies. Biotechnol Adv 2006, 24:452-481.
• [13]Simmons B, Loque D, Blanch HW: Next-generation biomass feedstocks for biofuel production. Genome Biol 2008, 9:242. BioMed Central Full Text
• [14]Yang B, Gray MC, Liu C, Lloyd TA, Stuhler SL, Converse A, Wyman CE: Unconventional relationships for hemicellulose hydrolysis and subsequent cellulose digestion. In ACS Symposium Series on Lignocellulose Biodegradation. Edited by Saha BS, Hayashi K. American Chemical Society, Washington; 2004:100-125.
• [15]Overned R, Chornet E: Fractionation of lignocellulosics by steam-aqueous pretreatments. Philos Trans R Soc London Set A 1987, 321:523-536.
• [16]Walsum G, Allen SG, Spencer MJ, Laser MS, Antal MJ, Lynd LR: Conversion of lignocellulosics pretreated with liquid hot water to ethanol. Appl Biochem Biotechnol 1996, 57-58:157-170.
• [17]Wooley R, Ruth M, Glassner D, Sheehan J: Process design and costing of bioethanol technology: a tool for determining the status and direction of research and development. Biotechnol Prog 1999, 15:794-803.
• [18]Lynd L, Elander RT, Wyman CE: Likely features and costs of mature biomass ethanol technology. Appl Biochem Biotechnol 1996, 57/58:741-761.
• [19]Liu C, Wyman CE: The effect of flow rate of compressed hot water on xylan, lignin and total mass removal from corn stover. Ind Eng Chem Res 2003, 5409:5416.
• [20]Liu C, Wyman CE: Impact of fluid velocity on hot water only pretreatment of corn stover in a flowthrough reactor. Appl Biochem Biotechnol 2004, 113-116:113-116.
• [21]Liu C, Wyman CE: The effect of flow rate of very dilute sulfuric acid on xylan, lignin, and total mass removal from corn stover. Ind Eng Chem Res 2004, 43:2781-2788.
• [22]Yang B, Wyman CE: Effect of xylan and lignin removal by batch and flowthrough pretreatment on the enzymatic digestibility of corn stover cellulose. Biotechnol Bioeng 2004, 86:88-95.
• [23]Yang B, Wyman CE: Characterization of the degree of polymerization of xylooligomers produced by flowthrough hydrolysis of pure xylan and corn stover with water. Bioresour Technol 2008, 99:5756-5762.
• [24]National Renewable Energy Laboratory: Standard biomass analytical procedures. http://www.nrel.gov/biomass/analytical_procedures.html webcite
• [25]Shao X, Jin M, Guseva A, Liu C, Balan V, Hogsett D, Dale BE, Lynd LR: Conversion for Avicel and AFEX pretreated corn sover by Clostridium thermocellum and simultaneous saccharification and fermentation: insights into microbial conversion of pretreated cellulosic biomass. Bioresour Technol 2011, 102:8040-8045.
• [26]Kadam K, Newman MM: Development of a low-cost fermentation medium for ethanol production from biomass. Appl Microbiol Biotechnol 1997, 47:625-629.
• [27]Zhang Y, Lynd LR: Quantification of cell and cellulase mass concentrations during anaerobic cellulose fermentation: development of an enzyme-linked immunosorbent assay-based method with application to Clostridium thermocellum batch cultures. Anal Chem 2003, 75:219-227.