Evaluation of continuous ethanol fermentation of dilute-acid corn stover hydrolysate using thermophilic anaerobic bacterium Thermoanaerobacter BG1L1
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Dilute sulfuric acid pretreated corn stover is potential feedstock of industrial interest for second generation fuel ethanol production. However, the toxicity of corn stover hydrolysate (PCS) has been a challenge for fermentation by recombinant xylose fermenting organisms. In this work, the thermophilic anaerobic bacterial strain Thermoanaerobacter BG1L1 was assessed for its ability to ferment undetoxified PCS hydrolysate in a continuous immobilized reactor system at 70°C. The tested strain showed significant resistance to PCS, and substrate concentrations up to 15% total solids (TS) were fermented yielding ethanol of 0.39–0.42 g/g-sugars consumed. Xylose was nearly completely utilized (89–98%) for PCS up to 10% TS, whereas at 15% TS, xylose conversion was lowered to 67%. The reactor was operated continuously for 135 days, and no contamination was seen without the use of any agent for preventing bacterial infections. This study demonstrated that the use of immobilized thermophilic anaerobic bacteria for continuous ethanol fermentation could be promising in a commercial ethanol process in terms of system stability to process hardiness and reactor contamination. The tested microorganism has considerable potential to be a novel candidate for lignocellulose bioconversion into ethanol.
KeywordsContinuous fermentation Corn stover Fluidized-bed reactor Hemicellulose Thermophilic anaerobic bacteria Xylose
We thank Quang Nguyen from Abengoa Bioenergy R&D, Chesterfield, MO and National Renewable Energy Laboratory (NREL), Golden, Colorado, for providing acid pretreated corn stover hydrolysate. We further thank Marie Just Mikkelsen from BioGasol ApS, Denmark for providing the strain and for performing the contamination tests.
- Aden A, Ruth M, Ibsen K, Jechura J, Neeves K, Sheehan J, Wallace B, Montague L, Slayton A, Lukas J (2002) Lignocellulosic biomass to ethanol process design and economics utilizing co-current dilute acid prehydrolysis and enzymatic hydrolysis for corn stover. NREL/TP-510–32438: http://www.nrel.gov
- Fenske JJ, Hashimoto A, Penner MH (1998) Relative fermentability of lignocellulosic dilute-acid prehydrolysates—application of a Pichia stipitis-based toxicity assay. Appl Biochem Biotechnol 73:145–157Google Scholar
- Georgieva TI, Mikkelsen MJ, Ahring BK (2007b) Ethanol production from wet-exploded wheat straw hydrolysate by thermophilic anaerobic bacterium Thermoanaerobacter BG1L1 in a continuous immobilized reactor. Appl Biochem Biotechnol DOI 10.1007/s12010-007-8014-1
- Hinman ND, Wright JD, Hoagland W, Wyman CE (1989) Xylose fermentation—an economic analysis. Appl Biochem Biotechnol 20–21:391–401Google Scholar
- Lynd LR (1989) Production of ethanol from lignocellulosic materials using thermophilic bacteria. Critical evaluation of potential and review. In: Fiechter A (eds) Advances in biochemical engineering/biotechnology, vol. 38. Springer, New York, pp 1– 52Google Scholar
- Qureshi N, Dien BS, Nichols NN, Saha BC, Cotta MA (2006) Genetically engineered Escherichia coli for ethanol production from xylose substrate and product inhibition and kinetic parameters. Trans IChemE 84(C2):114–122Google Scholar
- Schmidt JE, Ahring BK (1999) Immobilization patterns and dynamics of acetate-utilizing methanogens immobilized in sterile granular sludge in upflow anaerobic sludge blanket reactors. Appl Environ Microbiol 65:1050–1054Google Scholar