Optimization of enzymatic hydrolysis of pretreated rice straw and ethanol production
- 967 Downloads
Cellulase, Tween 80, and β-glucosidase loading were studied and optimized by response surface methodology to improve saccharification. Microwave alkali-pretreated rice straw used as substrate for onsite enzyme production by Aspergillus heteromorphus and Trichoderma reesei. The highest enzymatic hydrolysis (84%) was obtained from rice straw at crude enzyme loading of 10 FPU/gds of cellulase, 0.15% Tween 80, and 100 international unit/g dry solids of β-glucosidase activities. Enzymatic hydrolyzate of pretreated rice straw was used for ethanol production by Saccharomyces cerevisiae, Scheffersomyces stipitis, and by co-culture of both. The yield of ethanol was 0.50, 0.47, and 0.48 gp/gs by S. cerevisiae, S. stipitis, and by co-culture, respectively, using pretreated rice straw hydrolyzate. The co-culture of S. cerevisiae and S. stipitis produced 25% more ethanol than S. cerevisiae alone and 31% more ethanol than S. stipitis alone. During anaerobic fermentation 65.08, 36.45, and 50.31 μmol/ml CO2 released by S. cerevisiae, S. stipitis, and by co-culture, respectively. The data indicated that saccharification efficiency using optimized crude enzyme cocktail was good, and enzymatic hydrolyzate could be fermented to produce ethanol.
KeywordsRice straw Ethanol Fungi Saccharomyces cerevisiae Scheffersomyces stipitis
The authors acknowledge the financial assistance to Ms. Anita Singh by CSIR, New Delhi in the form of Senior Research Fellowship and University Grant Commission, New Delhi for providing financial support under the Major Research Project scheme F-33-144/2007(SR).
- Caputi AJ, Ueda M, Brown T (1968) Spectrophotometric determination of ethanol in wine. American J Enol Vitti 19:160–165Google Scholar
- Cheng YS, Zheng Y, Yu CW, Dooley TM, Jenkins BM, VanderGheynst JS (2010) Evaluation of high solids alkaline pretreatment of rice straw. Appl Biochem Biotechnol 162:1768–1784Google Scholar
- Dehkhoda A, Tomas B, Mohammad MJ (2008) Comparison of vacuum and high pressure evaporated wood hydrolyzate for ethanol production by repeated fed batch using flocculating Saccharomyces cerevisiae. BioResources 4(1):309–320Google Scholar
- Goering HK, Van Soest PJ (1970) Forage fiber analysis (apparatus, reagent, procedures, and some applications). Agricultural handbook no. 379. Agriculture Research Service-United States Department of Agriculture, Washington, DC, pp 1–20Google Scholar
- Hamidimotlagh R, Iraj N, Giti E, Sorah A (2007) Mixed sugar fermentation by Pichia stipitis, Sacharomyces cerevisiaea, and an isolated xylose fermenting Kluyveromyces marxianus and their cocultures. African J Biotechnol 6(9):1110–1114Google Scholar
- Jeffries TW, Grigoriev IV, Grimwood J, Laplaza JM, Aerts A, Salamov A, Schmutz J, Lindquist E, Dehal P, Shapiro H, Jin YS, Passoth V, Richardson PM (2007) Genome sequence of the lignocellulose-bioconverting and xylose-fermenting yeast Pichia stipitis. Nature Biotechnol 25:319–326CrossRefGoogle Scholar
- Kurtzman CP, Suzuki M (2010) In: Kurtzman CP, Fell J, Boekhout T (eds) The yeasts, a taxonomic study, volume 2, 5th edn. Elsevier, New York, pp 773–777Google Scholar
- Maeda RN, Serpa VI, Rocha VAL, Mesquita RAA, Anna, LMMS, Castro AM, Driemeier CE, Pereira N, Polikarpov I (2011) Enzymatic hydrolysis of pretreated sugarcane bagasse using Penicillium funiculosum and Trichoderma harzianum cellulases. Process Biochem. doi: 10.1016/j.procbio.2011.01.022
- Mamma D, Christakopoulos P, Koullas D, Kekos D, Macris BJ, Koukios E (1995) An alternative approach to the bioconversion of sweet sorghum carbohydrates to ethanol. Biomass Bioenerg 8:99–103Google Scholar
- Saha BC, Nichols NN, Qureshi N, Cotta MA (2011) Comparison of separate hydrolysis and fermentation and simultaneous saccharification and fermentation processes for ethanol production from wheat straw by recombinant Escherichia coli strain FBR5. Appl Microbiol Biotechnol 92:865–874CrossRefGoogle Scholar