A newly isolated fungus Aspergillus niger SOI017 was shown to be a good producer of β-glucosidase from all isolated fungal strains. Fermentation condition (pH, cellobiose concentration, yeast extract concentration, and ammonium sulfate concentration) was optimized for producing the enzyme in shake flask cultures. Response surface methodology was used to investigate the effects of 4 fermentation parameters (yeast extract concentration, cellobiose concentration, ammonium sulfate concentration, and pH) on β-glucosidase enzyme production. Production of β-glucosidase was most sensitive to the culture medium, especially the nitrogen source yeast extract. The optimized medium for producing maximum β-glucosidase specific activity consisted of 0.275% yeast extract, 1.125% cellobiose, and 2.6% ammonium sulfate at a pH value of 3. 1. Introduction Lignocellulose is the major component of biomass, representing the most abundant renewable organic source in soil. It consists of three polymers types, cellulose, hemicelluloses, and lignin that are strongly intermeshed and chemically bonded by noncovalent forces and by covalent cross-linkages [1]. The enzymatic hydrolysis of cellulosic material into glucose involves the synergistic action of at least three different enzymes: endoglucanase or endo-β-1,4-glucanase, exoglucanase or exocellobiohydrolase, and β-1,4-glucosidase or cellobiase [2]. Endo-β-1,4-glucanase catalyzes the hydrolysis of cellulose by randomly splitting the sugar residues within the molecule, whereas exo-β-1,4-glucanase removes monomers and dimmers, from the end of the glucan chain. The β-1,4-glucosidase hydrolyzes glucose dimers and in some cases, cellulose oligosaccharides to glucose. Since cellobiose inhibits the action of endo- and exoglucanases, β-glucosidase contributes to the efficiency of this process. Very strong activity of β-glucosidase is thus needed for the pretreatment step of lignocellulose before a further ethanol conversion. In addition to the role in cellulose degradation, β-glucosidase has also been attributed to several other applications. This includes the applications in pharmaceutical, cosmetic, and detergent industries [3]. Most of the commercially available β-glucosidase are served as parts of cellulase enzymes. There are only two of those served as the actual β-glucosidase; one is the Novozym188 from Aspergillus niger (Novo Industri A/S, Denmark) and another one is β-glucosidase also from A. niger (Fluka, Switzerland). More screenings have been attempted for the novel sources of much higher β-glucosidase activity. Vaithanomsat
References
[1]
C. Sánchez, “Lignocellulosic residues: biodegradation and bioconversion by fungi,” Biotechnology Advances, vol. 27, no. 2, pp. 185–194, 2009.
[2]
R. S. R. Leite, H. F. Alves-Prado, H. Cabral, F. C. Pagnocca, E. Gomes, and R. Da-Silva, “Production and characteristics comparison of crude β-glucosidases produced by microorganisms Thermoascus aurantiacus e Aureobasidium pullulans in agricultural wastes,” Enzyme and Microbial Technology, vol. 43, no. 6, pp. 391–395, 2008.
[3]
J. Job, R. K. Sukumaran, and K. Jayachandran, “Production of a highly glucose tolerant β-glucosidase by Paecilomyces variotii MG3: optimization of fermentation conditions using Plackett-Burman and Box-Behnken experimental designs,” World Journal of Microbiology and Biotechnology, vol. 26, no. 8, pp. 1385–1391, 2010.
[4]
P. Vaithanomsat, T. Malapant, and Khomkamon, “Preliminary isolation of β-glucosidase producing fungi for biomass utilization,” in Proceedings of the 36th Congress on Science and Technology Thailand (STT '10), 2010.
[5]
M. S. Revankar and S. S. Lele, “Increased production of extracellular laccase by the white rot fungus Coriolus versicolor MTCC 138,” World Journal of Microbiology and Biotechnology, vol. 22, no. 9, pp. 921–926, 2006.
[6]
J. I. Mitchell, P. J. Roberts, and S. T. Moss, “Sequence or structure? A short review on the application of nucleic acid sequence information to fungal taxonomy,” Mycologist, vol. 9, no. 2, pp. 67–75, 1995.
[7]
H. Wang, M. Qi, and A. J. Cutler, “A simple method of preparing plant samples for PCR,” Nucleic Acids Research, vol. 21, no. 17, pp. 4153–4154, 1993.
[8]
T. J. White, T. Bruns, S. Lee, and J. Taylor, “Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics,” in PCR Protocols, M. A. Innis, D. H. Gelfand, J. J. Sninsky, and T. J. White, Eds., pp. 315–322, Academic Press, San Diego, Calif, USA, 1990.
[9]
B. A. Bunyard, M. S. Nicholson, and D. J. Royse, “A systematic assessment of Morchella using RFLP analysis of the 28S ribosomal RNA gene,” Mycologia, vol. 86, no. 6, pp. 762–772, 1994.
[10]
S. Landvik, “Neolecta, a fruit-body-producing genus of the basal ascomycetes, as shown by SSU and LSU rDNA sequences,” Mycological Research, vol. 100, no. 2, pp. 199–202, 1996.
[11]
K. L. Pang, M. A. Abdel-Wahab, S. Sivichai, H. M. El-Sharouney, and E. B. G. Jones, “Jahnulales (Dothideomycetes, Ascomycota): a new order of lignicolous freshwater ascomycetes,” Mycological Research, vol. 106, no. 9, pp. 1031–1042, 2002.
[12]
J. D. Thompson, D. G. Higgins, and T. J. Gibson, “CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice,” Nucleic Acids Research, vol. 22, no. 22, pp. 4673–4680, 1994.
[13]
T. Hall, “BioEdit Version 7.0.5.3. A user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT,” Nucleic Acids Symposium Series, vol. 41, pp. 95–98, 1999.
[14]
S. F. Altschul, T. L. Madden, A. A. Sch？ffer et al., “Gapped BLAST and PSI-BLAST: a new generation of protein database search programs,” Nucleic Acids Research, vol. 25, no. 17, pp. 3389–3402, 1997.
[15]
D. L. Swofford, PAUP. Phylogenetic Analysis Using Parsimony, Sinauer Associates, Sunderland, Massachusetts, 2002.
[16]
A. M. Barbosa, E. C. Giese, R. F. H. Dekker, D. Borsato, A. I. Briones Pérez, and J. F. úbeda Iranzo, “Extracellular β-glucosidase production by the yeast Debaryomyces pseudopolymorphus UCLM-NS7A: optimization using response surface methodology,” New Biotechnology, vol. 27, no. 4, pp. 374–381, 2010.
[17]
T. A. A. Moussa and N. A. Tharwat, “Optimization of cellulase and β-glucosidase induction by sugarbeet pathogen Sclerotium rolfsii,” African Journal of Biotechnology, vol. 6, no. 8, pp. 1048–1054, 2007.
[18]
B. Lewin, Genes III. An Up-to-Date Treatment of the Molecular Genetics of Both Eukaryotes and Prokaryotes, along with Related Cell and Molecular Biology, John Wiley & Sons, New York, NY, USA, 1987.
