Monday, May 5, 2008
6-30

Transglycosylation reactions by a purified β-glucosidase from the thermophilic fungus, Thermoascus aurantiacus, using glucose, cellobiose and maltose as substrates: Potential applications

Ellen C. Giese1, Rodrigo S. R. Leite1, Osvaldo Santos Junior2, Aneli M. Barbosa3, Robert Dekker4, Maria de Lourdes Corradi da Silva2, Eleni Gomes1, and Roberto Da Silva1. (1) Instituto de Biociências, Letras e Ciências Exatas, UNESP, São José do Rio Preto, Brazil, (2) Faculdade de Ciências e Tecnologia, UNESP, Presidente Prudente, Brazil, (3) Departamento de Bioquímica e Biotecnologia, UEL, Londrina, Brazil, (4) Instituto Regional de Investigación Científica Aplicada, UCLM, Ciudad Real, Spain

β-Glucosidases (EC3.2.1.21) are responsible for catalyzing the final step in the enzymatic saccharification process of cellulose into glucose. These enzymes are also known to catalyze transglycosylation reactions and under certain environmental conditions produce gluco-oligosaccharides that find applications as prebiotic and nutraceutical molecules. In this study, the β-glucosidase purified from Thermoascus aurantiacus str. 179-5 was used to catalyze the reverse synthesis of gluco-oligosaccharides from glucose, cellobiose and maltose. The b-glucosidase was precipitated from the extracellular fluid with 80% ammonium sulfate, and applied to a DEAE-Sephadex-A-50 ion-exchange column and eluted with a linear NaCl (0-1.0M) gradient. Fractions showing β-glucosidase activity (assayed against p-nitrophenyl-β-D-glucoside) were applied to a Sephadex-G-50 column and eluted with 50mM sodium-acetate buffer (pH5.0). The purified β-glucosidase preparation was concentrated by ultra-filtration. Transglycosylation reactions were performed using glucose, cellobiose and maltose (50mM) in 5ml solution containing 1.0-unit of β-glucosidase, and the mixture incubated at 40ºC and pH6.0 for glucose, 60ºC and pH4.0 for cellobiose, and 40ºC and pH4.0 for maltose. The reverse synthesis products produced over various time intervals were identified by HPAEC-PAD. The main products arising from glucose transglycosylation were gluco-oligosaccharides of DP≥2 (31%), and 12% unidentified with TR7.5 min (retention time). With cellobiose, the products included glucose (TR3.03 min; 15%), and gluco-oligosaccharides of DP≥2 (11%). The action of β-glucosidase on maltose resulted in 38% conversion that comprised glucose (13%), and an array of gluco-oligosaccharides (25%). The results are important in elucidating the mode of action of β-glucosidases from T. aurantiacus in transglycosylation reactions, and their potential applications as nutraceuticals.

See more of Poster Session Two
See more of General Submissions

See more of The 30th Symposium on Biotechnology for Fuels and Chemicals (May 4 -- 7, 2008)