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Electronic Journal of Biotechnology
Universidad Católica de Valparaíso
ISSN: 0717-3458
Vol. 8, No. 2, 2005, pp. 177-184
Bioline Code: ej05020
Full paper language: English
Document type: Research Article
Document available free of charge

Electronic Journal of Biotechnology, Vol. 8, No. 2, 2005, pp. 177-184

 en Hyper-production of a thermotolerant β-xylosidase by a deoxy-D-glucose and cycloheximide resistant mutant derivative of Kluyveromyces marxianus check for this species in other resources PPY 125
Rajoka, Muhammad Ibrahim & Khan, Sana

Abstract

Production of β-xylosidaseby a cycloheximide and 2-deoxy-D-glucose-resistant mutant of Kluyveromyces marxianus check for this species in other resources PPY125 was studied when cultured on growth media containing galactose, glucose, xylose, cellobiose, sucrose and lactose as carbon sources. Xylose, cellobiose, lactose and sucrose were the key substrates. Both K. marxianus PPY125 and its mutant (M 125) supported maximum β-xylosidase specific product yield (YP/X) following growth on xylose. Basal level of activity was observed in non-induced cultures grown on glucose. The mutant produced 1.5 to 2-fold more β-xylosidase than that produced by the wild cells. Synthesis of β-xylosidase was regulated by an induction mechanism in both wild and mutant cells. Addition of glucose did not inhibit the synthesis of β-xylosidase in both parental and mutant cultures in the presence of corn steep liquor. Partially purified enzyme showed good stability when incubated at 60°C and was quite stable at pH 5.0-7.0. Thermodynamic studies revealed that the enzyme derived by the mutant M125 was more thermostable as evidenced by higher midpoint inactivation temperature, lower activation energy demand for β-xyloside hydrolysis, as well as lower enthalpy and entropy demand for reversible denaturation of enzyme.

Keywords
enthalpy, entropy, enzyme kinetics, fermentation, induction, thermodynamics.

 
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