Original scientific paper

Hyperproduction and Thermal Characterization of a Novel Invertase from a Double Mutant Derivative of Kluyveromyces marxianus

Shaheen Aziz ; Department of Chemical Engineering, Mehran University of Engineering and Technology (MUET), Jamshoro, Sindh, PK-76062 Pakistan
Fatima Jalal ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Muhammad Nawaz ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Bushra Niaz ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Farman Ali Shah ; Department of Chemical Engineering, Mehran University of Engineering and Technology (MUET), Jamshoro, Sindh, PK-76062 Pakistan
Muhammad Hafeez-ur-Rahman Memon ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Farooq Latif ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Shahid Nadeem ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan
Muhammad Ibrahim Rajoka ; Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, PK-38000 Pakistan

Abstract

Kinetics of intracellular invertase production employing a double mutant derivative of Kluyveromyces marxianus was optimized by varying different process variables in a 23-litre fermentor. The maximum volumetric rate (QP) and invertase yield (YP/S) by M15 mutant were 1222 U/(L·h) and 160 U/g of substrate utilized, respectively (2-fold more than those of parental strain) at 50 °C on the molasses (150 g/L of total fermentable sugars) at pH=5.5. Glucose or sucrose (100, 150 or 170 g/L) did not repress invertase catabolically under the optimized fermentation conditions, contrary to the previous reports on other yeasts and filamentous fungi, where catabolite repression of sugars was predominant. Invertases derived by the wild (IW) and mutant (IM) strains were purified employing ammonium sulphate precipitation, and then characterized by column chromatographic techniques both kinetically and thermodynamically. The acidic limb of invertases was missing and collation of pKa and the heat of ionization values indicated that carboxyl groups were involved in proton transfer during active catalysis. Ratios of Kcat/Km and vmax/Km indicated that IM was significantly more specific for sucrose hydrolysis. The IM exhibited stability in different buffers at pH=3.0–10.0 and temperature of 50–70 °C, as reflected by long half-lives. IM showed significantly lower values of enthalpy of activation (ΔH*) and entropy of activation (ΔS*), while Gibbs free energy (ΔG*) was significantly increased at higher temperatures, making the IM thermodynamically more thermostable. Thus IM could be used as a catabolite-resistant invertase for the production of fructose syrup or high gravity ethanol.

Keywords

enthalpy/entropy; invertase; Kluyveromyces marxianus; medium optimization; purification; thermostability

Hrčak ID:

75185

URI

https://hrcak.srce.hr/75185

Publication date:

20.12.2011.

Article data in other languages: croatian

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