Browsing by Author "Ozdemir, F. Inci"

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    Engineering of Geobacillus Kaustophilus Lipase for Enhanced Catalytic Efficiency and Methanol Tolerance in Biodiesel Production from Sunflower Oil
    (Elsevier, 2025) Tulek, Ahmet; Poyraz, Yagmur; Sukur, Gozde; Pacal, Nurettin; Ozdemir, F. Inci; Yildirim, Deniz; Essiz, Sebnem
    Lipase-mediated biodiesel production offers a sustainable and environmentally friendly alternative to conventional chemical methods. However, enzyme limitations such as low activity, poor thermal stability, and limited solvent tolerance remain challenges. In this study, a lipase from Geobacillus kaustophilus (Gklip) was engineered for improved biodiesel production using molecular docking, molecular dynamics (MD) simulations, and molecular mechanics/generalized born surface area (MM/GBSA) free energy calculations. Five mutants (Y29S, Q114T, F289D, Q184M, and Q114F) were generated via site-directed mutagenesis and expressed in Escherichia coli. Biochemical characterization revealed that all mutants retained the wild-type's optimal temperature (50 degrees C) and pH (8.0), while showing varying pH ranges, with the broadest observed in Q184M. Thermal stability increased significantly in Q184M (32.86-fold) and Q114F (5.93-fold). Catalytic efficiencies improved by 2.07-, 2.05-, and 2.63-fold in Q184M, F289D, and Y29S, respectively, compared to the wild-type (0.57). In the presence of 60 % methanol, the wild-type retained only 30.4 % activity, while Q184M maintained 67.5 %, highlighting superior solvent tolerance. Biodiesel conversion assays using sunflower oil showed no product formation by the wild-type, whereas Q184M, Q114F, and F289D achieved yields of 58.7 %, 56.3 %, and 49.2 %, respectively. These findings identify Q184M and Q114F as promising enzyme candidates for enzymatic biodiesel production.