Characterization of a purified novel Aureobasidium pullulans NAC8 lipase and covalent-immobilization for use in the biodegradation of oil-contaminated wastewater.

The aim of this study was to purify, characterize, and evaluate the potential of the immobilized extracellular lipase from Aureobasidium pullulans NAC8 (ApL) for the biodegradation of oil-contaminated wastewater. ApL was purified using aqueous two-phase partitioning (ATPS) and its biochemical properties determined. The enzyme was then covalently immobilized and characterized through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The performance of immobilized ApL in oil-contaminated wastewater was tested for its ability to remove chemical oxygen demand (COD), hydrolyze lipids, and produce free fatty acids. The purification fold and yield of ApL were 3.5 and 66 %, respectively. The purified enzyme had a subunit molecular weight of 30 kDa, with an optimum pH of 6.5 and an optimum temperature of 50 °C. The enzyme's catalytic efficiency for pNPP and pNPB was 1.53 × 10 ⁵ and 2.3 × 10 ⁵ in aqueous media, and 1.74 × 10 ⁵ and 2.7 × 10 ⁵ in organic solvent. Thermodynamic analysis revealed values for ∆H* (16.4 kJ/mol), ∆S* (-214 J/mol/K), and ∆G* (70.1-88.4 kJ/mol), indicating stability against thermal denaturation between 40 and 70 °C. The immobilized enzyme retained 70 % of its activity after ten catalytic cycles. In oil-contaminated wastewater, it achieved 83 % COD removal, 7.4 % lipid hydrolysis, and 15 % free fatty acid production after five cycles. The biochemical characteristics of the purified and immobilized ApL suggest that it has significant potential for industrial applications, particularly in the biodegradation of oil-contaminated wastewater. Its stability and high catalytic efficiency make it a promising candidate for long-term environmental and industrial use.
Competing Interests: Declaration of competing interest All authors declare no conflict of interest.
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