Kinetic and thermodynamic characterization of lipase from Aspergillus melleus and its biocatalytic performance for degradation of poly(e-caprolactone)

BACKGROUND Lipases are an interesting class of enzymes that can be used as biocatalysts for poly(e-caprolactone) degradation. This work reports on the biochemical characterization of a lipase produced through solid-state fermentation by Aspergillus melleus and its application to degrade poly(e-caprolactone). RESULTS Lipase demonstrated the best activity and remained stable even after 24 h at an optimal pH of 7.5 and 40 degrees C. The K-m and V-max values for p-nitrophenyl palmitate hydrolysis derived from Lineweaver-Burk plot were 0.286 mmol L-1 and 142.86 mu mol mL(-1) min(-1), respectively. Thermal inactivation studies revealed a half-life of 1732.5 min (28.88 h) at 40 degrees C, and dramatically reduced at elevated temperatures. The activation energy for substrate hydrolysis was 28.81 kJ mol(-1), whereas the entropy, enthalpy (Delta H degrees) and free energy (Delta G degrees) of thermal inactivation of lipase were determined to be 168.73 J mol(-1) K-1, 160.60 and 107.79 kJ mol(-1), respectively, at 40 degrees C. Increase in temperature showed a decline in Delta G degrees, but increment H* remained constant. Incubation with organic solvents did not influence the enzyme stability; however, urea and guanidine hydrochloride reduced the lipase activity. Under optimal operating conditions, the enzyme presented excellent biocatalytic ability to poly(e-caprolactone) film degradation, leading to 53% weight loss. Characterization techniques, such as Fourier transform infrared, differential scanning calorimetry and scanning electron microscopy, corroborated the effective biodegradation of poly(e-caprolactone). CONCLUSION In conclusion, broad working pH, marked stability in the presence of organic solvents, and poly(e-caprolactone) degradation constitutes a lipase from A. melleus as a promising candidate for large-scale bioremediation of solid waste.

Automated summary

The study focuses on the biochemical characterization of a lipase produced by Aspergillus melleus through solid-state fermentation, showcasing its broad working pH, stability in the presence of organic solvents, and excellent ability to degrade poly(e-caprolactone). The lipase exhibited optimal activity at pH 7.5 and 40°C, with good stability even after 24 hours, making it a promising candidate for large-scale bioremediation of solid waste.