Enhancing Lipase Biosynthesis by Aspergillus Melleus and its Biocatalytic Potential for Degradation of Polyester Vylon-200

Abstract

Herein, response surface methodology (RSM) was employed to optimize the bioprocess parameters for improved production of extracellular lipase by Aspergillus melleus and evaluated its biocatalytic potential for degradation of polyester vylon-200. Our previous report showed that pH, incubation time, temperature, and additional nitrogen source had significant effects on lipase biosynthesis. The variance analysis revealed that the established RSM model based on a central composite design for lipase production was significant (p < 0.0001, R2 = 0.9925). Under the optimized bioprocess conditions of pH 5.68, incubation time 96 h, temperature 30 °C, and diammonium tartrate as a nitrogen source, maximum lipase titer of 1346.87 U/gds was achieved, 1.92-fold higher than lipase yield in basal medium. The optimally synthesized cell-free lipase extract was partially purified by ammonium sulfate fractionation and dialysis and used to degrade polyester vylon 200. The degradation profile revealed that the lipolytic enzyme demonstrated excellent hydrolytic potential resulting in a 76% weight of polyester vylon-200. Differential scanning calorimetry revealed a noticeable decrease in the glass transition temperature of PV-200 (from 72.6 oC to 63.9 oC). Scanning electron microscopy envisaged various micron-scale cracks and holes on the surface of film after enzymatic treatment. Likewise, significant weight loss of the PV-200 films was also corroborated by FTIR analysis. This study's findings illustrate lipase's potential as a green and ecofriendly biocatalyst for robust polyester degradation and depolymerization.