Optimization of laccase production by Pleurotus pulmonarius through solid substrate fermentation of tender coconut fiber: enhanced laccase production and biomass delignification

Abstract

Tender coconut fiber, an abundant agro-waste, requires chemical or biological pretreatment to enhance its potential for value-added applications due to its complex lignocellulosic composition. Pretreatment of tender coconut fiber with laccase-producing white rot fungi presents a sustainable strategy for effective delignification and waste management. This study investigated the biological pretreatment of tender coconut fiber using the white rot fungus, Pleurotus pulmonarius, for delignification through enhanced laccase production via solid-state fermentation. This research involved exploring the influence of different factors on laccase production and understanding the relationships between these factors through response surface methodology (RSM) to obtain the maximum laccase production. A central composite design was employed to optimize the process parameters, including pH, temperature, incubation time, and concentration of corn steep liquor (CSL). The optimized process parameters were a pH of 5.6, a temperature of 27 °C, an incubation time of 21 days, and a CSL concentration of 3%. This optimization resulted in a remarkable increase in enzyme activity, reaching 663.76 ± 10.67 IU/ml, indicating a substantial 13.16-fold increase after the optimization process. Scanning electron microscopy (SEM) and FTIR analysis were performed to observe the changes in the surface structures of the raw and delignified fiber. The enhanced laccase activity suggests the potential for tender coconut fiber to be used to produce laccase enzymes, which has not been explored before. This approach offers a solution for managing tender coconut fiber and unlocks the potential for valorization due to the enhanced properties of the modified fiber.