Optimizing Coconut Coir Pith as a Substrate for Kraft Lignin Production: Insights into the Lignin-Degrading Potential of Pusillimonas noertemannii

Coconut coir pith (CCP), a lignocellulosic waste from the coconut industry, offers opportunities for environmental management through kraft lignin (KL) production and the isolation of lignin-degrading bacteria. This study evaluated KL, obtained via alkaline pretreatment of CCP, as a substrate for bacterial growth and lignin degradation. Bacterial isolates were cultured in mineral salt medium (MSM) supplemented with KL, revealing laccase activity indicative of effective lignin degradation. The effects of KL concentrations (1000 to 16000 mg/L) on bacterial growth and degradation efficiency were assessed. Moderate KL levels (2000 mg/L) significantly enhanced bacterial growth and achieved a 92.03% degradation rate, while higher concentrations diminished efficiency, suggesting an inverse relationship. Color reduction of up to 94.12% was noted at 4000 mg/L, indicating strong decolorization capabilities. Molecular characterization identified the most promising isolate as Pusillimonas noertemannii, demonstrating its efficacy in degrading complex lignin structures and facilitating the recovery of valuable byproducts. The study highlights the importance of optimal KL concentrations for maximizing microbial performance. This research confirms the potential of CCP for KL production and positions P. noertemannii as a viable candidate for biotechnological lignin biodegradation applications, contributing to sustainable waste management and environmental conservation.