Lignocellulose Degradation of Cotton Stalks through Solid State Fermentation Using Fungal Isolates

Abstract

Background and Aim: Lignocellulosic biomass such as cotton stalks represents an abundant agricultural residue with significant potential for conversion into value-added products; however, its utilization is limited due to high lignin content. This study aimed to isolate and identify efficient lignocellulolytic fungi capable of enhancing cotton stalk degradation through solid-state fermentation (SSF). Methodology: A total of 26 fungal isolates were obtained from soil samples collected in Nagpur District, Maharashtra, India, and screened for cellulolytic and ligninolytic activities. Promising isolates were identified through ITS gene sequencing, and their enzymatic activities including carboxymethyl cellulase (CMCase), β-glucosidase, and filter paperase (FPase) were evaluated under SSF conditions. Results: Four efficient fungal isolates were identified as Trichoderma asperellum, Trichoderma sp., Penicillium chrysogenum, and Alternaria sp. Among them, Alternaria sp. CICR4 exhibited the highest CMCase activity (30.46 IU mL⁻¹), while T. asperellum CICR1 showed the maximum β-glucosidase activity (40.8 IU mL⁻¹). Alternaria sp. CICR4 demonstrated the highest FPase activity (25.6 IU mL⁻¹). Temperature optimization indicated that 30 °C was the most favorable condition for maximum enzyme production. Under solid-state fermentation of cotton stalks, co-culturing P. chrysogenum CICR3 with T. asperellum CICR1 significantly enhanced enzymatic activities, resulting in CMCase activity of 28.4 IU mL⁻¹, β-glucosidase activity of 21.7 IU mL⁻¹, and FPase activity of 24.4 IU mL⁻¹. Conclusion: The study demonstrates that selected lignocellulolytic fungi, particularly T. asperellum CICR1 and P. chrysogenum CICR3, possess strong enzymatic potential for efficient degradation of cotton stalks under solid-state fermentation. The synergistic interaction observed in co-culture significantly enhances cellulolytic enzyme production, indicating a promising strategy for sustainable lignocellulosic biomass valorization and agricultural waste management.