Development of an integrated bioprocess using Trichoderma harzianum BPGF1 for hexavalent chromium remediation and cellulolytic enzyme production

This study establishes a unique integrated bioprocess of using Trichoderma harzianum BPGF1 as a promising fungal candidate to concurrently accomplish two industrially significant goals, hexavalent chromium Cr(VI) removal and the co-production of cellulolytic enzymes. The isolate exhibited high tolerance to Cr(VI) concentrations up to 400 mg/L. However, increasing Cr(VI) levels led to a decline in removal efficiency, attributed to reduced fungal biomass and diminished availability of surface functional groups. Notably, at a sub-lethal concentration of 50 mg/L Cr(VI), both cellulase and xylanase activities were significantly enhanced relative to the control, indicating a potential metal-induced stimulatory effect. While many studies have been focused on optimizing either chromium removal or enzyme production individually, no research has yet simultaneously optimized both processes in a single system. The current study employed multi-objective optimization (MOO) to optimize a single set of conditions that maximizes both outcomes. A multi-objective optimization approach identified an optimal operational condition achieving 93.56 ± 3.12 % Cr(VI) removal (from 100 mg/L), along with cellulase and xylanase yields of 5.62 ± 0.75 IU/mL and 470 ± 5.42 IU/mL, respectively. SEM analysis showed relatively irregular, aggregated, and swollen hyphae compared to the control, which was adapted as a detoxification mechanism. EDX and FTIR analysis confirmed chromium adsorption onto the fungal mycelium. This study presents an eco-efficient, low-cost bioprocess that addresses environmental detoxification and enzyme co-production, offering practical relevance for industrial wastewater treatment and circular bioeconomy applications.