Humidified Column Solid-State Bioreactor for Enhanced Laccase Production under Forced Aeration

Solid-state fermentation (SSF) offers a promising route for enzyme production from lignocellulosic biomass; however, process scale-up remains constrained by gas–solid transport limitations within substrate beds. This study investigates the production of laccase by Trichoderma asperellum LBKURCC1 in a humidified column bioreactor using rice straw as the substrate. The effects of bed height, humidified airflow rate, and fermentation time were evaluated using Central Composite Design (CCD) combined with Response Surface Methodology (RSM). The quadratic model exhibited strong predictive capability (R² = 0.964, p < 0.001). Analysis of variance revealed that humidified aeration exerted the strongest nonlinear influence on reactor performance, highlighting its critical role in balancing oxygen availability and moisture retention. An operating window of 11 cm, a humidified airflow rate of 1 L·min^-1, and a fermentation time of 4 days yielded a validated laccase activity of 253.8 U·L^-1. Compared with the optimized flask-based SSF system previously reported for Trichoderma asperellum LBKURCC1 cultivated on rice straw, the humidified column bioreactor increased laccase activity from 57.7 to 253.8 U·L^-1 (339.9%) while reducing the time required to reach peak activity from 8 to 4 days (50%). The findings demonstrate that the interaction among airflow, bed configuration, and fermentation time govern laccase production, providing an engineering framework for the design and scale-up of a humidified packed-bed column bioreactors for filamentous fungi cultivation under solid-state fermentation.

Aeration, Bed Height, Laccase, Packed-bed bioreactor, Solid-state fermentation

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