Chemically defined solid-state fermentation of Pleurotus ostreatus

Pleurotus ostreatus, a white-rot edible mushroom, was cultivated on perlite particles supplemented with basidiomycete growth medium, and compared to that grown on a lignocellulosic substrate, cotton stalks. Extracellular proteins were extracted and fungal biomass was measured directly. Concomitant vigorous growth of P. ostreatus aerial hyphae was observed with glucose utilization. Uniform growth over the solid particle surface resulted in small variances in both mineralization rates of radiolabeled glucose and lignin and physiological parameters. Totals of 60% and 40% of the [¹⁴C]glucose were mineralized during solid-state fermentation on perlite-defined medium and and cotton stalks, respectively. A higher mineralization of [¹⁴C]lignin was also observed during fermentation on perlite-defined medium vs. that on natural substrate (cotton stalks). The presence of CO₂ in the headspace was found to be essential for P. ostreatus growth. A modified biometer flask was therefore developed to periodically trap the ¹⁴CO₂ released by mineralization of [¹⁴C]substances.