Abstract

Biological degradation of torpedo grass, Panicum repens L. residues by Pleurotus ostreatus and suitability of using the highly digestible, protein-enriched, as a non conventional feedstuff in diets of Nile tilapia, Oreochromis niloticus, fingerlings were investigated. The optimal pH and temperature for growth Pleurotus ostreatus and its cellulase production were 6 and 25°C, respectively. The cellulase was induced in submerged culture with presence of the carboxymethyl cellulose and Torpedo grass residues in MSL, while the presence of additional carbon sources such as glucose, dextrose or a complex media (Potato Dextrose) suppressed enzyme production. The amount of reducing sugar present in the biodegraded biomass by cellulase after 30 min incubation time was 2.5 (U/ml/min) but was 2.1 (U/ml/min) by Pleurotus ostreatus after 14 days incubation time under optimum growth conditions. The solid substrate fermentation (SSF) was carried out at pH 6 and 25°C for 32 days. Protein contents of the biodegraded biomass increased from 7.52 to 8.91% and crude fiber contents decreased from 23.27 to 11.28. This biodegraded biomass was used as non conventional feedstuff in diets ofOreochromis niloticus fingerlings. The results showed that Nile tilapia fingerlings received diets containing 25% treated torpedo grass showed the best results in growth parameters, feed efficiency and economic efficiency.

Key words: Biodegradation, Pleurotus ostreatus, torpedo grass, Panicum repens L., Nile tilapia, growth parameters.