Comparative effect of gamma irradiated and steam sterilized composted 'wawa' (Triplochiton scleroxylon) sawdust on the growth and yield of pleurotus ostreatus (Jacq. Ex Fr) Kummer

Abstract

Pretreatment of lignocellulosic materials is essential for bioconversion because of the various physical and chemical barriers that greatly inhibit their susceptibility to bioprocesses such as hydrolysis and fermentation. Composted wawa (T. scleroxylon) sawdust were subjected to physical pretreatment techniques of moist heat sterilization and gamma irradiation to evaluate their comparative effects on the growth and yield of Pleurotus ostreatus. Substrates were moist heat sterilized at 95-100oC for 2.5 hours and irradiated with a CO60 source at 0 kGy, 5 kGy, 10 kGy, 15 kGy, 20 kGy, 24 kGy and 32 kGy at a dose rate of 1.7 kGy/hour using the ethanol chlorobenzene (ECB) dosimetry. Sorghum grains for spawns were also irradiated and autoclaved similarly as stated above and their interactive effects measured. Economical yield, biological efficiency, total fresh weight and flush weights recorded from the various interactions, showed significant differences (P<0.05). Number of primordial, effective fruit bodies, stipe length and cap diameter represented growth attributes were also significantly different (P<0.05). Autoclaved spawn + steam sterilized sawdust (S + S) of 32 kGy set up recorded the greatest yield of 1779g of total fresh weight or economic yield and corresponding and biological efficiency of 68.4%. Steam spawn + non steam sterilized (S + nS) and irradiated spawn + non steam sterilized (I + nS) both recorded the lowest total fresh weight and biological efficiency of 0g, 0% respectively from the 0 kGy set up