The objective of the study was to determine the biodegrading capacity of oyster mushroom Pleurotus ostreatus on paddy straw, banana stalk and banana leaf naturally from 0 to 45 days. Lignocellulosic compounds, production of extracellular enzymes, protein content, amount of reducing sugar, pH, degraded weight and ash content were determined on every 15 days interval using the substrates which were degraded by P. ostreatus. Percentage of lignin content decreased from 16.7% to 2.4% in paddy straw from 17.9% to 8.2% in banana stalk and from 28.7% to 14.3% in banana leaf. Cellulose content of the paddy straw showed a significant decrease from 35.1% to 6.6%, in banana stalk from 50.1% to 29.9% and in banana leaf from 29.0% to 12.6%, within 45 days. Hemicellulose content was decreased from 20.7% to 5.4% in paddy straw, from 12.9% to 6.7% in banana stalk and from 19.1 % to 8.7% in banana leaf, in 45 days. MnPase enzyme activity was optimum on 30^th day in all the three substrates. Endo-1,4-β-D- Gluconase activity was higher in paddy straw and in banana leaf on 30^th day and significantly higher on 15^th day in banana stalk. Exo-1,4-β-D- Gluconase activity was significantly higher on 45^th day in all three substrates. Percentage of protein content was increased and percentage of reducing sugar content was decreased in all three substrates with increase in incubation period. pH of the substrate showed varying trend in all the 3 substrates used. Ash content of the substrates were significantly decreased from 7.1 to 1.3 in paddy straw, from 4.3 to 2.1 in banana stalk and from 3.5 to 0.084 in banana leaf in, 45 days. Degraded weight of all the substrates decreased significantly from the beginning towards the end. Degrading capacity of P.ostreatus was significantly higher in paddy straw (53 %) in 45 days, than the other wastes. Therefore, P.ostreatus mushroom could be recommended as a natural degrader of paddy straw left over in the field, after harvesting, which would later increase the soil fertility.

Key words: Agro-wastes, paddy straw, Gluconase