Yield on agricultural wastes and antimicrobial efficacy of selected wild Pleurotus and Ganoderma mushrooms of Uganda

Abstract

Cotton seed husks dominate mushroom cultivation as a substrate in Uganda. However, their scarcity and cost reduce profitability of the venture yet there is a wide range of other potential unutilized wastes. Further, mushroom cultivation in Uganda which started in 1989; is dependent on exotic species. This study assessed selected indigenous and exotic Pleurotus and Ganoderma mushroom yield on a variety of agricultural wastes, and their antibacterial activity against selected human pathogens. Indigenous Pleurotus and Ganoderma mushrooms were collected from Mabira Forest and together with the exotic varieties were cultured on Potato Dextrose Agar (PDA) prior to cultivation on substrates namely; saw dust (SD), dry cynodon grass (DG), cotton seed husks (CSH), sugarcane baggase (SB), forest litter (FL), upland rice straws (RS) and dry banana leaves (BL). Exotic Ganoderma had a faster growth rate (4.5mm/day) on PDA than the indigenous species (1.9mm/day), but indigenous Pleurotus had a faster growth rate (7.8mm/day) than its exotic counterpart (5.8mm/day). Both Ganoderma species failed to colonize the substrates due to contamination. CSH and BL were the best performing substrates giving 113.4% and 86% biological efficiency with respect to Pleurotus spp, while SD and SB were the least performing substrates giving 39% and 36.7% biological efficiency respectively. Generally the results demonstrated that all the test substrates can be successfully used as substrates for Pleurotus mushroom cultivation. Antimicrobial analyses demonstrated that at 0.5mg/ml methanol extracts were active against P. aeruginosa, while methanol and petroleum mushroom extracts were active against S. aureus with diameter of inhibition zone ranging between 10 to 25mm. Methanol and petroleum extracts from both the exotic and indigenous Pleurotus and Ganoderma exhibited good antibacterial activity.