This study was conducted to investigate the microorganisms associated with substrate
used in the cultivation of mushroom (Pleurotus ostreatus) in a mushroom farm. The
substrate which is a mixture of sawdust, rice bran, lime, and water was composted for
30 days and pasteurized for use in the cultivation. Samples of pasteurized substrates
were randomly collected for the analyses using standard microbiological techniques.
Microorganisms isolated and characterized and their frequency of isolation from the
substrate include species of fungal genera Aspergillus (40.9%), Fusarium (22.7%),
Mucor (5.6%) Penicillium (17.0%), Rhizopus (11.6%) and Trichoderma (2.3%). The
species of bacteria genera isolated and frequency of isolation was Bacillus (36.67%)
Clostridium (16.67%), Enterobacter (18.33%), Escherichia (15%), and Pseudomonas
(13.33%). Aspergillus and Bacillus species had the highest frequency of occurrence for
fungi and bacteria respectively. Proper composting promotes the development of a
number of saprophytic soil microorganisms that helps in the degradation of the
substrate. The presence of cellulolytic fungi such as Aspergillus, Penicillium and
Trichoderma are associated with the composting process and do accelerate composting
for efficient recycling. Generally, the presence of fungi and bacteria in the pasteurized
substrate is attributed to the ineffectiveness of the method adopted for pasteurization
and the possession of spores that were heat tolerant by most of the isolates. The
presence of E. coli which is an indicator of faecal contamination is attributed to the
feacal contamination of the streams and river banks around the Sawmill where logs are
retained before being sawn with the sawdust as a by-product. The presence of
potential pathogens such as Bacillus, Clostridium, E. coli and Enterobacter can lead to
bacterial disease of edible mushrooms and economic loss. The presence of these
microorganisms also has serious implications for human health.
(EN)
