Author : Vasun Petcharat

Summary : Forty-five samples of rice straw were collected from straw mushroom beds during outdoor cultivation of Volvariella volvacea. These were used to isolate bacteria, actinomycetes, and fungi using the dilution plate technique both at room temperature (28-32 degree C) and at 50 degree C. Fifty-five species (433 isolates, 37 genera) of fungi, 376 isolates of unidentified bacteria, and 94 isolates of filamentous actinomycetes were collected. The frequency of each identified fungus' occurrence was calculated at various stage of bedding. Verticillium sp. was the most dominant at the beginning of bedding while aspergillus fumigatus was the most common after harvesting. Relative cellulolytic activity of each fungus was measured. Thirteen species of mesophilic and five species of thermophilic fungi showed strong cellulolytic activity. Volvariella volvacea mycelium were grown in dual cultures of each isolated organism and in media supplemented with culture filtrate of selected organisms to observe antagonistic and/or enhancing effects. Thermoactinomycete isolate TA-1 promoted growth of mushroom mycelium probably by producing some metabolites secreted into the medium. Changes in the population of each group of microorganism, pH, moisture, and temperature within the straw mushroom were investigated throughout bedding time. The pH increased very fast during the first and second days of bedding, after which there was a slight change. The moisture content decreased toward the end of the bedding time. The general pattern found in this study was an increase in temperature during bedding time, which stimulated the growth of thermophiles.