Laetiporus sulphureus is an edible wood-rotting basidiomycete, growing on decaying logs, stumps, and trunks of many deciduous and coniferous tree species. This fungus produces relatively large striking yellowish or orange-coloured bracket-like fruitbodies. L. sulphureus is widely consumed as a nutritional food because of its fragrance and texture. In this study, two L. sulphureus strains, MFLUCC 12-0546 and MFLUCC 12-0547, isolated from Chiang Rai, Thailand, were investigated for optimal conditions of mycelia growth. Potato dextrose agar and malt extract agar were observed as the favourable medium for mycelia growth. The optimum pH and temperature for the mushroom mycelia were 6–8 and 25–30℃, respectively.

Four strains of Phyllosticta were selected to study their antimicrobial activities. The tested strains were identified as Phyllosticta capitalensis, P. citriasiana, and P. cordylinophila based on the internally transcribed spacer (ITS) sequences and morphologies. Initially, the fungal strains were cultured on the potato dextrose agar (PDA) and cultivated at 27℃ for 3 weeks. After incubation, the fungal metabolites were extracted using ethyl acetate. The crude extracts were then concentrated using evaporation and subsequently used in antimicrobial activity assay. Our results showed that these fungal crude extracts could inhibit the growth of Escherichia coli, Bacillus cereus, and Pseudomonas aeruginosa but were not active against Aspergillus niger.

Six saprobic fungal isolates were assayed for the in vitro antimicrobial activity against nine pathogenic microorganisms. The results showed that four fungal isolates including Clonostachys rosea MFLU10-0261, Fusicoccum aesculi MFLU10-0260, MFLU10-0266, and Ophioceras cf. leptosporum MFLU10-0281 were effective inhibitors against some test microorganisms. Of these, Ophioceras cf. leptosporum MFLU 10-0281 and Fusicoccum aesculi MFLU10-0260 exhibited a maximum inhibition zone of 15 ± 1 mm and 11 ± 1.6 mm against Staphylococcus aureus TISTR 1466 and Candida albicans TISTR 5779, respectively. These fungi also act as strong decomposers on leaves of Magnolia liliifera during the decay process from previous study. The results suggest that saprobic fungi could be a promising resource of useful bioactive compounds.