Changes in activity of extracellular enzymes in dual cultures of Lentinula edodes and mycoparasitic Trichoderma strains.

AIMS: The main problem that arises during the cultivation of Lentinula edodes, the Asian Shiitake mushroom, is that the logs on which the cultivation is performed are contaminated by competing micro-organisms, especially Trichoderma spp. The aim of this study was to examine the changes in activity of extracellular enzymes in dual cultures of Trichoderma spp. and L. edodes. METHODS AND RESULTS: Extracellular enzyme activities were determined spectrophotometrically. Trichoderma enzymes important for the degradation of fungal cell walls (N-acetyl-beta-glucosaminidase and laminarinase) were shown to be induced by inactive L. edodes mycelia in liquid culture. The changes that occurred in the extracellular enzyme activities of L. edodes and mycoparasitic Trichoderma spp. (T. aureoviride, T. harzianum and T. viride) were examined during antagonistic interactions on solid medium. The extracellular enzyme patterns of both partners proved to be altered. Trichoderma spp. were induced to produce N-acetyl-beta-glucosaminidase and laminarinase in the presence of active L. edodes mycelia, similarly as observed in liquid culture. The activities of both laccase and manganese peroxidase of L. edodes decreased after physical contact with active Trichoderma mycelia, possibly in consequence of the beginning of degradation of L. edodes by the Trichoderma enzymes. However, besides a decrease in manganese peroxidase activity, an enhancement of L. edodes laccase activity was observed on solid media containing crude culture fluids from Trichoderma liquid cultures. The metabolites responsible for these effects proved to be heat stable. CONCLUSIONS: Induction and inhibition of several extracellular enzymes of both partners were shown in dual cultures of L. edodes and Trichoderma strains, indicating the important role of these enzymes in the antagonistic interaction between the two species. SIGNIFICANCE AND IMPACT OF THE STUDY: As the main problem during the large-scale cultivation of L. edodes is the contamination of the growth substrate by Trichoderma mycelia, the particular knowledge of the mechanism of this competition might be relevant.

Antibacterial effect of the culture fluid of Lentinus edodes mycelium grown in submerged liquid culture.

The antimicrobial activity of the culture fluid of Lentinus edodes mycelium grown in submerged liquid culture was tested against some common bacterial species and Candida albicans. The mycelium-free culture fluid was bacteriostatic against Streptococcus pyogenes, Staphylococcus aureus and Bacillus megaterium. The substance responsible for the activity was heat-stable, could be extracted with chloroform and had a molecular weight under 10000. These characteristics suggested that the component might be lenthionine, an antibacterial and antifungal sulphur-containing compound. The culture fluid was less toxic to human tissue culture cells than to microbes. The antibacterial activity and toxicity could not be attributed to the same component.