Mushrooms as food and supplements - batch culture fermentation of Coriolus versicolor as a promising process for antibacterial compounds production

Abstract

Researches have reported antimicrobial, antioxidative, antitumor, immunomodulatory and other activities of more than 2000 mushroom species. Thanks to the promising results, both, fruiting body and mycelia are recognized as potential functional food and dietary supplement. On the market, there are already many products based on the fungi extracts. For certain types of mushrooms, submerged production of bioactive compounds stands out as the best method from the standpoint of industrial applications. Mushrooms are becoming an attractive functional food and overview about type of food suitable for enrichment with this valuable compounds were given. The aim of the research was also to grow Coriolus versicolor mushroom in liquid culture, to isolate bioactive compounds from obtained biomass (by methanol extraction), and fermentation broth (exopolysaccharides EPS, by ethanol precipitation), and to determine their antimicrobial potential. During fermentation residual glucose was quantified by HPLC. Mycelia products were characterized by FTIR spectroscopy and scanning electron microscopy. Antibacterial activity of isolated bioactive compounds was tested against eight Gram-positive and ten Gram-negative bacteria strains using broth microdilution method. Results showed that after 48h glucose concentration started to decrease and after day seven slowed down, when process was terminated saving energy and time. Applied gentle stirring during cultivation provided constant oxygen and nutrient supply and pellet fragmentation was avoided. As a result, preferred fluffy pellets with long, branched and anastomosed hyphae of high density were formed. In prepared mycelia samples, bands characteristic for polysaccharides were revealed. Also, more complex chemical composition of methanol extracts comparing to EPS was noted. That might be the explanation for the differences in antimicrobial activity. Microbicidal activity of mycelia methanol extract (20 to 40 mg/ml) was recorded against seven tested Gram-negative bacteria. This sample showed significant activity against both Gram-positive and Gram-negative strains. Based on obtained inhibitory and bicidal concentrations, it can be concluded that Gram-positive strains were more susceptible to EPS. Results makes submerged cultivation of C. versicolor as a prommising process for bioactive compounds production.