Preliminary evaluation of inhibitory activity of medicinal mushroom extracts against pathogenic bacteria and spoilage yeasts

Abstract

A bacterial contamination in processed foods has been a continuing challenge for the food industry. Many chemical preservatives are showing signs of inefficiencies as microorganisms build resistance. Therefore, research into novel antimicrobial compounds is critical in improving food safety. The ethanolic extracts of medicinal mushrooms (MM; Agaricus blazei Murrill, Ganoderma lucidum, Grifola frondosa, Inonotus obliquus, Lentinula edodes, and Phellinus linteus) were tested for antimicrobial activities against the common foodborne pathogens (Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes) and food spoilage yeast (Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Zygosaccharomyces bailii/bisporus). Inhibitory activities were measured using a disk diffusion assay (DD). Additional analysis for L. monocytogenes and Z. bailii were carried out using Optical density measurements (OD). HPLC was used to fractionate MM extracts (6–8 fractions per MM). The results from DD and OD showed that most MMs displayed statistically significant inhibition compared to the ethanol control. Stronger inhibition was observed for yeasts than bacteria. Also, the antimicrobial activities were fraction dependent. Further work is required to identify the bioactive compounds.