Antimicrobial efficacy of edible mushroom extracts: assessment of fungal resistance

Authors: Kim, Jong Heon; Tam, Christina; Chan, Kathleen - Kathy; MAHONEY, NOREEN - Former ARS Employee; CHENG, LUISA - Former ARS Employee; Friedman, Mendel; LAND, KIRKWOOD - University Of The Pacific

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2022
Publication Date: 4/30/2022
Citation: Kim, J., Tam, C.C., Chan, K.L., Mahoney, N., Cheng, L.W., Friedman, M., Land, K.M. 2022. Antimicrobial efficacy of edible mushroom extracts: assessment of fungal resistance. Applied Sciences. 12(9). Article 4591. https://doi.org/10.3390/app12094591.
DOI: https://doi.org/10.3390/app12094591

Interpretive Summary: Edible mushrooms have been utilized as a sustainable source of bioactive compounds, and constituents of certain medicinal mushrooms have emerged as integral ingredients of dietary supplements. The antimicrobial activity of alcoholic and water extracts from the mushrooms Antrodia cinnamomea, Agaricus blazei Murrill and Ganoderma lucidum was investigated against pathogenic or foodborne fungal/bacterial contaminants in defined medium or commercial food matrices. The results showed the A. cinnamomea methanol extract possessed potent antifungal/antibacterial activity, whereas the A. cinnamomea water extract exhibited limited antibacterial activity against Listeria monocytogenes. In a proof-of-concept resistance testing using the natural benzo derivative, salicylaldehyde (SA), antioxidant mutants of Penicillium expansum or Aspergillus fumigatus treated with SA exhibited a fungal tolerance, thus indicating that natural ingredients in mushrooms, such as benzoic compounds, could negatively affect the antimicrobial efficacy of mushroom extracts. Alternatively, antioxidant mutants can be adopted as risk assessment tools in compound screening processes, whereby selected molecules do not disrupt food integrity by triggering resistance of the mutants adventitiously contaminated in the food matrices. This approach will promote sustainable food production/processing, thus ensures food safety and public health.

Technical Abstract: We investigated antimicrobial activities of the water or methanol extracts of the medicinal mushrooms Antrodia cinnamomea, Agaricus blazei Murrill and Ganoderma lucidum against yeast (Candida albicans) and filamentous (Aspergillus fumigatus, Aspergillus flavus, Aspergillus para-siticus, Penicillium expansum, Neosartorya fischeri) fungal pathogens, and also against the patho-genic (Escherichia, Listeria, Salmonella, and Staphylococcus species) as well as against commensal (Lactobacillus species) bacteria. In the cell proliferation or zone of inhibition bioassays, the meth-anol extract of A. cinnamomea (AcM) exhibited both potent antifungal and antibacterial activity, while the water extract of A. cinnamomea (AcW) showed limited antibacterial activity against Listeria monocytogenes. Antifungal activity of AcM was investigated further in commercial food matrices (apple, grape juice agar). Of note, two P. expansum antioxidant mutants resistant to the phenolpyrrole fungicide, fludioxonil, were also resistant to AcM compared to the wild type strain. Results indicated the antimicrobial activity of AcM operates via the intact antioxidant signaling system in microbes; however, mutants lacking genes in the antioxidant signaling system escape the toxicity triggered by AcM. In an exemplary, proof-of-concept bioassay using the natu-ral benzoic salicylaldehyde (SA), P. expansum and A. fumigatus antioxidant mutants showed similar tolerance to SA, suggesting that natural ingredients in AcM, such as benzoic derivatives, could negatively affect the efficacy of AcM when antioxidant mutants are targeted. Collectively, AcM could be developed as a food ingredient having antimicrobial potential. Caution should, however, be exercised in the use of AcM so as not to adversely affect food safety and quality by triggering the resistance of antioxidant mutants in the contaminated food.