Process development for the extraction of bioactive compounds from endemic South African mushrooms

This study established an initial bioprocess pipeline for producing and extracting bioactive fungal compounds, using two endemic South African mushrooms, Hericium ophelieae and Pleurotus overstrandensis, as case studies. This is the first applied study into these novel species from economically important genera. The bioprocess development encompassed bioprospecting (identification, domestication), upstream (submerged and solid-state fermentation), and downstream (extraction, screening, separation, compound identification, varying cultivation parameters, and comparisons to industry-relevant fungi) stages, providing a model for future bioprospecting studies into local fungi. Morphological and phylogenetic analyses, including microscopy and ITS sequencing, confirmed species identities. Domestication involved culturing mycelium from wild fruiting bodies on potato dextrose agar, and the cultivation of these strains, where P. overstrandensis was able to grow by both submerged fermentation and solid-state fermentation, while H. ophelieae was limited to static submerged fermentation, possibly due to host-specific ecology. Hydro-ethanolic extraction of the freeze-dried fermentation biomass and H. ophelieae fruiting bodies yielded 7–26% crude extract (w/w), soluble in water and ethanol. Extracts exhibited selective anti-cancer activity against MDA-MB-231 breast cancer without cytotoxicity to MCF-12A healthy epithelial breast cells, in contrast to doxorubicin, a chemotherapeutic drug. Antioxidant assays revealed high free-radical scavenging capacity, particularly in H. ophelieae mycelium extracts. Size-exclusion chromatography was used to separate bioactive fractions from the crude extracts, where fraction 3 of the H. ophelieae extract and fraction 5 of the P. overstrandensis extract demonstrated significantly more anti-cancer activity than their peers. LC-MS tentatively identified compounds similar to citbismine C, xylobiose, and herbicidin B, with several unmatched peaks suggesting novel structures. Nitrogen supplementation enhanced P. overstrandensis bioactivity. Pleurotus overstrandensis also outperformed the commercially cultivated and previously studied P. ostreatus in anti-cancer and antioxidant assays, while H. ophelieae produced unique compounds when compared to its relative, H. erinaceus, the well-known lion’s mane mushroom. Of the most abundant metabolites produced by both species of Hericium, many were produced at higher concentrations by H. ophelieae. This study highlighted the possibilities these fungi have as sources of bioactive compounds for nutraceutical, therapeutic, and industrial applications, as well as further demonstrating the unexplored potential of local mushroom species. This research represents a promising start to the application of African fungal species as bioprospecting targets.

Grantor dc:publisher

Stellenbosch : Stellenbosch University

Year dc:date.issued

2026

Author dc:creator

• Van der Merwe, Breyten

Advisors dc:contributor.advisor

• Van Rensburg, Eugene
• Pott, Robert
• Jacobs, Karin

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/135690

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/135690