In vivo toxicity of bioreactor-grown biomass and exopolysaccharides from Malaysian tiger milk mushroom mycelium for potential future health applications

Natural mycelial biomass (MB) and exopolysaccharides (EPS) of Malaysian tiger milk mushroom Lignosus rhinocerus are considered high-end components due to their high commercial potential value in drug discovery. This study aims to evaluate the toxicity of the mushroom extracts' generated in a bioreactor using the zebrafish embryo toxicity (ZFET) model assay as a new therapy for treating asthma. Both MB and EPS extracts, at concentrations 0.16-10 mg/mL, were tested for ZFET and early development effects on Zebrafish Embryos (ZE) during 24-120 h post-fertilisation (HPF). Findings revealed that MB was deemed safe with an LC50 of 0.77 mg/mL; the EPS were non-toxic (LC50 of 0.41 mg/mL). Neither MB nor EPS delayed hatching nor teratogenic defects in the treated ZE at a 2.5 mg/mL dose. There were no significant changes in the ZE heart rate after treatments with MB (130 beats/min) and EPS (140 beats/min), compared to that of normal ZE (120-180 beats/min). Mixing both natural compounds MB and EPS did not affect toxicity using ZFET testing; thus, intimating their safe future use as therapeutic interventions. This represents the first study to have used the ZFET assay on MB and EPS extracts of L. rhinocerus for future health applications.