Bioactivity and toxicity of polysaccharides derived from the phytopathogenic mushroom Ganoderma orbiforme cultured in a bioreactor

The phytopathogenic status of G. orbiforme as the causative agent of basal stem rot on oil palm has masked its biotechnological potential. This study explored its growth profile in an Air-L-Shaped Bioreactor along with the antibacterial and antioxidant activities of its extracellular (EPS) and intracellular polysaccharides (IPS), and evaluated their toxicity using the zebrafish embryo toxicity (ZFET) assay. The biomass pellet peaked at 2.53 ± 0.44 g/L, with EPS and IPS yields reaching 0.15 ± 0.06 g/L (Day 6) and 0.06 ± 0.01 g/L (Day 10), respectively. Morphological observations revealed that the hairy starburst-shaped pellet correlated with peak EPS release. Then, the antibacterial assays revealed EPS as the better antibacterial agent compared to IPS, highlighted by a broader spectrum activity with the most prominent inhibition against Streptomyces griseus and Staphylococcus epidermidis with a minimum inhibitory concentration of 5 mg/mL. Both EPS and IPS showed strong antioxidative capabilities, demonstrated in DPPH assay-IC₅₀ of 15.59 ± 0.42 mg/mL for EPS and 26.85 ± 1.60 mg/mL for IPS, and FRAP assay-74.30 ± 0.38 mM Fe(II)/g for EPS and 74.18 ± 0.62 mM Fe(II)/g for IPS. Lastly, the LC₅₀ values of 1.88 mg/mL and 1.56 mg/mL for EPS and IPS, respectively, demonstrated their harmless nature in the ZFET assay. After 120 h of post-fertilization, the zebrafish embryos did not show abnormalities, with vital organs and structures remaining intact (fins, guts and melanophores). Collectively, this study underscores the importance of exploring the untapped potential of G. orbiforme while ensuring its safety status, opening a new possibility of bioprospecting a phytopathogen for oil palm. From a sustainable perspective, the production pattern and bioactivities are well aligned with SDG 15: Life on Land and SDG 3: Good Health and Well-Being, respectively.