Evaluating the Antioxidant and Heavy Metal Content of Pleurotus ostreatus Mushrooms Cultivated using Sugar Cane Agro-Waste

Abstract

The sugar cane tops were obtained from farms around the northern part of KwaZulu-Natal province, South Africa (UVS farm at longitudes 28°42'24.9"S 31°54'09.0"E). The bagasse substrate, WB supplement and test mushrooms (P. ostreatus) were all obtained at the South African Department of Agriculture and Rural Development. The mushroom strain (P. ostreatus) was pre-cultured on potato dextrose agar and incubated in the dark environment at 25 ºC and then maintained as working spawn cultures at 4 ºC.The modified method outlined by Crisan and Sands (1978) was utilized for spawn preparation, whereby 1 kg of sorghum grains were soaked overnight in 1.5 l ABSTRACT Background: Pleurotus ostreatus, is one of the most cultivated mushrooms with great economic and medicinal value that can be easily grown on various bio-waste substrates. However, biosafety evaluations on these mushrooms are rarely conducted. Thus, we sought to evaluate the concentration or presence of Heavy metals in P. ostreatus mushrooms cultivated on agro-bio-waste products. Furthermore, the effect of adding agro wastes on wheat bran (WB) cultivated mushrooms was evaluated. Methods: Mushrooms grown in sugar cane tops and bagasse were supplemented with varying levels of WB. Atomic absorption spectrophotometer was applied to evaluate the concentration of heavy metals in the substrates and within mushrooms. Furthermore, DPPH free radical scavenging activity was used to determine antioxidant activity of mushroom extracts. Results: The transfer factor analysis (TF) showed that mushrooms have an affinity to absorb Zn, Cd, Cu and Cr from all tested substrates during cultivation (TF>1). The addition of WB supplement into substrates resulted into significant increase in mushroom yield. However, the increased addition of WB, inversely affected the DPPH scavenging activity of the P.ostreatus methanolic extracts. Conclusion: The bioabsorption of heavy metals by P. ostreatus is depended on the metal type. Based on these findings, mushrooms grown on these agro-waste appear to be safe and potent scavenging ability against free radicals.

Growth response and mycoremediation of heavy metals by fungus Pleurotus sp.

“…These fungi are used to remove or reduce toxic pollutants in water or soil. The threshold of the fungus in heavy metal tolerance is different depending on the type of species and the type and concentration of that heavy metal, so that inhibition of growth by a low concentration of one metal does not create an obstacle in the tolerance of another metal with a high concentration 23 , 24 . The variation in fungal response to trace metals is most likely due to intrinsic physiological factors.…”

Bioprospecting the Biological Effects of Cultivating Pleurotus ostreatus Mushrooms from Selected Agro-Wastes and Maize Flour Supplements

“…Two diferent agro-waste substrates (sugarcane bagasse and sugarcane top) were used for the cultivation of P. ostreatus mushrooms. A slightly modifed method by Mkhize et al [17] was adopted during the cultivation of the P. ostreatus mushroom. Te P. ostreatus mushroom was obtained from the KwaZulu-Natal (KZN) Department of Agriculture and Rural Development (DARD).…”