Proximate composition and heavy metal content of Pleurotus tuberregium mushroom grown on different substrates in (Aba) Nigeria

Mushrooms have been widely used as food and food supplements in Nigeria and other countries of the world for millennia. They are highly nutritious so they contain good quality carbohydrates, proteins, vitamins and minerals. This study determined the proximate, the effects of some substrates (best medium) on the yield and the heavy metal content of mushrooms of Pleurotus tuberregium (Fr.) Sing., grown in the laboratory. Four different substrates were used in the experiment to grow the mushrooms namely: topsoil, sawdust, riversand, and mixture of riversand and sawdust respectively. The quality of the fruit body produced was measured with the use of ruler and vernier calipers. Some heavy metals (Cd, Cr and Pb) were analyzed using Atomic Absorption Spectrophotometer. The parameters measured were: number of fruiting bodies, height of stipe, fresh weight, diameter of pileus and diameter of stipe. The result of the experiment on production of mushroom revealed that mushrooms on riversand substrate had the highest mean stipe height, the widest mean pileus and the significantly (p<0.05) highest yield. Nutritional parameters were measured and it was found that highest crude fiber content was found in the mushroom grown in mixture of riversand and sawdust substrate; mushrooms on riversand substrate had the highest carbohydrate percentage content and ash content was highest in Pleurotus tuberregium mushroom grown on topsoil substrate. The contents of Cd, Cr and Pb were all below the detection limit of the instrumentation for Pleurotus tuberregium mushroom grown on all substrates. From this study, the choice of substrate for the growth of mushroom for human and industrial use should be considered to enhance yield and prevent exposure to heavy metal contaminants.