Assessment of the Phytochemical, Proximate, Mineral and Heavy metal constituents of some grass straws used in cultivating Pleurotus ostreatus var florida Eger.

Abstract

The proximate, phytochemical, mineral and heavy metal contents of the straws of Andropogon gayanus, Panicum maximum, Pennisetum purpurea and Oryza sativa were investigated. The straws contained different levels of crude alkaloids, (0.25 ± 0.03-0.05 ±0.014), flavonoids, (0.25±0.024-0.09±0.024), Hydrogen cyanide (HCN) (4.18 ±0.03%-2.59±0.09%) phenols, (0.16±0.001%-0.013±0.007%), saponins, (0.37±0.014%-0.13± 0.014% and tannins, (0.27±0.002%-0.137±0.001%). The nutrient content of the straws also varied and ranged as Carbohydrate (CHO), 30.13±13 in Andropogon straw (ANS), to 27..49±1.26 in Panicum straw (PAS), Protein, 17.74 ± 0.47 in ANS to 13.07 ± 0.22 in PAS, Fats, 1.86 ± 0.02 in ANS to 0.53 ± 0.02 in Oryza straw (ORS), ASH, 5.49 ± 0.097 .in Pennisetum straw (PES) to 3.83 ± 0.12 in PAS, Fibre, 49.74 ± 1.97 in PAS to 41.33 ± 0.15 in PES, Moisture, 9.33 ± 0.02 in PES to 5.15 ± 0.03 in PAS to 5.0 ± 0.09 in ORS. The mineral composition of the straws (mg/100g) ranged as follows, Calcium: 305.94 ± 2.35 in ANS to 203.072±2.32 in ORS' Magnesium: 27.2± 2.8 in ORS to 8.8 ±1.39 in PAS, Potassium: 352.3 ± 2.32 in ORS to176.1 ± 0.54 in PAS, Sodium: 12.67 ±0.58 in ORS to 9.2 ± 02 in ANS, Phosphorus: 233.47 ± 1.63 in PES to 158.09 ± 05 in ANS. For heavy metals Andropogon traw contained the highest ppmCadmium (7.18), Zinc, (25.08), Lead, (8.44), and copper, (9.96), than the other straws. Oryza straw contained next highest of zinc, but lead was not present. The result of the investigations were discussed in relation of the usefulness of the straws in the cultivation of the edible mushroom Pleurotus ostreatus var florida.