Comparative Bioconversion of Rice Lignocellulosic Waste and Its Amendments by Two Oyster Mushrooms (Pleurotus Species) And The Use of the Spent Mushroom Compost as Bio-Fertilizer for The Cult

ABSTRACT

Oyster mushrooms (Pleurotus species) have been an important food item in both developed and developing countries serving an invaluable resource for nutrition, health and disease prevention. Although several agricultural wastes lignocellulose have been used for cultivation of oyster mushrooms worldwide and in Ghana, the most utilized is the wawa (Triplochiton scleroxylon) sawdust and its amendments for the cultivation of Pleurotus ostreatus in Ghana. However, a longer period of 28 days is required for fermentation of substrates by resident microorganisms to make it suitable for bioconversion. In this thesis, seven differently formulated composts of rice waste (rice straw (RS), rice husk (RH), rice bran (RB) and its amendments; 1. Rice straw only; 2. Rice straw +1% CaCO3 +10% rice bran; 3. Rice straw +1% CaCO3 +10% rice bran+ 5, 10 0 or 15% of rice bran (RB); 4. Rice straw amended with Rice husk (1:1w/w) + 1% CaCO3 +10% RB + rice bran+ 5, 10 or 15% of rice bran; 5. Engelberg mixture only; 6. Engelberg mixture + 1% CaCO3 +10% rice bran) were tested for efficiency by Pleurotus ostreatus strain EM-1 and P. eous strain P-31. The seventh composted medium was wawa sawdust for comparison purposes only. The compost formulation methods, composting, bagging, sterilization, spawning were done using the standard International Methods. The formulated substrates were composted for 0-12 days before utilization. The sterilized bags were incubated in the Mushroom House at the Food Research Institute (CSIR) Ghana. The assessment of resident mycoflora in the raw materials and composted substrates was done by using the Standard Decimal Serial Dilution Technique on two media (Cooke’s and DRBC medium). At the end of the prescribed incubation period the following parameters were determined; surface mycelial density, total number of fruit bodies after 3 flushes, total number of pinheads formed, total yield and biological efficiency, record of stipe length, pileus width, average weight of fruit bodies of the mushroom and correlation between stipe length, pileus length and Biological Efficiency were calculated. To ascertain the influence of the formulated composts on the nutritional quality of the substrates and the sporophore formed, proximate analysis (nutrient quality and mineral elements concentration (Cu, Zn, Mg, Mn, Fe, Pb, Na, K, P and Ca) were determined using International Standard Methods in the Mushroom Industry. The use of spent mushroom compost from (P. eous strain P-31) as a bio-fertilizer was tested under xxiii greenhouse conditions using tomato (Lycopersicon esculentum), pepper (Capsicum annum) and cowpea (Vigna unguiculata). The plants were grown in pots contained soil only (0%) and soil: compost mixtures to give 5-100% Spent Mushroom Compost proportions. Data was collected for 8 weeks at 30±2oC on plant height, leaf area, number of leaves, chlorophyll content, dry matter accumulation by shoot and root and in the case of cowpea, nodulation and nodule quality were assessed. The species of fungi resident in the seven differently formulated and composted substrates used for the cultivation of Pleurotus ostreatus strain EM-1 and P. eous strain P-31 varied but belong to the genera Aspergillus, Fusarium, Cladosporium, Curvularia, Rhizoctonia, Rhizopus, Rhodotorula, Trichoderma, Penicillium, Neosartorya, Byssochlamys, Geotrichum, other Yeasts and Mycelia sterilia. In each compost substrate Aspergillus species predominated followed by Penicillium. The most frequently encountered species were A. flavus, A. fumigatus, Rhodotorula sp., Penicillium citrinum and Trichoderma harzianum. Culture metabolites of A. flavus, P. citrinum and T. harzianum variably depressed radial and vegetative growth of P. ostreatus and P. eous in concentrations (1:1- 1:10v/v dilutions). The effect was severer on P. ostreatus than P. eous. The best pH was 5.4-7.0. Surface mycelium density, spawn run period (weeks), number of fruit bodies and pinheads per flush, total yield and Biological Efficiency as well as the stipe length and pileus width of the two Pleurotus species on the different compost was influenced by the composition of the substrate. Generally, P. eous strain P-31 performed better than P. ostreatus strain EM-1 on the same substrates by all the criteria used to ascertain substrate performance. The correlation coefficient R2 value of the stipe length and pileus width against Biological Efficiency showed a high correlation R2 =0.94 for all but one substrate. R2 value for fruit bodies on ‘wawa’ sawdust amended with 1% CaCO3 and 10% rice bran was lower R2