Optimization of Pleurotus ostreatus production through response surface methodology and simplex centroid mixture designs

Abstract

Despite the increased recognition of the nutritional value of the Oyster mushroom, coupled with its ability to tolerate a wide range of climatic conditions, its production is still at infancy stage with low adoption rate in Kenya. The low uptake could be attributed to lack of skills for substrates and spawns preparations, cost of buying substrates and spawns coupled with poor knowledge on its production and consumption benefits. The objective of this study was to optimize Pleurotus ostreatus (Oyster mushroom) production through response surface methodology and simplex centroid mixture designs. The specific objectives were to optimize the spawns production, screen the local suitable substrates for the oyster mushroom cultivation, establish yield as a function of proportions of mixture components and then conduct the economic return analysis for the oyster mushroom farming in Machakos County. To achieve the objectives the spawns propagation was optimized by varying the temperature level, sterilization time and culture media concentration in order to establish the feasible levels which minimized the days of mycelium full development using central composite designs. One factor at a time approach was used to determine the local suitable substrate among them, the star grass, euphorbia, cattle manure, sugarcane bagasse and sawdust. Simplex-centroid mixture design was used to determine the substrates mixture that maximized the yield and lastly the contribution margin formula was used to determine the economic returns on the oyster mushroom 0 production. Based on the study findings 26.30 C, 17.40 minutes and and 60.89g/L of temperature level, sterilization time and culture media concentration level respectively minimized the days to full coverage of mycelium in a petri dish. There was no pinning on the cattle manure and the euphorbia substrates hence they were eliminated at the screening stage. The results showed significant variability on the different substrate compositions used under the study. Sawdust yielded the most under the pure blend at 1.1 kg per experimental unit while on the mixed blend sugarcane bagasse and sawdust produced the highest yield at 1.3 kg per experimental unit (1kg of dry substrate), giving 10% and 30% biological efficiency respectively. The economic returns analysis indicated that, the break-even point was at 54 kilograms of the oyster mushroom production, beyond that point each succeeding kilogram was produced at a diverging profit. Therefore oyster mushroom production was economically viable against the continued arable land decrease in Machakos County coupled with the rainfall unreliability. Central Composite Designs in controlling the temperature level, sterilization time and culture media were recommended for spawns maximum production. Since the mixture response was found to be more valuable than the pure blend responses then simplex- centroid mixture design for rightly proportioned substrates was recommended for improved oyster mushroom production. A further research on determining suitability of alternative locally found substrates which may be more cost effective and multiple response optimizations aimed at achieving maximal nutritional value and yield against minimal cost of spawns and substrates are recommended.