Optimization of cultivation conditions for extracellular polysaccharide and mycelium biomass by Morchella esculenta As51620

Abstract

The quantitative effects of fermentation time, temperature and broth content on mycelial growth in terms of dry cell weight and extracellular polysaccharide content produced by the fungus Morchella esculenta As51620 in submerged fermentation were investigated separately using response surface methodology (RSM). The three factors chosen for the present investigation were based on the results of a previous Plackett–Burman (PB) design. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and also analyzed by appropriate statistical methods. By solving the regression equation and also by analyzing the response surface contour plots, the optimal batch fermentation conditions were determined: under conditions of fermentation time 5.31 days, temperature 23.46 °C, broth content 59.53 ml; the yield of extracellular polysaccharide reached 2427.93 μg ml −1 of fermentation liquor. When fermentation time, temperature and broth content were 5.6 days, 25.13 °C and 67.01 ml, respectively, the yield of mycelium biomass reached 6.951 mg ml −1. In order to obtain simultaneously the maximum yield of extracellular polysaccharide and mycelium biomass, the above conditions would be 4.71 days, 24.82 °C and 62.64 ml, and under these conditions, the maximum predicted yield of extracellular polysaccharide and mycelium biomass were 2318.52 μg ml −1 and 6.921 mg ml −1, respectively. These predicted values were also verified by validation experiments.