Optimization of liquid fermentation medium for Pholiota microspora based on response surface methodology

【Objective】Based on the response surface method,the effects of different carbon sources,nitrogen sources,inorganic salt types and concentrations on the production of liquid strain of Pholiota microspora were investigated,which provided theoretical basis for finding the most suitable formula for the growth of Pholiota microspora,shortening the production cycle,reducing the production cost and promoting the large-scale production of Pholiota microspora.【Method】The Pholiota microspora strain Hua 99 was selected as the study object,and the basic medium was the blank control （CK）.Five carbon sources （corn flour,sucrose,maltose,soluble starch and mannitol）,five nitrogen sources （soybean flour,beef extract,yeast infusion powder,peptone and sodium tartrate） and five inorganic salts （MgSO₄,KH₂PO₄,NaCl,MnSO₄and CaCl₂） were used as formula screening factors.Single factor test was used to screen the most suitable carbon sources,nitrogen sources and inorganic salts.The concentration gradient test was set up to screen the best carbon source,nitrogen source and inorganic salt concentrations,and the response surface method was used to optimize the fermentation formula of liquid strain of Pholiota microspora and verify it.【Result】When corn flour was used as carbon source,the globule count（70） and the mycelium growth rate （1.471 cm/d） were significantly higher than CK and other carbon sources （P＜0.05,the same below）.When soybean flour was used as nitrogen source,the mycelium biomass was the highest （6.200 g/L）.When MgSO₄ was used as inorganic salt,the mycelium growth rate was the fastest （0.638 cm/d）,and the mycelium biomass was the highest （3.102 g/L）.Corn flour,soybean flour and MgSO₄ were the best carbon source,nitrogen source and inorganic salt for liquid strain of Pholiota microspora respectively.The results of single factor test showed that the optimal concentrations of corn flour,soybean flour and MgSO₄ were 30,20 and 3 g/L.With corn flour （A）,soybean powder（B） and MgSO₄ （C） as dependent variables and mycelium biomass as response value （Y）,a quadratic multinomial regression equation was established: Y=15.448+1.531A+1.739B-0.063C+0.312AB+0.223AC-0.914BC-0.176A²-3.139B²-1.046C²,according to the F value,the order of mycelium biomass influence by each factor was determined as follows:soybean flour （B）＞corn flour （A）＞MgSO₄ （C）;the interaction between soybean flour and MgSO₄ （BC） was obvious.The validation experiment results showed that the measured mycelium biomass was 17.223 g/L,which was basically consistent with the theoretical value of 17.143 g/L.【Conclusion】The fermentation formula of liquid strain of Pholiota microspora optimized by response surface method was as follows:corn flour 30 g/L+soybean flour 16.67 g/L+MgSO₄ 2.93 g/L,and the optimized formula is effective and feasible.