Optimization of Fermentation Conditions of Paraconiothyrium variabile GHJ-4 for Laccase Production by Response Surface Methodology

In order to enhance the production of laccase by Paraconiothyrium variabile GHJ-4,response surface methodology was applied to optimize the fermentation conditions.Plackett-Burman design was used to investigate the main factors affecting laccase yield of Paraconiothyrium variabile GHJ-4.The results showed that four factors played important roles in the fermentation conditions,including inoculation volume(X1),culture time(X2),broth content(X3) and rotating speed(X4).After steepest ascent experiment approaching the optimal level of the four factors,central composite design and response surface analysis were applied to establish the second-order regression equation model,Y = 698.72 –13.64X1 + 3.46X2 + 25.45X3 – 11.64X4 + 44.94X1X3 + 0.31X2X3 + 23.14X2X4 – 19.55X3X4 – 44.65X12 – 45.07X22 – 36.52X32 – 21.60X42,for the yield of laccase.Based on this model,the optimal fermentation conditions were obtained as following: 6.43%(φ) of inoculation,28 ℃ of culture temperature,initial pH value 4,182 h of culture time,72.5 mL of broth content,157 r/min of rotating speed,and 96 h of seed age.Under the optimum conditions,the activity of laccase increased nearly 1.73 times to 710.44 U/mL and the experimental values argreed with the predicted values.These results suggested that the predicted model was reliable and available for the optimization of laccase fermentation conditions.Fig 1,Tab 6,Ref 20