The Research Of Bjerkandera Fumosa Mutagenized To Improve Laccase Production

Laccase have broad application prospects which can apply in the fields of textile, food, paper, medicine, agriculture and so on. The White rot fungi from Basidiomycotina is the most efficient producer for laccase. However, the laccase activity from wild strains is too low to adapt to product in industrial produce. This paper choose Bjerkandera fumosa to mutate by UV and60Co-y rays in order to selecting the yielding strains of laccase, which can provide a theoretical basis for the industrial production.Mutate Bjerkandera fumosa by UV, the best mutation time was180s, mutation rate was33.3%. Selected the stable strain ZW-7which laccase activity was320.2U/L, improved27.8%that compared with the original. The highest enzyme production time was the ninth days, which was earlier in2days. The ZW-7was mutagenized by treating with60Co-y ray radiation and the best radiation dose was500Gy, mutation rate was41.7%. Selected the stable strain Co-11which laccase activity was380.5U/L, that was improved18.9%of the ZW-7and51.8%of the original strain.The highest enzyme production time was eleven days, which was the same to the original strain.Optimizing the best medium through single factor experiment and response surface for the mutagenic strain Co-11.The ingredient of medium for1liter was15g glucose,10g bran,0.17g urea,0.75mmol/L Cu2+,2.25mmol/L resveratrol,2g KH2PO4,1.5g MgSO47H2O,10-20mg Vitamin B1,1g Tween80, trace elements70mL. Response surface showed that carbon-nitrogen ratio, Cu2+concentration and esveratrol concentration have significant impact to laccase activity. The most significant effect was esveratrol concentration. The laccase activity is maximum through single factor experiment and orthogonal optimization of fermentation external conditions when the temperature is28℃, inoculation of five bacteria blocks which diameter is5mm, pH5.5, the liquid volume of100mL and the speed of120r/min. Orthogonal experiment showed that various factors’ influences of the order on laccase activity was liquid volume, pH, temperature and inoculum. Under the optimal conditions, laccase activity was828.1U/L, which was increased117.6%that compared with the original conditions.Under culture conditions optimized for Co-11carried out progressively expanding culture. Respectively in500mL and1L flask expanding culture, the production trends and activity of laccase remained the same with250mL flask system.