Abstract: [Objective] The initialized culture conditions for two Aspergillus nidulans tranformant stains TN02A7-He-mnp1 and TN02A7-He-mnp2 to produce manganese preoxidase(MnP)were optimized so as to enhance MnP activity and yield significantly. The decolorizing capacity of optimized culture solutions of two stains to 3 kinds of dyes was determined.[Method] Single-factor test was conducted to screen the optimal temperature for two strains to produce MnP. An orthogonal test was conducted to determine the effects of four factors- hemin concentration, Mn²⁺ concentration, pH value, and rotation speed on MnP activity, and a confirmation test was conducted to measure MnP activity. The absorbance value was determined to evaluate the decolorizing capacity of optimized culture solutions to 3 kinds of dyes.[Result] Results showed that the most optimal culture parameters for TN02A7-He-mnp1 to produce MnP were Mn²⁺ 267 μmol·L^-1, hemin 0.05 g·L^-1, 2 tablets of φ=10 mm inoculum, 50 mL culture solution of pH=7.5 in 100 mL flask at 180 r·min^-1 shaking condition, and under culture temperature of 37℃, on the basis of MMPGRT liquid medium plus to 2 g wood chip of Populus ussuriensis as substrate. The most optimal culture parameters for TN02A7-He-mnp2 to produce MnP were similar to those of TN02A7-He-mnp1, but only hemin 0.03 g·L^-1 and at 220 r·min^-1 shaking condition. Under above-mentioned optimal culture conditions, the highest MnP activity reached 133.62 and 147.09 U·L^-1 after 120 h culture for TN02A7-He-mnp1 and TN02A7-He-mnp2, respectively, which was 2.89 and 3.46 times higher than that produced at initial conditions. Decolorization tests showed that decolorization percents of two strains to heterocyclic dye neutral red and azo dye congo red surpassed 58% at 4 h, as high as or nearly to 100% at 16 h to neutral red and 20 h to congo red, respectively.[Conclusion] The MnP yield produced by two A. nidulans tranformants could be enhanced under optimal medium composition and culture conditions, and optimized extracellular MnP solutions of two strains could effectively decolorize heterocyclic dye neutral red and azo dye congo red.

Key words: manganese peroxidase(MnP), Aspergillus nidulans, tranformant, optimized culture, dye decolorization