Intense pulse light (IPL) technology is a new non-toxic and environmentally friendly cold treatment technology, which can be applied to mutation breeding of microorganisms and to obtain high-producing strains. Aspergillus Niger is the main strain producing pectinase in food industry at present, but its pectinase yield is low. In order to verify the feasibility of applying intense pulse light technology to mutagenize Aspergillus Niger strains for high yield of pectinase, this experiment used intense pulse light technology to mutagenize Aspergillus Niger. With pulse voltage, pulse number and pulse distance as independent variables and ratio of transparent circle to colony diameter as dependent variables, steepest slope moving tests, response surface tests and result analysis are carried out to determine the optimum conditions for high-yield pectinase induced by the intense pulse light. At the same time, secondary screening of mutant strains was carried out and the genetic stability of the mutant strain was determined and the enzymatic properties of the mutant strain with high pectinase production were explored. The results showed that the multiple quadratic regression equation of transparent circle and colony diameter ratio (Y) against impulse voltage (A), pulse number (B) and pulse distance (C) is as follows: Y=1.59+0.068A+0.048B-0.033C- 0.011AB-0.019AC-0.022BC-0.071A2-0.087B2-0.13C2.All the factors in the response surface design test were significant, and the interaction between two factors was not significant. The optimum mutagenesis conditions were when the pulse voltage was 2 075 V, the pulse number 36 times and the pulse distance 5.4 cm. Under the optimum conditions, the ratio of transparent circle to colony diameter could reach 1.58, which was in good agreement with the predicted value of response surface fitting equation, indicating that the model was credible. Induce mutation to the Aspergillus Niger under such optimized condition, screen mutant strains using transparent circle for 60 mutant strains with bigger ratio of transparent circle to colony diameter. The mutant strain L9 with high pectinase production was finally selected by re-screening the above-mentioned 60 strains by determining pectinase activity, which was as high as (188.21+1.22) U/mL, which was 82.2% higher than that of the original strains. The results of genetic stability analysis showed that the mutant strain L9 had stable pectinase performance within 6 generations and no significant changes were seen in terms of pectinase activity, which indicated that the mutant strain L9 had good genetic stability. The optimum pH value and temperature for producing pectinase were 5.0 and 45℃. Compared with the original strain, the mutant strain L9 produced pectinase with better activity at the optimum pH and temperature. The range of the pH stability and thermal stability of the mutant strain were also significantly wider than that of the original strain, indicating that the mutant strain had good pH stability and thermal stability. Through the above experimental results, we can know that the application of intense pulse light technology to Aspergillus Niger mutation is feasible. After the intense pulse light induced mutation and secondary screening, a mutant strain of Aspergillus Niger with higher pectinase production with high enzymatic activity and good genetic stability can be obtained. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.
