Carbon-nitrogen regulation of a laccase-producing mutant of Phanerochaete chrysosporium resisting carbon and nitrogen nutritional repression

Abstract:

Abstract:［Objective］Comparing the effects of different carbon-nitrogen nutrition and their consumption on laccase production，we studied the ecophysiological characteristics of Phanerochaete chrysosporium resisting nutritional repression，and the carbon-nitrogen physiological regulation mechanism of the white-rot fungi.［Methods］ The mutant and the wildtype strains were respectively cultured under the conditions of: carbon and nitrogen limitation，carbon limitation and nitrogen sufficiency，carbon sufficiency and nitrogen limitation，carbon and nitrogen sufficiency，to compare their laccaseproduction kinetics，cell growth and glucose and ammonia nitrogen consumption to show the characteristics and the regulation pathway of carbon-nitrogen nutrition on laccase production．［Results］The wild-type strain produced 0.107U/L，0.029U/L，12.84U/L and 18.05U/L of laccase respectively on 11th，14th，19th and 19th day when glucose or ammonia nitrogen was consumed to the lowest value; the mutant produced laccase throughout the whole process with two peaks respectively on 8th，7th，12th and 12th day with laccase of 298.83U/L，343.14U/L，271.22U/L and 251.49U/L and on 12th，13th，19th and 19th day with laccase of 257.69U/L，298.78U/L，213.81U/L and 216.93U/L. The enzyme-production kinetics trends were similar between the two strains on the condition of the same initial carbon concentration but were different on the same initial nitrogen concentration， which showed that carbon source had more effect on laccase production.［Conclusion］The laccase production of the wild-type strain was regulated by carbon or nitrogen starvation． Under different conditions，it was regulated by different nutrient．For example，under carbon limitation condition it was started by the glucose starvation，however under carbon sufficient condition the ammonia nitrogen starvation aroused it．The laccase production of the mutant didn t repress by carbon and nitrogen nutrition．Maybe it referred to a global regulation change which relieved nutritional repression on the laccase production．