Production of catalytic cells for formaldehyde production and alcohol oxidase by a catabolite repression-insensitive mutant of a methanol yeast Candida boidinii A5

A catabolite repression-insensitive mutant of Candida boidinii A5, strain ADU-15, was investigated as to alcohol oxidase production and the production of cells exhibiting the maximum catalytic activity for formaldehyde production. The mutant strain ADU-15 showed higher cell productivity and higher alcohol oxidase activity when grown on mixed substrates (glucose-methanol), especially with a high concentration of glucose in the medium. Thus, even under substrate (glucose-methanol)-limited chemostat conditions, where the glucose concentration was low, partial derepression of alcohol oxidase by glucose in mutant strain ADU-15 was detected. The chemostat culture conditions with the glucose-methanol medium were optimized for alcohol oxidase production and the production of cells exhibiting the maximum catalytic activity for formaldehyde production, respectively. By means of chemostat culturing on mixed substrates, we improved the alcohol oxidase productivity 5.0-fold and the productivity of cells exhibiting the maximum catalytic activity for formaldehyde production 3.8-fold, in comparison with the parent strain chemostat cultured with methanol as the single substrate.