Enhancement of dihydroxyacetone production by a mutant of Gluconobacter oxydans

Abstract

To improve the yield of 1,3-dihydroxyacetone (DHA) and the bioconversion rate of glycerol by Gluconobacter oxydans ( G. oxydans), He–Ne laser irradiation technology was employed in this work. Under the optimal irradiation doses of 21 mW, 21 min, mutant G. oxydans GM51 with high DHA production capacity and stable heredity was obtained through tolerance tests to glycerol and DHA. Activity of the key enzyme, glycerol dehydrogenase, in GM51 was 5.01 U/mL after 30 h culture, 75.17% higher than that in the wild (2.86 U/mL) with the same initial glycerol concentration of 100 g/L. The culture time of GM51 had been shortened by 16 h (conventional culture time is 58 h). DHA yield of GM51 was up to 91.5%, increased by 77.6% with an improvement of DHA productivity from 1.29 to 2.29 g L −1 h −1 when cultivated in 7 L bioreactor. Moreover, comparative studies on kinetics of the mutant and wild further confirmed the decrease in inhibitory of substrate and product through He–Ne laser irradiation. The mutagenesis mechanism was speculated as the mutation of the gene encoding glycerol dehydrogenase, which led to improvement in the activity of this enzyme. Therefore, He–Ne laser irradiation could efficiently enhance the DHA production ability of G. oxydans.