High efficiency canthaxanthin production by a novel mutant isolated from Dietzia natronolimnaea HS-1 using central composite design analysis

The bacterium Dietzia natronolimnaea HS-1 is biotechnologically important due to its ability to biosynthesis the pigment canthaxanthin (CX). This study presents a promising direction to attain to the highest feasible levels in biomass dry weight (BDW), total carotenoid (TC) and CX by using the selection of superior mutant type in combination with optimization of nutrient medium components. The mutant strains were obtained using UV irradiation and ethyl methane sulfonate (EMS) treatment. Results showed that the mutants induced by EMS had higher survival and growth rates compared to UV mutants. EMS was effective mutagenic agent for strain improvement of D. natronolimnaea HS-1 for enhanced CX productivity. Also, preliminary batch experiments were carried out to achieve the suitable conditions for CX production analysis and found that D-glucose, mannose and Fe3+ have significant influences on the CX biosynthesis and microorganism growth. The medium formulation in a batch bioreactor was optimized by a central composite design-response surface methodology (CCD-RSM). Second-order empirical equations with high R-2 (0.989-0.996) between the responses and independent variables were derived. The optimum conditions for the maximum of BOW (9.95 g/l), TC(7.67 mg/l) and CX (7.10 mg/l) amounts were: D-glucose (25 g/l), mannose content (15.12 g/l) and Fe3+ concentration (36.77 ppm). (C) 2012 Elsevier B.V. All rights reserved.