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 R2 (0.989–0.996) between the responses and independent variables were derived. The optimum conditions for the maximum of BDW (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).

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► We improved the yield of canthaxanthin production from Dietzia natronolimnaea HS-1.
► Mutagenesis and response surface methodology (RSM) used to enhance the production.
► The ethyl methanesulfonate (EMS) mutants had better growth rate than to UV mutants.
► The polynomial equations obtained by RSM were efficient to predict the responses.
► Developed empirical models adequately verified experimental results.