Optimisation and kinetic studies on the production of intracellular canthaxanthin in fed-batch cultures of Dietzia natronolimnaea HS-1

A critical optimisation and kinetic study on the production improvement of carotenoid pigment extracted from Dietzia natronolimnaea HS-1 under fed-batch fermentation was conducted. High pressure liquid chromatography revealed that the most abundant pigment biosynthesised by this bacterium was canthaxanthin. The constant feeding rates (CFRs; 5.59-8.41 ml/h) for different concentrations of enzymatic hydrolysed molasses (EHM; 40.76-49.24 g/l) were optimised to achieve the highest cell biomass, total carotenoid and canthaxanthin amounts using a response surface method. Spectrophotometric and optimisation analysis showed that the maximum cell mass (17.79 g/l), total carotenoid (16.37 mg/l) and canthaxanthin (14.63 mg/l) can be obtained at 45.90 g/l EHM with a CFR of 6.40 ml/h. A very close agreement between experimental and predicted data was found. A substantial increase (123.4%) in production of canthaxanthin was achieved after 152 h fed-batch process under optimal CFR mode as compared with batch process. Moreover, the maximum specific growth rate and, the volumetric productivities and yields of cell mass, total carotenoid and canthaxanthin in fed-batch culture were significantly more than the batch one.