Increasing biosynthesis of a carotenoid by Deinococcus radiodurans R1 in the presence of tricarboxylic acid cycle intermediates using response surface methodology

The application of carotenoids in the pharmaceutical industry has received great attention in recent years. In this regard, extremophile microorganisms, such as Deinococcus radiodurans R1 (ATCC 13939), have shown to be a promising source of carotenoids. However, there is no previous study concerning the effect of tricarboxylic acid cycle intermediates on the carotenoid biosynthesis of this bacterium. In the present study, the influence of process parameters (citrate, malate, succinate, glutamate, and pH) on the carotenoid production of D. radiodurans R1 was evaluated using the response surface methodology. A total of 32 experiments at five levels for each factor were analyzed using the Design Expert 7 software. According to the results, the response surface methodology was a robust optimization method to enhance the production of carotenoid by D. radiodurans R1 (52.3 mg/L) as much as 21.8-fold more than the unoptimized conditions (2.4 mg/L). For the studied strain, the optimum cultural condition for carotenoid biosynthesis was observed in the fermentation medium (pH 7) containing citrate (10mM), malate (15mM), succinate (10mM), and glutamate (10 mM). Overall, the results of this study revealed that the microbial biomass and carotenoid production were affected by malate more significantly than the other studied tricarboxylic acid cycle intermediates.