The Effect of Carbon Sources on Carotenoid Synthesis by the Novel Rhodococcus corynebacterioides TAO1

The financial feasibility of microbial carotenoid synthesis can be markedly improved by using widely available and renewable carbon sources. In this study, different carbon sources including molasses, were tested as carbon sources for Rhodococcus corynebacteioides TAO1. The effect of different molasses concentrations (50–250 mL/L) on bacterial growth, carotenoid synthesis, and exopolysaccharide production was determined during a 30-day period. The results demonstrated an upward trend between molasses concentration and bacterial dry weight up to 200 mL/L, with the highest dry weight measured as 0.656 ± 0.049 g. Bacterial growth was decreased at 250 mL/L molasses concentration due to possible carbon-source inhibition. However, carotenoid production exhibited a negative interaction with a maximum yield of 1.572 ± 0.108 mg/g in basal medium, while the lowest carotenoid production was determined as 0.84 ± 0.007 mg/g at 250 mL/L molasses concentration, showing that increased carbon availability might inhibit pigment biosynthesis. FTIR analysis indicated significant functional groups, such as C=O, O-H, C=C, and =CH, with significant peaks at 1713, 1655, and 1459 cm−1, indicating the presence of carotenoid intermediates. The data highlight the interaction between carbon source concentration and microbial metabolism, emphasizing the importance of optimal nutrient factors for improving both carotenoid and EPS production. This research presents significant insights into economical biotechnological methods for the production of microbial pigments and biopolymers from industrial by-products.