Enhanced production of carotenoids and lipids by Rhodococcus opacus PD630

BACKGROUND Low‐value waste organics can be upgraded to higher‐value products using microorganisms. The bacterium Rhodococcus opacus PD630 was used to produce colorants (carotenoids) and lipids (potential fuel oils) from glycerol. RESULTS Submerged culture of R. opacus PD630 produced carotenoids and lipids on glycerol as the primary carbon source, although supplementation with glucose was necessary. A 1:1 mixture (50 g L ‐1 each) of glucose and glycerol in a batch culture afforded a final biomass concentration of nearly 9.0 g L ‐1 , a carotenoids concentration of 0.75 mg L ‐1 and a lipids concentration of nearly 2.2 g L ‐1 . Compared with using only glycerol (100 g L ‐1 ) in the medium, the final biomass concentration was nearly 4‐fold greater, the carotenoids concentration was 7.5‐fold greater and the lipids concentration was 8.6‐fold greater when a 1:1 mixture of glucose and glycerol was used. A combination of glucose (70 g L ‐1 ), glycerol (30 g L ‐1 ) and ammonium acetate (4.32 g L ‐1 ) further increased the final biomass concentration to nearly 10.2 g L ‐1 . With this formulation, the carotenoids concentration rose to 0.99 mg L ‐1 and lipids concentration rose to nearly 2.4 g L ‐1 in batch culture. A repeated fed‐batch operation with an optimal feeding regimen raised the final biomass concentration to 12.1 g L ‐1 . The final concentration of carotenoids was 0.7 mg L ‐1 and the final lipids concentration was nearly 4.9 g L ‐1 . CONCLUSION Glycerol can partly displace the more expensive glucose in production of carotenoids and lipids from R. opacus PD630. Biomass with ∼40% lipids (dry basis) can be produced. © 2017 Society of Chemical Industry