BACKGROUND Light quality influences biomass and carotenoid production in microalgae, yet no information is available for Chlorococcum humicola. This work performed a series of batch cultivations of Chlorococcum humicola to assess biomass and carotenoid production in stirred tank and airlift photobioreactors under different light qualities and supplying strategies. RESULTS White light was preferred for growth while blue light was suitable for carotenoid production during stationary phase. Batch cultivation in stirred tank photobioreactors subjected to two-staged lighting yielded higher carotenoid productivity than single-staged lighting, with the highest productivity obtained when providing white light at 5000 lx during growth phase and combination of white (100 000 lx) and blue (5000 lx) lights during stationary phase. Subsequent cultivation in internal-loop airlift photobioreactors under optimal light setting based on two-staged study produced higher biomass (855 +/- 26 mg L-1) and carotenoid (8.11 +/- 0.20 mg L-1 or 9.23 +/- 0.23 mg g(-1)) than the cultivation in stirred tank systems with the same volume and operating condition. High-performance liquid chromatography (HPLC) analysis of carotenoid from airlift photobioreactors revealed that lutein, violaxanthin and neoxanthin were major carotenoids. CONCLUSIONS This work reported for the first time the effect of light quality and supplying strategy on growth and carotenoid production in Chlorococcum humicola. Two-staged lighting with white light following by combination of white light at high intensity and blue light offered new strategy to improve carotenoid productivity. Cultivation in airlift photobioreactor yielded higher biomass than the cultivation in stirred tank photobioreactors and offered an alternative for future photobioreactor selection. (c) 2019 Society of Chemical Industry