Carotenoid production of Botryococcus braunii CCAP 807/2 under different growth conditions

Abstract

Botryococcus braunii CCAP 807/2 has been studied intensively for biofuel production due to its high hydrocarbon content. This strain is also capable of producing high value carotenoids. The aim of the study was to analyse the carotenoid produc- tion of B.braunii 807/2 under different growing conditions, first, by using different media and light intensities in indoors, and next, to examine the carotenoid composition between green, intermediately pigmented and red B. braunii grown in indoors and outdoors. The alga was cultured indoors under two different light intensities (100 and 500 μmol photons m−2 s−1) using three different media: a control with complete modified CHU 13 medium, modified CHU 13 without N and modified CHU13 without N + 2Fe. All cultures were grown at 25 °C with 12:12 h light:dark cycle and were mixed with magnetic stirrers. For the determination of carotenoid composition at different stages, the green, intermediately pigmented and red cells were collected from indoor and outdoor cultures and analysed for their carotenoid composition using HPLC. The cultures grown at high light intensity reached the highest biomass yield at 0.6 g L−1 on day 16, whereas their counterparts at low light intensity took 30 days to reach the same biomass yield. The carotenoid production of B. braunii 807/2 at high light intensity increased up to twofold in 2 days compared to the ones grown at low light. Botryococcus braunii 807/2 accumulates lutein, canthaxanthin and astaxanthin and β,β-carotene as the main carotenoids. Whilst lutein was the major carotenoids of the green/intermediate cells, canthaxanthin and astaxanthin were the predominant carotenoids of the red cells under indoor and outdoor culture, respectively. This study suggests that Botryococcus braunii 807/2 is a potential candidate for the produc- tion of lutein and/or astaxanthin. It accumulates a high amount of lutein when grown under optimum conditions and a high amount of astaxanthin when grown under sub-optimum conditions outdoors. Keywords Astaxanthin · Chlorophyceae · Light · Lutein · Outdoor culture