Temperature effect and two-step cultivation on biomass production and carotenoid accumulation in green microalga Scenedesmus PY215

Abstract

Microalgae are considered the principal source for secondary carotenoids in both pigment biosynthesis and production. These carotenoids possess potent antioxidant activity hence they are more favorable to others. In this study, the green microalga PY215, from Pong Yoob soil (Ratchaburi), was isolated and identified. Algal identification by morphological characteristics and molecular trait, using a partial sequence of tufA gene, indicated that PY215 alga is Scenedesmus bijugus. The temperature effect on biomass production and carotenoid accumulation were also investigated. This alga is classified as a mesophilic alga due to its well propagation under mixotrophic condition (light/acetate in liquid TAP) at 25°C and 35°C with the obtained dry cell of 0.84, 0.82 gDW.l^-1, respectively. After cultivation of S. bijugus PY215 (PY215) in nitrogen-reduced TAP (to 10%), the alga accumulated a greater number of carotenoid derivatives and content. The accumulation of secondary carotenoids such as ß-carotene, echinenone, canthaxanthin and astaxanthin was revealed by thin layer chromatography with a total carotenoid production of 448.74±18.70 µg.gDW^-1 (1.19-fold in comparison to a control). In adequate, biomass reduction was prominently obtained (less than 4-fold). Thereafter, two-step cultivation was employed in order to maximize the total carotenoid production in PY215. Higher biomasses were mixotrophically achieved from the two-step cultivations (25°C in TAP then nitrogen reduction TAP) in both 50% and 0% nitrogen conditions compared to the control (continuously cultivated in TAP) subsequently potentially enhancing the total carotenoid production in PY215.