Improvement in lipid production and biodiesel quality of Pavlova sp. by monochromatic illumination

Pavlova sp. is not only one of the most popular microalgae in aquaculture, but also a source of high-quality biodiesel feedstock. With white light as a control (W), Pavlova sp. was cultured in this study under varying light quality, including monochromatic red light (R), blue light (B), and combinations thereof with different proportions (illuminators of mRnB, comprised of m red light units and n blue ones, m+n=7), to examine the effects of illuminating light quality on biocomponent production and biodiesel quality. The results show that combined monochromatic light, especially 2R5B, 3R4B, 4R3B, and 5R2B, could improve the growth of Pavlova sp. The dry weight of harvested algae powder in the 5R2B group reached 418.03 mg/L, and was 22.65% higher than that in the control group (W). Lipid production under combined monochromatic light of 4R3B reached 107.86 mg/L, and was 25.61% higher than in the control (W). In addition, illumination using 4R3B increased the proportion of C16:0 (palmitic acid) and C16: 1 (palmitoleic acid) fatty acids in Pavlova sp. by 15.55% and 21.94%, respectively, which translates into improved biodiesel quality. All cetane numbers (CN) for 4R3B-6R1B were over 51, while iodine values (IV) and degrees of unsaturation (DU) were reduced, leading to more stable biodiesel suitable for long-term storage. In addition, protein production under 6R1B was as high as 31.56 mg/L, 1.8 times greater than under W. Light quality is proposed as an effective tool to regulate biocomponent production by microalgae.