Enhanced hydrocarbon production and improved biodiesel qualities of Botryococcus braunii KMITL 5 by vitamins thiamine, biotin and cobalamin supplementation

Botryococcus braunii, a green microalga which is a potentially good biodiesel feedstock, was isolated from a freshwater fish pond in Bangkok, and the effects of B-vitamins-thiamine, biotin and cobalamin as well as their mixes-on its biomass, hydrocarbon production, carbohydrate content and biodiesel properties were investigated, using a control group that was not supplemented with any vitamins. The addition of thiamine increased the alga's biomass and hydrocarbon content, whereas addition of biotin, cobalamin and mixes of all three vitamins did not increase its hydrocarbon content. Among the vitamins tested, thiamine 150 μg L− 1 was the best for producing high biomass (2.08 ± 0.07 g L− 1), hydrocarbon content (37.29 ± 0.41%), hydrocarbon yield (0.77 ± 0.03 g L− 1) and hydrocarbon productivity (90.32 ± 3.05 mg L− 1 d− 1). Maximum carbohydrate content (386 ± 39 mg g− 1) was achieved by addition of 1 μg L− 1 cobalamin. Compared to the control group, the alga cultured in media supplemented with 100 μg L− 1 thiamine showed better biodiesel properties with lower iodine value (76.42 g I2 100 g− 1), cold filter plugging point (9.90 °C) and higher cetane number (54.30). Therefore, thiamine was shown to be a promising culture medium supplement for this strain for using it as a feedstock for biodiesel production. An investigation of vitamin B-related gene in B. braunii KMITL 5 found related genes for thiamine (thi), biotin (bioB and bioF) and cobalamin (metE and metH) vitamins, which are marks of vitamin autotrophy in algae.