Composition of fatty acids from cultivated Botryococcus braunii algae in dome-shaped photovioreactor for biofuel production

Abstract

Dome-shaped photobioreactor (PBR) was characteristically designed to cultivate for Botryococcus braunii (Bb) algae for investigating oil production. Its volumetric capacity was 30 L in each culture unit. Experimental treatments were designed to circulate a Bb culture solution in 4 different flow rates as 1, 5, 10 and 15 L/min. In these experiments, 12 culture units were structured to demonstrate comparison in various different conditions which each unit was arranged with a completely randomize design (CRD). The experiments were performed in 3 replicates. Experimental site was established at Rim Si Muang Sub district, Khao Kho District, Phetchabun Province, Thailand (16° 33ʹ 29.8ʺ N and 101° 01ʹ 19.6ʺ E). Elevation of the location is 815 m. above mean sea level where a Bb strain was found and collected from a fish pond. Then Bb algae were cultured from February 23 - March 14, 2012 with modified Chu 13 media for 20 days as previously done by Velichkova et al. (2012) under an ambient condition without adding CO₂ for photosynthesis. Mean daily ambient temperature was in range of 16.6 - 35.9 °C. Bb algae were harvested after 20 days of cultivation. Next, the water was staved off from Bb algae using a centrifuge (FALCON 6/300) at 3,000 rpm for 15 min. In addition, algal broth was preliminarily dried using a hot air oven (Memmert, Model 100-800) at temperature of 90 °C for 48 hrs. And was powdered using a cylindrical ball mill for 4 hrs. Algae oil extraction was done in a hexane and using sonication for 60 min. Finally, hexane was evaporated from the algae oil using a rotary evaporator. The results showed that dry weights of biomass production were 0.009±0.02, 0.137.0±0.06, 0.696±0.06, and 0.006±0.06 g dry weight/L with flow rates of 1, 5, 10 and 15 L/min, respectively. Algae oil production was 0.0753 ±0.02 and 0.383 ±0.01 g/ with flow rates of 5 and 10 L/min, respectively, whereas it was regardless for flow rates 1 and 15 L/min because of insufficient quantity of biomass. Highest dry weight of biomass production was 0.696± 0.06 g/L with flow rates 10 L/min. Conclusion; the suitable flow rate of 10 L/min had significantly a great effect in an increase of biomass concentration of Bb algae when cultured in a prototype of dome-shaped PBR. Fatty acid composition was analyzed by a gas chromatography – mass spectrometry (GC-MS) that was Docosanoic acid (Behenic acid: C22:0), Heptadecanoic acid (Margaric acid: C17:0) and Octadecanoic acid (Stearic acid: C18:0). The quantity of fatty acids was approximately 6.96 % v/v (all contain) were which can utilize to compound for biofuel production.