Effect of photoperiod on growth and hydrocarbon content of Botryococcus braunii cultured in effluent from seafood processing plant.

Abstract

The hydrocarbon-rich alga, Botryococcus braunii was cultivated in Modified Chu13 medium at pH 6.7. Growth of B. braunii was studied by using batch culture in 2L conical flasks with an initial algal density of 0.75 g dry weight/l under air-lift condition (air-1% CO2, rate of 7 l/min). The alga was incubated at the temperature of 25ºC, with light intensity of 120 μE/m2/s and diurnal illumination cycles under 12 hours of light / 12 hours of dark; 16 hours of light / 8 hour of dark and continuous illumination (24 hours). The best growth of this alga was achieved under continuous illumination with a dry weight of 11.97 g/l on day 14 cultivation. The highest specific growth rate was 3.6 per day and significantly higher than that of the culture under diurnal light cycles (P<0.05). Moreover, cultivation of Botryococcus braunii in effluent (nitrate 78 mg/l) from seafood processing plant and adjusting effluent to a three-fold reduction in nitrate (nitrate 26 mg/l) compared with synthetic medium (Modified Chu13) under continuous illumination were investigated. The highest algal growth was obtained in effluent with a dry weight of 13.61 g/l. B. braunii could reduce nitrate, phosphate and ammonia-nitrogen concentrations in the effluent by 73%, 74% and 79%, respectively. In addition, the hydrocarbon synthesis by the alga B. braunii was 34% of its dry weight.

Keywords

• Botryococcus braunii
• growth rate
• hydrocarbon
• effluent