Potential fuel oils from the microalga Choricystis minor

BACKGROUND: Continuous culture of the freshwater microalga Choricystis minor was investigated for possible use in producing lipid feedstock for making biofuels. The effects of temperature (10-30 degrees C) and dilution rate (0.005-0.017 h(-1)) on lipid productivity in a nutrient sufficient medium in a 4 L stirred tank bioreactor under continuous illumination at an incident irradiance level of 550 mu E . m(-2) s(-1) and a controlled pH of 6 under carbon dioxide supplemented conditions are reported. RESULTS: The maximum lipid productivity was 82 mg L-1 d(-1) at 25 degrees C and a dilution rate of 0.014 h(-1). Lipid contents of the biomass were 21.3 +/- 1.7 g per 100 g of dry biomass, irrespective of the culture temperature and dilution rate. After the biomass had been grown in nutrient sufficient conditions in continuous culture, it was recovered and subjected to various postharvest treatments. With the best postharvest treatment, the neutral lipid contents of the algal biomass were raised similar to 6-fold relative to untreated biomass. CONCLUSION: At 82 mg L-1 d(-1), or 21000 L ha(-1) year(-1), the lipid productivity of C. minor was nearly four times the lipid productivity of oil palm, a highly productive crop. Therefore, C. minor is potentially a good source of renewable lipid feedstock for biofuels. (C) 2009 Society of Chemical Industry