Effects of LED irradiation and sea water culture on the lipid characteristics of Nannochloropsis oculata

Abstract

Microalgae have higher lipid production conversion efficiency via photosynthesis among all bio-organisms and are therefore considered the most promising feedstock for biofuel production. This experimental study was conducted to investigate the effects of light-emitting diode (LED) irradiation at various wavelengths and the type of sea water used for culture on the biomass growth rate and lipid characteristics of Nannochloropsis oculata. Microalgae were cultured separately in deep and surface sea water and irradiated with LEDs. The experimental results indicated that among the various culture conditions, culture in deep sea water under red LED irradiation yielded the largest microalgae biomass quantity. However, microalgae cultured in deep sea water under blue LED irradiation appeared to have the highest elemental carbon content, heating value, and crude microalgae lipid formation and lowest carbon residue. Hence, the use of deep sea water as a culture medium, together with blue LED irradiation, would lead to the production of microalgae biodiesel with superior fuel properties compared to those produced under various other conditions. Moreover, microalgae grown in deep sea water possessed significantly superior lipid characteristics and biodiesel properties compared to those grown in surface sea water. Hence, deep sea water is more effective for microalgae cultivation. In addition, microalgae biodiesel contained higher levels of both saturated and long carbon-chain fatty acids (ranging between C20 and C22) than used cooking-oil biodiesel.