Cultivation of microalgae using palm oil mill effluent for lipid production

Abstract

Microalgae are reported as the potential resources to produce lipid from their biomass cell. Lipid is generally a group of organic compound that important as primary biofuel raw material, and also as component for foods, cosmetic products, fertilizers, animal feed, etc. As the resources of lipid production from synthetic media are costly, therefore the derivation of cheap sources from waste is useful in massive scale. Therefore, the study is emphasized on the effectiveness of industrial wastewater such as palm oil mill effluent (POME) as main carbon source to maintain the growth of microalgae and simultaneously increase the lipid content. In addition, glucose (C6H12O6) is also used to compare the effectiveness of their cultivations. Furthermore, investigation of five selected strains of green microalgae are applied namely Chlorella vulgaris (Korean Collection for Type Cultures (KCTC) Biological Resource Center (BRC)), Chlorella pyrenoidosa (POME), Chlorella sorokiniana (UTEX 1602), Botryococcus sudeticus (UTEX 2629), and Tetraselmis sp (UTEX 2767). All cultivation of microalgae were initially carried out in 250 mL erlenmeyer flask containing 100 mL medium under ± 30oC of temperature with continuous illumination (± 14 µmol/m2/s) and up to 20 days of cultivations. The study demonstrated that Chlorella sorokiniana, is the predominant species for specific growth rate (µ), biomass productivity and lipid content in diluted POME with the value 0.099/day, 8.0 mg/L.day, 2.68 mg lipid/mg Cell Dry Weight (CDW), respectively. However, Chlorella sorokiniana showed that there was about one and half times more lipid productivity when the biomass cells utilized C6H12O6 as carbon source, compared to POME. The optimization condition was determined with various carbon-to-total nitrogen (C:TN) ratio and light/dark (L:D) cycles, respectively. As a result, the highest lipid content achieved when the condition controlled at C:TN (100:7) and continuous light duration (24 hr), with recorded value of 17 mg lipid/mg CDW. These results conclude that Chlorella sorokiniana had highest growth rates and lipid production in diluted POME compared to other strains of microalgae. Finally, the study suggested several improvement of the experiment to achieve higher lipid production at steady - state condition by manipulating the ratio of carbon-to-total nitrogen and the medium of light intensity.