Lipid production from palm oil mill effluent by microalgae

Abstract

In tropical countries, the palm oil industry discharges a large amount of wastewater. The wastewater can serve as an economical nutrient source or substrate that can support the cultivation of microalgae. This study aimed to identify the local species of microalgae potentially existing in the industrial wastewater of palm oil mill effluent (POME). POME was selected as the key source of waste due to its higher potential in producing lipids from microalgae as biofuel substrate. A novel green microalgal strain was isolated from POME of Kulai-Johor west Palm Oil Mill in Malaysia and was identified as Chlamydomonas sp. and subsequently named Chlamydomonas sp. UTM 98 with Catalogue No. of KR349061. This strain was cultivated in media with different volume ratios of POME and Basal Bald Medium (BBM). Lipid is generally a group of organic compound that serves as the primary raw material for biofuel. Therefore, this study emphasizes the effectiveness of POME as the main carbon source to maintain the growth of microalgae and simultaneously to increase the lipid content. In addition, glucose (C6H12O6) was also used to compare the effectiveness of their cultivations against POME. Furthermore, four selected strains of green microalgae are applied namely Chlorella vulgaris, Chlorella pyrenoidosa, Chlorella sorokiniana, Tetraselmis sp and isolated microalgae from POME. All cultivation of microalgae were initially carried out in 250mL Erlenmeyer flask containing 100 mL medium at ± 30oC with continuous illumination (± 14 µmol-1 m-2 s-1) and up to 20 days of cultivations. The study demonstrated that Chlamydomona incerta (C. incerta) is the predominant species for specific growth rate (µ), biomass productivity and lipid content in the diluted POME with the value of 0.099/d, 8.0 mg L-1.d, 2.68 mg lipid mg-1 Cell Dry Weight (CDW), respectively. However, C. incerta showed that there was about one and the half times more lipid productivity when the biomass cells utilized glucose as carbon source, compared to POME. The best 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 was achieved when the condition was controlled at C:TN (100:7) and with continuous light (24 hr) which recorded a value of 17 mg lipid mg-1 CDW. These results concluded that C. incerta had the highest growth rates and lipid production in the 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 light intensity on the bio-substrate. The Nile Red method was used to measure the lipid content in the culture. Fatty Acid Methyl Esters (FAMEs) and samples were analyzed via gas chromatography. POME with COD 250mg L-1 concentration showed the greater lipid content with absorbance 3.138a.u. The result showed that Chlamydomonas sp UTM 98 grown in the media of diluted POME exhibited a high potential of microalgae for biomass production and POME nutrients removal.