Chlorella pyrenoidosa mediated lipid production using Malaysian agricultural wastewater: effects of photon and carbon

Abstract

Light and carbon being the vital ingredients of photosynthetic reactions can be exploited for algal culture productivity and yield enhancement to effectively treat wastewater by significantly reducing the presence of organic and inorganic compounds. This communication reports the photon flux (light intensity) and glucose (C6H12O6) concentration (as carbon source) dependent improvement of the biomass and lipid production in Chlorella pyrenoidosa (CP) microalgae abundant in Malaysian palm oil mill sewage. Cultures having density 150 mol.m−2 s−1 are grown under varying light flux and temperature. Evaluations of algal productivity are made for three light cycles (ratio of h in light to dark) such as 24:0, 16:8, and 8:16. CP culture with continuous illumination (24:0) produced highest lipid content of 17 mg. Conversely, two other cycles (16:8 and 8:16) yielded 13.10 and 9.43 mg, respectively. The CP growth efficacy of palm oil mill effluent (POME) and subsequent drop in nutrients is demonstrated. Furthermore, the specific growth rate with light is observed to be comparable to the one achieved via C6H12O6 mediated growth. Production of CP for the biomass and lipid generation is optimized using 5 L batch culture grown for 2 weeks duration, where amounts of biomass as high as 0.68 gL−1 d−1 mgCDW−1 is achieved. However, 250 mL batch culture grown for 4 weeks generated a maximum biomass of 0.009 gL−1 d−1 mgCDW−1. The gradual reduction (after 2 days) of organic carbon and nutrients in the culture is attributed to the usage of carbon source mediated microalgae growth and subsequent lipid production. Eventually, CP manifested the removal of organic carbon amounts to 34, 65, and 47 % with the carbon per total nitrogen (C/TN) ratio of 100:7, 100:13, and 100:32, respectively. It is established that POME (as carbon enriched media) assisted enhanced CP growth under illumination can considerably reduce the presence of organic and inorganic compounds.