Real-time lipid production and dairy wastewater treatment using Rhodococcus opacus in a bioreactor under fed-batch, continuous and continuous cell recycling modes for potential biodiesel application

Abstract

ABSTRACTThis study focused on lipid production from dairy wastewater using Rhodococcus opacus PD630 in a bioreactor. Simultaneous wastewater COD removal, biomass production and lipid accumulation by R. opacus were evaluated using the bioreactor operated under three different culture modes: fed-batch, continuous and continuous cell recycling. To support the R. opacus growth, the dairy wastewater was supplemented with 25% (v/v) mineral salt media. Results from the fed batch operated bioreactor revealed that a maximum COD removal efficiency of 93% could be achieved along with 1.1 g L-1 of lipid accumulation by the bacteria. Continuous mode experiments provided the best results with almost 100% COD removal efficiency and a maximum lipid accumulation of 1.8 g L-1 at a hydraulic retention time (HRT) of 6.6 h. However, lipid production was even more superior under continuous cell recycle mode with a maximum lipid accumulation of 3.4 g L-1. Thus, the present study proved that R. opacus can be successfully scaled up for efficient dairy wastewater treatment along with lipid accumulation for potential biofuel application.