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

This 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.

KEYWORDS:

• R. opacus
• dairy wastewater
• bioreactor
• fed-batch
• continuous
• cell recycling

Acknowledgements

The authors thank the Department of Biosciences and Bioengineering, IIT Guwahati, for providing the necessary facilities to carry out this research work.

Disclosure statement

No potential conflict of interest was reported by the authors.