Valorization of Dairy Wastewater for the Production of Lipids, Carotenoids, and β-Carotene in Rhodotorula mucilaginosa

Abstract

One of the leading causes of environmental pollution in India is the waste generated from the dairy sector. Significant amounts of organic and inorganic components are characteristics of the wastewater generated by this industry. To address this problem, sustainable and economical methods of lowering its ecological footprint are obligatory. The present study uses raw dairy wastewater (RDW) to synthesise lipids and carotenoids from Rhodotorula mucilaginosa. Batch and fed-batch experiments were used to scale up the process after shake flask experiments using mineral salt media with RDW. In batch fermentation studies with only RDW resulted in the generation of lipid content, carotenoids, and β-carotene at values of 52.02 ± 1.52 (% w/w), 30.63 ± 0.15 µg.g-1, and 12.42 ± 0.06 µg.g-1. Furthermore, the observed chemical oxygen demand (COD) removal efficiency was approximately 48.5±0.24%. Additionally, intriguing findings were obtained when RDW was supplemented with 15gL-1 of sodium acetate, increasing the lipid content (% w/w), carotenoids, and β-carotene levels by 66.3 ± 0.3 (% w/w), 64.0 ± 0.32 µg.g-1, and 19.7 ± 0.09 µg.g-1, respectively. The maximum chemical oxygen demand (COD) removal efficiency was around 62.3±0.31%. When fed-batch reactor studies were conducted with RDW while maintaining 15gL-1 sodium acetate, notable improvements over batch reactor studies were observed. The experimental outcomes revealed a lipid content of 72.14 ± 0.3 (% w/w), carotenoid levels of 67.16 ± 0.3 µg.g-1, β-Carotene content of 31.7± 0.15 µg.g-1, and a chemical oxygen demand (COD) removal efficiency of approximately 78± 0.3%. A comprehensive study of the lipid samples using gas chromatography revealed a wide range of fatty acid compositions. This thorough characterization underscores their significant potential for utilization in biodiesel production.