ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Elevated production of lipids and carotenoids from Rhodotorula mucilaginosa using raw dairy wastewater as crude renewable substrate: a waste to wealth transformation approach

Ravi Gedela, Shagun Sharma, Ashish A. Prabhu, Kannan Pakshirajan, and Venkata Dasu Veeranki

Biochemical Engineering Laboratory, Department of Biosciences and Bioengineering, Indian Institute Technology Guwahati, Guwahati, India

E-mail: ashishp@nitw.ac.in

Received: 10 May 2024  Accepted: 9 April 2025

Abstract:

The present study explores the utilization of raw dairy wastewater (RDW) for the production of lipids and carotenoids by Rhodotorula mucilaginosa. Following initial shake flask experiments using mineral salt media with RDW, the process was scaled up through batch and fed-batch fermentation studies. In batch fermentation using only RDW, the lipid content, carotenoid concentration, and β-carotene levels were recorded at 52.02 ± 1.52% (w/w), 30.63 ± 0.15 µg g⁻¹, and 12.42 ± 0.06 µg g⁻¹, respectively. Additionally, the observed chemical oxygen demand (COD) removal efficiency was approximately 48.5 ± 0.24%. Further enhancement was observed when RDW was supplemented with 15 gL⁻¹ sodium acetate, resulting in increased lipid content of 66.3 ± 0.3% (w/w), carotenoid levels of 64.0 ± 0.32 µg g⁻¹, and β-carotene concentration of 19.7 ± 0.09 µg g⁻¹. The COD removal efficiency also improved, reaching approximately 62.3 ± 0.31%. In fed-batch reactor studies, where RDW was supplemented with a consistent sodium acetate concentration of 15 g L⁻¹, further improvements over batch fermentation were noted. The experimental results demonstrated a lipid content of 72.14 ± 0.3% (w/w), carotenoid concentration of 67.16 ± 0.3 µg g⁻¹, β-carotene levels of 31.7 ± 0.15 µg g⁻¹, and a COD removal efficiency of approximately 78 ± 0.3%. A detailed lipid composition analysis using gas chromatography revealed a diverse fatty acid profile. The FAME analysis identified the presence of various fatty acids with their respective concentrations: lauric acid (C12:0) 0.31 ± 0.11%, myristic acid (C14:0) 1.04 ± 0.03%, palmitic acid (C16:0) 27.05 ± 1.11%, palmitoleic acid (C16:1) 1.85 ± 0.15%, margaric acid (C17:0) 0.39 ± 0.03%, ginkgolic acid (C17:1) 0.71 ± 0.01%, stearic acid (C18:0) 3.97 ± 0.25%, oleic acid (C18:1) 47.23 ± 1.43%, linoleic acid (C18:2) 5.15 ± 0.29%, and linolenic acid (C18:3) 0.78 ± 0.12%. These findings highlight the significant potential of R. mucilaginosa produced lipids for biodiesel production, emphasizing their suitability as a sustainable alternative fuel source.

Graphical abstract

Keywords: Aquaculture; Biodiesel; Biofuels; Biogas; Food Production; Synechocystis; Yield; Biomass; Sodium acetate; Batch fermentation; Fed-batch

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04064-x

Chemical Papers 79 (7) 4403–4418 (2025)