Concomitant strategy of wastewater treatment and biodiesel production using innate yeast cell (Rhodotorula mucilaginosa) from food industry sewerage and its energy system analysis

In many recent studies, the wastewater with high organic matter and high utilization value compounds was treated using yeast. It decreases the effluent contaminants and makes it applicable for reuse in many food industries. This present study focuses on the combined approach of treatment and biorefinery to increase the circular economy in food industries. The two primary goals of the work were to screen the potential oleaginous yeast from the food industry effluent (FIE) collected from the food flavourant producing industry and used for FIE remediation through bioaugmentation and to extract microbial oil of yeast biomass harvested after remediation. Further, the extracted microbial oil was trans-esterified to produce biodiesel. The process of transesterification was optimized for its influencing parameters. After 10 days of treatment of FIE with the yeast cell, the treatment efficiency was analyzed and found to be precise with the typical discharge value. The overall lipid content of the oleaginous yeast (Rhodotorula mucilaginosa SML) used for the FIE treatment was 67.95 w/w% of dry cell biomass. The extracted microbial oil was used for transesterification; the process was optimized through the one-variable analysis approach and response surface methodology optimization using a central composite design. The transesterification process showed maximum conversion (98%) at oil to methanol ratio - 5.0, catalyst concentration - 2.8% and time - 1.15 h. The fatty acid composition and the physicochemical characteristics were compatible with petroleum diesel, making it applicable for alternative biofuel production. Thus, this concomitant strategy has proved efficient for reducing contaminants in FIE and suggested a new sustainable source for biodiesel production. The exergy, energy and mass balance analysis of the biodiesel conversion process proved that this process is the most economically viable one to increase the circular economy of food industries.