The Potential of <i>Kluyveromyces marxianus</i> in Mixed Culture to Produce Single-Cell Proteins from Whey and Reduce the Biological Oxygen Demand

Human activities and food shortages threaten civilization. A solution is the production of single-cell proteins (SCPs) from industrial waste, such as cheese whey. This method reduces environmental impact by converting high-biological oxygen demand (BOD) waste into SCPs. Kluyveromyces spp., a lactose-utilizing yeast species, can produce SCPs while reducing whey BOD. The research aims to establish a sustainable, environmentally friendly approach to using this abundant resource. The study focused on a response surface methodology (RSM) to optimize SCP production from whey through yeast culture. The yeast strains Kluyveromyces marxianus and Saccharomyces cerevisiae were employed. Plackett-Burman design and RSM were employed to determine the most influential variables on SCP production. The mixed yeast culture was prepared and inoculated into pasteurized whey. The β-galactosidase enzyme activity was measured using Miller’s method to determine minimum and maximum biomass production in design experiments. A BOD measurement of whey was used to measure the oxygen needed for organic matter breakdown in a wastewater sample. The optimal conditions and resources for cultivation, β-galactosidase enzyme assay, and BOD assay were evaluated through Minitab 17.0 software. Optimal production was achieved at 200 g/L of powdered whey. This was combined with 14.5% ammonium sulfate at a concentration of 7 g/L and a pH of 8. Under these conditions, biomass production reached 21.04 g/L. The activity level of the β-galactosidase enzyme at concentrations of 50 g/L, 150 g/L, and 200 g/L of whey powder was 492 U/L, 930 U/L, and 1082 U/L, respectively. The BOD at the same concentrations was 7400 mg/L, 7800 mg/L, and 6100 mg/L. Results from the study indicated that biomass production increased by 40.39% in mix culture compared to pure culture. β-galactosidase activity is correlated with biomass production, and as biomass production increases, BOD decreases by approximately 75.6%.