Bioprocess parameter screening and condition selection for single-cell protein production using yeast co-culture and agro-food waste substrates

Global protein scarcity challenges food security, and single-cell protein (SCP) offers a sustainable solution by converting agro-food waste into high-quality protein through microbial fermentation. This study demonstrates the efficient conversion of agro-food waste to SCP production using a rationally designed yeast co-culture system. Unlike prior studies that mainly focus on monoculture fermentation, this work demonstrates that a yeast co-culture significantly improves substrate utilization and protein yield, providing an environmentally friendly alternative for SCP production. Under selected screened conditions (waste-to-water ratio 1:6, pH 6, 160 rpm, 7 days), biomass and protein concentrations reached 15.23 +/- 1 g/L and 8.2 +/- 0.5 g/L, respectively. These conditions corresponded to 0.53 g biomass/g substrate, 0.29 g protein/g substrate, and a protein productivity of 1.17 g/(L.day), providing an objective assessment of process performance. Kinetic evaluation using the Modified Stover-Kincannon model (R2 = 0.95-0.96) supported reactor scalability and process stability. A 30-day continuous fermentation demonstrated stable biomass and protein accumulation, peaking on Day 7 with 63% of total SCP yield highlighting continuous fermentation's industrial applicability by enabling sustained productivity and process scalability for commercial SCP production. Amino acid profiling confirmed high levels of lysine, leucine, and valine, supporting suitability for animal feed applications. By valorizing agro-food waste into nutritious protein, this approach contributes to circular bioeconomy goals, mitigates environmental pollution, and supports global efforts to enhance food security sustainably.