Influence of substrate concentration on single-cell protein production from green biorefinery residual juice

Producing single-cell protein (SCP) using an underutilized side-stream from green biorefineries, brown juice (BJ), addresses global food security and environmental challenges. In this work, BJ from a green biorefinery was investigated as a fermentation medium for cultivating the SCP yeast Cyberlindnera jadinii . Effects of C/N ratio, BJ concentration, and maceration methods on yeast growth and yields were analyzed. Results showed C. jadinii could not utilize pentoses within 24 h, reducing protein yield. Adding nitrogen increased protein and biomass yields, with a maximum protein yield of 0.37 g g −1 sugar at a C/N ratio of 5.3 g g −1 . Concentrating BJ extended the lag phase but maintained protein yield, reaching a maximum crude protein concentration of 11.9 g L −1 . Both one-stage and multi-stage macerated BJ supported growth, with one-stage maceration achieving slightly higher yields. Adjusting the C/N ratio in concentrated BJ enhanced SCP production, demonstrating its potential as a sustainable fermentation medium. • Grass-clover residual liquid (BJ) was used as a fermentation medium for C. jadinii . • Nitrogen addition increased yields significantly in regular and concentrated BJ. • A mathematical model represented protein yield improvements when nitrogen was added. • Concentrating BJ boosted biomass production without reducing protein yield.