Biomass and bioethanol production from pretreated mixed fruit peel hydrolysate using Saccharomyces cerevisiae strains at different pH and oxygen conditions

Fruit peels as a lignocellulosic biomass are rich in sugars and nutrients, thus making them favorable medium for yeast growth and various materials production. This study showed the potential of fuit peels hydrolysate (FPH) as a substrate for single-cell protein (SCP) and bioethanol production, depending on substrate concentration, pH, oxygen availability. The highest specific growth rate (0.50 ± 0.01 h − 1 ) was observed at pH 6.5 in non-diluted hydrolysates, which corresponds to ~ 250.0 g L − 1 carbohydrates and 0.2 g L − 1 total nitrogen concentration. The maximal protein production yield (~ 50% by dry weight) was recorded during 24 h cultivation of S. cerevisiae ATCC 13,007 under oxygen-limited conditions at pH 6.5, while the maximal ethanol production (109.00 ± 4.00 g L − 1 ) was observed at 6 h for S. cerevisiae ATCC 9804 and ATCC 13,007 starins under aerobic conditions. The maximal fermentation efficiency (~ 99%) was observed at 24 h cultivation of S. cerevisiae ATCC 13,007 in 2-fold diluted hydrolysate under oxygen-limited conditions at pH 6.5, while the same strain exhibited the highest carbon conversion efficiency (CCE) (~ 56%) during aerobic cultivation in 2-fold diluted hydrolysate at pH 3.0. Thus, FPH can serve as a favorable substrate for SCP and bioethanol production using S. cerevisiae strains ATCC 13,007 and ATCC 9804. Nitrogen supplementation and combination with fruit and vegetable processing industries could further enhance SCP production and process efficiency which aligns with circular economic strategy.