Chain elongation may occur in protein mixed-culture fermentation without supplementing electron donor compounds

This study focuses on verifying the occurrence of elongation processes during protein mixed culture fermentation, without supplementation electron donor compounds. During casein mixed-culture fermentation at pH 5, it was observed that longer chain volatile fatty acid production increased, which could not be justified by associated amino consumption. Consequently, hypothesized. To verify this hypothesis, three batch tests, with and acetic initial supplementation, were performed 5. The results suggest propionic acids are indeed consumed to selectively generate n-valeric through coupling acids, whose consumption further verified analysis. Prolonged simultaneous availability suitable short an equivalent concentration threshold identified as key parameters for elongation. beginning test changed selectivity process, promoting n-butyric iso-valeric production. mechanisms preliminary conceptualized, constituting a first step studies subject. best our knowledge, is demonstrating feasibility supplementation. • Protein-based in time. External donors required. only occurred low values. Amino redox roles determine protein-based