The highest propionic acid production was observed with an HRT of 6 h, which was related to a decrease in H2 generation, where a low diversity and low evenness were obtained compared with those of the reactor samples obtained from different HRTs.
The highest propionic acid productionwas observed with an HRT of 6 h, which was related to a decrease in H2 generation,where a low diversity and low evenness were obtained compared with those of the reactorsamples obtained from different HRTs.