Continuous Hydrogen Production And Microbial Community Profile In The Dark Fermentation Of Tequila Vinasse: Response To Increasing Loading Rates And Immobilization Of Biomass

Dark fermentation of concentrated and undiluted tequila vinasse, without extra nutrients, in a CSTR was the objective of this study. Organic loading rates (OLR) from 40 to 160 gCOD/L-d and influence of presence of biomass carriers were assessed. With suspended biomass, a stable hydrogen production rate (HPR) of 1.1 L H-2/L-d was obtained at an OLR of 80 gCOD/L-d. Adding biomass carriers in the CSTR increased the stable HPR from 0.3 to 0.7 L H-2/L-d when an OLR of 120 gCOD/L-d and 6%-20%-diluted vinasse were used. Influent formic, and valeric acids were consumed consistently, while lactic, butyric and acetic acids were produced suggesting that carboxylic acids metabolism, besides sugar fermentation, contributed to hydrogen production. Clostridium predominance over Sporolactobacillus changed after a 160 gCOD/L-d shock load, however correlation analyses showed that the original COD content of vinasse, rather than the OLR, influenced HPR, carboxylic acids profile and bacterial population.