Microbial Population Dynamics in Continuous Hydrogen Production Systems by Dark Fermentation of Tequila Vinasse

Bioenergy production from agro-industrial waste has been a topic of interest for many years and now, with technological developments, and the identification of microbial species involved in the biodegradation of substrates, it is possible to establish population dynamics in waste biodegradation processes that promote a circular economy. This work presents a comparative study of continuous hydrogen production systems by dark fermentation of tequila vinasse emphasizing the analysis on the operational conditions and the microbial population dynamics. In particular, the comparative study aims to understand the synergy between the biohydrogen production in continuous systems, and the microbial population dynamics in systems with or without immobilized biomass. Interactions between H2-producing bacteria (HPB) (e.g., Clostridium, Enterobacter), lactic acid bacteria (LAB) (e.g., Lactobacillus, Sporolactobacillus, Streptococcus), and acetic acid bacteria (AAB) (e.g., Acetobacter), are described considering the impact on hydrogen production. The study includes experiments in CSTR reactors, where the effect of increasing organic load; the use of carriers; type of inoculum; hydraulic residence time; feed concentration and type of vinasse is evaluated in terms of the biohydrogen production rate and composition of the biogas generated. The results show clear tendencies of hydrogen production and presence of specific microbial populations in the continuous dark fermentation of tequila vinasse. Also, it was observed that productivity of hydrogen is governed by the organic loading rate in combination with key hydrogen-producing bacterial genera while vinasse from different tequila manufacture processes did not affect the dominant bacterial genera in fermentation.