Metatranscriptomic Analysis Reveals the Coexpression of Hydrogen-Producing and Homoacetogenesis Genes in Dark Fermentative Reactors Operated at High Substrate Loads.

Microbial communities in dark fermentation continuous systems are affected by substrate type, concentration, and product accumulation (e.g., H and CO).

Knowing the enemy: homoacetogens in hydrogen production reactors.

One of the bottlenecks of the hydrogen production by dark fermentation is the low yields obtained because of the homoacetogenesis persistence, a metabolic pathway where H and CO are consumed to produce acetate. The central reactions of H production and homoacetogenesis are catalyzed by enzyme hydrogenase and the formyltetrahydrofolate synthetase, respectively. In this work, genes encoding for the formyltetrahydrofolate synthetase (fthfs) and hydrogenase (hydA) were used to investigate the diversity of homoacetogens as well as their phylogenetic relationships through quantitative PCR (qPCR) and next-generation amplicon sequencing.

Acetotrophic sulfate-reducing consortia develop active biofilms on zeolite and glass beads in batch cultures at initial pH 3.

Sulfate-reducing microbial communities remain a suitable option for the remediation of acid mine drainage using several types of carrier materials and appropriate reactor configurations. However, acetate prevails as a product derived from the incomplete oxidation of most organic substrates by sulfate reducers, limiting the efficiency of the whole process. An established sulfate-reducing consortium, able to degrade acetate at initial acidic pH (3.

Continuous thermophilic hydrogen production from an enzymatic hydrolysate of agave bagasse: Inoculum origin, homoacetogenesis and microbial community analysis.

In this research, the performance of two thermophilic inocula of different origin on continuous hydrogen production from an enzymatic hydrolysate of agave bagasse were compared; one of them was obtained from a thermophilic reactor and the second one was taken from a mesophilic reactor and acclimated to thermophilic conditions. The acclimation process in one-step quickly established a high-performance hydrogen producing community, obtaining a volumetric hydrogen production rate of 3811 ± 19 mL H/L-d with an hydrogen yield of 121 L H/kg bagasse compared to 1473 ± 6 mL H/L-d and 26.6 L H/kg obtained with the thermophilic-origin inoculum.

Standardized protocol for determination of biohydrogen potential.

Biohydrogen production potential (BHP) depends on several factors like inoculum source, substrate, pH, among many others. Batch assays are the most common strategy to evaluate such parameters, where the comparison is a challenging task due to the different procedures used. The present method introduces the first internationally validated protocol, evaluated by 8 independent laboratories from 5 different countries, to assess the biohydrogen potential.