ABSTRACT
The performance of biological reactors for producing bioenergy is closely related to microbial activity and diversity. Understanding the relationship between process operating conditions and the response of microflora to changes in reactor variables is essential to guarantee a successful outcome during long-term operation. A description of the main biological systems frequently studied in the scientific literature is performed, focusing on processes intended for biofuels and bioenergy production. A review of the frequent anaerobic organisms found in the literature is made, considering anaerobic digestion, fermentative hydrogen production, solvent generation and bioelectrochemical systems as the most promising processes capable of evolving into an industrial scale. Although many challenges regarding process stability and the removal of inhibitory compounds still need an urgent solution, the current degree of development of many of these processes brings a light of hope in materialising the circular economy model.
