Australian Centre for Water
and Environmental Biotechnology

AWMC Seminar Program: The Role Of Conductive Materials In Propionate Degradation During Anaerobic Digestion

Abstract: Anaerobic digestion (AD) stabilises organic wastes by breaking down macromolecules and producing renewable energy in the form of methane, via metabolic processes, i.e. hydrolysis, acidogenesis/primary fermentation, acetogenesis/secondary fermentation, and methanogenesis. Although AD is an established and globally used technology for organic wastes treatment, the process performance can be sensitive to changes in operational and environmental conditions, which may lead to imbalances and deterioration of digesters. For example, high organic loading rate (OLR) will lead to the deterioration of AD systems performance. Propionate accumulation is a common problem in high OLR anaerobic digesters. Propionate is an intermediate in AD process, produced during primary fermentation and consumed during secondary fermentation. Primary fermentation is the most rapid step in AD process, while biodegradation of propionate is thermodynamically unfavourable and relies on the syntrophic balance among different trophic groups. Hence propionate may accumulate when its production increases disproportionally to its consumption, e.g. in an organically overloaded system. Propionate degradation can be improved by facilitating direct interspecies electron transfer (DIET) during acidogenesis by adding conductive materials (CMs) to an AD system. To date, only a limited number of CMs has been studied for their ability to promote propionate degradation, such as magnetite, hematite, biochar, and the mechanisms behind the increase in propionate degradation rates are largely unknown. While it has been suggested that CMs promote DIET in defined cocultures in which one of the partners was Geobacter, the contribution of DIET to propionate degradation in mixed AD cultures has not received much attention in literature.

In this project, the effects of CMs on propionate degradation will be investigated and the mechanisms will be revealed. Consistent methodology will be constructed to identify how different CMs affect the biodegradation of propionate and propionate inhibition. Anaerobic microorganism acclimation over propionate with and without CMs will be studied as well. Most importantly, the mechanism behind will be disclosed, including the influence of materials properties and identification of activated microbes. This study will provide the theoretical basis of increasing propionate degradation by addition of CMs. By eliminating the accumulation of propionate in AD systems, the performance of anaerobic digesters with high OLR will be improved significantly.


Event Details
Date & Time: 
Friday, 24 January 2020
Venue: AIBN Seminar Room
  • Ms Jingjing Wan (PhD student, AWMC)

Event Contact: AWMC Seminar Team