Abstract
Since the observation of direct interspecies electron transfer (DIET) in anaerobic mixed cultures in 2010s, the topic “DIET-stimulation” has been the main route to enhance the performance of anaerobic digestion (AD) under harsh conditions, such as high organic loading rate (OLR) and the toxicants’ presence. In this review article, we tried to answer three main questions: (i) What are the merits and strategies for DIET stimulation? (ii) What are the consequences of stimulation? (iii) What is the mechanism of action behind the impact of this stimulation? Therefore, we introduced DIET history and recent relevant findings with a focus on the theoretical advantages. Then, we reviewed the most recent articles by categorizing how DIET reaction was stimulated by adding conductive material (CM) and/or applying external voltage (EV). The emphasis was made on the enhanced performance (yield and/or production rate), CM type, applied EV, and mechanism of action for each stimulation strategy. In addition, we explained DIET-caused changes in microbial community structure. Finally, future perspectives and practical limitations/chances were explored in detail. We expect this review article will provide a better understanding for DIET pathway in AD and encourage further research development in a right direction.
Highlights
Anaerobic digestion (AD) is a traditional biological process utilized for treating various organic wastes including wastewater and complex solid wastes
Through the studies of last ten years, it was found that direct interspecies electron transfer (DIET) reaction could be stimulated either either by the supplementation of a conductive material (CM) and/or applying external voltage (EV)
It could be stimulated through the supplementation of CM and/or the application of EV
Summary
Anaerobic digestion (AD) is a traditional biological process utilized for treating various organic wastes including wastewater and complex solid wastes. Syntrophic acetogens convert C2 –C6 organic acids/alcohols to electron donors of low-molecular weight, mainly H2 and acetic acid, which would be consumed by methanogens. This is a well-known indirect interspecies electron transfer (IIET) route, and many attempts were made to enhance this reaction. Methanosaeta harundinacea cannot metabolize H2, and the is 1 mole CH4 /mole ethanol From this result, the authors indicated DIET between two species, which theoretical maximum CH4 yield is 1 mole CH4/mole ethanol. Through the studies of last ten years, it was found that DIET reaction could be stimulated either either by the supplementation of a conductive material (CM) and/or applying external voltage (EV).
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