Perspectives on Potential Applications of Nanometal Derivatives in Gaseous Bioenergy Pathways: Mechanisms, Life Cycle, and Toxicity

Abstract

Nanosized metal derivatives (NMDs), referring to metals and their oxides, are extensively utilized as additives for anaerobic digestion (AD) and dark fermentation (DF) processes, for enhancing the production of methane (CH 4 ) and hydrogen (H 2 ), respectively. NMDs-derived positive impacts were widely confirmed in many previous studies; however, no consensus exists about how these have been acquired. Undoubtedly, NMDs affect extracellular electron transfer (EET). Consequently, we explore how biotic−biotic interactions, referring to direct interspecies electron transfer (DIET) among AD partners, and biotic−abiotic exchanges, which are mediated by redox reactions with metals, are affected. In this perspective, the mechanisms behind all those effects are reviewed and explained in detail, considering the specific properties of each NMD, e.g., size and type. We discuss previous studies that offer contradicting interpretations about which process dominates metal oxidation, metal reduction, or DIET. In addition, the fate of NMDs residues in the digestate after the treatment process is discussed, focusing on NMDs toxicity. From previous literature, the environmental impacts are evaluated for the production process of NMDs that are utilized in AD and DF processes via life-cycle assessment. This review provides a comprehensive understanding of NMDs−microbes interactions, which are mandatory for (i) building clear scientific knowledge about processes in play and (ii) engineering favorable conditions to achieve optimum yields in AD and DF processes.

Adaptation of a microbial community to demand-oriented biological methanation

“…In contrast, the discolouration during non-feeding periods (data did not showed) could be related to oxidation of Fe 2+ from magnetite delivering additional electrons for methanogenesis [ 15 ]. Furthermore, magnetite itself is a conductive mineral and has been shown to compensate for the deficiency of e-pilins, enabling probably direct electron transfer from fermenting organisms to methanogens [ 32 , 35 , 36 ].…”

Expectations for Perspectives in ACS Sustainable Chemistry & Engineering

“…ACS SCE perspectives that contain a compelling account of scientific and sustainability attributes of the reviewed topic will not only satisfy the desired quality features but also have a high probability of paving the way for future scientific and technological advances. We refer prospective authors to a sampling of recent articles, − where they will gain a better understanding of the attributes of published ACS SCE perspectives.…”

Stimulating the Fermentation Process of Industrial Food Waste via Nonionic Surfactant/Graphene Nanosheet Combined Supplementation

“…Microbial activity is directly responsible for the biohydrogen generating process and is the most crucial aspect to consider. Supplementing highly conductive nanomaterials (such as graphene, graphene oxide (GO), and reduced graphene oxide (RGO)) to anaerobes has been considered a promising solution for enhancing H 2 -producing bacterial activities in the fermentation process. , Graphene has unique characteristics such as large specific surface area, high mechanical strength, high chemical stability, high biocompatibility, and excellent electrical and thermal conductivity, with a great potential to improve the stability and efficiency of fermentation. , Previous studies have shown that graphene is a strong candidate for improving bacterial proliferation and enhancing biological activity. Despite the aforementioned merits, graphene is still a prohibitively costly material for large-scale applications.…”