# Strategies for Enhancing Extracellular Electron Transfer in Environmental Biotechnology: A Review
## 3 Strategies for Enhancing EET in Environmental Biotechnology
### Electron Shuttles and Mediators
Further research and development in this field will likely lead to the discovery of new and improved electron shuttles, enabling even greater advancements in environmental biotechnology. The use of conductive nanowires  
E-pili or conductive nanowires serve as effective pathways for long-distance electron transfer, facilitating intercellular aggregation and the production of EABs. Advancements in protein design have facilitated the simplification of the fabrication process for synthetic nanowires. A study was conducted to provide a regulatory framework for the fabrication of very stable nanowires. This was achieved by developing protein templates through the utilization of specifically designed linker proteins. [PERSON] et al. [67] employed \(\gamma\)PFD (a helical protein produced by the microorganism _Methanocaldooccus junnaschi_), as a nanomaterial scaffold to facilitate the localization and alignment of cytochromes, resulting in the construction of a nanowire structure within _G. sulfuruducus_. This methodology not only contributes to the existing conventional techniques for constructing nanowires but also enables the manipulation of nanowire structures, hence broadening the potential applications of natural bioelectrical materials. In recent years, there has been a lot of focus on promoting the synthesis and assembly of e-pili in addition to changing their structure to increase their electrical conductivity. In a study, the nanowire-related genes _omcS_ and _omcB_ in _S. oneidensis_ were modified using genome editing (iEditing), the modified strain was expressed and the growth was assessed. The data showed an increase in cytochrome content and an improvement in EET efficiency, as evidenced by a peak power generation of 310 mA/m\({}^{2}\) in the modified strain compared to wild-type [68]. Furthermore, the application of peptides in modifying pili monomers can enhance the adherence of fimbiae, facilitate the development of electrically conductive nanowire structures known as pilis, and ultimately enhance the possible utilization of biomaterials. To enhance the adaptability of the e-pili surface for improved sensing capabilities or enhanced compatibility with different substances, a study has devised a strategy involving the integration of a concise peptide tag at the carboxyl-terminal of pilA [69]. This modification facilitated the formation of a conductive nanowire structure that exhibited targeted adhesion properties while preserving its ability to conduct electricity. The gene segments that have been produced consist of _pilA-6 His_ and _pilA-HA_. These fragments gave rise to conductive pili that possess a \"His-tag\" and a peptide \"HA-tag\". These tags are located on the external surface of the pili and can bind to metals and antibodies that are specific to them. This approach exhibits considerable promise for application in the development of innovative materials and products. Although there has been significant research conducted on the characteristics and functionalization of conducting nanowires for almost two decades, the number of innovative electronic devices utilizing these nanowires remains extremely limited. The complexity and time-consuming nature of producing conductive nanowires, along with the early stage of their integration into circuits, account for this phenomenon. Hence, it is imperative to employ a straightforward bottom-up methodology that encompasses dependable nanowire biogenesis and enables the regulated production of nanowire electronics.