Novel 3-dimensional bioelectrode for mediatorless bioelectrochemical denitrification

De Novo Approach to Encapsulating Biocatalysts into Synthetic Matrixes: From Enzymes to Microbial Electrocatalysts

Biocatalysts hold great promise in chemical and electrochemical reactions. However, biocatalysts are prone to inhospitable physiochemical conditions. Encapsulating biocatalysts into a synthetic host matrix can improve their stability and activity, and broaden their operational conditions. In this Review, we summarize the emerging de novo approaches to encapsulating biocatalysts into synthetic matrixes. Here, de novo means that embedding of biocatalysts and construction of matrixes take place simultaneously. We discuss the advantages and limitations of the de novo approach. On the basis of the nature of the biocatalysts and the synthetic frameworks, we specifically focus on two aspects: (1) encapsulation of enzymes (in vitro) in metal-organic frameworks and (2) encapsulation of microbial electrocatalysts (in vivo) on the electrode. For both cases, we discuss how the encapsulation improves biocatalysts' performance (stability, viability, activity, and etc.). We also highlight the benefit of encapsulation in facilitating the transport of charge carriers in microbial electrocatalysis.

100th Anniversary of Macromolecular Science Viewpoint: Soft Materials for Microbial Bioelectronics

Bioelectronics brings together the fields of biology and microelectronics to create multifunctional devices with the potential to address longstanding technological challenges and change our way of life. Microbial electrochemical devices are a growing subset of bioelectronic devices that incorporate naturally occurring or synthetically engineered microbes into electronic devices and have broad applications including energy harvesting, chemical production, water remediation, and environmental and health monitoring. The goal of this Viewpoint is to highlight recent advances and ongoing challenges in the rapidly developing field of microbial bioelectronic devices, with an emphasis on materials challenges. We provide an overview of microbial bioelectronic devices, discuss the biotic-abiotic interface in these devices, and then present recent advances and ongoing challenges in materials related to electron transfer across the abiotic-biotic interface, microbial adhesion, redox signaling, electronic amplification, and device miniaturization. We conclude with a summary and perspective of the field of microbial bioelectronics.

Three-Dimensional Electrodes for High-Performance Bioelectrochemical Systems

Bioelectrochemical systems (BES) are groups of bioelectrochemical technologies and platforms that could facilitate versatile environmental and biological applications. The performance of BES is mainly determined by the key process of electron transfer at the bacteria and electrode interface, which is known as extracellular electron transfer (EET). Thus, developing novel electrodes to encourage bacteria attachment and enhance EET efficiency is of great significance. Recently, three-dimensional (3D) electrodes, which provide large specific area for bacteria attachment and macroporous structures for substrate diffusion, have emerged as a promising electrode for high-performance BES. Herein, a comprehensive review of versatile methodology developed for 3D electrode fabrication is presented. This review article is organized based on the categorization of 3D electrode fabrication strategy and BES performance comparison. In particular, the advantages and shortcomings of these 3D electrodes are presented and their future development is discussed.

Denitrification of simulated municipal wastewater treatment plant effluent using a three-dimensional biofilm-electrode reactor: operating performance and bacterial community

A three-dimensional biofilm-electrode reactor (3D-BER) was applied for nitrate removal from simulated municipal wastewater treatment plant (WWTP) effluent. It was found that when the influent C/N ratio ranged from 1.0 to 2.0, both heterotrophic and autotrophic denitrifying microorganisms played important roles in nitrate removal. The extension of hydraulic retention time (HRT) could enhance nitrate removal, but too long HRT was not necessary. A phylogenetic tree of gene sequences in biofilm was established, and the biofilm was abundant with Thauera-like and Enterobacter-like bacteria. The results illustrated that 3D-BER is a feasible and effective technology for the denitrification of WWTP effluent with poor organic carbon source. A nitrate removal of 98.3% was obtained with C/N ratio of 3.0 and HRT of 7h. About 85.0-90.0% of nitrate removal was found at a C/N ratio of 1.5 and HRT of 10h due to cooperative heterotrophic and autotrophic denitrification.

Partial nitrification using an electrolytic aerating bioreactor with ammonia-oxidizing bacteria-dominant activated sludge

An electrolytic aerating bioreactor was used to partially nitrify ammonia from wastewater. Activated sludge was cultured for 8 months to increase the population of ammonia-oxidizing bacteria (AOB) and then used in the bioreactor. The maximum ammonia removal rate was 0.64 mM NH(3)/l h in a 50 ml reactor using 5.4 g mixed liquor suspended solids per litre of AOB-dominant activated sludge.