Abstract
SummaryA microbial electrochemical system could potentially be applied as a biosynthesis platform by extracting wastewater energy while converting it to value-added chemicals. However, the unfavorable thermodynamics and sluggish kinetics of in vivo whole-cell cathodic catalysis largely limit product diversity and value. Herein, we convert the in vivo cathodic reaction to in vitro enzymatic catalysis and develop a microbe-enzyme hybrid bioelectrochemical system (BES), where microbes release the electricity from wastewater (anode) to power enzymatic catalysis (cathode). Three representative examples for the synthesis of pharmaceutically relevant compounds, including halofunctionalized oleic acid based on a cascade reaction, (4-chlorophenyl)-(pyridin-2-yl)-methanol based on electrochemical cofactor regeneration, and l-3,4-dihydroxyphenylalanine based on electrochemical reduction, were demonstrated. According to the techno-economic analysis, this system could deliver high system profit, opening an avenue to a potentially viable wastewater-to-profit process while shedding scientific light on hybrid BES mechanisms toward a sustainable reuse of wastewater.
Highlights
A wastewater-energy-chemical nexus can lead to a sustainable paradigm shift for the wastewater treatment industry, in which wastewater can be employed as a power source for energy production and chemical synthesis (Li et al, 2015; Lu et al, 2018; Mohan et al, 2016; Rabaey and Rozendal, 2010; Zou and He, 2018)
A stack of three microbial fuel cells (MFCs) was required to achieve a reduction potential of À0.5 V versus Ag/AgCl at the working electrode, and a similar conversion rate of 1b was observed (Figure S8). These results demonstrated that a hybrid bioelectrochemical system (BES) could feasibly upgrade the diluted waste energy to high-value chemicals by injecting electrons from the MFC into the cascade reaction of electrosynthesis cell (EESC) mediated by H2O2
With the in vitro transmembrane electron transfer (EET)-free design, electrons from the MFC were seamlessly wired to the reactant, cofactor, or reaction intermediate, which greatly facilitated electron flux control and overcame the thermodynamic and kinetic limitations of in vivo microbial electrosynthesis systems
Summary
A wastewater-energy-chemical nexus can lead to a sustainable paradigm shift for the wastewater treatment industry, in which wastewater can be employed as a power source for energy production and chemical synthesis (Li et al, 2015; Lu et al, 2018; Mohan et al, 2016; Rabaey and Rozendal, 2010; Zou and He, 2018). The wastewater-energy-chemical nexus holds high potential to bring tremendous value to the wastewater industry. Microbial electrosynthesis cells can provide comprehensive solutions for wastewater-energy-chemicals nexus by extracting the wastewater energy and efficiently converting it into various value-added chemicals (Harnisch and Schroder, 2010; Zou and He, 2018). The integration of microbial electrosynthesis cells with MFCs has accomplished the wastewater-powered production of different commodities, such as biomethane (Ning et al, 2021), acetic acid (Nevin et al, 2010), butanol (Zaybak et al, 2013), and hexanol (Vassilev et al, 2018), thereby opening the window for bringing value to wastewater treatment (Christodoulou et al, 2017; Jiang and Zeng, 2018). The scaling-up feasibility of microbial electrosynthesis has been studied (Zou et al, 2021)
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