How to Sustainably Feed a Microbe: Strategies for Biological Production of Carbon-Based Commodities with Renewable Electricity

Abstract

As interest and application of renewable energy grows, strategies are needed to align the asynchronous supply and demand. Microbial metabolisms are a potentially sustainable mechanism for transforming renewable electrical energy into biocommodities that are easily stored and transported. Acetogens and methanogens can reduce carbon dioxide to organic products including methane, acetic acid, and ethanol. The library of biocommodities is expanded when engineered metabolisms of acetogens are included. Typically, electrochemical systems are employed to integrate renewable energy sources with biological systems for production of carbon-based commodities. Within these systems, there are three prevailing mechanisms for delivering electrons to microorganisms for the conversion of carbon dioxide to reduce organic compounds: (1) electrons can be delivered to microorganisms via H2 produced separately in a electrolyzer, (2) H2 produced at a cathode can convey electrons to microorganisms supported on the cathode surface, and (3) a cathode can directly feed electrons to microorganisms. Each of these strategies has advantages and disadvantages that must be considered in designing full-scale processes. This review considers the evolving understanding of each of these approaches and the state of design for advancing these strategies toward viability.

Energy Efficiency and Productivity Enhancement of Microbial Electrosynthesis of Acetate

“…Alternatively, during direct MES the microbes are incubated with the cathode of an electrochemical cell where they capture H 2 or possibly electrons directly from an electrode (Butler and Lovley, 2016; Tremblay et al, 2016). Productivity and efficiency data from these two approaches are presented in Table 1 .…”

Methanogens: biochemical background and biotechnological applications

“…The whole process belongs to the field of microbial electrosynthesis (MES), which includes processes that convert a substrate into a desired organic product by using microorganisms and electrical current (Schröder et al 2015 ; Lovley 2012 ; Holtmann et al 2014 ). The advantage of a BES system compared to the external production of hydrogen is that short time storage and gassing in of the hardly soluble hydrogen can be avoided (Butler and Lovley 2016 ).…”

An insoluble iron complex coated cathode enhances direct electron uptake by Rhodopseudomonas palustris TIE-1

“…(3) Direct ET to drive microbial CO2 fixation [9]. Also, the production of biochemicals from CO2 is directly linked to the quantity of electrical energy supplied by the cathodically poised electrode [5][6][7][8][9].…”