Harnessing noncanonical redox cofactors to advance synthetic assimilation of one-carbon feedstocks.

One-carbon (C1) feedstocks, such as carbon monoxide (CO), formate (HCO2H), methanol (CH3OH), and methane (CH4), can be obtained either through stepwise electrochemical reduction of CO2 with renewable electricity or via processing of organic side streams. These C1 substrates are increasingly investigated in biotechnology as they can contribute to a circular carbon economy. In recent years, noncanonical redox cofactors (NCRCs) emerged as a tool to generate synthetic electron circuits in cell factories to maximize electron transfer within a pathway of interest. Here, we argue that expanding the use of NCRCs in the context of C1-driven bioprocesses will boost product yields and facilitate challenging redox transactions that are typically out of the scope of natural cofactors due to inherent thermodynamic constraints.