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

One-carbon (C1) feedstocks, such as carbon monoxide (CO), formate (HCO 2 H), methanol (CH 3 OH), and methane (CH 4 ), can be obtained either through stepwise electrochemical reduction of CO 2 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. • We discuss the use of NCRCs for supporting one-carbon assimilation. • Engineered one-carbon oxidizing enzymes can accept NCRCs. • NCRCs can lower the barrier of thermodynamically challenging reactions. • Coupling one-carbon utilization and NCRCs to growth is not trivial. • One-carbon assimilation and NCRCs can improve yields in mixotrophic cultivations.