The cofactor challenge in synthetic methylotrophy: bioengineering and industrial applications

Methanol is a promising feedstock for industrial bioproduction: it can be produced renewably and has high solubility and limited microbial toxicity. One of the key challenges for its bio-industrial application is the first enzymatic oxidation step to formaldehyde. This reaction is catalysed by methanol dehydrogenases (MDH) that can use NAD+, O2 or pyrroloquinoline quinone (PQQ) as an electron acceptor. While NAD-dependent MDH are simple to express and have the highest energetic efficiency, they exhibit mediocre kinetics and poor thermodynamics at ambient temperatures. O2-dependent methanol oxidases require high oxygen concentrations, do not conserve energy and thus produce excessive heat as well as toxic H2O2. PQQ-dependent MDH provide a good compromise between energy efficiency and good kinetics that support fast growth rates without any drawbacks for process engineering. Therefore, we argue that this enzyme class represents a promising solution for industry and outline engineering strategies for the implementation of these complex systems in heterologous hosts.

Automated summary

Methanol is a promising feedstock for industrial bioproduction due to its renewable production, high solubility, and limited microbial toxicity. The first enzymatic oxidation step to formaldehyde is a key challenge for its bio-industrial application. Different types of methanol dehydrogenases (MDH) can catalyze this reaction using NAD+, O2, or PQQ as an electron acceptor. NAD-dependent MDH have high energetic efficiency but mediocre kinetics, while O2-dependent methanol oxidases require high oxygen concentrations and do not conserve energy. PQQ-dependent MDH provide a good compromise between energy efficiency and kinetics, making them a promising solution for industry.