Engineering unnatural methylotrophic cell factories for methanol-based biomanufacturing: Challenges and opportunities

Methanol is a very promising feedstock alternative to sugar-based raw materials for biomanufacturing because it does not compete with food production, is abundant and potentially sustainable in the future. Although methylotrophic fermentations have been practiced for decades, their applications are limited by technical drawbacks and insufficient knowledge of the physiology and metabolic regulation of native methylotrophs. Synthetic biology offers great opportunities for engineering efficient methylotrophic microbial cell factories by enabling non-methylotrophic model organisms to utilize methanol via the introduction of C1 utilization pathways. This review critically comments C1 metabolism with a focus on comparing different methanol-utilization pathways in light of biomanufacturing, and highlights recent advances in the engineering of synthetic methylotrophs. Most importantly, the unique challenges in the engineering process and possible solutions are also discussed in detail.