Physiological role of the FDH1 gene in methylotrophic yeast Komagataella phaffii and carbon recovery as formate during methylotrophic growth of the fdh1-deletion strain.

During methylotrophic growth of Komagataella phaffii, a large amount of carbon is lost as CO2. In this study, we aimed to construct a recovery system for carbon atoms, which emit as CO2 along the methanol dissimilation pathway in the form of formate when using strain fdh1Δ, the deletion mutant of formate dehydrogenase gene (FDH1). Strain fdh1Δ showed a severe growth defect when using methanol as the sole carbon source. However, using YPM medium (1 % yeast extract, 2 % peptone and 1 % methanol) with pH adjustment, the strain recovered methylotrophic growth and methanol utilization, accumulating high levels of extracellular formate in the medium. In strain fdh1Δ, the final carbon conversion rate of formate from methanol reached 12.9 % by batch cultivation. Moreover, by fed-batch cultivation in a jar fermentor, the formate productivity of strain fdh1Δ achieved approximately 540 mM. These results indicated that strain fdh1Δ possessed a high potential for recovering carbon atoms as formate, which can be a valuable precursor for various industrial applications.