Evaluating the toxicity of methanol, formaldehyde and formate on the growth fitness of Yarrowia lipolytica

Abstract

Liquid C1 feedstock, including methanol, formaldehyde and formic acid can be easily manufactured from greenhouse gases CO2 and CH4. Yarrowia lipolytica, isolated from marine ecosystem, is a non-conventional yeast which is capable of assimilating multiple range of hydrophobic compounds including alcohols, lipids, hydrocarbons, and volatile fatty acids et al. This yeast has been extensively engineered to produce lipids, carotenoids, squalene and other natural products. Herein we tested the growth fitness of Y. lipolytica when exposed to various one-carbon (C1) liquid feedstocks (methanol, formaldehyde, and formic acid). We firstly captured the cell growth kinetics with an automatic Cell Growth Analyzer and fitted the data with a Monod-type growth model. We obtained the inhibition constants of the three liquid C1s from the growth fitness dose-response curves. We found that the lagging phase duration is exponentially correlated with the toxicity of the tested C1 solvents. Notably, Y. lipolytica exhibited tolerance to methanol (IC50 871 mM) and formic acid (IC50 42.6 mM), but showed sensitivity to formaldehyde (IC50 3.8 mM). We next chose fromate as the co-substrate to cultivate Y. lipolytica, confirmed that Y. lipolytica can upcycle formic acid to improve lipid yields and biomass in fed-batch culture. This work broadens Y. lipolyticas substrate scope and facilitates sustainable and cost-efficient production of fuels and chemicals.