Systematic metabolic engineering of Yarrowia lipolytica for highly efficient biosynthesis of mannitol from glucose

Mannitol is widely utilised in the food and pharmaceutical industries. Current commercial production primarily depends on chemical synthesis, a process that is expensive, environmentally detrimental, and requires high-temperature/pressure as well as complex purification steps. While microbial production of mannitol has been explored, most studies employ fructose as the substrate, which is associated with high costs. Yarrowia lipolytica is a commonly used chassis strain that naturally synthesises various sugar alcohols. In this study, the engineered strain Y. lipolytica Ylzy27 was developed through systematic metabolic engineering, which included chassis optimisation, bypath blocking, heterologous mannitol-1-phosphate dehydrogenase expression, and transporter engineering. During fed-batch cultivation in a 3-L bioreactor, strain Ylzy27 produced 220.22 ± 0.98 g/L mannitol, with a productivity of 3.02 ± 0.01 g/(L·h) and a yield of 0.55 ± 0.01 g/g glucose, representing the highest value thus far reported from glucose. Mannitol crystals with a purity exceeding 99.95% were obtained directly through concentration and crystallisation.