In a significant stride toward sustainable biomanufacturing, researchers have successfully engineered the yeast Komagataella phaffii to produce high levels of mannose, a sugar with wide-ranging applications in food, pharmaceuticals, and agriculture. This breakthrough, published in *Microbial Cell Factories*, demonstrates the potential of metabolic engineering to create efficient microbial factories for valuable compounds.
Mannose, a C6 sugar, is traditionally derived from plant sources, a process that can be costly and environmentally taxing. The team, led by Sijia Zhao from the State Key Laboratory of Animal Nutrition at the Chinese Academy of Agricultural Sciences, tackled this challenge by rewiring the central metabolism of K. phaffii. Their strategy involved a dual carbon source system: glycerol for biomass generation and glucose for mannose synthesis.
“By attenuating glycolytic flux and redirecting carbon flow, we were able to accumulate fructose-6-phosphate (F6P), a key precursor for mannose biosynthesis,” Zhao explained. The researchers knocked out the phosphofructokinase II (pfk2) gene and downregulated phosphofructokinase I (pfk1) to slow down glycolysis. Simultaneously, they reduced flux through the pentose phosphate pathway by downregulating glucose-6-phosphate dehydrogenase (zwf1).
To further boost mannose production, the team suppressed phosphomannose isomerase (PAS_chr3_1115) and overexpressed the Escherichia coli-derived phosphatase gene yniC, enhancing the conversion of F6P into mannose. Additionally, they deleted three genes involved in byproduct formation to minimize waste.
The engineered strain achieved an impressive mannose titer of 121.1 grams per liter in high-cell-density, fed-batch fermentation, setting a new record for microbial mannose production. This achievement not only offers a sustainable alternative to traditional extraction methods but also paves the way for the production of other high-value compounds using K. phaffii as a platform.
The implications for the agriculture sector are substantial. Mannose derivatives are used in various applications, from plant growth regulators to animal feed additives. A cost-effective, scalable microbial production method could revolutionize these industries, making these compounds more accessible and affordable.
“This research establishes a model framework for engineering K. phaffii to produce a range of bioactive compounds,” Zhao noted. The study’s success highlights the power of metabolic engineering in creating sustainable solutions for agriculture and beyond.
As the world seeks to reduce its reliance on petrochemicals and move towards greener alternatives, this breakthrough offers a promising path forward. By harnessing the power of microbial fermentation, we can create a more sustainable future, one sugar molecule at a time.