Metabolic Engineering of Komagataella phaffii and Process Optimization for Biosynthesis of 1,2,4-Butanetriol From Xylose.

1,2,4-butanetriol (BTO) is a four-carbon polyol used as a precursor for synthesizing pharmaceuticals, polymers, and energetic plasticizers. The present study demonstrates the microbial production of BTO from xylose by engineered Komagataella phaffii yeast strains for the first time. The pathway was established through the overexpression of the enzymes xylose dehydrogenase (XylB), xylonate dehydratase (XylD), and 2-ketoacid decarboxylase (KDC). Two xylonate dehydratase genes, xylD-CC from Caulobacter crescentus and xylD-HL from Halomonas lutea, were evaluated in the constructions, both enabling BTO production. Furthermore, to improve BTO production, a central composite design analysis (CCD) was employed, identifying the best cultivation conditions to improve yeast performance. Under these optimized conditions, the engineered K. phaffii strain produced 1.3 g/L of BTO, achieving a 147% increase compared to the initial setup. Although further genetic engineering efforts are required to enhance BTO production, this study provides insights into potential improvement targets and highlights K. phaffii as a promising platform for the bio-based synthesis of chemical compounds like BTO.