In a groundbreaking development, researchers have engineered a yeast strain to enhance the production of 3-hydroxypropionic acid (3-HP) from methanol, a process that could significantly impact the energy sector and the fight against global warming. Led by Sílvia Àvila-Cabré from the Department of Chemical, Biological and Environmental Engineering at Universitat Autònoma de Barcelona, the study published in the Journal of Biological Engineering, explores the potential of the methylotrophic yeast Komagataella phaffii (formerly known as Pichia pastoris) to convert methanol into valuable chemicals.
Methanol, derived from CO2 reduction, serves as a carbon and energy source for the yeast, which then produces 3-HP. This compound is a crucial building block for various biobased products, including acrylates and 1,3-propanediol. However, achieving commercially viable concentrations, yields, and productivities of 3-HP has been a challenge. Àvila-Cabré and her team aimed to overcome these hurdles through metabolic engineering, focusing on increasing the supply of metabolic precursors and redirecting carbon flux towards 3-HP production.
The researchers employed a combinatorial metabolic engineering strategy, targeting precursors supply and 3-HP export. They overexpressed several genes encoding enzymes that catalyze reactions immediately upstream of the β-alanine pathway, which is essential for 3-HP production. Among these, the overexpression of the pyruvate carboxylase PYC2 gene significantly increased the 3-HP yield on biomass in small-scale cultivations.
A key finding was the effectiveness of lactate permeases ESBP6 and JEN1 in enhancing 3-HP production. Co-overexpression of PYC2, ESBP6, and JEN1 led to a 55% improvement in 3-HP titer and product yield in methanol deep-well plate cultures. “The activity of Esbp6 as a 3-HP transporter proved to be particularly effective,” Àvila-Cabré noted, highlighting the potential of lactate transporters in driving 3-HP export.
The engineered strain was further tested in fed-batch cultures at pH 5, achieving a 3-HP concentration of 27.0 g l− 1, with a product yield of 0.19 g g− 1, and a volumetric productivity of 0.56 g l− 1 h− 1 during the methanol feeding phase. These results represent a 42% increase in final concentration and over 20% improvement in volumetric productivity compared to the original 3-HP-producing strain. Bioreactor-scale cultivations at pH 3.5 revealed increased robustness of the strains overexpressing monocarboxylate transporters.
The implications of this research are profound. By enhancing the production of 3-HP from methanol, the study opens new avenues for mitigating global warming and reducing dependence on fossil fuels. The ability to convert CO2-derived methanol into valuable chemicals could revolutionize the energy sector, providing a sustainable and efficient pathway for chemical production. The findings, published in the Journal of Biological Engineering, underscore the potential of metabolic engineering in driving innovation in biobased product development. As Àvila-Cabré puts it, “Our results point out the potential of lactate transporters to efficiently drive 3-HP export in K. phaffii, leading to higher titers, yields, and productivities, even at lower pH conditions.” This research not only advances our understanding of metabolic engineering but also paves the way for future developments in sustainable chemical production.
