Scientists engineer enzyme to turn plant waste into high-value plastics
Researchers have modified a heat-resistant enzyme to efficiently convert a tough plant compound into a building block for premium polymers and cosmetics. The breakthrough addresses a major industrial bottleneck: making biofuel-derived chemistry economically viable at commercial scale.
Originaltitel: Engineering the substrate scope of the thermostable phenolic acid decarboxylase N31 towards sterically hindered phenolic acids.
Forskare vid Graz University of Technology har utvecklat en muterad fenolsyraomvandlase (PAD) som öppnar vägen för att producera värdefullt 4-vinyl siringol via enzymatisk dekarboxylering. 4-vinyl siringol är efterfrågat inom polymerproduktion eftersom det ger polymerer med högre glasövergangstemperatur än dagens alternativ, men naturliga enzymer är långsamma på sinapinsyra. Genom riktad mutagenes framställde forskarna varianten Ile29Ser-Leu80Ser-Ile93Ala, som ökar katalytisk effektivitet för sinapinsyra 11-falt och bibehåller väsentligt högre termisk stabilitet än referensenzym från Bacillus subtilis — halvtid på 1,12 dagar vid 50°C. För branschen betyder detta att industriell skalning av bio-baserad polymerproduktion blir genomförbar under mildare förhållanden. Leverantörer av specialkemikalier och polymertillverkare bör notera att kommersialisering ligger nära — enzymets termostabilitet tacklar en kritisk bryggpunkt mellan lab och produktion.
Phenolic acid decarboxylases (PADs) convert bio-based hydroxycinnamic acids into valuable hydroxystyrene monomers under mild reaction conditions. These compounds are in high demand in polymer production, cosmetics, and flavoring. Especially 4-vinyl syringol, the decarboxylation product from sinapic acid, generates polymers with similar thermal stability and higher glass transition temperatures than vinyl guaiacol, the decarboxylation product from ferulic acid. However, natural PAD enzymes typically show slow turnover with sinapic acid. In addition, establishing a viable industrial process requires enzymes operating under elevated temperatures. To tackle these issues, we assessed five thermostable ancestral PADs towards their activity and stability for the conversion of ferulic acid and sinapic acid at different temperatures. A combinatorial active site library was prepared for the most thermostable ancestor. We expanded the substrate scope of a selected PAD ancestor to include sinapic acid through directed mutagenesis. A trade-off between ferulic-/caffeic acid and sinapic acid was observed and investigated via molecular dynamics simulations. The most stable ancestor was identified with a half-life of 3.65 days, analyzed at 50°C. We found the Ile29Ser-Leu80Ser-Ile93Ala triple mutation (SSA) to effectively expand the substrate scope with an 11-fold increase in catalytic efficiency for sinapic acid, and a half-life of 1.12 days at 50°C, being approximately 1.6-fold higher than the frequently used PAD from Bacillus subtilis.