Model-based optimization of the enzymatic aldol addition of propanal to formaldehyde: A first step towards enzymatic synthesis of 3-hydroxybutyric acid

Morana Česnik, Martina Sudar, Raquel Roldan, Karel Hernandez, Teodor Parella, Pere Clapés, Simon Charnock, Đurđa Vasić-Rački, Zvjezdana Findrik Blažević

    Research output: Contribution to journalArticleResearch

    3 Citations (Scopus)

    Abstract

    © 2019 Institution of Chemical Engineers 3-Hydroxyisobutyric acid is an important intermediate in the biosynthesis of methacrylic acid. Its biocatalytic synthesis can be performed by aldolase-catalyzed aldol addition of propanal to formaldehyde followed by an enzymatic oxidation of the resulting 3-hydroxy-2-methylpropanal to 3-hydroxyisobutyric acid. In this work, D-fructose-6-phosphate aldolase D6Q variant was investigated as a key step for the biocatalytic preparation of 3-hydroxy-2-methylpropanal, a commercially unavailable precursor of 3-hydroxyisobutyric acid. The kinetic model of this step was developed for the purpose of reactor selection and process optimization. It was found that enzyme operational stability decay is co-dependent on the initial formaldehyde concentration. Thus, the choice of the initial conditions is crucial for a successful process set-up. It was concluded that fed-batch was the best reactor choice for this reaction due to enzyme inhibition by formaldehyde and propanal, and its operational stability decay. At the optimal process conditions, the product concentration, product yield, and volume productivity after 5.5 h were 72 g L−1, 88.5% and 313.7 g L−1 d−1, respectively. Enzymatic oxidation of 3-hydroxy-2-methylpropanal to the corresponding acid was performed as a proof of concept using an aldehyde dehydrogenase in the presence of NAD+, regenerated by water-forming NADH oxidase, and 2.5 g L−1 (24 mM) of 3-hydroxyisobutyric acid was obtained.
    Original languageEnglish
    Pages (from-to)140-152
    Number of pages13
    JournalChemical Engineering Research and Design
    Volume150
    DOIs
    Publication statusPublished - 1 Oct 2019

    Keywords

    • Aldol addition
    • D-fructose-6-phosphate aldolase
    • Mathematical model
    • Methacrylic acid
    • NUCLEOPHILES
    • Optimization

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