Temperature‐Directed Biocatalysis for the Sustainable Production of Aromatic Aldehydes or Alcohols

Abstract

The biosynthesis of aromatic aldehydes and alcohols from renewable resources is currently receiving considerable attention because of an increase in demand, finite fossil resources, and growing environmental concerns. Here, a temperature‐directed whole‐cell catalyst was developed by using two novel enzymes from a thermophilic actinomycete. Ferulic acid, a model lignin derivative, was efficiently converted into vanillyl alcohol at a reaction temperature at 30 °C. However, when the temperature was increased to 50 °C, ferulic acid was mainly converted into vanillin with a productivity of 1.1 g L−1 h−1. This is due to the fact that the redundant endogenous alcohol dehydrogenases (ADHs) are not active at this temperature while the functional enzymes from the thermophilic strain remain active. As the biocatalyst could convert many other renewable cinnamic acid derivatives into their corresponding aromatic aldehydes/alcohols, this novel strategy may be extended to generate a vast array of valuable aldehydes or alcohols.

In Vivo Biocatalytic Cascades Featuring an Artificial‐Enzyme‐Catalysed New‐to‐Nature Reaction**

“… Carboxylic acid reductase (CAR) from Nocardia iwensis , along with its one time activator phosphopantetheinyl transferase (SFP) from Bacillus subtilis , reduces benzoic acids into their corresponding benzaldehydes in a NADPH and ATP dependent fashion [39, 40] . A codon‐optimised gene for CAR‐SFP was harboured on a pETDuet‐1 vector to achieve overexpression in E. coli K‐12 MG1655. Through a combination of feruloyl CoA synthase (encoded by Atfcs ) and enoyl CoA hydratase/aldolase (encoded by Atech ) from Amycolatopsis thermoflava N1165 p‐ coumaric acid is converted into p‐ hydroxybenzaldehyde [41] . The conversion proceeds by the initial formation of the SCoA derivative by FCS, followed by the conjugate addition of water by ECH/hydratase and retro‐aldol condensation by ECH/aldolase to produce the corresponding aldehyde [42–44] .…”

“…Through a combination of feruloyl CoA synthase (encoded by Atfcs ) and enoyl CoA hydratase/aldolase (encoded by Atech ) from Amycolatopsis thermoflava N1165 p‐ coumaric acid is converted into p‐ hydroxybenzaldehyde [41] . The conversion proceeds by the initial formation of the SCoA derivative by FCS, followed by the conjugate addition of water by ECH/hydratase and retro‐aldol condensation by ECH/aldolase to produce the corresponding aldehyde [42–44] .…”

In Vivo Biocatalytic Cascades Featuring an Artificial‐Enzyme‐Catalysed New‐to‐Nature Reaction**

“… Carboxylic acid reductase (CAR) from Nocardia iwensis , along with its one time activator phosphopantetheinyl transferase (SFP) from Bacillus subtilis , reduces benzoic acids into their corresponding benzaldehydes in a NADPH and ATP dependent fashion [39, 40] . A codon‐optimised gene for CAR‐SFP was harboured on a pETDuet‐1 vector to achieve overexpression in E. coli K‐12 MG1655. Through a combination of feruloyl CoA synthase (encoded by Atfcs ) and enoyl CoA hydratase/aldolase (encoded by Atech ) from Amycolatopsis thermoflava N1165 p‐ coumaric acid is converted into p‐ hydroxybenzaldehyde [41] . The conversion proceeds by the initial formation of the SCoA derivative by FCS, followed by the conjugate addition of water by ECH/hydratase and retro‐aldol condensation by ECH/aldolase to produce the corresponding aldehyde [42–44] .…”

Lignin valorization meets synthetic biology

“…Ferulic acid, a common lignin unit, was catalyzed to produce the vanillin using a temperaturerouted system in E. coli, by expressing Fcs and Ech from thermophilic actinomycete A. thermoflava N1165. In this system, vanillyl alcohol was formed at 30 • C, while vanillin was accumulated at 50 • C due to high activities of functional Fcs and Ech at the high temperature and elimination of ADHs activities [31]. Nevertheless, the biosynthetic route containing Fcs and Ech has seriously hindered the effective conversion of lignin-derived aromatics due to constant requirement for ATP and CoA [32].…”