Overcoming the Gas–Liquid Mass Transfer of Oxygen by Coupling Photosynthetic Water Oxidation with Biocatalytic Oxyfunctionalization

Abstract

Gas–liquid mass transfer of gaseous reactants is a major limitation for high space–time yields, especially for O2‐dependent (bio)catalytic reactions in aqueous solutions. Herein, oxygenic photosynthesis was used for homogeneous O2 supply via in situ generation in the liquid phase to overcome this limitation. The phototrophic cyanobacterium Synechocystis sp. PCC6803 was engineered to synthesize the alkane monooxygenase AlkBGT from Pseudomonas putida GPo1. With light, but without external addition of O2, the chemo‐ and regioselective hydroxylation of nonanoic acid methyl ester to ω‐hydroxynonanoic acid methyl ester was driven by O2 generated through photosynthetic water oxidation. Photosynthesis also delivered the necessary reduction equivalents to regenerate the Fe2+ center in AlkB for oxygen transfer to the terminal methyl group. The in situ coupling of oxygenic photosynthesis to O2‐transferring enzymes now enables the design of fast hydrocarbon oxyfunctionalization reactions.

A Facile Direct Route to N‐(Un)substituted Lactams by Cycloamination of Oxocarboxylic Acids without External Hydrogen

“…In contrast, the pathways via the precursor FPAC and FPAM toward MPD require 32 kJ mol À1 and 63 kJ mol À1 higher activation energy,r espectively,c learly demonstrating that the pathway involving MDPY is preferred. [22] In addition, AL formation hinders LA dehydration (Figure 2a nd S13), as proven by the poor GVL yield. In view of gaseous NH 3 and HCOOHb eing simultaneously formed in ac ertain amount by thermalh ydrolysis of H 2 NCHO,t he initial amination of LA with NH 3 instead of H 2 NCHO wasa lso takeni nto consideration (Figure 2).…”

Catalytic Aerobic Oxidation of C(sp3)−H Bonds

“…Alargescale synthesis of (R)-4-hydroxyisophorone using awhole cell paste containing wild type (non-engineered) CYPs enzymes from bacillus megaterium was reported by Kaluzna et al (Scheme 29). [145] By engineering the phototrophic cyanobacterium Synechocystis sp.PCC6803 to synthesize alkane monooxygenase AlkBGT from Pseudomonas putida Gpo1, light can be used to generate O 2 in situ through oxygenic photosynthesis.T he O 2 produced is trapped within the cell and is thus readily available to bind with the monooxygenase for oxygenation. Catalyst recovery and reuse were not attempted.…”

Artifizielle Lichtsammelkomplexe ermöglichen Rieske‐Oxygenase‐ katalysierte Hydroxylierungen in nicht‐photosynthetischen Zellen

“…Um diese Herausforderung zu lösen, werden derzeit viele alternative Ansätze in Betracht gezogen . Neben der Verknüpfung der Photochemie mit Enzymen in vitro zur Cofaktor‐Regeneration, haben autotrophe und chemolithoautotrophe Organismen in jüngster Zeit Aufmerksamkeit erhalten, da sie dazu in der Lage sind, anorganische Verbindungen als Elektronendonoren zu nutzen . Licht‐getriebene Ganzzellreaktionen in Cyanobakterien zeigen die gleichen Reaktionsgeschwindigkeiten wie E. coli .…”

“…Dieses System bietet insbesondere für solche anspruchsvolle Mehrkomponenten‐Enzyme den Vorteil, auf die gut untersuchte genetische Toolbox von E. coli als Wirt zurückgreifen zu können, wodurch eine breite Anwendbarkeit der Licht‐getriebenen künstlichen Photosynthese ermöglicht wird. Die erhaltenen Produktbildungen von bis zu 1.3 g L −1 und Geschwindigkeiten von bis zu 1.6 m m h −1 zeigen, dass im Vergleich zu Cyanobakterien kompetitive Produktivitäten erzielt werden konnten …”