Cofactor recycling is important in the synthesis of chiral alcohols via bioreduction of ketones. Herein, a carbonyl reductase from Scheffersomyces stipitis (SsCR) and a glucose dehydrogenase from Bacillus megaterium (BmGDH) were confined in bacteriophage P22 nanoparticles. The recycling efficiency of nicotinamide adenine dinucleotide phosphate (NADPH) in these nanoparticles was enhanced by a factor of from 3 to 45 compared with the free enzyme system, which is attributed to the higher local concentrations of NADPH resulting from the confinement of the enzymes in the P22 nanoparticles. The consumption of NADPH can be reduced by an order of magnitude in scale-up synthesis compared with a free enzyme system.

Poly(ethylene terephthalate) (PET) and phthalate esters (PAEs) are used extensively as plastics and plasticizers. Enzymatic degradation of PET and PAEs has drawn great attention in recent years; however, evolution of PET-and PAE-degrading enzymes is still a big challenge, partly because of the lack of an effective screening method to detect phthalic acid (PA) and terephthalic acid (TPA), which are the main hydrolysis products of PAEs and PET. Here, by directed evolution of a promiscuous transcription factor, XylS from Pseudomonas putida, we created two novel variants, XylS-K38R-L224Q and XylS-W88C-L224Q, that are able to bind PA and TPA and activate the downstream expression of a fluorescent reporter protein. Based on these elements, whole-cell biosensors were constructed, which enabled the fluorimetric detection of as little as 10 μM PA or TPA. A PAE hydrolase, GoEst15, was preliminarily engineered using this new biosensor, yielding a mutant GoEst15-V3 whose activity toward dibutyl phthalate (DBP) and p-nitrophenyl butyrate was enhanced 2.0-and 2.5-fold, respectively. It was shown that 96.5% DBP (5 mM) was degraded by GoEst15-V3 in 60 min, while the wild-type enzyme degraded only 55% DBP. This study provides an effective screening tool for directed evolution of PAE-/PET-degrading enzymes.

Engineering of a promiscuous lactonase via semi-rational evolution gave a 1007-fold improvement in its catalytic activity in the degradation of triphenyl phosphate (TPHP). TPHP is a typical bulky organophosphate flame...

Enzymes in living organisms work efficiently in confined environments through spatial organization. Constituting a bio-cascade reaction in nano-confined space in vitro for the efficient synthesis of high-value chiral chemicals is challenging. Herein, we confined a cofactor-dependent cascade in bacteriophage P22 nanoparticles for the synthesis of chiral alcohols. Compared to free enzymes, this supramolecular ensemble, P22-SP-BmGDH-SsCR, exhibited enhanced catalytic efficiency up to 14.5-fold towards various ketones and improved stereoselectivity up to > 99% ee towards 8 substrates, and 10 chiral alcohols with > 96% ee were synthesized. The recycling efficiency of nicotinamide adenine dinucleotide phosphate (NADPH) was increased by 7.5-fold. We demonstrated that the enhancement in cofactor recycling originates from the higher local concentration of NADPH in the nanoparticles due to the proximity effect of enzymes and confinement of nanoparticles. The preparative synthesis of chiral alcohols showed that the consumption of NADPH can be reduced by one magnitude compared with the conventional free enzyme system.