Enantioselective Palladium-Catalyzed Directed Migratory Allylation of Remote Dienes.

Chain walking has been an efficient route to realize the functionalization of inert C(sp3 )-H bonds, but this strategy is limited to mono-olefin migration and functionalization. Herein, we demonstrate the feasibility of tandem directed simultaneous migrations of remote olefins and stereoselective allylation for the first time. The adoption of palladium hydride catalysis and secondary amine morpholine as solvent is critical for achieving high substrate compatibility and stereochemical control with this method. The protocol is also applicable to the functionalization of three vicinal C(sp3 )-H bonds and thus construct three continuous stereocenters along a propylidene moiety via a short synthetic process. Preliminary mechanistic experiments corroborated the design of simultaneous walking of remote dienes.

Immobilization of recombinant Escherichia coli cells expressing glucose isomerase using modified diatomite as a carrier for effective production of high fructose corn syrup in packed bed reactor.

To improve the operational stability of glucose isomerase in E. coli TEGI-W139F/V186T, the immobilized cells were prepared with modified diatomite as a carrier and 74.1% activity of free cells was recovered after immobilization. Results showed that the immobilized cells still retained 86.2% of the initial transformational activity after intermittent reused 40 cycles and the yield of D-fructose reached above 42% yield at 60 °C. Moreover, the immobilized cells were employed in the continuous production of High Fructose Corn Syrup (HFCS) in a recirculating packed bed reactor for 603 h at a constant flow rate. It showed that the immobilized cells exhibited good operational stability and the yield of D-fructose retained above 42% within 603 h. The space-time yield of high fructose corn syrup reached 3.84 kg L-1 day-1. The investigation provided an efficient immobilization method for recombinant cells expressing glucose isomerase with higher stability, and the immobilized cells are a promising biocatalyst for HFCS production.

Immobilization of recombinant Escherichia coli whole cells harboring xylose reductase and glucose dehydrogenase for xylitol production from xylose mother liquor.

In this study, recombinant E. coli BL21(DE3)/pCDFDuet-1-XR-GDH harboring xylose reductase (XR) and glucose dehydrogenase (GDH) were immobilized and applied for the production of xylitol from xylose mother liquor (XML). Various immobilization methods were screened and the cross-linking approach with diatomite and polyetherimide as the raw materials and glutaraldehyde as the cross-linking agent was the optimal one, and the recovery activity reached of 80.3% after immobilization. The half-life of immobilized cells was 1.52 times to that of free cells. Batch experiments showed that the enzyme activity of immobilized cells remained 70.5% of the initial activity after 10 batches and the space-time yield of xylitol reached of 11.5 g/(L h). The production of xylitol from xylose mother liquor by immobilized E. coli cells containing xylose reductase and glucose dehydrogenase was reported for the first time, which paved a foundation for industrial production of xylitol from waste xylose mother liquor.