Construction Of Tissue Engineering Cell Gel Coated Tablets For The Synthesis Of Chiral Alcohols

Polymer polyvinyl alcohol is used as the immobilized cells or tissue engineering, has good mechanical strength, but its poor biocompatibility, high expansion rate lead to its limitations when applied. And when silk fibroin is used to tissue engineering with good biocompatibility. In addition, the whole cell could ensure its main enzymes and cofactors played key role, when used as biological catalyst, but the free cells had low utilization rate when repeated. Therefore, in this article, we constructed disk shape scaffolds with polyvinyl alcohol (PVA) / silk fibroin complex materials and cultured with Saccharomyces cerevisiae cells in it. The loading cells scaffolds were coated with nanocomposite gel of polyvinyl alcohol (PVA) / organic montmorillonite(OMMT). The characteristics of composite scaffolds and the properties of this coated cell-scaffold were studied in this article. In this study, ethyl (S) - 3 - hydroxyl butyrate ((S) - EHB) was asymmetric synthesized from bioreduction of ethyl acetoacetate by the coated cell-scaffold as biocatalyst. First of all, the disk shape three-dimensional porous scaffolds(5mm diameter, 2mm thickness) were prepared with PVA/SF composites by crosslinking with saturated boric acid, and its porosity reached 92%. After screening concentration of PVA, the ratio of PVA and SF and quantity of porogen, optimization result is that the ratio of gel beads of 14% PVA and 9.8% SF is 4∶1 and amount of porogen is 1.4g/ml. The porous scaffolds prepared according above conditions possess high mechanical strength, low-expansion ratio and preparation of them also were easily operated. It was suitable for cells culture.Secondly, this kind of disc scaffolds as a carrier for seeding of Saccharomyces cerevisiae were cultured. Then the cell-scaffold composites were coated with about 200μm thickness PVA/OMONT nanocomposite gel. We investigated embedding situation, cells load of the coated cell-scaffold, effects of pH and temperature on intracellular ADH activity of the coated cell-scaffold and storage stability of it. The experimental results indicate that the cells load capacity of the coated cell-scaffold reach to 34% and it has not cells leakage after coating. In addition, the optimum pH and temperature on ADH activity of the coated cell-scaffold at pH7.0-8.0 and 35℃and the intracellular ADH in the coated cell-scaffold retained over 74% of it original activity after one month of storage. It can be seen that the coated cell-scaffold had good storage stability.Finally, we investigated that pH and temperature affect on the yield and the enantiomeric excess (e.e.) of the (S)-ethyl-3-hydroxy butyrate when using the coated cell-scaffold as biocatalyst. The result showed that the yield reached 96.5% and e.e reached 97.3% at pH7.0-8.0 and 35℃. Furthermore, the coated cell-scaffold also showed good reusability. The intracellular alcohol dehydrogenase (ADH) in the coated cell-scaffold retained 67% of its initial activity after 9 cycles.