Xtraction, Isolation And Purification Of Theanine From Summer-Autumn Green Tea And Its Influence On Intestinal Microecology

Theanine is a special amino acid of tea which has many benefits such as anti-tumour, improvement of the memory and it has great potential in application to functional foods. In China, summer-autumn tea has the highest yield but the consumption is very low.Extraction and isolation of theanine directly from the tea is the safest and most effective productive method, by which the natural authenticity of theanine can be assured. Based on the previous studies, a combine technique of optimization of extraction, ultrafiltration, static adsorption and dynamic chromatography was built, which was high-purity, low-cost and industrially feasible. Theanine was extracted with this technique and used to study its influence on intestinal microecology. Major research results were as follows:Optimization of the theanine extraction was optimizated with orthogonal test and the following optimum conditions were obtained:the raw-liquid ratio was1:20, the extraction temperature was95℃and the extraction time was45min.Ultrafiltration could get rid of most protein, polysaccharide and floccules in tea soup and made the tea liquid more clear.The present study showed that10K CA membrane performed at35℃and0.3MPa work condition may be the best.Under the optimum conditions, the protein and floccules were mostly removed, the removal rate of polysaccharide was more than40%, TP was30%and the low-molecular metabolites such as caffein and theanine were retained almost as unprocessed.Absorption can further remove the TP in the tea soup. For this three kinds of adsorbents were used to study adsorption performance of TP. The study showed that the maximum adsorbance of TP obtained by PA resin was76.36mg/g. The high adsorbance, high recovery rate and minimum adsorbance for theanine, made PA resin a great source to separate and enrich TP.NKA-II resin dynamic chromatography was used to separate theanine.Theanine was obtained by elution with distilled water and the purity was99.12%.the first yield was59.26%. Eluent was collected between1.5BV to2.5B, concentrated, re-loaded and that the theanine yield was improved to75.12%. Again elution was done with80%ethanol, finally caffein as a by-product of purity99%was produced. The NKA-II resin is reusable and can maintain good separation effect after using for five times. It may be well applied in industrial production.Anaerobic fermentation was carried out for theanine, prepared by anaerobe faecal fermentation in vitro and the change in beneficial bacterial count, harmful bacterial count and total bacterial count were detected by fluorescent in situ hybridization, the variation of different short chain fatty acid in the fermentation process was detected by HPLC during24hours. The result showed that theanine may promote lactic acid bacteria growth to an extend and inhibit other bacterial growth and the total bacterial count was little less than the blank (control group). For SCFA, the theanine made great distinction, hence the group of theanine may be employed for producing large amount of lactic acid as well as lowering the pH of the intestine.