The Study On Mixed Culture Fermentation Of Immobilized Cells In Production Of Kombucha Beverage

Kombucha is a kind of traditional acid health drink. It is made by allowing a variety of microorganisms (mainly yeasts and acetic acid bacteria) to ferment using sweetened tea as the main raw materials. At present, Kombucha is cultivated with free mixed strains in the static condition. The traditional culture way has many disadvantages, for instance, easy miscellaneous bacteria pollution, long period, spawn degeneration, etc, which cause it very difficult to manage the product quality and further development and utilization. Thus, it is necessary to optimize the fermentation process of Kombucha. In this research, mixed culture fermentation of immobilized cells was used to produce Kombucha beverage. The study was focus on screening immobilized carrier, the preparation process of immobilized carrier and the Kombucha fermentation process by immobilized cells. Besides, the components and content of Kombucha beverage were analyzed.1. The growth curve of yeast J and acetic acid bacteria C were determined. Their adaptation period, growing period and stable period were obtained. Comparing of four types of immobilized carrier’s making simple level, physical performance and immobilized microorganism fermentation broth quality, the calcium alginate-gelatin was selected for embedding, and the microstructure of its surface was observed.2. The preparation process of immobilized carrier was studied by response surface methodology, on the base of single factor investigation, effects of sodium alginate concentration, gelatin concentration and calcium chloride concentration on the immobilized carrier mechanical strength and immobilized cells fermentation performance. The optimized preparation process is sodium alginate concentration5.5%, gelatin concentration1.5%, calcium chloride concentration0.51%. Under these conditions, both the mechanical strength of immobilized carrier and the total sugar utilization of fermentation broth are high.3. Through the single factor experiment and orthogonal experiment, the optimum conditions of Kombucha fermentation process by immobilized cells is obtained:the amount of sucrose added is70g/L, the inoculum rate is7.5%, the ratio of strain inoculum is6:4, fermentation lasts6days. Compared with free cells fermentation, the adjustment period of immobilized cells in fermentation process is longer, but the immobilized cells tolerance to the adverse environment is stronger. Besides, indicators of fermentation broth are better than that of free cells. What’s more, the fermentation performance of immobilized yeast J and immobilized acetic acid bacteria C is stable. 4. By experiment, the components and their content of Kombucha beverage were determined. It was verified that Kombucha beverage contains a variety of beneficial ingredients, such as protein, acetic acid, glucuronic acid, D-saccharic acid-1,4-lactone, tea polyphenol, caffeine, vitamin C, vitamin B2, vitamin B12, selenium and various mineral elements and so on.