Optimization Of Fermentation Process For Exo-polysaccharides Production By Kombucha ZJU1 And The Application Of Fermentation Broth

As a mixed microorganism system of yeasts, acetic acid bacteria and lactic acid bacteria, kombucha is generally used to prepare fermented sugared tea with a sour and sweet flavor. Kombucha fermentation broth has outstanding physiological functions for the multiple types of beneficial ingredients. Polysaccharides from plants, microorganism (fungi and bacteria), algae and animals have various bioactivities such as immuno-modulating, antitumor, antivirus, antioxidant, lowering blood sugar, etc. Therefore, they are ideal for making medicine and health food. Kombucha exo-polysaccharides (EPS) may have similar bioactivities to fungal polysaccharides from mushrooms, Ganoderma, Poria cocos, etc. And it has the value of further study. In this paper, the bacterial biological diversity of Kombucha ZJUl was analyzed. Moreover, influencing factors of liquid fermentation process for the production of exo-polysaccharides by Kombucha ZJUl, optimization of liquid fermentation process for improved exo-polysaccharides production by Kombucha ZJU1 and application of kombucha fermentation broth in the jelly making were also researched. The main research results were as follows:16S rDNA hypervariable region sequencing technology was adopted to sequence the PCR products of 16S rDNA V6 variable region of Kombucha ZJU1 sample. Bioinformation analyses were carried out according to the tags overlapped to get the bacterial species diversity information of Kombucha ZJU1.Influencing factors (tea types, carbon source, nitrogen source, cultivation modes, cultivation temperature and cultivation time) of liquid fermentation process for the production of exo-polysaccharides by Kombucha ZJU1 were studied. The liquid fermentation process after conditions screening was as follows:brown sugar 50 g/L, Pu-erh tea 4 g/L, (NH4)2SO41 g/L, KH2PO41 g/L, initial pH natural, inoculation level of Kombucha ZJU1 20%, cell age 5 days, cultivation at 30℃for 6 days on the rotary shaker (150 r/min). Under such fermentation process, the Kombucha ZJU1 exo-polysaccharides production of 0.43 g/L could be achieved.A fractional factorial design (FFD) and central composite design (CCD) were applied to optimize the liquid fermentation process for improved exo-polysaccharides production by Kombucha ZJU1. After response surface analysis, the optimized fermentation process was as follows:280 g/L brown sugar,4 g/L Pu-erh tea,1 g/L KH2PO4 and 1 g/L (NH4)2SO4 initial pH unadjusted, the culture medium was inoculated with 1.95%(v/v) Kombucha ZJU1, the cell age was 5 days, then incubated at a temperature of 30±1℃for 6 days on the rotary shaker. The predicted maximal EPS concentration was 2.66 g/L using this optimized fermentation process, which was significantly higher than that the original fermentation conditions (0.43 g/L).The technological parameters for making kombucha fermented nutritional jelly were investigated. The best formula was as follows:citric acid 0.18%, composite gelling agent 1.2%(carrageenan:konjac gel:CMC-Na was 10:7:3), sucrose 18%, kombucha fermentation broth 18%, sodium citrate 0.1%, black tea powder suitable amount, potassium sorbate 0.3%o. Kombucha jelly made with this formula was of such characteristics as possessing unique fermentation flavor, nutrient-rich, sweet and sour, good flexibility and toughness, colour-natural and smooth.