Polysaccharides

Polysaccharides

In general, tea polysaccharides consist of 44% neutral sugar and 43% uronic acid. Neutral polysaccharides, comprising 83% total sugar, contain 12.9% uronic acid, whereas acid polysaccharides encompass approximately 86% total sugar, with 39.8% being uronic acid. The primary basic units of tea polysaccharides include rhamnose, arabinose, galactose, glucose, xylose, mannose, ribose, galacturonic acid, and glucuronic acid. Galactose is the main component of neutral polysaccharides, while acid polysaccharides contain rhamnose, arabinose, galactose, and galacturonic acid (Du at al., 2016). The profiles of polysaccharides are influenced by tea cultivars, growth environment, and processing. For green tea, the composition includes galacturonic acid (65%), arabinose (19%), galactose (7%), glucose (7%), and rhamnose (2%). In contrast, black tea consists of galacturonic acid (35%), arabinose (30%), galactose (16%), rhamnose (3%), and glucose (16%). Polysaccharides with arabinose, ribose, and galactose reduce blood fat, while those primarily composed of galactose exhibit hypoglycemic activity (Ai et al., 2016).

While saccharides in tea leaves influence both the Kombucha fermentation process and its health-promoting properties, available data on saccharide profiles in fermented tea are limited to sucrose, fructose, and glucose—the main sugars utilized by microorganisms in the SCOBY. The activity of invertase, and consequently the yeast strain composition in the consortium, affects the release of glucose and fructose, impacting subsequent metabolites such as organic acids and ethanol. For instance, glucose is metabolized to lactic acid by homofermentative lactic acid bacteria (LAB) through the Embden–Meyerhof–Parnas (EMP) pathway, while heterofermentative LAB metabolize glucose via the pentose phosphate pathway, producing lactic acid, ethanol, and CO2. In the presence of fructose, acetic acid is produced instead of ethanol, and fructose is reduced to mannitol (Wisselink et al., 2002). Generally, yeast cells prefer fructose as a carbon source, while acetic acid bacteria prefer glucose (Sievers et al., 1995). The sugar type used in Kombucha fermentation influences the metabolism of the microbial consortium, their interactions, and consequently, the profile of obtained metabolites.

Section references

Du L.L., Fu Q.Y., Xiang L.P., Zheng X.Q., Lu J.L., Ye J.H., Li Q.S., Polito C.A., Liang Y.R. Tea Polysaccharides and Their Bioactivities. Molecules. 2016;21:1449. doi: 10.3390/molecules21111449.

Ai Y., Yu Z., Chen Y., Zhu X., Ai Z., Liu S., Ni D. Rapid Determination of the Monosaccharide Composition and Contents in Tea Polysaccharides from Yingshuang Green Tea by Pre-Column Derivatization HPLC. J. Chem. 2016;2016:6065813. doi: 10.1155/2016/6065813.

Wisselink H.W., Weusthuis R.A., Eggink G., Hugenholtz J., Grobben G.J. Mannitol Production by Lactic Acid Bacteria: A Review. Int. Dairy J. 2002;12:151–161. doi: 10.1016/S0958-6946(01)00153-4.

Sievers M., Lanini C., Weber A., Schuler-Schmid U., Teuber M. Microbiology and fermentation balance in Kombucha beverage obtained from a tea fungus fermentation. Syst. Appl. Microbiol. 1995;18:590–594. doi: 10.1016/S0723-2020(11)80420-0.