Antibacterial activity and mechanism of green tea polysaccharide conjugates against Escherichia coli

The effect of green tea polysaccharide conjugate (gTPC) on the growth of E. coli was evaluated. gTPC has optimal antibacterial concentrations for E. coli DH5 alpha (4.00 mg/mL) and 25,922 (1.00 mg/mL), with the antibacterial rates of 55.75 % and 50.65 % respectively. The results of scanning electron microscopy (SEM) and transmission electron microscope (TEM) indicated that gTPC-treated E. coli cells showed obvious morphological changes, part of the cell wall became blurred, and the leakage of cytoplasmic content were observed. The proportion of the propidium iodide (PI) permeable E. coli cells treated using 0.50-2.00 mg/mL gTPC was between 8.79 %-9.49 % as well as 14.10 % (4.00 mg/mL gTPC) and 15.10 % (6.00 mg/mL gTPC). Reactive oxygen species (ROS) production of 1.00-4.00 mg/mL gTPC treated E. coli increased by 26.57 %-38.19 % with a significant increase level (p < 0.01). The outer membrane disruption played a key role in the antibacterial activity of gTPC against E. coli. This research result will open a new application field of tea polysaccharide conjugates.