Inhibitory Effect of Depolymerized Sulfated Galactans from Marine Red Algae on the Growth and Adhesion of Diarrheagenic Escherichia coli

Abstract

Active polysaccharides as safe and natural polymers against bacterial diarrhea have been reconsidered as an alternative to antibiotics. This work investigated the inhibiting effect of depolymerized sulfated galactans from Eucheuma serra and Gracilaria verrucosa on the growth and adhesion of diarrheagenic enterotoxigenic Escherichia coli (ETEC) K88. Results showed that the sulfated polysaccharides with molecular weight distribution ≤20.0 kDa exhibited antibacterial activity against ETEC K88. A structure–activity study revealed that the anti-ETEC K88 activity of sulfated polysaccharides is strictly determined by their molecular weight distribution, sulfate group content, and monosaccharide composition. In addition, the promoted nucleic acid release and the fluorescence quenching of membrane proteins were observed after the treatment with selected polysaccharides. Scanning electron microscopy further confirmed that the depolymerized sulfated galactans can effectively inhibit ETEC K88 adhesion. In conclusion, depolymerized sulfated galactans exhibited an inhibitory effect on the growth and adhesion of ETEC K88.

Antibacterial Activity of Sulfated Galactans from Eucheuma serra and Gracilari verrucosa against Diarrheagenic Escherichia coli via the Disruption of the Cell Membrane Structure

“…Zhang et al (2017) found that the soluble proteins in the E. coli culture increased after treating with polysaccharides from Cordyceps cicadae [ 27 ]. Previous studies also confirmed that the sulfated polysaccharides could cause an increase in nucleic acid levels of the ETEC K88 culture [ 11 , 18 ].…”

“…After high-temperature and high-pressure treatment, the microstructure of the polysaccharides showed a visible change where the flaky structure was broken into porous flocculent. In previous research, an increase in reducing sugar and a decrease in viscosity were evident after the sulfated polysaccharides were hydrolyzed in high-temperature and high-pressure conditions [ 18 ].…”

“…The collection and pretreatment of red algae E. serra and G. verrucosa were performed according to the methods used in an earlier study [ 18 ]. The sulfated galactans from E. serra were extracted and isolated based on previous studies [ 18 , 30 ].…”

“…The collection and pretreatment of red algae E. serra and G. verrucosa were performed according to the methods used in an earlier study [ 18 ]. The sulfated galactans from E. serra were extracted and isolated based on previous studies [ 18 , 30 ]. Briefly, 100 g of the dried E. serra powder were macerated in water at 50 °C for 4 h. Then, the E. serra syrup was filtered through filter cloth, concentrated to 1/4th of the original volume, cooled, and precipitated overnight with three volumes of ethanol at 4 °C.…”

“…Eucheuma serra ( E. serra ) and Gracilaria verrucosa ( G. verrucosa ) are seaweeds from the southeast coastal areas of China and are the primary raw materials for the production of carrageenan and agar productions, respectively [ 17 ]. Previous studies have found that depolymerized sulfated galactans from both E. serra and G. verrucosa exhibited an inhibitory effect on diarrheagenic ETEC K88 [ 18 ]. This study investigated how the anti-ETEC K88 activity of sulfated galactans is enhanced by metal ion desorption since algae are responsible for enriching seawater with metal ions.…”