Antibacterial and probiotic promotion potential of a new soluble soybean polysaccharide‑iron(III) complex

In this study soluble soybean polysaccharide‑iron(III) (SSPS-Fe(III)) was synthesized to investigate the effects on the growth of Escherichia coli, Staphylococcus aureus and Bacillus licheniformis. Two new detection methods of real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) and microcalorimetry were used to evaluate the effects of different concentrations of SSPS-Fe(III) on the growth of three bacteria. The copy numbers of three bacteria showed that SSPS-Fe(III) had different impacts on the growth of E. coli, S. aureus and B. licheniformis. E. coli growth was inhibited by SSPS-Fe(III) in the higher concentration range and S. aureus growth was inhibited at any concentration, however B. licheniformis growth was promoted. The thermogenic curves for growth metabolism of E. coli and S. aureus presented peak shapes while those of B. licheniformis did platform shapes. As SSPS-Fe(III) concentration increased, the peak heights lowered for E. coli and S. aureus, and the time reaching stationary phase advanced for B. licheniformis. These findings demonstrate that SSPS-Fe(III) has an inhibitory effect on the foodborne pathogens of E. coli and S. aureus, and an enhancement on the probiotics of B. licheniformis.