Antipathogenic activity and preservative effect of levan (β-2,6-fructan), a multifunctional polysaccharide

The objective of this study was to investigate the antibacterial activity of levan compounds, including high-molecular-weight levan, low-molecular-weight levan and difructose dianhydride IV (DFA IV). The levans exhibited broad antibacterial spectra against foodborne pathogenic bacteria, in a concentration-dependent manner. From comparison with simple saccharides, often regarded as by-products of levan production, it turned out that the antibacterial activity of levans was primarily caused by themselves. The strongest effect was observed with low-molecular-weight levan as compared to the others, and oligosaccharides as well. The low-molecular-weight levan was therefore applied to bread making. The bread samples inoculated with pathogenic bacteria were divided into two groups: bread with sugar alone (control) and bread with both sugar and levan (treatment). It was found from the in situ test that the viability of pathogenic bacteria in bread was reduced by the addition of low-molecular-weight levan. Therefore, levan compounds have potential as alternative sweeteners for reduction in pathogenic contamination.