Methods: As a negative control, a TPY culture medium containing 5% sucrose was used to culture the selected dental caries related bacteria strain, Streptococcus mutans ATCC 25175. In the different test culture mediums, sucrose was substituted by one of the followings: 1) 5% chitooligosaccharide, 2) 5% xylitol, 3) 2.5% sucrose + 2.5% chitooligosaccharide, 4) 2.5% sucrose + 2.5% xylitol, 5) 5% sucrose + 5% chitooligosaccharide, 6) 5% sucrose + 5% xylitol. The initial pH of all the culture mediums was adjusted to be 7.4. After incubated anaerobically at 37°C for 48 hours, the growth of the bacteria was investigated by using a cell counting method. The final pH of the mediums was measured and the change in pH was calculated.
Results: The growth and the acid production of Streptococcus mutans in 5% chitooligosaccharide medium was significantly lower than that in 5% sucrose medium (p<0.001), and also lower than that in 5% xylitol medium (p<0.01). When mixed with sucrose, 5% chitooligosaccharide decreased both the growth and the acid production of the bacteria significantly (p<0.001). In the mediums with mixtures of sucrose and xylitol, the acid production of Streptococcus mutans was slightly higher than that in sucrose medium (p<0.001), and the growth of the bacteria was significantly higher than that in the mediums with sucrose and chitooligosaccharide mixtures (p<0.001).
Conclusion: Chitooligosaccharide can hardly be utilized by Streptococcus mutans. When mixed with sucrose, chitooligosaccharide may be better than xylitol in inhibiting the growth and the acid production of the bacteria. It has the potential to be used as sucrose substitutes in food.