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Recent Research
Effects of α-Amylase and Its Inhibitors on Acid Production from Cooked Starch by Oral Streptococci
Aizawa S et al.
Caries Research 2009; 43: 17-24
An evaluation of acid production in vitro from cooked starch by Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis and Streptococcus mitis, and the effects of α-amylase inhibitors (maltotriitol and acarbose) and xylitol on acid production. Streptococcal cell suspensions were anaerobically incubated with different carbohydrates (glucose, sucrose, maltose), including cooked potato starch (either with or without α-amylase). The fall in pH and the acid production rate at pH 7 were noted. When α-amylase was not present, the fall in pH and the acid production rate from cooked starch added to S. mutans were negligible. However, when α-amylase was present, the pH fall was almost equal to that from maltose, which reached 3.8 at 20 minutes. Similar results were obtained for S. sobrinus. When added to S. sanguinis, starch in the absence of α-amylase produced an obvious fall in pH that was smaller than that observed for glucose, sucrose and maltose. However, in the presence of α-amylase, the pH fall was closer to that observed for the other carbohydrates. Similar results were obtained for S. mitis, although the drop in pH in the absence of α-amylase was negligible. Acid production rate of cooked starch in the absence of α-amylase was small, but in the presence of α-amyalse, acid was produced at a rate of 0.61-0.92 µmol per optical density unit per min, which was similar to maltose. Acarbose and maltotriitol inhibited the pH fall from cooked starch in the presence of α-amylase with all bacterial strains: Xylitol only inhibited the pH fall in S. mutans and S. sobrinus. The study shows that cooked starch in the presence of salivary α-amylase is a potential source of acids that could be produced by oral steptococci.
July 2009
