Effect of different starches on Escherichia coli (S1) beta-glucuronidase expression.

Studies with pure cultures growing in laboratory media indicated that beta-glucuronidase expression of Escherichia coli S1 was considerably affected by starch added to the medium as the only carbon source. This result, which may be an aspecific modulation of enzyme expression, was independent of the starch molecular structure and effects were analogous for maize, rice, wheat or potato starches. It was observed that enzyme expression was little affected by the growth rate. The beta-glucuronidase activities of starch-grown bacteria found in the present study agree with those observed in animal and human models performed for in vivo evaluation of effects of dietary starch effects on gut microbial ecosystems.