Selective in vitro degradation of the sialylated fraction of germ-free rat mucins by the caecal flora of the rat

Mucins, which are synthesized throughout the gastrointestinal tract, may be degraded by the microflora of the large intestine. The present study was undertaken to determine the differential fate of the various types of mucins. Mucins from germ-free rats were incubated in vitro in the presence of whole caecal flora from the conventional rat. Neutral, acidic and acidic sulphated mucins were spectrophotometrically assayed over time upon anaerobic incubation. Sialylated mucins were more rapidly degraded (90 %) than the other two types after 1 h and almost completely within 4 h. Neutral and acidic sulphated mucins, with a 10-fold and 30-fold lower content than the sialylated fraction in the original substrate, were more slowly degraded and to a lesser extent within 4 h, (55 and 40 %, respectively). The method used in the present study made it possible to investigate the activity of gut bacteria towards the various types of mucins. The degradation of the three mucin types was not uniform, the highest rate and extent of degradation being observed for sialylated mucins. (C) Inra/Elsevier, Paris.