ULVA-LACTUCA IS POORLY FERMENTED BUT ALTERS BACTERIAL METABOLISM IN RATS INOCULATED WITH HUMAN FECAL FLORA FROM METHANE AND NONMETHANE PRODUCERS

In vivo fermentation of Ulva lactuca was studied in previously germ-fr ee rats inoculated with human flora obtained from non-, low- and high- methane producers (groups NMP, LMP and HMP, respectively), in comparis on to germ-free rats. Rats were fed either a control diet or a diet co ntaining 4% of dried Ulva lactuca. Production of metabolites varied ac cording to the flora and diet. Ulva lactuca induced a specific high pr oduction of methane in the HMP group. With the three human flora, Ulva diet induced a similar increase in caecal pH. In the NMP and HMP grou ps, this increase was associated with a fall of lactic acid caecal con centration. In the LMP group it was related to a decrease in the conce ntration of short-chain fatty acids. Ulva lactuca appeared to be able to regulate the beta-glucuronidase and beta-glucosidase activities, re ducing the relatively high levels observed in groups NMP and HMP and i ncreasing the low levels obtained in the LMP group. Results show that, although it was poorly fermented, Ulva induced significant effects on the gut microflora metabolism. The methanogenic status of the human d onor appeared to be an important factor. (C) 1998 SCI.