Intestinal microbiota have marked metabolic activity and influences the host in both beneficial and harmful ways. In the present study, we developed an apparatus to measure the amount of CO₂ in the gas excreted during defecation and investigated whether this amount of CO₂ can be used as an indicator of the intestinal environment. The apparatus consists of a fan and a commercial CO₂ sensor attached to a toilet stool. Fecal pH, fecal water content, concentrations of short chain organic acids (SCFAs) and intestinal putrefactive products and composition of fecal microbiota were analyzed as indicators of the intestinal environment. The apparatus could measure the amount of CO₂ in the gas with good reproducibility, irrespective of the open area at the top of the toilet stool, position of gas injection and composition of the gas. In a volunteer study, the amount of CO₂ in defecation gas correlated with pH, water content and concentrations of SCFAs and intestinal putrefactive products in the feces, although correlation with the composition of intestinal microbiota was not be observed. The results indicate that the amount of CO₂ in defecation gas can be measured with simple and sanitary procedures and is a good indicator of the intestinal environment.

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In this study, the effects of enumeration methods on viable bifidobacterial counts in powder products were examined to determine the most appropriate enumeration conditions. The bifidobacterial counts of nine commercial powder products containing Bifidobacterium species were determined by a pour plate method using different diluents including Mitsuoka's buffer and Ringer's solution. Mitsuoka's buffer gave significantly higher bifidobacterial counts than Ringer's solution when used as diluent for eight of nine commercial powder products containing various Bifidobacterium species. The counts obtained with Ringer's solution were on average 51.6% of those obtained using Mitsuoka's buffer. Addition of Tween 80 or phosphate buffer to Ringer's solution increased the bifidobacterial counts. Also, the diluent had a significantly greater impact in the suspension step than in the subsequent dilution step. In conclusion, the diluent has great effect on the enumeration of bifidobacteria when using the plate count method. Also, the composition of diluents influences bifidobacterial counts.

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