Metabolic Fate of 13C-Labeled Polydextrose and Impact on the Gut Microbiome: A Triple-Phase Study in a Colon Simulator.

The present study introduces a novel triple-phase (liquids, solids, and gases) approach, which employed uniformly labeled [U-13C] polydextrose (PDX) for the selective profiling of metabolites generated from dietary fiber fermentation in an in vitro colon simulator using human fecal inocula. Employing 13C NMR spectroscopy, [U-13C] PDX metabolism was observed from colonic digest samples. The major 13C-labeled metabolites generated were acetate, butyrate, propionate, and valerate. In addition to these short-chain fatty acids (SCFAs), 13C-labeled lactate, formate, succinate, and ethanol were detected in the colon simulator samples. Metabolite formation and PDX substrate degradation were examined comprehensively over time (24 and 48 h). Correlation analysis between 13C NMR spectra and gas production confirmed the anaerobic fermentation of PDX to SCFAs. In addition, 16S rRNA gene analysis showed that the level of Erysipelotrichaceae was influenced by PDX supplementation and Erysipelotrichaceae level was statistically correlated with SCFA formation. Overall, our study demonstrates a novel approach to link substrate fermentation and microbial function directly in a simulated colonic environment.

At-line determination of octanoic acid in cultivation broth--an electronic tongue (ET) feasibility study.

Production monitoring of "natural" 2-heptanone from octanoic acid in an industrial fed-batch cultivation based on Penicillium roqueforti requires development of a method for determination of octanoic acid dissolved in the water phase. An electronic tongue array using six non-specific potentiometric sensors with solid inner contact, and a pH electrode, has been introduced by spiking octanoic acid to a substrate obtained from four different cultivations, representing variations in the relevant industrial matrix. Multivariate calibration was performed on acid concentrations spanning 0.65-20 mmol l(-1). Excluding the lowest concentration a global Partial Least Square regression model with a predicted versus measured correlation of 0.98 and a relative root mean square error of prediction of 5.1% (ln units) (RPD=5.5) signifies a highly acceptable prediction facility. This model was further tested by subjecting it to undiluted as well as diluted samples obtained from a cultivation process in which octanoic acid was catabolized; this led to acceptable prediction errors within the same range as for the global model. It is concluded that the ET sensor array can be applied for determination of octanoic acid in cultivation systems of the general P. roqueforti type.