Real time microcalorimetric profiling of prebiotic inulin metabolism

The in vitro assessment of prebiotics involves elaborate microbiological techniques or a combination of culture techniques and molecular methods. In this study, the isothermal microcalorimeter, an instrument which can monitor the real time growth of bacteria was applied to investigate the prebiotic effect of inulin in real time. Fresh and standardized frozen faecal slurries were prepared, placed and monitored in the isothermal microcalorimeter. The faecal samples and commercial probiotic strains Lactobacillus acidophilus LA-5®, Bifidobacterium lactis BB-12® were cultured in a mixed medium of cooked meat medium (CMM) and brain heart infusion (BHI) broth with and without supplementation with inulin and monitored in the microcalorimeter. The results showed power-time (p-t) curves that were characteristic for the samples. The p-t curves of the fresh and frozen faecal samples were similar. Augmented microbial activity was observed when the faecal sample was inoculated into CMM-BHI mixed broth with significant enhancement of microbial activity detected in the presence of inulin which was reproducible. Deconvoluted p-t curves showed multiple peaks with time and intensity variance depending on presence or absence of inulin suggesting possible differences in utilization of inulin by the different groups of bacteria in the polymicrobial sample. P-t curves of the pure species did not show any significant change when inulin was supplemented into the medium likely due to the inability of the bacteria to primarily utilize inulin.