A comprehensive study of glucose transfer in the human small intestine using an in vitro intestinal digestion system (i-IDS) based on a dialysis membrane process

Human digestion is a complex process that involves several phenomena: chemical and enzymatic reactions, absorption, hydrodynamic processes, and mass transfer. The most accurate way to determine the bioavailability of different nutrients is through human studies. However, there are ethical, economic, and technical reasons that restrict their application. Aiming at contributing with a new experimental prototype and phenomenological model to study nutrient absorption in the human small intestine, an in vitro intestinal digestion system (i-IDS), based on a hollow fiber dialysis membrane process, was constructed and tested under different operational conditions of feed flow/dialysate flow ratio. This dialysis membrane process here presented, allowed to simulate and extrapolate results of the process of glucose transfer in the human small intestine, where the glucose mass transfer reached around 90% at times ranging between 25 and 40 min. The mathematical model was validated with respect to the experimental results, obtaining a good agreement (root mean square error, % RMS, between 3% and 19%) among them. Overall permeabilities for the experimental conditions ranged between 3.85 x 10(-6) and 4.86 x 10(-6) m(3)/s. The experimental results of glucose absorption were extrapolated to those found in the human small intestine using a phenomenological model, where a good agreement among results of glucose absorption was found in human studies. This first experimental and phenomenological approach allows to acquire a better knowledge of the complex mass transfer processes found in human small intestine for nutrient absorption.