Ultrasonic/microwave-assisted extraction, simulated digestion, and fermentation in vitro by human intestinal flora of polysaccharides from Porphyra haitanensis.

In this study, we employed a response surface methodology to optimize the ultrasonic/microwave-assisted extraction (UMAE) conditions of Porphyra haitanensis polysaccharides (PHP), and subjected it to a stimulated in vitro digestion and fermentation model in order to investigate the digestion properties of PHP and the effects on human intestinal flora. The optimum extraction conditions consisted of an extraction time of 29.64 min, extraction temperature of 79.94 °C, and solid-liquid ratio of 1:41.79 g/mL. Under these conditions, the maximum yield of PHP predicted was 20.98%. The ζ-potential and thermal properties analysis verified that PHP was a negatively charged polymer, and possessed good thermal stability. Meanwhile, PHP was not digested in vitro by human saliva, simulated gastric and small intestinal juice. Furthermore, PHP modulated the microbiome structure, mainly increasing the relative abundance of Bacteroides and decreasing in the Escherichia_Shigella group. LEfSe analysis illustrated that Bacteroides, Lachnospiraceae_UCG_006 and Bacteroidales_S24_7_group could serve as potential biomarkers for the PHP supplement. This current study proved that the UMAE method was a highly efficient method to extract PHP to the maximum extent, and also provided insight concerning the stability performance of PHP and its prospects for application as a prebiotics candidate in the functional food industries.