Enzymatic Preparation of Low-Molecular-Weight Laminaria japonica Polysaccharides and Evaluation of Its Effect on Modulating Intestinal Microbiota in High-Fat-Diet-Fed Mice

Abstract

Recent studies have shown that seaweed polysaccharides can ameliorate high-fat-diet (HFD)-induced metabolic syndromes associated with the regulatory function of gut microbiota. However, kelp, a natural source of seaweed polysaccharides, is highly viscous, making it difficult to prepare dietary fiber by simple degradation. Therefore, we developed a novel method of preparing low-molecular-weight polysaccharides from <i>Laminaria japonica</i> by combining high-pressure pretreatment and composite enzymatic degradation and evaluated the obesity prevention activity of these polysaccharides. Seaweed <i>L. japonica</i> polysaccharides (SJP) were rapidly utilized by the human fecal microbiota <i>in vitro</i>, resulting in the generation of short-chain fatty acids (SCFAs), specifically acetate and propionate. The <i>in vivo</i> effects of SJP on the intestinal microbiota were also investigated using HFD-fed C57BL/6J mice. SJP reduced weight gain and fat deposition in HFD-fed mice and increased the concentration of total SCFAs, including acetate, propionate, and butyrate in the feces. SJP ameliorated HFD-induced gut microbiota dysbiosis, resulting in increased abundance of <i>Faecalibaculum</i>, <i>Romboutsia</i>, and <i>Clostridium sensu stricto 1</i> and decreased abundance of <i>Blautia</i> and <i>Lactobacillus</i>. Further, SJP enhanced the abundance of <i>Akkermansia muciniphila</i> in mice provided with HFD and normal chow. Single-strain culture experiments also revealed that SJP promoted the growth of <i>A. muciniphila</i>. This study highlights the potential use of SJP, prepared using composite enzymatic degradation (cellulase and recombinant alginate lyase), in preventing obesity and restoring intestinal homeostasis in obese individuals.