Hypertension is known as an important factor in cardiovascular disease. An angiotensin-I-converting enzyme (ACE) inhibitor is one of the synthetic drugs that is widely used to control hypertension. Here, we have prepared and investigated the ACE inhibitory peptide from Ruditapes philippinarum fermented with Bacillus natto. The fermented product obtained under optimized fermentation conditions exhibited ACE inhibitory activity. The ACE inhibitory peptides were purified by ultrafiltration, gel filtration chromatography and RP-HPLC, sequentially. A novel peptide with high ACE inhibitory activity (IC₅₀ of 8.16 μM) was isolated and the amino acid sequence was identified to be Val-Ile-Ser-Asp-Glu-Asp-Gly-Val-Thr-His (VISDEDGVTH) by LC-MS/MS. The Lineweaver–Burk plots suggested that VISDEDGVTH acts as a competitive inhibitor against ACE. Our in vitro study indicated the stability of VISDEDGVTH against gastrointestinal proteases. An in vivo study in rats proved the significant anti-hypertension effect of the peptide. Furthermore, the cellular mechanism of VISDEDGVTH moderating hypertension was investigated. We found that VISDEDGVTH enhanced the release of NO, inhibited the secretion of EF-1, and scavenged ROS in human vascular endothelial cells. Our study suggests that VISDEDGVTH serves as an anti-hypertension and anti-inflammatory drug and as a beneficial ingredient in functional foods and pharmaceuticals.

To understand the mode of action of low molecular weight phlorotannins (LMPs) from Sargassum thunbergii against Vibrio parahaemolyticus, effects of LMPs on the growth curve and the content changes of some substances in culture media were investigated, and those on morphological and ultramicrostructure were also observed by scanning electron microscope and transmission electron microscopy. The results showed that LMPs inhibited thalli growth at logarithmic phase and damaged the cell membrane and cell wall of tested bacteria which led to the leakage of cytoplasm and the deconstruction of membrane permeability. The present study indicates that LMPs as natural products in seaweeds deserve further investigation for food safety control and aquacultural drugs.

Pullulan with different molecular-weight could be applied in various fields. A UV-induced mutagenesis Aureobasidium pullulans UVMU6-1 was obtained from the strain A. pullulans CGMCC3.933 for the production of low-molecular-weight pullulan. First, the obtained polysaccharide from A. pullulans UVMU6-1 was purified and identified to be pullulan with thin-layer chromatography, Fourier transform infrared, and nuclear magnetic resonance. Then, culture medium and conditions for this strain were optimized by flask fermentation. Based on the optimized medium and culture conditions (pH 4, addition of 4 g/L Tween 80 for 96 hr of cultivation), continuously fermentation was performed. The highest pullulan production and dry biomass was 109 and 125 g/L after fermentation for 114 hr, respectively. The average productivity was about 1 g/L/hr, which was intensively higher than the previous reported. This study would lay foundations for the industrial production of pullulan.

In this study, bioactive peptides (RBPs) from Ruditapes philippinarum were prepared by fermentation with Bacillus natto and the effect and mechanisms of RBPs on obesity and hyperlipidemia were explored in mice. We found that RBPs significantly reduced body weight, adipose tissue weight, accumulation of hepatic lipids, and serum levels of total cholesterol (CHO), triglyceride (TG), and low-density lipoprotein (LDL). Mechanistic studies showed that RBPs up-regulated the hepatic expression of genes related to lipolysis, such as hormone-sensitive lipase (HSL), phosphorylated AMP-activated protein kinase (p-AMPK), and peroxisome proliferator-activated receptors $\mathsf{\alpha }$ (PPAR$\mathsf{\alpha }$), and down-regulated the expression of peroxisome proliferator-activated receptors $\mathsf{\gamma }$ (PPAR$\mathsf{\gamma }$) which is related to lipid synthesis. In addition, RBPs could attenuate obesity and hyperlipidemia by regulating disordered gut microbiota composition, such as increasing the abundance of microflora related to the synthesis of short chain fatty acids (SCFAs) (Bacteroidetes, Prevotellaceas_UCG_001, norank_f_Muribaculaceae, and Odoribacter) and controlling those related to intestinal inflammation (reduced abundance of Deferribacteres and increased abundance of Alistipes and ASF356) to exert anti-obesity and lipid-lowering activities. Our findings laid the foundation for the development and utilization of RBPs as a functional food to ameliorate obesity and hyperlipidemia.