Bacillus subtilis (B. subtilis) JZXJ-7 isolated from shrimp paste can significantly degrade histamine under salt stress but the mechanism is unclear. This study aims to evaluate the effect of 170 and 340 mmol/L NaCl on B. subtilis JZXJ-7 growth, histamine degradation, antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST)] activities and Na⁺, K⁺-ATPase activity. Furthermore, comparative metabolomics was used to investigate histamine biodegradation mechanism by B.subtilis JZXJ-7 subjected to salt stress. Both 170 and 340 mmol/L NaCl promoted B. subtilis JZXJ-7 growth in late stages of reproduction (32 − 48 h), increased histamine degradation rate by 64.85% and 79.87% (P < 0.05), Na⁺, K⁺-ATPase activity to 6.28 U/mg (P < 0.05) and 11.63 U/mg (P < 0.01) respectively. NaCl treatment significantly increased the activities of CAT, GST and SOD (P < 0.05), amino acids and its metabolites (33.39%), benzene and substituted derivatives (12.05%), heterocyclic compounds (10.62%), organic acids and derivatives (9.75%), aldehydes, ketones, esters (5.59%) and nucleotides and its metabolites (4.58%). Metabolite set enrichment analysis revealed NaCl induced differential metabolic pathways of D-glutamine, D-glutamate, L-arginine, L-proline, histidine and glycerophospholipids, L-lysine degradation, and aminoacyl-tRNA biosynthesis. Exposure to 340 mmol/L NaCl up-regulated carbohydrate, glutathione and glycerophospholipid metabolism. The new insights into the mechanism of salt stress to promote B. subtilis JZJX-7 growth, energy metabolic pathways and to degrade histamine provide the theoretical basis for application of B. subtilis JZXJ-7 in food fermentation industry.

This study aimed to characterize and identify calcium-chelating peptides from rabbit bone collagen and explore the underlying chelating mechanism. Collagen peptides and calcium were extracted from rabbit bone by instant ejection steam explosion (ICSE) combined with enzymatic hydrolysis, followed by chelation reaction to prepare rabbit bone peptide-calcium chelate (RBCP-Ca). The chelating sites were further analyzed by liquid chromatography-tandem mass (LC-MS/MS) spectrometry while the chelating mechanism and binding modes were investigated. The structural characterization revealed that RBCP successfully chelated with calcium ions. Furthermore, LC-MS/MS analysis indicated that the binding sites included both acidic amino acids (Asp and Glu) and basic amino acids (Lys and Arg). Interestingly, three binding modes, namely Inter-Linking, Loop-Linking and Mono-Linking were for the first time found, while Inter-Linking mode accounted for the highest proportion (75.1%), suggesting that chelation of calcium ions frequently occurred between two peptides. Overall, this study provides a theoretical basis for the elucidation of chelation mechanism of calcium-chelating peptides.

The concept of healthiness and sustainability have triggered consumers into choosing healthier food, especially “clean-label” products. Porcine skin is a natural “clean-label” raw material, and direct usage of whole pork skin as an additive has been proven as an efficient way to deal with the by-product issues and also satisfies the “clean label” demands of consumers. However, efficient approaches to convert bulk skin into handy powders in a green-fabrication manner while maintaining its unique properties have yet to be fully investigated. Herein, we provided two green approaches, drying-grinding, and wetting-grinding, to prepare pork skin functional protein powder (FPP), and their chemical composition, structure, properties, stability, and functionality are systematically investigated. Specifically, FPP prepared by two methods exhibit similar chemical composition and great thermal stability. Notably, FPP prepared by drying-grinding method is superior in flow ability, water dispersion, and texture properties of FPP gels as compared to wetting-grinding method. Structural analyses revealed that the superior properties of FPP prepared by drying-grinding method depend on the intrinsic natural triple helix structure of collagen. Overall, this work revealed the underlying key factors for the preparation of FPP with excellent properties, and highlighted that the FPP prepared by drying-grinding method is more suitable for practical application as “clean-label” additives in the food industry.

Ultraviolet (UV)-induced photoaging skin has become an urgent issue. The functional foods and cosmetics aiming to improve skin photoaging are developing rapidly, and the demand is gradually increasing year by year. Collagen peptides have been proven to display diverse physiological activities, such as excellent moisture retention activity, hygroscopicity, tyrosinase inhibitory activity and antioxidant activity, which indicates that they have great potential in amelioration of UV-induced photoaging. The main objective of this article is to recap the main mechanisms to improve photoaging skin by collagen peptides and their physiological activities in photo-protection. Furthermore, the extraction and structural characteristics of collagen peptides are overviewed. More importantly, some clinical trials on the beneficial effect on skin of collagen peptides are also discussed. In addition, prospects and challenges of collagen peptides are emphatically elucidated in this review. This article implies that collagen peptides have great potential as an effective ingredient in food and cosmetics industry with a wide application prospect.