We aimed to investigate the expression of selenocysteine (Sec)-containing selenoproteins in natural Lactococcus lactis and to analyze the differences in glutathione peroxidase (GPx) activity among the recombinant L. lactis NZ9000/pNZ8148-GPx (NG1) and mutants specifically producing selenoproteins generated by introducing the stop codon UGA (encoding Sec) and the cis-acting selenocysteine insertion sequence (SECIS) into the three cysteine sites (C36, C63 and C81) and the penultimate lysine site (L156) of LlGPx (the glutathione peroxidase expressed by NG1) under non-induced conditions, under nisin induction and under Se-enriched conditions. The results showed that under Se-enriched conditions, the activity of LlGPx (89.10 mU/mg) was comparable to that of the mutants (56.17-84.45 mU/mg). NG1 showed a band of 17.8 kDa on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), while none of the mutants showed complete or truncated bands corresponding to selenoproteins. This suggested that introduction of UGA and SECIS alone was insufficient for efficient read-through to detectable levels in L. lactis NZ9000 under the experimental conditions. This study lays a foundation for the construction of novel selenoproteins and their production in lactic acid bacterial cell factories.

In recent years, the incidence of chronic inflammatory bowel disease (IBD) has been increasing, posing a serious threat to human health. Medication can lead to off-target, systemic side effects and serious complications, and safer treatments are urgently needed. Selenium (Se) supplementation can alleviate IBD by modulating gut flora and increasing antioxidant enzyme activities. Glutathione peroxidase (GPx) is a selenoprotein with good antioxidant capacity to eliminate inflammation and protect the intestinal. Herein, this paper comprehensively reviews the recent research progresses of Se-containing GPxs (GPx1-4) in alleviating IBD with oxidation stress as the main thread, summaries the underlying mechanisms of Se-containing GPx on the regulation of IBD. The different effects of inorganic Se, organic Se, and Se nanoparticles in the treatment of IBD are discussed.

Flavour characteristics of Allium tenuissimum L. (AtL) flowers processed by the Chinese traditional stir-frying method were investigated by electronic nose (E-Nose) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). E-nose detection with principal component analysis (PCA) revealed that the main volatile components of AtL flowers were nitrogen oxides, terpenes, organic sulfides and sulfur-containing organic compounds, while the stir-frying process distinctly changed the flavor pattern of AtL flowers, resulting in significantly increased levels of sulfur-containing compounds. A total of 56 components were detected across fried AtL (FAtL) and raw AtL flowers, of which 25 were identified as volatile compounds by HS-GC-IMS. The contents of five fat-soluble and two water-soluble compounds in FAtL were far higher than those in AtL, confirming that stir-frying changed the flavor of AtL flowers. In conclusion, the combination of E-Nose and HS-GC-IMS represents an efficient, accurate and sensitive method for the determination of flavor components in Allium plants.

Trehalose is an autophagy-promoting disaccharide, which can improve and delay chronic diseases like neurodegenerative diseases and atherosclerosis, but its bioavailability is severely restricted by endogenous trehalase in mammals. Trehalase inhibitor is a promising and effective way to enhance trehalose bioavailability by preventing trehalose from hydrolyzing. However, previously reported trehalase inhibitors still face safety of long-term use and promiscuous inhibition on intestinal glycosidases. This study carried out a high-throughput virtual screening through molecular pool-based molecular docking combined with in vitro inhibition experiments to screen trehalase inhibitors naturally derived from foods. Out of 1769 small molecules, which include 115 analogs of trehalose, natural monosaccharides, disaccharides, trisaccharides, imidazoles and their derivatives, as well as 20 natural amino acids and their 400 dipeptides, isomaltose, α-isomaltulose, and isomaltitol exhibited the best inhibitory activities, beyond as traditional sweetener and prebiotic. Best of all, isomaltose showed the half maximal inhibitory concentration (IC₅₀) and inhibition constant (K_i) values on trehalase of 5.59 and (2.1760 ± 0.3431) mmol/L, respectively. Moreover, isomaltose was resistant to the simulated digestive environment and did not affect intestinal glycosidases such as α‍-glucosidase and glucoamylase, making it a reliable edible candidate for a trehalase inhibitor. This study provides new insights into the virtual screening-based identification of new food-derived trehalase inhibitors for enhanced integrity and bioavailability of orally administered trehalose, especially repurposing a prebiotic for another new use as trehalase inhibitor.

Hyperuricemia (HUA) is characterized by elevated levels of uric acid (UA) in the bloodstream, resulting from either excessive production or insufficient excretion of UA within the body. If left untreated, progressive or persistent HUA can lead to gout, causing significant harm to human health. Lactic acid bacteria (LAB), generally recognized as safe (GRAS) probiotics, have been shown to alleviate symptoms associated with gastrointestinal disorders such as irritable bowel syndrome and inflammatory bowel disease while supporting overall bodily functions and health. Recently, LAB has emerged as a potentially safe, cost-effective and efficient treatment for HUA. This comprehensive review aims to explore the current literature on the mechanisms through which LAB controls HUA. These mechanisms include suppressing purine metabolism, absorbing purine compounds, modulating microbiota to maintain host global purine homeostasis, reducing intestinal permeability, producing metabolites that alleviate HUA symptoms, promoting the expression of urate excretory proteins and inhibiting the expression of urate reabsorption proteins. The findings presented in this review provide a framework for further investigation into how probiotic LAB can alleviate HUA by influencing UA metabolism and elucidating their underlying action mechanisms.

The traditional nutritional and medical hemp (Cannabis sativa L.) seed protein were explored for the discovery and directional preparation of new xanthine oxidase inhibitory (XOI) peptides by structure-based virtual screening, compound synthesis, in vitro bioassay and proteolysis. Six subtypes of hemp seed edestin and albumin were in silico hydrolyzed by 29 proteases, and 192 encrypted bioactive peptides were screened out. Six peptides showed to be XOI peptides, of which four (about 67%) were released by elastase hydrolysis. The peptide DDNPRRFY displayed the highest XOI activity (IC₅₀ = (2.10 ± 0.06) mg/mL), acting as a mixed inhibitor. The pancreatic elastase directionally prepared XOI hemp seed protein hydrolysates, from which 6 high-abundance XOI peptides encrypted 3 virtually-screened ones including the DDNPRRFY. The novel outstanding hemp seed protein-derived XOI peptides and their virtual screening and directed preparation methods provide a promising and applicable approach to conveniently and efficiently explore food-derived bioactive peptides.

This study investigated the combinatorial expression of xanthine dehydrogenase (XDH) and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in the beer, beef and yeast. Naturally occurring xdhABC gene clusters of A. baumannii CICC 10254 and R. capsulatus CGMCC 1.3366 as well as two refactored clusters constructed by exchanging their xdhC genes were overexpressed in Escherichia coli and purified to near homogeneity. RcXDH chaperoned by AbXdhC showed nearly the same catalytic performance as that by RcXdhC, except for the decreased substrate affinity. While the AbXDH co-expressed with RcXdhC displayed enhanced acidic adaptation but weakened catalytic activity. All the XDHs degraded purines in beer, beef and yeast extract effectively, indicating potential applications in low-purine foods to prevent hyperuricemia and gout. The study also presents a method for exploiting the better chaperone XdhC and novel XDHs by functional complement activity using existing XdhCs such as RcXdhC.

The aim of this study was to isolate a new purine-degrading potential probiotic strain from Chinese fermented rice-flour noodles and investigate its potential application in purine-degrading food development for promising anti-gout therapy. A new lactic acid bacteria strain designated as Lactobacillus fermentum 9-4 was screened out from 10 Shengzhamifen samples by a comprehensive method integrating agar plate selection, in vitro purine-metabolizing enzymatic activities of xanthine oxidase and urate oxidase, 16S rRNA gene sequencing and identification. The resting cells of L. fermentum 9-4 showed the maximum degradation rates of inosine and guanosine by respective 2.13 × 10⁻³ and 2.78 × 10⁻³ g/(L·min), and the highest assimilation ratio of guanosine by (55.93 ± 3.12)%, which are improvements over LAB strains characterized previously. Yogurt fermented by L. fermentum 9-4 also efficiently assimilated the inosine and guanosine, with respective degradation rates of 98.10 % and 98.56 % higher than those of the commercial ones. The L. fermentum 9-4 showed excellent survival (> 80 %) under the conditions of pH 2.5 and 0.1 % bile salt. The results suggest that L. fermentum 9-4 may be a promising candidate as a probiotic for developing low-purine foods.