Xylo-oligosaccharides ameliorate high cholesterol diet induced hypercholesterolemia and modulate sterol excretion and gut microbiota in hamsters

Efficient production of xylooligosaccharides from Camellia oleifera shells pretreated by pyruvic acid at lower temperature

XOS production from lignocellulose using organic carboxylic acids and alkyd acids has been widely reported. However, it still faces harsh challenges such as high energy consumption, high cost, and low purity. Pyruvic acid (PYA), a carbonyl acid with carbonyl and carboxyl groups, was used to produce XOS due to its stronger catalytic activity. In this work, XOS was efficiently prepared from COS in an autoclave under the condition of 0.21 M PYA-121 °C-35 min. The total yield of XOS reached 68.72 % without producing any toxic by-products, including furfural (FF) and 5-hydroxymethylfurfural (5-HMF). The yield of xylobiose (X2), xylotriose (X3), xylotetraose (X4), and xylopentaose (X5) were 20.58 %, 12.47 %, 15.74 %, and 10.05 %, respectively. Meanwhile, 89.05 % of lignin was retained in the solid residue, which provides a crucial functional group for synthesizing layered carbon materials (SRG-a). It achieves excellent electromagnetic shielding (EMS) performance through graphitization, reaching -30 dB at a thickness of 2.0 mm. The use of a PYA catalyst in the production of XOS has proven to be an efficient method due to lower temperature, lower acid consumption, and straightforward operation.

Interactions between dietary cholesterol and intestinal flora and their effects on host health

The interactions between dietary cholesterol and intestinal microbiota strongly affect host health. In recent years, relevant studies have greatly advanced this field and need to be summarized to deepen the understanding of dietary cholesterol-intestinal microbiota interactions and their effects on host health. This review covers the most recent frontiers on the effects of dietary cholesterol on the intestinal microbiota and its metabolites, the metabolism of cholesterol by the intestinal microbiota, and the effects of the interactions on host health. Several animal-feeding studies reported that dietary cholesterol altered different intestinal microbiota in the body, while mainly causing alterations in intestinal microbial metabolites such as bile acids, short-chain fatty acids, and tryptophan derivatives. Alterations in these metabolites may be a novel mechanism mediating cholesterol-related diseases. The cholesterol microbial metabolite, coprostanol, has a low absorption rate and is excreted in the feces. Thus, microbial conversion of cholesterol-to-coprostanol may be an important way of cholesterol-lowering by the organism. Cholesterol-3-sulfate is a recently discovered microbial metabolite of cholesterol, mainly metabolized by Bacteroides containing the Bt_0416 gene. Its effects on host health have been preliminarily characterized and are mainly related to immune modulation and repair of the intestinal epithelium.

Efficient co-production of xylo-oligosaccharides and fermentable sugars from sugarcane bagasse by glutamic acid pretreatment

In the production of xylo-oligosaccharides (XOS) by organic acid pretreatment, it is often difficult to isolate organic acids from XOS. Here, an acidic amino acid, glutamic acid (GA), was used to pretreat sugarcane bagasse (SCB) to prepare XOS and fermentable sugars. The effects of GA concentration, hydrolysis temperature, and pretreatment time on the yield and polymerization distribution of XOS were investigated. After hydrolysis by 0.2 M GA at 140 °C for 30 min, the maximum yield of X2-5 was 53.3%, and the concentrations of xylose and furfural were 1.8 g/L and 0.1 g/L, respectively. Meanwhile, GA increased the pore size and porosity of SCB as well as the number of functional groups of amino acid residues, which improved the enzymatic efficiency and the maximum yield of glucose was 95.3%. Thus, GA pretreatment provides a more economical, environmentally friendly and sustainable method for the co-production of XOS and glucose from SCB.

Marine Chitosan-Oligosaccharide Ameliorated Plasma Cholesterol in Hypercholesterolemic Hamsters by Modifying the Gut Microflora, Bile Acids, and Short-Chain Fatty Acids

This study evaluated the cholesterol-alleviating effect and underlying mechanisms of chitosan-oligosaccharide (COS) in hypercholesterolemic hamsters. Male hamsters (n = 24) were divided into three groups in a random fashion, and each group was fed one particular diet, namely a non-cholesterol diet (NCD), a high-cholesterol diet (HCD), and an HCD diet substituting 5% of the COS diet for six weeks. Subsequently, alterations in fecal bile acids (BAs), short-chain fatty acids (SCFAs), and gut microflora (GM) were investigated. COS intervention significantly reduced and increased the plasma total cholesterol (TC) and high-density lipoprotein-cholesterol (HDL-C) levels in hypercholesteremic hamsters. Furthermore, Non-HDL-C and total triacylglycerols (TG) levels were also reduced by COS supplementation. Additionally, COS could reduce and increase food intake and fecal SCFAs (acetate), respectively. Moreover, COS had beneficial effects on levels of BAs and GM related to cholesterol metabolism. This study provides novel evidence for the cholesterol-lowering activity of COS.

Three Molecular Modification Strategies to Improve the Thermostability of Xylanase XynA from Streptomyces rameus L2001

Glycoside hydrolase family 11 (GH11) xylanases are the preferred candidates for the production of functional oligosaccharides. However, the low thermostability of natural GH11 xylanases limits their industrial applications. In this study, we investigated the following three strategies to modify the thermostability of xylanase XynA from Streptomyces rameus L2001 mutation to reduce surface entropy, intramolecular disulfide bond construction, and molecular cyclization. Changes in the thermostability of XynA mutants were analyzed using molecular simulations. All mutants showed improved thermostability and catalytic efficiency compared with XynA, except for molecular cyclization. The residual activities of high-entropy amino acid-replacement mutants Q24A and K104A increased from 18.70% to more than 41.23% when kept at 65 °C for 30 min. The catalytic efficiencies of Q24A and K143A increased to 129.99 and 92.26 mL/s/mg, respectively, compared with XynA (62.97 mL/s/mg) when using beechwood xylan as the substrate. The mutant enzyme with disulfide bonds formed between Val3 and Thr30 increased the t_1/2^{60 °C} by 13.33-fold and the catalytic efficiency by 1.80-fold compared with the wild-type XynA. The high thermostabilities and hydrolytic activities of XynA mutants will be useful for enzymatic production of functional xylo-oligosaccharides.

An updated review on food-derived bioactive peptides: Focus on the regulatory requirements, safety, and bioavailability

Food-derived bioactive peptides (BAPs) are recently utilized as functional food raw materials owing to their potential health benefits. Although there is a huge amount of scientific research about BAPs' identification, purification, characterization, and physiological functions, and subsequently, many BAPs have been marketed, there is a paucity of review on the regulatory requirements, bioavailability, and safety of BAPs. Thus, this review focuses on the toxic peptides that could arise from their primary proteins throughout protein extraction, protein pretreatment, and BAPs' formulation. Also, the influences of BAPs' length and administration dosage on safety are summarized. Lastly, the challenges and possibilities in BAPs' bioavailability and regulatory requirements in different countries were also presented. Results revealed that the human studies of BAPs are essential for approvals as healthy food and to prevent the consumers from misinformation and false promises. The BAPs that escape the gastrointestinal tract epithelium and move to the stomach are considered good peptides and get circulated into the blood using different pathways. In addition, the hydrophobicity, net charge, molecular size, length, amino acids composition/sequences, and structural characteristics of BAPs are critical for bioavailability, and appropriate food-grade carriers can enhance it. The abovementioned features are also vital to optimize the solubility, water holding capacity, emulsifying ability, and foaming property of BAPs in food products. In the case of safety, the possible allergenic and toxic peptides often exhibit physiological functions and could be produced during the hydrolysis of food proteins. It was also noted that the production of iso-peptides bonds and undesirable Maillard reaction might occur during protein extraction, sample pretreatments, and peptide synthesis.