Mechanism by which β-glucanase improves the quality of fermented barley flour-based food products

Overview of various protein engineering strategies to improve the catalytic activity, thermostability, and acid/base stability of β-glucanase

β-Glucan is highly valued in the food and medical industries due to its various physiological functions. However, its aqueous solution tends to have high viscosity, which negatively impacts the brewing and feed industries. By hydrolyzing β-glucosidic bonds, β-glucanase could reduce the adverse effects of β-glucan. For this reason, β-glucanase is widely utilized in the brewing and animal feed production. The limited thermal and acid stability of β-glucanase restricts its applications in industrial settings. Therefore, it is of great importance to enhance the stability of existing β-glucanases through protein engineering. This review summarizes current integrated technical methods for the molecular modification of β-glucanases, including error-prone PCR, site-saturation mutagenesis, DNA recombination, sequence alignment, N- and C-terminal modifications, surface charge optimization, intermolecular force optimization, and rigidity of flexible regions. The aim is to provide a theoretical basis and practical guidance for the further modification of β-glucanases.

Synergistic effects of multi-enzyme supplementation on nutrient digestion and absorption in the foregut and hindgut

This study was conducted to investigate the effect of dietary multi-enzyme (MCPC) supplementation on synergistically enhancing the functions of both the foregut and hindgut, ultimately improving the nutrient digestion and utilization throughout the gastrointestinal tract. In vitro results demonstrated that MCPC increased the phosphorus and reducing sugar levels in the supernatant during enzymatic hydrolysis. Furthermore, during the fermentation of the enzymatic hydrolysis products, MCPC significantly increased the FRD0 value of the enzymatic hydrolysis products from both the positive control (PC) and negative control 1 (NC1) diets (p < 0.05). MCPC reduced the T1/2 value of in vitro fermentation products from the PC diet (p < 0.01), and decreased the VF (p = 0.082) and K (p < 0.05) values for the NC1 diet. Additionally, 72 crossbred barrows [Duroc × (Landrace × Yorkshire)], weighing 25 kg, were fed one of six diets until their live weight approached 50 kg. The basal diets consisted of PC, NC1 and negative control 2 (NC2), while the remaining three diets were prepared by adding 100 mg/kg MCPC to the respective basal diets. The results showed that MCPC supplementation significantly upregulated the expression of solute carrier family 17 member 4 (SLC17A4) and vitamin D receptor (VDR) genes in the duodenum (p < 0.05), while downregulating the expression of Calbindin-D28k (CaBP-D28K) and solute carrier family 1 member 4 (SLC1A4) genes (p < 0.05) in growing pigs. Moreover, MCPC supplementation significantly upregulated the expression of VDR, glucose transporter 2 (GLUT2) and intestinal fatty acid binding protein (FABP2) genes in the jejunum of growing pigs. Furthermore, MCPC supplementation significantly increased the relative abundances of Bacteroidota, Prevotella and Phascolarctobacterium (p < 0.05), while reducing the relative abundances of Verrucomicrobiota and Clostridium_sensu_stricto_1 (p < 0.05) in the colon of growing pigs. In conclusion, MCPC enhances nutrient digestion and absorption in the foregut, provides fermentable substrates for hindgut microbial fermentation, and improves gut microbiota composition. This improves hindgut fermentation and supports the synergistic interaction between the foregut and hindgut, ultimately improving nutrient utilization and benefiting animal health.

Research Progress in the Extraction, Structural Characteristics, Bioactivity, and Commercial Applications of Oat β-Glucan: A Review

Oats (Avena sativa L.) are an important cereal crop with diverse applications in both food and forage. Oat β-glucan has gained attention for its beneficial biological activities, such as reducing cardiovascular risk, preventing diabetes, and enhancing intestinal health. Despite its potential, more comprehensive research is required to explore its preparation, modification, bioactivities, and applications. This review highlights recent advancements in the determination and preparation of oat β-glucan, explores its biological activities and mechanisms, and examines the impact of food processing techniques on its properties. This review is intended to provide a theoretical foundation and reference for the development and application of oat β-glucan in the functional food industry.

Effect of different molecular weight β-glucan hydrated with highland barley protein on the quality and in vitro starch digestibility of whole wheat bread

Whole wheat bread has high nutritional value, but it has inferior baking quality and high glycemic index, which needs to be improved by methods such as adding protein and β-glucan. This study investigated the effects of β-glucan and highland barley protein of different molecular weights (2 × 104, 1 × 105, and 3 × 105 Da) and different hydrate methods (pre-hydrate and not pre-hydrate) on the characteristics of whole wheat dough and bread. The mixing properties and rheological properties demonstrated that β-glucan pre-hydrated with highland barley protein were able to reduce the dough tan δ, reduce the dough viscoelasticity, while enhance the gluten network structure and dough deformation resistance. Compared to the control sample, the medium molecular weight pre-hydrate bread had a better specific volume of 3.21 mL/g, lower hardness of 527.28 g. In vitro starch digestion characteristics and ATR-FTIR showed that low and high molecular weight pre-hydrate increased the short-range ordered structure of starch and reduced the starch digestibility, while not pre-hydrated medium molecular weight hydrate had the lowest level of starch digestibility.

Expression and characterization of β-1,3-1,4-glucanase of Aspergillus usamii in Escherichia coli and its application in sourdough bread making

A β-1,3-1,4-glucanase gene (Auglu12A) from Aspergillus usamii was successfully expressed in Escherichia coli BL21(DE3). The recombinant enzyme, reAuglu12A was efficiently purified using the one-step nickel-nitrilotriacetic acid affinity chromatography. The specific activity of reAuglu12A was 694.8 U/mg, with an optimal temperature of 55°C and pH of 5.0. The reAuglu12A exhibited stability at temperatures up to 60°C and within the pH range of 4.0-5.5. The reAuglu12A hydrolytic activity was increased in the presence of metal ions, especially K+ and Na+ , whereas it exhibited a Km and Vmax of 8.35 mg/mL and 1254.02 µmol/min/mg, respectively, toward barley β-glucan at pH 5.0 and 55°C. The addition of reAuglu12A significantly increased the specific volume (p < 0.05) and reduced crumb firmness and chewiness (p < 0.05) of wheat-barley sourdough bread during a 7-day storage period compared to the control. Overall, the quality of wheat-barley sourdough bread was improved after incorporation of reAuglu12A (especially at 3000 U/300 g). These changes were attributed to the synergistic effect of acidification by sourdough and its metabolites which provided a conducive environment for the optimal action of reAuglu12A in the degradation of β-glucans of barley flour in sourdough. This stabilized the dough structure, thereby enhancing the quality, texture, and shelf life of the bread. These findings suggest that reAuglu12A holds promise as a candidate for β-glucanase application in the baking industry.

Mechanism underlying the weakening effect of β-glucan on the gluten system

The high β-glucan content in barley disrupts the gluten network in dough. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (NMR) techniques were used to clarify how β-glucan affected the quality of the gluten network structure with β-glucan contents of 0-2%. The results suggest that the physical hindrance of the β-glucan gel destroyed the formation of the gluten network structure. When 1.0-2.0% β-glucan was added, the percentage of α-helical structures increased significantly. When the added amount of β-glucan reached 2.0%, the sulfhydryl group (SH) content increased from 8.06 to 10.27 µmol/g, and the disulfide bond (SS) content decreased from 240.09 to 217.38 µmol/g. The interaction between β-glucan and gluten mainly resulted from the interaction of electron-withdrawing groups, such as carbonyl groups (CO) and double bond carbons (CC), and carbon atoms on the side chains of β-glucan, which play an important role in the central structure of glutenin.

Biogenetic nanocarriers with enhanced pH stability formed by zein and selectively depolymerized mushroom hyperbranched β-glucans

Hyperbranched polysaccharide from Pleurotus tuber-regium (PTR-HBPS) is a β-glucan with high degree of branching (DB, 0.69) and a molecular weight (Mw) of 31.2 × 10⁵ g/mol with mixed β-1, 4/β-1, 4, 6/β-1, 6 glucosidic linkages. PTR-HBPS was depolymerized by cellulase and β-glucosidase under optimized conditions to form PC (PTR-HBPS depolymerized by cellulase) and PG (PTR-HBPS depolymerized by β-glucosidase) fractions with a minimum Mw of 2.74 × 10⁵ and 3.98 × 10⁵ g/mol, respectively. PC fractions had no significant changes for its primary structure in terms of glycosidic linkages, DB, and triple helical structure, while the DB of PG fractions was reduced to 0.63 with the loss of triple helical structure. Nanoparticles fabricated by PC fractions with zein showed better stability under different pH conditions. Enzymatic depolymerized low Mw β-glucan derived from PTR-HBPS with similar structural characteristics as the native one has potential as nanocarriers for food bioactive substances.

Effect of Lactobacillus plantarum fermented barley on plasma glycolipids and insulin sensitivity in subjects with metabolic syndrome

Fermented barley (FB) flour by Lactobacillus plantarum is richer in dietary fiber, polyphenols, gamma-aminobutyric acid, and other biologically active ingredients. This study aimed to determine the impacts of fermented barley - wheat flour compound noodle (FBWN) on glucose and fat metabolism in subjects with metabolic syndrome. This was a single-blinded and parallel 10-week clinical trial study. Subjects were randomly assigned into the trial group (FBWN) and whole wheat noodles group (WWN), and were measured on the beginning of week 3 and the ending of week 10. The glucose level at 30 and 60 min was significantly decreased after FBWN intervention. Levels of fasting blood glucose, HbA1c, and TG were all declined after FBWN intervention compared to before in the trial group. Moreover, the fat mass, fat rate, and visceral fat were decreased by 6.48, 7.19, 6.3 kg after FBWN intervention, respectively, while muscle mass and basal metabolic rate rose 7.44 kg and 252.60 kcal. PRACTICAL APPLICATIONS: Many studies have illustrated that the extraction of fermented barley held the activities of anti-obesity, antitumor, and so on. Moreover, this present study evaluated the effects of fermented barley by Lactobacillus plantarum on patients with metabolic syndrome. Results indicated that FB benefits the subjects on improving plasma glycolipids and insulin sensitivity, decreasing visceral fat level, and increasing satiety. The findings showed that the products of FB may be beneficial to dietary manipulations, thus, reducing the burden of patients.

Kinetic interactions of nanocomplexes between astaxanthin esters with different molecular structures and β-lactoglobulin

The influence of different fatty acid carbon chains on the kinetic interactions of nanocomplexes between esterified astaxanthin (E-Asta) and β-lactoglobulin (β-Lg) were investigated by multi-spectroscopy and molecular modeling techniques. We synthesized ten different E-Asta bound to β-Lg and formed nanocomplexes (< 300 nm). Fluorescence spectroscopy showed moderate affinities (binding constants Ka = 10³-10⁴ M^-1). Docosahexaenoic acid astaxanthin monoester (Asta-C22:6) had the strongest binding affinity towards β-Lg (Ka = 3.77 × 10⁴ M^-1). The fluorescence quenching of β-Lg upon binding of E-Asta displayed a static mechanism, with binding sites (n) equal to 1. Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectroscopy revealed that E-Asta might enter the β-Lg hydrophobic cavity, leading to unfolding of the peptide chain skeleton. In summary, β-Lg and E-Asta can form stable nanocomplex emulsions to achieve an effective delivery process for E-Asta.