Inhibition of dipeptidyl peptidase-4 (DPP-4) is an effective way to control blood glucose in diabetic patients. Tenebrio (T.) molitor is an edible insect containing abundant protein. T. molitor protein-derived peptides can suppress the DPP-4 activity. However, the amino acid sequence and binding mechanism of these DPP-4 inhibitory peptides remain unclear. This study used the flavourzyme for T. molitor protein hydrolysis, identified the released peptides with DPP-4 inhibitory effect, and investigated the binding interactions of these peptides with DPP-4. The results showed that flavourzyme efficiently hydrolyzed the T. molitor protein, as demonstrated by the high degree of hydrolysis, disappearance of protein bands in SDS-PAGE, and changes to protein structure. The 4-h flavourzyme hydrolysates showed a good inhibitory effect on DPP-4 (IC₅₀ value of 1.64 mg/mL). The fragment of 1000–3000 Da accounted for 10.39% of the total peptides, but showed the strongest inhibitory effect on DPP-4. The peptides LPDQWDWR and APPDGGFWEWGD were identified from this fraction, and their IC₅₀ values against DPP-4 were 0.15 and 1.03 mg/mL, respectively. Molecular docking showed that these two peptides interacted with the DPP-4 active site via hydrogen bonding, hydrophobic interactions, salt bridge formation, π-cation interactions, and π-π stacking. Our findings indicated that T. molitor protein-derived peptides could be used as natural DPP-4 inhibitors.

Allergic diseases, derived from the dysregulation of immune tolerance mechanisms, have been rising in the last two decades. Recently, increasing evidence has shown that probiotic-derived polysaccharide capsules exhibit a protective effect against allergic diseases, involving regulation of Th1/Th2 balance, induction of differentiation of T regulatory cells and activation of dendritic cells (DCs). DCs have a central role in controlling the immune response through their interaction with gut microbiota via their pattern recognition receptors, including Toll-like receptors and C-type-lectin receptors. This review discusses the effects and critical mechanism of probiotic-derived polysaccharide capsules in regulating the immune system to alleviate allergic diseases. We first describe the development of immune response in allergic diseases and recent relevant findings. Particular emphasis is placed on the effects of probiotic-derived polysaccharide capsules on allergic immune response. Then, we discuss the underlying mechanism of the impact of probiotic-derived polysaccharide capsules on DCs-mediated immune tolerance induction.

The antifungal effect of metabolites produced by a new strain of Lactiplantibacillus (Lpb.) plantarum LPP703, isolated from naturally fermented yak yogurt, was investigated. The results showed that Lpb. plantarum LPP703 significantly inhibited four fungal species, including Penicillium sp., Rhizopus delemar, Aspergillus flavus, and Aspergillus niger. The metabolites produced after 20 h of Lpb. plantarum LPP703 fermentation showed the highest antifungal activity against Penicillium sp. Compared with the control group, the Lpb. plantarum LPP703 metabolites-treated Penicillium sp. spores were stained red by propidium iodide, indicating that the cell membrane of the fungal spores was damaged. Moreover, the antifungal effect of the Lpb. plantarum LPP703 metabolites on Penicillium sp. was not changed after heating or treatment with various proteases, but showed a sharp decrease when the pH value was regulated to 5.0 or above. The oleamide, trans-cinnamic acid, and citric acid were the three most abundant in the Lpb. plantarum LPP703 metabolites. Molecular docking predicated that the oleamide interacted with the active site of lanosterol 14-alpha-demethylase (CYP51, a crucial enzyme for fungal membrane integrity) through hydrogen bonds and had the lowest docking score, representing the strongest binding affinity to CYP51. Taken together, the metabolites from a new strain of Lpb. plantarum, LPP703, had potent antifungal activity against Penicillium sp., which might be associated with the damage of the active ingredient to fungal membrane integrity. This study indicated that Lpb. plantarum LPP703 and its metabolites might act as biological control agents to prevent fungal growth in the food industry.

Pomegranate peels powder (PPP) contain total phenolic compounds and antioxidation activity, which can provide numerous health benefits. White soft cheese was prepared from mixture of buffalo’s and cow’s milk and supplemented with different levels of pomegranate peels powder (0.5, 1 and 1.5%) and estimated for numerous storage quality parameters and oxidative stability under ambient (18±2°C) and refrigerated (6±2°C) conditions. Adding of PPP increased antioxidant activity, total nitrogen, soluble nitrogen, fat content and Lactococci count. Whilst the total bacterial counts, yeast & moulds and acid degree value decreased. Coliforms groups were not detected in all treatments. The counts of lactic acid bacteria increased up to the thirty days of storage and then decreased up to the end of storage period. Cheese sample supplemented with 1.5% PPP gained the highest total antioxidant activity. Moreover, T2 & T3 stored in 60 days at room temperature had lower total scores than other treatments. While T2 & T3 stored at ambient temperature for 30 days as well as T1 & T2 stored at refrigerator temperature for 45 days had superior total scores than other treatments. Generally, PPP contained elevated levels of phenolic compounds, consequently it revealed efficacy antimicrobial properties and high antioxidant activity. Therefore, the PPP can be used in production of functional white soft cheese. This study indicates that peel of pomegranate can be used commercially in the dairy industry as potential natural preservative.

The purpose of this study was to improve the functional properties of bio-yogurt, which is one of the most popular fermented dairy products widely, consumed worldwide, and to evaluate the effect of whey protein concentrate (WPC) and Arabic Gum (AG) on promoting growth and survival of Bifidobacterium longum. Bio- yogurt was manufactured by using 2% Bifi. longum and enriched with 1% WPC or 2% AG, after milk inoculation by bacterial culture it was incubated at 42±1°C until complete coagulation and then stored at 5±1°C. Chemical, bacteriological analysis and sensory evaluation had been carried out in fresh and after 7 & 14 days of storage. The obtained results indicated that, acid development in control samples without probiotic bacteria or WPC & AG was less compared with Bio-yogurt containing Bifi. longum, WPC and AG, which scored highest acidity and lowest pH values during storage. Moreover, during storage there were an increase in total solids, soluble nitrogen, total nitrogen and acidity and slight decrease in pH values of cheese made with 1% WPC or 2% AG in all treatments. Concerning the bacteriological determinations, there were a slight increase in total bacterial, Streptococci, Lactobacilli and Bifi. longum counts during first 7 days of storage, and then decrease gradually during the second week of storage. In addition, WPC and AG increased the total bacteria, Lactobacilli, Streptococci and Bifi. longum counts comparing with control samples. Generally, the addition of WPC increased organoleptic properties of the product, while the addition of AG did not

Cheese has recently been the focus of a number of marketing and scientific investigations, due to its effectiveness in delivering probiotics to the digestive tract. The objective of this study was to examine the effect of using yeast extract (YE) 0.1, 0.5, and 1% with cheese cultures (Lactococcus lactis sub sp lactis 2% and Lactococcus lactis sub sp cremoris 2%) and Bifidobacterium breve at 1, 3, and 5% on the chemical composition, microbiological quality, organoleptic properties, and shelf-life stability of probiotic soft cheese (PSC) during storage at 5˚± 2˚C for 60 days. The acidity, moisture, salt, Lactic acid bacteria (LAB) count, total bacterial count (TBC), Bif. breve count, yeasts & molds, coliform count, and organoleptic properties were examined in the PSC after 0, 15, 30, 45, and 60 days of storage. The addition of YE increased the total CFU of Bif. breve, LAB, TBC, content of salt, and development titratable acidity (DTA) during storage. On the other side, moisture content was decreased (P < 0.05) during storage. The antimicrobial activity of Bif. breve delayed the growth of yeast, molds, and coliform bacteria during storage. The overall acceptability of PSC had improved (P < 0.05) by the addition of synbiotics (Bif. breve and YE), as compared with the control. using 5% Bif. breve + 0.1, 0.5, and 1% YE and 3% Bif. breve +1% YE resulted increase in significant flavor, texture, and overall acceptability, compared with the control