Fabrication of dry S/O/W microcapsule and its probiotic protection against different stresses.

BACKGROUND: Encapsulation is commonly used to protect probiotics against harsh stresses. Thus, the fabrication of microcapsules with special structure is critical. In this work, microcapsules with the structure of S/O/W (solid-in-oil-in-water) emulsion were prepared for probiotics, with butterfat containing probiotics as the inner core and with whey protein isolate fibrils (WPIF) and antioxidants (epigallocatechin gallate, EGCG; glutathione, GSH) as the outer shell. RESULTS: Based on the high viscosity and good emulsifying ability of WPIF, dry well-dispersed microcapsules were successfully prepared via the stabilization of the butterfat emulsion during freeze-drying with 30-50 g L-1 WPIF. WPIF, WPIF + EGCG, and WPIF + GSH microcapsules with 50 g L-1 WPIF protected probiotics very well against different stresses and exhibited similar inactivation results, indicating that EGCG and GSH exerted neither harm or protection on probiotics. This significantly reduced the harmful effects of antioxidants on probiotics. Almost all the probiotics survived after pasteurization, which was critical for the use of probiotics in other foods. The inactivation values of probiotics in microcapsules were around 1 log in simulated gastric juice (SGJ), about 0.5 log in simulated intestinal juice (SIJ), and around 1 log after 40 days of ambient storage. CONCLUSION: Dry S/O/W microcapsule, with butterfat containing probiotics as the inner core and WPIF as the outer shell, significantly increased the resistance of probiotics to harsh environments. This work proposed a preparation method of dry S/O/W microcapsule with core/shell structure, which could be used in the encapsulation of probiotics and other bioactive ingredients.

Effects of protein fibrillation and antioxidants on probiotic survival during ambient storage.

Drying of probiotic cultures is the main form of stabilization but dry probiotics face oxidative stress. The addition of antioxidants has been employed for protection of probiotics against oxidative stress, but results on the addition of antioxidants remain inconclusive. In this work, matrices of whey protein isolate fibrils (WPIF) with epigallocatechin gallate (EGCG) or glutathione (GSH) were used. Probiotic viability during ambient storage decreased in the order of WPIF > WPIF + EGCG > WPIF + GSH > WPI > WPI + EGCG > WPI + GSH. The improved protection of WPIF might be explained by its better cell encapsulation and the high antioxidant activity of WPIF. Both antioxidants accelerated the death of probiotic, which might be related with the antimicrobial activity or the cytotoxicity of the reaction products. This study proposed an excellent wall material of amyloid fibrils for probiotic protection during ambient storage, and questioned the "common sense" that antioxidants protect probiotics from oxidative stress.

Characterization of a recombinant 10-linoleic acid hydratase from Lactiplantibacillus plantarum ZS2058 and biosynthesis of 10- hydroxy-cis-12-octadecenoic acid.

BACKGROUND: 10-Hydroxy-cis-12-octadecenoic acid (10-HOE, 10-OH C18:1), an emerging functional fatty acid, has anti-fungal and anti-inflammatory effects. 10-HOE is synthesized by bacterial 10-linoleic acid hydratase (10-LHT) with linoleic acid as the substate. However, the characterization of 10-LHT and its targeted synthesis of 10-HOE have been rarely reported. In this study, the recombinant 10-LHT from Lactiplantibacillus plantarum ZS2058 was characterized, and the biocatalysis of 10-HOE using crude enzyme was optimized. RESULTS: The recombinant 10-LHT catalyzed the conversion of linoleic acid (C18:2) to 10-HOE as identified using gas chromatography-mass spectrometry (GC-MS). It showed a molecular weight of about 70 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and was a flavin adenine dinucleotide (FAD)-dependent enzyme. The activity of 10-LHT was optimal at pH 6.5 and 25 °C, and it was pH-stable but thermo-sensitive. The optimal condition for the 10-HOE biosynthesis using crude enzyme was 5 g L-1 linoleic acid (C18:2), 148.0 U mL-1 10-LHT, 0.05 mmol L-1 FAD, 2% methanol and 100 mmol L-1 sodium chloride at 25 °C and pH 6.5. A conversion yield of 47.8 ± 1.5% and the corresponding 10-HOE concentration of 2.4 ± 0.1 g L-1 were achieved at 48 h under the optimal reaction conditions. CONCLUSION: This work achieved the highest conversion yield of 10-HOE with the highest substrate concentration, and provides some useful information for the industrial production of 10-HOE. © 2021 Society of Chemical Industry.

Interaction between bovine serum albumin and chitooligosaccharides: I. Molecular mechanism.

The interaction between chitooligosaccharides (COS2-6) and bovine serum albumin (BSA) is worthy of investigation, which provides support for improving the physical properties (gelling, foaming, and emulsifying) of food proteins via COS addition and in vivo research on COS bioactivity. Component analysis indicated that COS2 and COS3 were enriched in the COS2-6-BSA precipitate. The fluorescence binding constant (1.73 × 103 M-1), ΔG of isothermal titration calorimetry (-6.7 kJ/mol), and the predicted ΔG of molecular docking (-10 to -5 kJ/mol) confirmed the weak interaction of COS2-6-BSA. Quartz crystal microbalance dissipation and molecular docking indicated that electrostatic and hydrophobic interactions were the main stabilization forces. Molecular docking showed that the predicted ΔG of COS2-6 to BSA decreased with the increasing degree of polymerization. This work clarified the weak and selective interaction between COS2-6 and BSA via various methods, which is useful for the food application of COS.