Ce Qi

Preparation and characterization of catalase-loaded solid lipid nanoparticles protecting enzyme against proteolysis.

Catalase-loaded solid lipid nanoparticles (SLNs) were prepared by the double emulsion method (w/o/w) and solvent evaporation techniques, using acetone/methylene chloride (1:1) as an organic solvent, lecithin and triglyceride as oil phase and Poloxmer 188 as a surfactant. The optimized SLN was prepared by lecithin: triglyceride ratio (5%), 20-second + 30-second sonication, and 2% Poloxmer 188. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322–0.354 and −36.4 ± 0.6, respectively, and the encapsulation efficiency reached its maximum of 77.9 ± 1.56. Catalase distributed between the solid lipid and inner aqueous phase and gradually released from Poloxmer coated SLNs up to 20% within 20 h. Catalase-loaded SLN remained at 30% of H2O2-degrading activity after being incubated with Proteinase K for 24 h, while free catalase lost activity within 1 h.

High-fat-diet-induced obesity is associated with decreased antiinflammatory Lactobacillus reuteri sensitive to oxidative stress in mouse Peyer's patches

OBJECTIVE Diet-induced inflammation in the small intestine may represent an early event that precedes and predisposes to obesity and insulin resistance. This is related to decrease of lactobacilli in Peyers patches (PP) revealed in our previous study. The present study aimed to clarify specific changes of PP Lactobacillus on the strain level and related biological activity. METHODS C57 BL/6 J male mice were fed with either low-fat diet (control [CT]; 10% calories from fat) or high-fat diet (HFD; 50% calories from fat) for 25 wk, and the HFD-fed mice were classified into obesity prone (OP) or obesity resistant (OR) on the basis of their body weight gain. Lactobacillus was isolated from PP using a selective medium. Oxidative resistance and cytokine-inducing effect were analyzed in vitro. RESULTS We obtained 52, 18, and 22 isolates from CT, OP, and OR mice, respectively. They belonged to 13 different types according to enterobacterial repetitive intergenic consensus sequence-PCR analysis. Lactobacillus reuteri was the most abundant strain, but its abundance in OP mice was much lower than that in CT and OR mice. This strain includes eight subgroups according to genotyping. L. reuteri L3 and L. reuteri L8 were the specific strains found in CT and OP mice, respectively. Oxidative-resistant L. reuteri was much higher in HFD-fed mice. When co-cultured with PP cells, L8 induced higher production of proinflammatory cytokines such as interleukin (IL)-6, IL-12, and tumor necrosis factor-α, whereas L3 induced higher production of an anti-inflammatory cytokine (IL-10). CONCLUSION HFD may induce oxidative stress that drives strain selection of Lactobacillus strains, resulting in decreased anti-inflammatory response in PP.

Preparation and characterization of catalase‐loaded solid lipid nanoparticles based on soybean phosphatidylcholine

BACKGROUND High-purity soybean phosphatidylcholine (SPC) (94%) were prepared using macroporous resin adsorption chromatography previously. Catalase is a food enzyme for promoting health and protecting against many age-related disease. Solid lipid nanoparticles (SLN) are safe immobilizing systems for efficient protein transportation to biomembranes while avoiding adverse degradation of protein. This study was aimed at developing and characterizing catalase-loaded SLN using SPC as solubilizers and stabilizing agents, to protect catalase from proteolysis. RESULTS Catalase-loaded SLN were prepared by the double emulsification method and solvent evaporation techniques, using acetone-methylene chloride (1:1, v/v) as an organic solvent, SPC-tripalmitin as oil phase and Poloxamer 188 as a surfactant. The optimized SLN were prepared using an SPC:tripalmitin ratio of 5% (w/w), 20 s plus 30 s sonication, 20 g L⁻¹ Poloxamer 188 and 1:2 (v/v) of oily phase:outer aqueous phase ratio. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322-0.354 and -36.4 ± 0.6, respectively, and encapsulation efficiency reached its maximum of 77.9 ± 1.56%. Catalase, which was found to distribute between the solid lipid and inner aqueous phase, was gradually released from SLN up to 20% within 20 h. Catalase-loaded SLN had stably retained 30% of H₂O₂-degrading activity for at least 24 h in a proteolytic environment, while free catalase lost its activity within 1 h. CONCLUSION Catalase can indeed be loaded in tripalmitin-based SLN using SPC as solubilizers and stabilizing agents, which protected it against proteolysis, suggesting the potential application of SPC in delivery and protection of functional food enzyme.

Mango kernel fat based chocolate fat with heat resistant triacylglycerols: production via blending using mango kernel fat mid-fraction and palm mid-fractions produced in different fractionation paths

Cocoa butter alternatives (CBAs) with heat resistance triacylglycerols (HRTs, including POP, POSt and StOSt) are increasingly popular in warm regions for producing hard chocolate. Three dominant palm mid fractions (PMFs), i.e., PMF-I from palm olein, PMF-II from the palm stearin and PMF-III from PMF-I, were found to be characterized by significant differences in physicochemical characterization and were selected as POP-rich fats. Mango kernel fat mid-fraction (MMF), a potential improver to increase the thermostability of chocolate, was enriched with POSt and StOSt and blended with PMFs in weight ratios of 10 : 90, 20 : 80 and 30 : 70 to prepare heat resistant CBAs. Non-fractionated mango kernel fat (MKF) was also mixed with PMFs in appropriate weight ratios as already reported to be contrasts. Chemical compositions and physical properties were analyzed to evaluate the qualities of the blends. The results revealed that non-fractionated MKF and partial fractionated fats PMF-I and PMF-II, contained higher levels of StOO, POO, OOO, PLP, PPP or diacylglycerols compared with those of cocoa butter (CB). Such ingredients would greatly change the thermal properties and soften the blends. While multi-stage fractionated PMF-III and MMF showed relatively high content of HRTs (83.3%), the blend with ratio 10 : 90 (PMF-III : MMF) was demonstrated to be best compared to the others because it resembled CB. It was recommended as the heat resistant CBA due to its improved thermal quality compared with CB.

Fatty Acid Profile and the sn-2 Position Distribution in Triacylglycerols of Breast Milk during Different Lactation Stages

Fatty acid (FA) is the major energy resource in breast milk, which is important for infant development. FAs profiles with sn-2 positional preference were an important part of triacylglycerols due to their better availability. This profile is still not replicated in artificial formulas. This study quantified the FAs profile of total and sn-2 position in human breast milk samples from 103 healthy volunteers during colostrum, transitional, and mature stages. Multicomponent analysis showed significant differences in FAs profiles of different lactation periods, due to that with relative percentage less than 1%. Linoleic acid (LA), mostly located at the sn-1,3 positions of TAGs, was more common in the milk of Chinese women than in western women. The majority of the breast milk did not meet the standard for the ratio of LA/α-linolenic acid for infant formula. FAs related to brain development, mainly at sn-2 in TAGs, were enriched in colostrum. Capric and lauric acids were enriched in transitional and mature breast milk, and capric acid showed sn-1,3 selectivity in TAGs. This study will aid the development of infant formula containing TAGs more similar to human breast milk.

Composition and immuno-stimulatory properties of extracellular DNA from mouse gut flora

AIM To demonstrate that specific bacteria might release bacterial extracellular DNA (eDNA) to exert immunomodulatory functions in the mouse small intestine. METHODS Extracellular DNA was extracted using phosphate buffered saline with 0.5 mmol/L dithiothreitol combined with two phenol extractions. TOTO-1 iodide, a cell-impermeant and high-affinity nucleic acid stain, was used to confirm the existence of eDNA in the mucus layers of the small intestine and colon in healthy Male C57BL/6 mice. Composition difference of eDNA and intracellular DNA (iDNA) of the small intestinal mucus was studied by Illumina sequencing and terminal restriction fragment length polymorphism (T-RFLP). Stimulation of cytokine production by eDNA was studied in RAW264.7 cells in vitro. RESULTS TOTO-1 iodide staining confirmed existence of eDNA in loose mucus layer of the mouse colon and thin surface mucus layer of the small intestine. Illumina sequencing analysis and T-RFLP revealed that the composition of the eDNA in the small intestinal mucus was significantly different from that of the iDNA of the small intestinal mucus bacteria. Illumina Miseq sequencing showed that the eDNA sequences came mainly from Gram-negative bacteria of Bacteroidales S24-7. By contrast, predominant bacteria of the small intestinal flora comprised Gram-positive bacteria. Both eDNA and iDNA were added to native or lipopolysaccharide-stimulated Raw267.4 macrophages, respectively. The eDNA induced significantly lower tumor necrosis factor-α/interleukin-10 (IL-10) and IL-6/IL-10 ratios than iDNA, suggesting the predominance for maintaining immune homeostasis of the gut. CONCLUSION Our results indicated that degraded bacterial genomic DNA was mainly released by Gram-negative bacteria, especially Bacteroidales-S24-7 and Stenotrophomonas genus in gut mucus of mice. They decreased pro-inflammatory activity compared to total gut flora genomic DNA.

Identification and quantification of triacylglycerols in human milk fat using ultra-performance convergence chromatography and quadrupole time-of-flight mass spectrometery with supercritical carbon dioxide as a mobile phase

An ultra-performance convergence chromatography (UPC2) method coupled with quadrupole time-of-flight mass spectrometry (Q-TOF-MS), was developed for the determination of complicated triacylglycerols (TAGs) in human milk fat. The use of supercritical carbon dioxide as the mobile phase improved the chromatographic separation of the TAGs significantly. By optimizing the scan modes of Q-TOF-MS and selecting parent ions for MS/MS ionization, the fragment ions of each TAG including TAG isomers with overlapping retention time were adequately resolved for identification and quantification. A total of 95 different TAGs were identified in the human milk samples from Chinese mother volunteers, with O-P-L representing the main TAG, followed by O-P-O and O-L-L. In addition, the compositions and contents of TAGs in different fats and oils were successfully measured. The developed method can serve as an advanced and reliable analytical tool for the determination of complicated TAGs in various biological samples.

Influence of Homogenization and Thermal Processing on the Gastrointestinal Fate of Bovine Milk Fat: In Vitro Digestion Study

Dairy lipids are an important source of energy and nutrients for infants and adults. The dimensions, aggregation state, and interfacial properties of fat globules in raw milk are changed by dairy processing operations, such as homogenization and thermal processing. These changes influence the behavior of fat globules within the human gastrointestinal tract (GIT). The gastrointestinal fate of raw milk, homogenized milk, high temperature short time (HTST) pasteurized milk, and ultrahigh temperature (UHT) pasteurized milk samples was therefore determined using a simulated GIT. The properties of particles in different regions of the GIT depended on the degree of milk processing. Homogenization increased the initial lipid digestion rate but did not influence the final digestion extent. Thermal processing of homogenized milk decreased the initial rate and final extent of lipid digestion, which was attributed to changes in interfacial structure. These results provide insights into the impact of dairy processing on the gastrointestinal fate of milk fat.