Systematic Characterization and Longitudinal Study Reveal Distinguishing Features of Human Milk Oligosaccharides in China.

BACKGROUND: Human milk oligosaccharides (HMOs) in breast milk contribute to the development of the neonatal microbiota and immune system. However, longitudinal studies examining HMO profiles of Chinese mothers remain scarce. OBJECTIVES: We aimed to analyze HMO profiles, including their composition, concentrations, and changes during lactation, in milk of Chinese mothers. METHODS: A total of 822 milk samples from 222 mothers were collected, of which 163 mothers provided single samples. Samples from the remaining 59 mothers were collected on day 3, day 7, and thereafter every 7 or 14 d until day 168. 24 HMOs were studied using high-performance anion-exchange chromatography. Secretor and nonsecretor status were determined based on Lewis blood types and a defined 2'-fucosyllactose (2'-FL) threshold. RESULTS: Of the 222 mothers, 77% were secretors and 23% were nonsecretors. The longitudinal study involving 59 mothers showed that the total HMOs in secretors were significantly greater than those in nonsecretors during the first 2 wk. Acidic HMOs decreased significantly during lactation and were similar between secretors and nonsecretors. Among neutral HMOs, distinctive differences were observed. Nonfucosylated and α-1-3/4-fucosylated HMOs in nonsecretors were significantly higher than those in secretors during the first month. In contrast, α-1-2-fucosylated HMOs in secretors were significantly higher than those in nonsecretors throughout 168 d. In secretors, 2'-FL concentrations peaked at (mean ± SEM) 3.02 ± 0.14 g/L (day 3) followed by significant decreases. In nonsecretors, 2'-FL concentrations were fairly low throughout 168 d. Of the 24 studied HMOs, only 3-fucosyllactose concentrations increased during lactation in both secretor and nonsecretor mothers. CONCLUSIONS: Our study showed dynamic changes of 24 HMOs in secretors and nonsecretors during lactation and revealed unique features of these HMO profiles in the milk of Chinese mothers. Interestingly, 2'-FL concentrations in secretors were found to be lower than those of Western populations but higher than those of African populations.

A copper-based metal-organic framework/graphene nanocomposite for the sensitive and stable electrochemical detection of DNA bases.

A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical detections of DNA bases, namely guanine and adenine. The nanohybrids were prepared via a simple ultrasonic method and were employed for the fabrication of a sensing interface. SEM, TEM, XRD, FT-IR, and electrochemical characterizations were used to characterize the general morphology and structure of the nonohybrids. The proposed Cu-MOF/ERGO/GCE exhibited ultra-stable and high-sensitivity performance in the simultaneous electrochemical detection of guanine and adenine. The recorded DPV curves revealed a linear increase in the faradaic signals with increase in the concentrations of guanine and adenine in the range of 0.02-10 µM and 20-100 µM for guanine, and 0.005-20 µM and 40-200 µM for adenine. The relative standard deviation of guanine and adenine for 50 consecutive detections is 1.37% and 1.92%, respectively. It was proved that the proposed Cu-MOF/ERGO/GCE can be performed for the detection of guanine and adenine in real samples, such as Herring sperm DNA, and satisfactory results were obtained. This strategy does not require complicated modification procedures, professional modification techniques, or sophisticated instruments, but it can provide a highly sensitive and stable detection method, which is expected to expand and deepen the applications of electrochemical detection in life science research.

Separation and Purification of Fructo-Oligosaccharide by High-Speed Counter-Current Chromatography Coupled with Precolumn Derivatization.

High-speed counter-current chromatography (HSCCC) coupled with precolumn derivatization was developed for isolating and purifying fructo-oligosaccharides (FOSs). Firstly, the total FOSs were precolumn derivatized and then separated by high-speed counter-current chromatography (HSCCC) with two-phase solvent system petroleum ether-n-butanol-methanol-water (3:2:1:4, v/v). Secondly, the obtained compounds were deacetylated and the fructo-oligosaccharides (FOSs) with high purity were obtained. Their structures were identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). This research successfully established a novel strategy for separation and purification of FOS. There is no doubt that the application of the research will be beneficial for the quantitative and qualitative analysis of products containing FOSs.

Enzymatic Synthesis of Sucrose-6-acetate by a Novel Immobilized Fructosyltransferase From Aspergillus sp. GX-0010.

BACKGROUND: Sucralose is an ideal food sweetener and sucrose-6-acetate (s-6-a) is a key intermediate for synthesis of sucralose. Synthesis of s-6-a was studied by free fructosyltransferase (FTase) from Aspergillus oryzae. Because of the limitations of free enzyme in stability and reusability, a FTase obtained from the new isolated Aspergillus sp. GX-0010 was immobilized and investigated for the potential of s-6-a synthesis. OBJECTIVES: The synthesis of s-6-a with sucrose and glucose-6-acetate (g-6-a) by immobilized fructosyltransferase (IFTase) from a novel Aspergillus sp. GX-0010 was studied, and its synthesis conditions were also optimized. MATERIALS AND METHODS: Aspergillus sp. GX-0010 was isolated. The effects of reaction time, ratio of g-6-a to sucrose, pH, substrate (sucrose and g-6-a) concentrations, IFTase concentration and temperature on the synthesis of s-6-a were investigated. RESULTS: IFTase was able to catalyze sucrose and g-6-a to synthesize the s-6-a. Thermal and pH stability of IFTase were promoted once compared to the FTase. The optimal condition for IFTase catalysis was obtained at 50 °C, 60 min reaction time, pH 6.5, 1:2 ratio of g-6-a to sucrose and 35.0 g.L-1 concentration of enzyme. Under this optimal condition, a g-6-a conversion rate of 24.96% was reached. CONCLUSIONS: This study showed IFTase has a great potential in the biosynthesis of s-6-a, a key intermediate of sucralose synthesis.

An innovative method for preparation of acid-free-water-soluble low-molecular-weight chitosan (AFWSLMWC).

The ozone generated from compressed oxygen by a laboratory-scale corona discharge generator was used for the preparation of acid-free-water-soluble low-molecular-weight chitosan (AFWSLMWC). Factors affecting the percent yield of AFWSLMWC were studied in batch experiments. AFWSLMWC with a molecular weight of 4.3-13.1kDa was obtained. IR spectra demonstrated that the chemical structures of AFWSLMWC were not modified during the depolymerisation process. There was no significant change of the total degree of deacetylation (DD) of AFWSLMWC, compared with the initial chitosan. The method is promisingly suitable for scale-up manufacture of acid-free-water-soluble low-molecular-weight chitosan.

[Determination of organic acids in cane vinasse by micellar electrokinetic capillary chromatography with indirect ultraviolet detection].

Micellar electrokinetic capillary chromatography (MECC) with indirect ultraviolet (UV) detection method for the separation and determination of several organic acids in cane vinasse, including malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acids, were developed. Electrophoretic conditions were as follows: uncoated fused silica capillary (56 cm/ 64 cm (effective/total length), 50 microm i. d. ), 7.5 mmol/L potassium acid phthalate-1. 5 mmol/L cetyltrimethyl-ammonium bromide (CTAB) at pH = 6.50 as buffer solution, applied voltage -25 kV, temperature 25 degrees C, detection wavelength 300 nm, reference wavelength 210 nm. Good linearities were obtained for nine organic acids, and the detection limits were 0.5 mg/L, 0.3 mg/L, 1.5 mg/L, 1.5 mg/L, 0.3 mg/L, 0.3 mg/L, 0.4 mg/L, 0.4 mg/L, 0.4 mg/L for malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acid, respectively. The relative standard deviations (RSDs) for migration times and peak areas of nine organic acids within a day were 0.4% - 0.6% and 2.3% - 4.8%, respectively. The corresponding data for five days were 0.5% -0.7% and 3.3% - 5.2%. The recoveries of acid standards were above 93%. The method can be applied to determine the organic acids in cane vinasse with satisfactory results.

Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards.

Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards is investigated. The UV absorbance of a pure chitosan solution is contributed additively by the N-acetylglucosamine and glucosamine residues; the absorbance divided by the total molar concentration of the residues (A/c(t)) is linearly related to the degree of acetylation (DA). Using acetyl glucosamine and glucosamine hydrochloride as standards in 0.1M hydrochloric acid solution, the equation obtained by linear regression is A/c(t)=3.3615 DA+0.0218, R(2)=0.9958. The DA of the analytical sample (m milligram of chitosan in V liters solution) can be calculated by.