Development of a quantitative assay for 2´-fucosyllactose via one-pot reaction with α1,2-fucosidase and l-fucose dehydrogenase

Determination of Seven Human Milk Oligosaccharides (HMOs) in Infant Formula and Adult Nutritionals: First Action 2022.07

BACKGROUND

Human milk oligosaccharides (HMOs) are important components of breast milk and may be responsible for some of the benefits of breastfeeding, including resistance to infections and the development of a healthy gut microbiota. Selected HMOs are now available for addition to infant formula, and suitable methods to control the dosing rate are needed.

OBJECTIVE

To develop and validate a suitable method for the analysis of HMOs in infant formula.

METHOD

A method was developed for the determination of seven human milk oligosaccharides (2'-fucosyllactose, 3-fucosyllactose, 3'-sialyllactose, 6'-sialyllactose (6'SL), 2',3-difucosyllactose, lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT)) in infant formula and adult nutritionals. The oligosaccharides are labeled at their reducing end with 2-aminobenzamide, separated by liquid chromatography and detected using a fluorescence detector. Maltodextrins are enzymatically hydrolyzed before analysis to prevent potential interference; likewise, an optional β-galactosidase treatment can be used to remove β-galactooligosaccharides. Fructooligosaccharides or polydextrose do not generally interfere with the analysis.

RESULTS

The method has been validated in a single laboratory on infant formula and adult nutritionals. The seven HMOs were spiked into eight matrixes at three or four spike levels, giving a total of 176 data points. Recoveries were in the range of 90.9-109% in all cases except at the lowest spike level in one matrix (elemental formula), where the LNT recovery was 113%, the LNnT recovery was 111%, and the 6'SL recovery was 121%. Relative repeatabilities (RSD(r)) were in the range of 0.1-4.2%. The performance is generally within the requirements outlined in the Standard Method Performance Requirements (SMPR®) published by AOAC INTERNATIONAL.

CONCLUSIONS

The method developed is suitable for the determination of seven HMOs in infant formula and demonstrated good performance during single-laboratory validation.

HIGHLIGHTS

A method has been developed that is suitable for the determination of seven HMOs in infant formula.

Method for the Determination of 2'-Fucosyllactose (2'-FL), 3-Fucosyllactose (3-FL), 6'-Sialyllactose (6'-SL), 3'-Sialyllactose (3'-SL), Lacto-N-Tetraose (LNT), and Lacto-N-neoTetraose (LNnT) by High-Performance Anion-Exchange Chromatography With Pulsed Amperometric Detection (HPAEC-PAD): First Action 2022.04

BACKGROUND

A method for simultaneous determination of six human milk oligosaccharides (HMOs) is described. The HMOs include 2'-fucosyllactose (2'-FL, CAS number 41263-94-9), 3-fucosyllactose (3-FL, CAS number 41312-47-4), 6'-sialyllactose (6'-SL, CAS number 35890-39-2), 3'-sialyllactose (3'-SL, CAS number 35890-38-1), lacto-N-tetraose (LNT, CAS number 14116-68-8), and lacto-N-neotetraose (LNnT, CAS number 13007-32-4). The method was designed to comply with the respective Standard Method Performance Requirements (SMPR®; seeTable 1), respectively.

OBJECTIVE

The method is valid for six HMOs in infant formula and adult nutritional matrixes, including samples with intact protein, protein hydrolysates, elemental formulations free of intact protein, and rice flour over the ranges defined in the SMPR (seeTable 2). The method is not valid for determination of difucosyllactose (DFL/DiFL).

METHOD

For most samples, reconstitution with water followed by filtration. For products containing interferences (fructans and maltodextrins), hydrolysis with enzymes is used. After preparation, samples are analyzed using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The method provides for separation of six HMOs and other carbohydrates commonly found in infant formula and adult nutritional products (e.g., lactose, sucrose, and GOS).

RESULTS

This study includes data from multiple matrixes evaluated by multiple laboratories globally. RSDr ranged from 0.0068 to 4.8% RSDr, and spike recovery results ranged from 89.4 to 109%. Calibration fit optimal with a quadratic curve; alternately linear fit showed no statistically significant impact to data (when correlation passes).

CONCLUSIONS

This method was reviewed by the AOAC SPIFAN Expert Review Panel (ERP) and determined to meet the SMPRs for the six noted HMOs.

HIGHLIGHTS

The method was granted First Action Official MethodsSM status.

Magnetic field-driven biochemical landscape of browning abatement in goat milk using spatial-omics uncovers

Influence of magnetic field (MF) treatment on the glycation of goat milk proteins is yet to be elucidated. Proteomic and metabolomic analyses of brown goat milk samples with and without MF treatment were performed. Assessed glycation degree and structural modification of proteins explained that MF treatment dramatically down-regulated the glycation of brown goat milk protein, possibly due to the aggregation behavior induced by MF treatment, which consumed additional glycation sites as well as altered their accessibility and preference. Integrated datasets uncovered that the energy metabolism-related biological events including carbohydrate metabolism, glycerophospholipid metabolism, TCA cycle may mainly account for the browning abatement mechanism of MF. In addition, MF treatment enhanced both the quality and flavor of brown goat milk. This study suggests the feasibility of MF treatment to reduce glycation in brown goat milk for producing high-quality dairy ingredients and products.

Development of fluorescent Escherichia coli for a whole-cell sensor of 2'-fucosyllactose

2′-Fucosyllactose (2′-FL), a major component of fucosylated human milk oligosaccharides, is beneficial to human health in various ways like prebiotic effect, protection from pathogens, anti-inflammatory activity and reduction of the risk of neurodegeneration. Here, a whole-cell fluorescence biosensor for 2′-FL was developed. Escherichia coli (E. coli) was engineered to catalyse the cleavage of 2′-FL into l-fucose and lactose by constitutively expressing α-l-fucosidase. Escherichia coli ∆L YA, in which lacZ is deleted and lacY is retained, was employed to disable lactose consumption. E. coli ∆L YA constitutively co-expressing α-l-fucosidase and a red fluorescence protein (RFP) exhibited increased fluorescence intensity in media containing 2′-FL. However, the presence of 50 g/L lactose reduced the RFP intensity due to lactose-induced cytotoxicity. Preadaptation of bacterial strains to fucose alleviated growth hindrance by lactose and partially recovered the fluorescence intensity. The fluorescence intensity of the cell was linearly proportional to 1–5 g/L 2′-FL. The whole-cell sensor will be versatile in developing a 2′-FL detection system.