Influencing emulsifying properties of egg yolk by enzymatic modification by phospholipase D from Streptomyces chromofuscus

Immobilization of Phospholipase A1 Using a Protein-Inorganic Hybrid System

In this study, four kinds of phospholipase A1-metal (Al/Co/Cu/Mn) hybrid nanostructures were prepared for enhancing the stability of the free PLA1. The formed hybrid complexes were characterized by scanning electron microscope (SEM), Fourier infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The stability and substrate specificity of immobilized enzymes were subsequently determined. After immobilization, the temperature tolerance of PLA1–metal hybrid nanostructures was enhanced. The relative activity of PLA1–Al/Co/Cu hybrid nanostructures remained above 60% at 50 °C, while that of free enzyme was below 5%. The thermal transition temperature measured by differential scanning calorimetry (DSC) was found to increase from 65.59 °C (free enzyme) to 173.14 °C, 123.67 °C, 96.31 °C, and 114.79 °C, referring to PLA1–Cu/Co/Al/Mn hybrid nanostructures, respectively. Additionally, after a storage for fourteen days at 4 °C, the immobilized enzymes could exhibit approximately 60% of the initial activity, while the free PLA1 was inactivated after four days of storage. In brief, using Co²⁺, Cu²⁺, Al³⁺, and Mn²⁺ as the hybridization materials for immobilization could improve the catalytic properties and stability of the free PLA1, suggesting a promising method for a wider application of PLA1 in many fields such as food, cosmetics, and the pharmaceutical industry.

Effect of Phospholipase A1 and High-Pressure Homogenization on the Stability, Toxicity, and Permeability of Egg Yolk/Fish Oil Emulsions

Enzymatic treatment of egg yolk with phospholipases can enhance its emulsifying properties and thermal stability. Additionally, a two-step process (primary and secondary homogenization) could form emulsions with better stability. Thus, in this study we used a split-split-plot in time design to assess the effect of enzymatic treatment, processing, and storage conditions on the encapsulation efficiency, stability, toxicity, and permeability of egg yolk/fish oil emulsions stored up to 10 days at 45 °C. Egg yolk solutions before and after treatment with phospholipase A₁ were used as carriers of fish oil containing ≥82% eicosapentaenoic and docosahexaenoic acids. Emulsions were formed by primary (24,000 rpm, 4 min) and secondary (200 MPa) homogenization. The combined effect of treatment with phospholipase A₁ and secondary homogenization resulted in emulsions with improved stability, increased the encapsulation efficiency of the carriers, and reduced the release of oil to the particle surface, resulting in lower formation of oxidation products. At the end of storage time, none of the emulsions were toxic to Caco-2 cells at a concentration of 75 μg/mL medium, while nonencapsulated fish oil reduced cell viability to 81%. Only eicosapentaenoic acid was detected in the basolateral side of Caco-2:HT29 monolayers, and its apparent permeability from nonencapsulated fish oil was significantly lower than that from emulsions.

Time course of nutritional and functional property changes in egg yolk from laying hens fed docosahexaenoic acid-rich microalgae

Marine microalgae (MA) has received wide attention as a promising source of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) enrichment in animal products to improve the health status and wellbeing of the consumers. This study evaluated dynamic changes in n-3 LC-PUFA, color, and functional properties as well as atherogenic and thrombogenic health lipid indices of egg yolk from hens fed graded levels (0, 0.5, and 1.0%) of docosahexaenoic acid (DHA)–rich MA (Aurantiochytrium sp.) during a 56-D feeding period. Egg freshness parameters and yolk lipid oxidative stability were also measured after 0, 14, and 28 D of refrigerated storage. The hen performance and egg quality (except for yolk color) were not affected (P > 0.05) by MA supplementation. Docosahexaenoic acid contents in yolk from hens fed 1.0% MA increased quadratically with feeding time with a plateau at about 30 D (P < 0.05). Afterward, the DHA content leveled off to a constant value (946.3 mg/100 g yolk) with the n-6/n-3 ratio at 3.5: 1. Dietary inclusion of 1.0% of MA also significantly decreased the atherogenic and thrombogenic indices of yolk lipid (P < 0.05). Because the microalgal carotenoids incorporated into egg yolk, the L∗ value of yolk from hens fed MA decreased whereas a∗ value increased (P < 0.05), corresponding to yolk Roche color scores. As expected, there were no significant changes in yolk functional properties (e.g., viscosity and emulsifying activity) related to DHA enrichment (P > 0.05). Microalgal carotenoids enrichment also helped attenuate fatty acid oxidation of the DHA-enriched yolk and increase their lipid oxidative stability. In conclusion, dietary supplementation with up to 1.0% of MA significantly increased DHA contents with more health-promoting n-6/n-3 ratio and atherogenic and thrombogenic indices, as well as more intense yolk color within consumers' acceptability, and the feeding strategy had a minimal impact on yolk physical and functional properties or oxidative stability during subsequent refrigerated storage.

Phosphoryl transfers of the phospholipase D superfamily: a quantum mechanical theoretical study

The HKD-containing Phospholipase D superfamily catalyzes the cleavage of the headgroup of phosphatidylcholine to produce phosphatidic acid and choline. The mechanism of this cleavage process is studied theoretically. The geometric basis of our models is the X-ray crystal structure of the five-coordinate phosphohistidine intermediate from Streptomyces sp . Strain PMF (PDB Code = 1V0Y ). Hybrid ONIOM QM:QM methodology with Density Functional Theory (DFT) and semiempirical PM6 (DFT:PM6) is used to acquire thermodynamic and kinetic data for the initial phosphoryl transfer, subsequent hydrolysis, and finally, the formation of the experimentally observed ″dead-end″ phosphohistidine product (PDB Code = 1V0W ). The model contains nineteen amino acid residues (including the two highly conserved HKD-motifs), four explicit water molecules, and the substrate. Via computations, the persistence of the short-lived five-coordinate phosphorane intermediate on the minutes times scale is rationalized. This five-coordinate phosphohistidine intermediate energetically exists between the hydrolysis event and ″substrate reorganization″ (the reorganization of the in vitro model substrate within the active site). Computations directly support the thermodynamic favorability of the in vitro four-coordinate phosphohistidine product. In vivo, the activation energy of substrate reorganization is too high, perhaps due to a combination of substrate immobility when embedded in the lipid bilayer, as well as its larger steric bulk compared to the compound used in the in vitro substrate soaks. On this longer time scale, the enzyme will migrate along the lipid membrane toward its next substrate target, rather than promote the formation of the dead-end product.

Effects of vitamin D(3) -enriched diet on egg yolk vitamin D(3) content and yolk quality

A 40-wk experiment was conducted using Hy-Line W-36 laying hens (19-wk old) to investigate the impact of feeding cholecalciferol-enriched diets on egg yolk quality. Feeds were enriched with 4 cholecalciferol levels, 9700 (diet 2), 17200 (diet 3), 24700 (diet 4), and 102200 (diet 5) IU/kg feed. The control (diet 1) contained 2200 IU cholecalciferol/kg feed. Eggs from each replicate group of enriched diets were collected daily and the yolks were pooled into 2-d period during the first 2 wk. During weeks 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, and 40, pooled samples were generated by daily collection of 3 consecutive days of egg production. The cholecalciferol content of egg yolk from the enriched diets increased rapidly during the first 3 wk. The peak cholecalciferol concentrations in egg yolk that occurred at week 3 were 865, 1641, 2411, and 34815 IU/100 g egg yolk (wet basis) from diet 2 to 5. The average cholecalciferol concentration in yolk during weeks 3 to 40 and the deposition rate of cholecalciferol during the first 3 wk were both linearly increased with the dietary cholecalciferol level when the feed contained no more than 24700 IU/kg cholecalciferol. Egg yolk lipid profile (total lipid content, fatty acid composition, phospholipid composition, and unsaponifiables), physical and functional properties (yolk viscosity and emulsifying property), and sensory quality of hard-boiled egg yolk were not affected by the cholecalciferol enrichment in the feed.

PRACTICAL APPLICATION

A linear dose-response relationship between dietary vitamin D(3) level and egg yolk vitamin D(3) content was established at relatively low enrichment levels. Such relationship can be used to formulate feed to achieve a target egg vitamin D level. High vitamin D yolk showed no difference from the conventional yolk in other compositional, functional, and sensory properties.

Phospholipases in food industry: a review

Mammal, plant, and mainly microbial phospholipases are continuously being studied, experimented, and some of them are even commercially available at industrial scale for food industry. This is because the use of phospholipases in the production of specific foods leads to attractive advantages, such as yield improvement, energy saving, higher efficiency, improved properties, or better quality of the final product. Furthermore, biocatalysis approaches in the food industry are of current interest as non-pollutant and cleaner technologies. The present chapter reviews the most representative examples of the use of phospholipases in food industry, namely edible oils, dairy, and baking products, emulsifying agents, as well as the current trend to the development of novel molecular species of phospholipids with added-value characteristics.