Dromedary Milk Protein Hydrolysates Show Enhanced Antioxidant and Functional Properties

Research background. Milk protein hydrolysates have received particular attention due to their health-promoting effects. Dromedary milk differs from the milk of other dairy animals in the composition and structure of its protein components, which give it unique properties. The bioactivity and functionality of whole dromedary milk proteins and their enzymatic hydrolysates have not received much attention, hence this study aims to investigate the effect of enzymatic hydrolysis of dromedary milk proteins on their antioxidant activities and functional properties. Experimental approach. Dromedary milk proteins were treated using four proteolytic enzymes (pepsin, trypsin, α-chymotrypsin and papain) and two mixtures of enzymes (pancreatin and pronase). The degree of hydrolysis was measured to verify the hydrolysis of the proteins. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography served to determine the molecular mass distribution of the hydrolysates while reversed phase-high performance liquid chromatography (RP-HPLC) was conducted to explore their hydrophobicity. The antioxidant activities were evaluated using various in vitro tests, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging capacities, iron(III) reducing ability and chelating activity. Besides, functional properties such as solubility, foaming and emulsification were assessed. Results and conclusions. Dromedary milk protein hydrolysates exhibited different degrees of hydrolysis ranging from 17.69 to 41.86 %. Apart from that, the hydrolysates showed different electrophoretic patterns, molecular mass distribution and RP-HPLC profiles demonstrating the heterogeneity of the resulting peptides in terms of molecular mass and polarity. The hydrolysates displayed significantly higher antioxidant capacities than the undigested proteins at all the tested concentrations. Iron(II) chelating activity was the most improved assay after proteolysis and the hydrolysate generated with pancreatin had the highest chelating power. Dromedary milk protein hydrolysates possessed good solubility (>89 %). Further, foaming and emulsifying properties of dromedary milk proteins were enhanced after their proteolysis. These interfacial properties were influenced by the enzymes employed during proteolysis. Novelty and scientific contribution. Enzymatic hydrolysis of dromedary milk proteins is an effective tool to obtain protein hydrolysates with great antioxidant and functional properties. These results suggest that dromedary milk protein hydrolysates could be used as a natural source of antioxidant peptides to formulate functional foods and nutraceuticals.

Antibacterial and antibiofilm activity of the bacteriocin-producing strain Leuconostoc mesenteroides CHBY46 isolated from Algerian dromedary milk against Pseudomonas aeruginosa and Staphylococcus aureus biofilms

In order to control biofilm formation of pathogenic and spoilage bacteria in foods, some species of Leuconostoc are very important in food industries, as they increase the shelf life of foods during preservation. In this study the strain CHBY46 a bacteriocin-producing strain belonging to Leuconostoc ge-nus isolated from dromedary milk in the south of Algeria was characterized by 16S rRNA gene sequencing and MALDITOF MS mass spectrometry, tested for its antibacterial and antibiofilm activities against Pseudomonas aeruginosa and Staphylococcus aureus. The produced bacteriocin was partially puri-fied with sulfate ammonium precipitation and RP-HPLC. The strain CHBY46 was classified as Leuc. mesenteroides after molecular identification. Among the bacteria tested the pathogens Staph. aureus ATCC 29213 and Ps. aeru-ginosa ATCC 27653 were sensitive to this bacteriocin with 480 AU/ml. Antibi-ofilm activity was investigated by crystal violet assay. The bacteriocin of Leuc. mesenteroides CHBY 46 exhibited significant biofilm inhibition ; 35.58% with Ps. aeruginosa, and 42.11% with Staph. aureus. Tricine-SDS-PAGE analysis of the partially purified bacteriocin indicated a low molecular weight of approximately 3.5 kDa. Therfore, we conclude that bacteriocins from Leuco-nostoc have the potential as a therapeutic strategy against pathogen’s bio-films, which contribute, to bacterial pathogenicity and resistance toward antibiotics or being used in foods as adjunsts to contribute food safety.

Draft Genome Sequence of the Moderately Heat-TolerantLactococcus lactissubsp.lactisbv. diacetylactis Strain GL2 from Algerian Dromedary Milk

Lactococcus lactissubsp.lactisbv. diacetylactis GL2 is a moderately thermotolerant lactic acid bacterium isolated from dromedary raw milk. Here, we present the draft genome sequence of this potential new dairy starter strain, which combines thermotolerance and the capacity to metabolize lactose, casein, and citrate.