Abstract
Simple SummaryCamels are an important part of the ecosystem in desert areas. Camels can survive well under difficult conditions, therefore, they play a key role in local herdsmen’s production, life, and economic structure. China’s Inner Mongolia region has unique environmental and geographical advantages, making it suitable for camel breeding. Camel milk has high nutritional value and unique functional characteristics. It not only has low sensitization, but also contains various immune active factors with high medicinal value. Currently, there are various products derived from cow and goat milk, but few related to camel milk, providing an opportunity for development. This study used trypsin to hydrolyze the whey proteins of camel milk, separated and purified peptide fragments with antibacterial activity, and conducted a comparative study with cow milk. The present study provided new ideas for the use and development of camel whey protein hydrolysates and their dextran purification fractions, and indicated the future development of these peptides as nutritional additives or food preservatives.Antibacterial peptides were isolated and purified from whey proteins of camel milk (CaW) and cow milk (CoW) and their antimicrobial activities were studied. The whey proteins were hydrolyzed using trypsin, and the degree of hydrolysis was identified by gel electrophoresis. The whey hydrolysate (WH) was purified using ultrafiltration and Dextran gel chromatography to obtain small peptides with antibacterial activity. The effect of the antimicrobial peptides on the morphology of bacterial strains was investigated using transmission electron microscopy. Their amino acid composition and antimicrobial activities were then determined. Polypeptides CaWH-III (<3 kDa) and CoWH-III (<3 kDa) had the strongest antibacterial activity. Both Fr.A2 (CaWH-Ⅲ’s fraction 2) and Fr.B1 (CoWH-Ⅲ’s fraction 1) had antibacterial effects toward Escherichia coli and Staphylococcus aureus, with minimum antimicrobial mass concentrations of 65 mg/mL and 130 mg/mL for Fr.A2, and 130 mg/mL and 130 mg/mL for Fr.B1, respectively. The highly active antimicrobial peptides had high amounts of alkaline amino acids (28.13% in camel milk Fr.A2 and 25.07% in the cow milk Fr.B1) and hydrophobic amino acids. (51.29% in camel milk Fr.A2 and 57.69% in the cow milk Fr.B1). This results showed that hydrolysis of CaW and CoW using trypsin produced a variety of effective antimicrobial peptides against selected pathogens, and the antibacterial activity of camel milk whey was slightly higher than that of cow milk whey.
Highlights
The main factor affecting food shelf life is microbial contamination, which might affect the health of consumers
We aimed to investigate the antibacterial activities of cow and camel whey protein trypsin hydrolysates (CoWH and CaWH, respectively) against selected spoilage and pathogenic bacteria, including Salmonella typhimurium, Staphylococcus aureus, Escherichia coli, and Streptococcus mutans
The results showed that the amino acid compositions of the trypsin hydrolysates were similar in cow and camel milk
Summary
The main factor affecting food shelf life is microbial contamination, which might affect the health of consumers. Given the aim to reduce the use of chemical agents, consumers have expressed more interest in foods containing natural preservatives. Numerous authors have reported that many different types of peptides can be released from milk whey proteins by proteolytic enzyme digestion [2]. Antibacterial peptides are bioactive peptides obtained from the enzymatic hydrolysis of different animal-derived milk proteins. One study showed that human gastrointestinal enzymes produce different peptides from goat whey than do non-human enzymes, and that the hydrolysates have higher antibacterial activities than the pure peptides. Undigested goat whey did not show a significant inhibitory effect; the antibacterial effect of goat milk hydrolysate was strongest in the duodenum during digestion [4]. Bovine whey beta lactoglobulin (β-Lg) has been hydrolyzed by trypsin to produce four bactericidal peptides [6]
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