Effect of pH on the Antimicrobial Activity and Peptide Population of Pepsin Hydrolysates Derived from Bovine and Porcine Hemoglobins

Abstract

Slaughterhouse blood is considered a valuable by-product of the meat industry that is mainly derived from the slaughter of cattle and pigs. Its cruor fraction is mainly constituted of hemoglobin, which has been widely described as an important source of several antimicrobial peptides that can be released by hydrolysis with pepsin. Despite the high sequence similarity between bovine (Hb-B) and porcine (Hb-P) hemoglobins, the release of antimicrobial peptides may be affected by varying hydrolysis conditions. This study presents, for the first time, the impact of pH (pH 2, 3, 4, and 5) on the antimicrobial peptide population of hydrolysates derived from the main hemoglobin sources by using pepsin (bovine and porcine). In the same way, their antibacterial, antifungal, and antiyeast activities are compared, as well as their type of mechanism of action (static or cidal effect). These characteristics have not been described previously in the literature. A total of 29 peptides from Hb-B and 35 peptides for Hb-P with potential antimicrobial peptides were identified by reversed-phase ultrahigh-performance liquid chromatography with tandem mass spectrometry (RP-UPLC–MS/MS) and bioinformatics tools. Similarities in the peptide population between Hb-B and Hb-P hydrolysates were observed by PCA, mainly in the enzymatic hydrolysis at pH 2 and pH 3. Both bovine and porcine hydrolysates produced at pH 2 and pH 3 showed antibacterial activity against L. ivanovii (MIC = 0.62–1.25 mg·mL–1) and antiyeast activity against R. mucilaginosa (0.31–1.25 mg·mL–1). Conversely, only antifungal activity against M. racemosus in the porcine hydrolysate at pH 3 was observed (1.25 mg·mL–1). This study confirms the similarities of Hb-B and Hb-P in terms of peptide profiles and antimicrobial activity, which indicates they are suitable sources of antimicrobial peptides with antibacterial, antifungal, and antiyeast activities that could be employed in the preservation of food products.