Exploring the DPP-IV Inhibitory, Antioxidant and Antibacterial Potential of Ovine "Scotta" Hydrolysates

Abstract

The aim of this work was to valorize the by-product derived from the ricotta cheese process (scotta). In this study, ovine scotta was concentrated by ultrafiltration and then subjected to enzymatic hydrolyses using proteases of both vegetable (4% E:S, 4 h, 50 °C) and animal origin (4% E:S, 4 h, 40 °C). The DPP-IV inhibitory, antioxidant, and antibacterial activities of hydrolysates from bromelain (BSPH) and pancreatin (PSPH) were measured in vitro. Both the obtained hydrolysates showed a significantly higher DPP-IV inhibitory activity compared to the control. In particular, BSPH proved to be more effective than PSPH (IC₅₀ 8.5 ± 0.2 vs. 13 ± 1 mg mL^-1). Moreover, BSPH showed the best antioxidant power, while PSPH was more able to produce low-MW peptides. BSPH and PSPH hydrolysates showed a variable but slightly inhibitory effect depending on the species or strain of bacteria tested. BSPH and PSPH samples were separated by gel permeation chromatography (GPC). LC-MS/MS analysis of selected GPC fractions allowed identification of differential peptides. Among the peptides 388 were more abundant in BSPH than in the CTRL groups, 667 were more abundant in the PSPH group compared to CTRL, and 97 and 75 of them contained sequences with a reported biological activity, respectively.

Keywords: bioactive peptides; bromelain; dipeptidyl peptidase IV inhibition; enzymatic hydrolysis; ovine scotta; ovine second whey cheese; pancreatin.

Figure 1

Distribution of the relative abundance (%) according to molecular weight obtained by gel permeation chromatography (GPC), and the comparison among BSPH, PSPH and CTRL. Values (n = 3) with the same letter do not differ significantly from each other according to LSD test (p < 0.05).

Figure 2

Effect of the different scotta-hydrolysates at concentration of 100 mg mL⁻¹ on the maximum growth rate (µmax) of bacteria strains target. BHI-WH, Brain Heart infusion broth medium without hydrolysates; BSPH, Bromelain filter sterilized hydrolysate; PSPH, Pancreatin filter sterilized hydrolysate; CTRL, Scotta not hydrolysate filter sterilized). (Panel (A–F): Listeria monocytogenes B (A); L. monocytogenes C (B); L. monocytogenes 20,600 DSMZ (C); L. monocytogenes E (D); Staphylococcus aureus 20,231 DSMZ (E), Salmonella bongori 13,772 DSMZ (F)). Different lowercase letters above the bar indicate statistically significant differences between different treatments (p < 0.001).

Figure 3

Distribution of the differential peptides more abundant in BSPH vs. CRTL (A) and PSPH vs. CRTL (B), according to their putative biological activities (DPP-IV inhibition, antioxidative and antibacterial properties).

Figure 4

Number of differential peptides (BSPH vs. PSPH) grouped by the proteins and biological activities.