The aim of this study was to identify Lactobacillus isolates derived from turkeys from six Polish farms and to characterize their phenotypic and genotypic antibiotic resistance profiles. Among 62 isolates identified by MALDI-TOF mass spectrometry and restriction analysis of 16S rDNA, the dominant species was L. salivarius (35%), followed by L. crispatus (21%), L. ingluviei (14.5%) and L. johnsonii (10%). A high prevalence of resistance to tetracycline (68% resistant isolates), lincomycin (64.5%) and enrofloxacin (60%) among the lactobacilli tested was observed. Fewer than 50% isolates were resistant to ampicillin (47%), erythromycin (45%), streptomycin (31%), chloramphenicol (29%) and gentamicin (10%). As many as 64,5% of the isolates showed multidrug resistance. High MIC values for ampicillin (≥64 μg/ml) were usually accompanied by elevated MICs for cephalosporins (≥16 μg/ml) and high MICs for tiamulin, i.e. ≥32 μg/ml, were noted in most of the turkey lactobacilli (61%). The occurrence of resistance genes was associated with phenotypic resistance, with the exception of five phenotypically susceptible isolates that contained the tetM, tetL, ermC, ermB or cat genes. The most frequently identified were ermB (45% isolates), tetL (40%), tetW (37%) and tetM (29%), and the occurrence of lnuA (18%), cat (10%), ermC (6%), ant(6)-Ia (5%) and aadE (5%) was less frequent. The mechanism of ampicillin resistance has not been elucidated, but the results of nitrocefin test confirmed that it is not involved in the production of beta-lactamases. The high rate of antibiotic resistance observed in this study indicates the need to implement the principles of rational use of antibiotics in poultry. The presence of transmissible resistant genes in lactobacilli may contribute to the development of antibiotic resistant pathogenic strains that pose a threat to both poultry and consumers. The results of these studies may be useful for committees providing guidance on antibiotic susceptibility of microorganisms in order to revise and supplement current microbiological cut-offs values within the genus Lactobacillus.

There is currently considerable interest on the use of animal, plant, and fungal sources in the production of bioactive peptides, as evidenced by the substantial body of research on the topic. Such sources provide cheap and environmentally friendly material as it often includes waste and by-products. Enzymatic hydrolysis is considered an efficient method of obtaining peptides capable of antioxidant activity. Those properties have been proven in terms of radical-scavenging capacity using the DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2-azinobis-(3-ethyl-benzothiazoline-6-sulphonic acid)), hydroxyl and superoxide radical methods. Additionally, the reducing power, ferrous ion-chelating (FIC), ferric reducing antioxidant power (FRAP), and the ability of the protein hydrolysates to inhibit lipid peroxidation have also been explored. The results collected in this review clearly indicate that the substrate properties, as well as the conditions under which the hydrolysis reaction is carried out, affect the final antioxidant potential of the obtained peptides. This is mainly due to the structural properties of the obtained compounds such as size or amino acid sequences.

A significant increase in interest in food-derived peptides obtained mostly through enzymatic reactions has been observed in the past few years. One of the best sources of bioactive peptides are defatted egg yolk proteins, which can potentially find application as high-quality nutritional supplements for infants with cow’s milk protein intolerance and as natural preservatives. The aim of this study was to obtain peptides from defatted egg yolk protein, to study their antioxidant and antimicrobial properties, and to identify peptides with bioactive properties To control the course of the process, MALDI-TOF/MS (matrix-assisted laser desorption/ionization time-of flight/mass spectrometry) spectra were also examined. The peptide mixture obtained through enzyme digestion was tested for its antioxidant properties by measuring the scavenging activity in 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation decolorization (ABTS•+), and ferric reducing activity (FRAP) assays. Antimicrobial activity was also studied. The peptide mixture exhibited significant antioxidant activity: DPPH—1776.66 ± 32.99, ABTS—390.43 ± 8.92, and FRAP—16.45 ± 0.19. The inhibition of bacterial growth by two concentrations of the peptide mixture was examined. The best result was obtained in Bacillus cereus, with an inhibition zone of 20.0 ± 1.0 and 10.7 ± 0.6 mm at the concentrations of 50 and 25 mg/mL, respectively. The results of the study suggest that the mixture of egg yolk peptides may exhibit a number of health-promoting properties.