## 3 Results and Discussion
### Antimicrobial Activity of LPH  
Infectious diseases are the primary cause of death worldwide and are becoming a global issue. Antibiotics are frequently used to treat bacterial infections, due to their active characteristics [75]. However, this caused the establishment and spread of resistant types of bacteria which have consequences on human health [76]. Even low concentrations of antibiotics put into the environment can \"enrich\" the population of resistant bacterial strains. In this regard, there is some evidence that peptides may be able to satisfy this need because of their ability to suppress the activity of several types of pathogenic microorganisms: Gram-positive (_Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus_, _Microoccus luteus_) and Gram-negative (_Escherichia coli_, _Yersinia enterocolitia_) [77]. The antibacterial activity of peptides is primarily caused by the presence of sequences rich in positive amino acids and the amphiphilic nature of the peptide sequence [78]. The structural characteristics of these physiologically active peptides, such as peptide size, amino acid content, or charge, influence their efficacy as antibacterial compounds [79]. It is established/demonstrated that lysine and arginine are the essential amino acids with the most substantial antibacterial effects [80]. These antimicrobial peptides' characteristics ultimately enable them to break through bacterial membranes, produce pores, and remove undesirable bacteria by modifying homeostasis. It was also demonstrated that peptide hydrolyses with molecular weights between 400 and 1400 Da had the strongest antibacterial activity [77]. Antimicrobial peptides were considered a new horizon in science because of the simplicity of their structure compared to that of proteins, which is related to the faster knowledge of the function-structure relationship. Peptides may satisfy this need because studies suggest that they can suppress the activity of several types of pathogenic bacteria.  
In our study, the antibacterial activity of nine lupin hydrolyses was tested by plate growth inhibition (Table 4). Strains of pathogenic bacteria reported causing infections, toxic infections, and toxicoses were used as test microorganisms. Antimicrobial assays were carried out against the following bacterial strains: _Escherichia coli_, _Salmonella enterica_,_S. aureus_ and _L. monocytogenes._ As positive control, tetracycline was used, and sterile water with the bacterial suspension as a negative control.  
From the obtained results, it could be concluded that LPH has enhanced inhibitory potential against Gram (-) bacterium (_Escherichia coli_). The strongest inhibition is demonstrated by sample P7, with an inhibition zone of 1.3 cm. Regarding Gram (+) bacteria (_S. aureus_), only one sample (P4) showed inhibition. None of the other hydrolyses tested have demonstrated significant activity against Gram (+) bacteria. The only published study on the topic was from [PERSON] et al. (2016) [81] who reported similar results for alcalase hydrolyses of lupin protein on _E. coli._ In addition, they reported inhibition of _S. aureus_ that was not detected in our study. The findings of this study demonstrated that lupin protein could demonstrate antibacterial activity against Gram (-) bacteria by enzymatic hydrolysis by papain at pH 6 and 65 \({}^{\circ}\)C for 120 min, and this method could be used as a bio-preservation technique in food systems. Such application of bioactive peptides of pea and red kidney on enhancing the quality and safety of raw buffalo meat was reported [82].