The emergence of antimicrobial‐resistant foodborne pathogens poses a continuous health risk and economic burden as they can easily spread through contaminated food. Therefore, the demand for new antimicrobial agents to address this problem is steadily increasing. Similarly, the development of rapid, sensitive, and accurate pathogen detection tools is a prerequisite for ensuring food safety. Phage‐derived proteins have become innovative tools for combating these pathogens because of their potent antimicrobial activity and host specificity. Phage proteins are relatively free from regulation compared to phages per se, and there are no concerns about the transduction of harmful genes. With recent progress in next‐generation sequencing technology, the analysis of phage genomes has become more accessible, and numerous phage proteins with potential for biocontrol and detection have been identified. This review provides a comprehensive overview of phage protein research on food safety from 2006 to the present, a pivotal period marked by the certification of phages as Generally Recognized As Safe (GRAS). Emphasizing recent advancements, we investigated the diverse applications of various phage proteins for biocontrol and detection purposes. While highlighting the successful implementation of these proteins, we also address the current bottlenecks and propose strategies to overcome these challenges. By summarizing the current state of research on phage‐derived proteins, this review contributes to a deeper understanding of their potential as effective antimicrobial agents and tools for detecting foodborne pathogens.

Bacteriophage endolysins have attracted attention as promising alternatives to antibiotics, and their modular structure facilitates endolysin engineering to develop novel endolysins with enhanced versatility. Here, we constructed hybrid proteins consisting of two different endolysins for simultaneous control of two critical foodborne pathogens, Staphylococcus aureus and Bacillus cereus. The full-length or enzymatically active domain (EAD) of LysB4, an endolysin from the B. cereus-infecting phage B4, was fused to LysSA11, an endolysin of the S. aureus-infecting phage SA11, via a helical linker in both orientations. The hybrid proteins maintained the lytic activity of their parental endolysins against both S. aureus and B. cereus, but they showed an extended antimicrobial spectrum. Among them, the EAD of LysB4 fused with LysSA11 (LysB4EAD-LyaSA11) showed significantly increased thermal stability compared to its parental endolysins. LysB4EAD-LysSA11 exhibited high lytic activity at pH 8.0–9.0 against S. aureus and at pH 5.0–10.0 against B. cereus, but the lytic activity of the protein decreased in the presence of NaCl. In boiled rice, treatment with 3.0 µM of LysB4EAD-LysSA11 reduced the number of S. aureus and B. cereus to undetectable levels within 2 h and also showed superior antimicrobial activity to LyB4EAD and LysSA11 in combination. These results suggest that LysB4EAD-LysSA11 could be a potent antimicrobial agent for simultaneous control of S. aureus and B. cereus.

Geobacillus stearothermophilus is a highly thermophilic, spore-forming Gram-positive bacterium that causes flat sour spoilage in low-acid canned foods. To address this problem, we isolated G. stearothermophilus-infecting phage GR1 from the soil and characterized its endolysin LysGR1. Phage GR1 belongs to the Siphoviridae family and possesses a genome of 79,387 DNA bps with 108 putative open reading frames. GR1 demonstrated a very low degree of homology to previously reported phages, indicating that it is novel. The endolysin of GR1 (LysGR1) contains an N-terminal amidase domain as an enzymatically active domain (EAD) and two C-terminal LysM domains as a cell wall binding domain (CBD). Although GR1 is specific to certain strains of G. stearothermophilus, LysGR1 showed a much broader lytic range, killing all the tested strains of G. stearothermophilus and several foodborne pathogens, such as Clostridium perfringens, Listeria monocytogenes, and Escherichia coli O157:H7. LysGR1_EAD, alone, also exhibits lytic activity against a wide range of bacteria, including Bacillus cereus, which is not terminated by a full-length endolysin. Both LysGR1 and its EAD effectively remove the G. stearothermophilus biofilms and are highly thermostable, retaining about 70% of their lytic activity after a 15-min incubation at 70°C. Considering the high thermal stability, broad lytic activity, and biofilm reduction efficacy of LysGR1 and its EAD, we hypothesize that these enzymes could act as promising biocontrol agents against G. stearothermophilus and as foodborne pathogens.

Bokyung Son, Youna Kim, Booyoung Yu, and Minsuk Kong. J. Microbiol. Biotechnol. 2023;33:1050-6. https://doi.org/10.4014/jmb.2303.03021