Antimicrobial potential of bacteria isolated from sediment and Avicennia germinans collected from the mangroves of Vichayal (Northern Peru, Piura) and their application in the preservation of Scomber japonicus peruanus.

Mangrove ecosystems in Peru represent largely unexplored reservoirs of bacterial diversity with considerable biotechnological potential. This study evaluated the antimicrobial activity of bacteria isolated from sediments and endophytic tissues of Avicennia germinans from the Vichayal mangroves (Piura, northern Peru) using the volatile organic compounds test (VOCt), the Over Plate Test (OpT), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) against Gram-positive pathogenic bacteria (Enterococcus faecalis, Staphylococcus epidermidis, S. aureus, and Listeria monocytogenes), Gram-negative pathogenic bacteria (Escherichia coli and Salmonella enterica sv. typhimurium), and two Candida species (Candida albicans and C. tropicalis), as well as their application in the preservation of Scomber japonicus fillets, prior to biosafety testing and phylogenetic analysis. A total of 34 isolates were obtained - 21 from sediments and 13 from A. germinans. Based on the VOCt and OpT assays, seven strains were identified by 16S rDNA sequencing as Bacillus albus ZB3, Priestia flexa (ZA5 and ZA9), Enterococcus faecalis ZB5, Pseudomonas monteilii (ZA1 and ZAAgR1), and Acinetobacter junii ZB7, yielding cell-free extracts containing bioactive substances (42.95-47.44 mg/mL). MIC results showed that 85.7% of the strains inhibited S. aureus ATCC25923 and E. coli O157:H7, while MBC activity was confirmed for ZA1, ZB3, and ZAAgR1 at extract concentrations ≥10%. The biosafety profile revealed gamma-hemolysis and the absence of DNase activity across all strains, consistent with a non-virulent phenotype; however, widespread antibiotic resistance was detected. Application of cell-free extracts to mackerel fillets demonstrated that B. albus ZB3 reduced aerobic mesophile counts (6.19 vs. 6.46 log₁₀ CFU/g) at ambient temperature (27 ± 2 °C, 2 days), while P. monteilii ZAAgR1 was more effective under refrigeration (6.19 vs. 6.36 log₁₀ CFU/g, 7 ± 2 °C, 7 days). These findings identify bacteria associated with the Vichayal mangroves as promising candidates for fishery product preservation, pending comprehensive genomic and safety characterization.