Authors : Alforque, Really Grace; Alforque, Risen Hope; Lacierda, Matt Gabriel; Tan, Faye Marie

Volume/Issue : Volume 11 - 2026, Issue 4 - April

Google Scholar : https://tinyurl.com/3yscar87

Scribd : https://tinyurl.com/esuj9st4

DOI : https://doi.org/10.38124/ijisrt/26apr1108

Note : A published paper may take 4-5 working days from the publication date to appear in PlumX Metrics, Semantic Scholar, and ResearchGate.

Abstract : The growing demand for biologically derived antioxidants has intensified interest in microorganisms as alternative sources of functional metabolites. This study evaluated the antioxidant potential of bacteria isolated from citrus fruit peels, specifically calamansi (Citrus microcarpa), orange (Citrus sinensis), and lemon (Citrus limon). Bacterial isolates were obtained using standard microbiological procedures and characterized through Gram staining, catalase, and oxidase tests. Cell-free supernatants were prepared and assessed for antioxidant activity using the 2,2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Among the citrus fruits examined, only calamansi yielded viable bacterial isolates, which were presumptively identified as Lactobacillus spp. This observation highlights Citrus microcarpa as a potentially underexplored reservoir of antioxidant-producing bacteria. The bacterial supernatant demonstrated statistically significant, concentration-dependent DPPH radical scavenging activity (p < 0.05), indicating the production of metabolites with antioxidant properties. These findings suggest that calamansi-derived Lactobacillus spp. may serve as promising natural antioxidant sources with potential applications in food, pharmaceutical, and biotechnological industries. Further molecular identification and expanded antioxidant profiling are recommended to support future functional investigations.

Keywords : Citrus Microcarpa; Lactobacillus Spp.; Lactic Acid Bacteria; Microbial Antioxidants; DPPH Radical Scavenging; Bioactive Metabolites.

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