Date of Publication
8-2025
Document Type
Bachelor's Thesis
Degree Name
Bachelor of Science in Biology major in Medical Biology
Subject Categories
Aquaculture and Fisheries
College
College of Science
Department/Unit
Biology
Thesis Advisor
Biena Marie S. Joaquin
Defense Panel Chair
Florabelle D. Querubin
Defense Panel Member
Raymond Vincent F. Castillo
Jandeil B. Roperos
Abstract (English)
Milkfish (Chanos chanos) holds a vital role in Philippine aquaculture, contributing significantly to the nation's food security and economic prosperity. This study aimed to isolate and identify lactic acid bacteria (LAB) from the gut microbiota of cultured milkfish in brackish water using comprehensive characterization methods. Five milkfish samples were utilized for the initial isolation and identification of lactic acid bacteria present in the fish’s gut microbiome. Thirteen bacterial isolates underwent morphological, biochemical, and molecular analysis. Morphological examination revealed all isolates to be Gram-positive, cocci-shaped, and non-spore-forming, consistent with Lactic Acid Bacteria (LAB). Biochemical testing further aligned most isolates with Enterococcus species, exhibiting catalase-negative reactions, positive Methyl Red and Voges-Proskauer tests and negative indole and Citrate tests. In addition to biochemical testing, most isolates possessed proteolytic activity, a trait known in Enterococcus species. Molecular identification through 16S rRNA gene sequencing and BLAST analysis confirmed a strong predominance of Enterococcus species where 8 out of 13 isolates suggesting a lactic acid bacteria. Identified species included E. faecium, E. durans, and E. lactis, valued for their adaptability, tolerance to bile salts and low pH, adherence, and antimicrobial production, making them suitable lactic acid bacteria (LAB) candidates for enhanced growth and disease resistance. Two isolates also resembled uncultured bacteria, highlighting unexplored gut diversity. This approach provides strong evidence for the identification of these Enterococcus strains as LAB, suggesting their valuable application in sustainable aquaculture practices.
Abstract Format
html
Abstract (Filipino)
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Abstract Format
html
Language
English
Format
Electronic
Keywords
Milkfish; Lactic acid bacteria; Enterococcus; Brackish water fishes
Recommended Citation
Figueroa, C. G., Hizon, M. D., & Malandac, D. L. (2025). Isolation and identification of culturable lactic acid bacteria from gut microbiota of cultured milkfish (Chanos chanos) in brackish water. Retrieved from https://animorepository.dlsu.edu.ph/etdb_bio/138
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Embargo Period
8-15-2026
