Aquaculture is a highly productive and fast-growing agricultural sector. The occurrence of epidemic or sporadic disease outbreak is a major limiting factor in this sector, thus better alternatives are the need of the hour. Use of indigenous probiotics is a promising strategy to control infectious diseases. Thus, the present study was aimed to screen and characterize potent indigenous probiotics from marine fish,
Moolgarda seheli,
towards enhancing sustainable aquaculture production. Totally 347 bacterial isolates were obtained from
M. seheli
gastrointestinal tract, out of these, four isolates (KAF121, 124, 135, 136) were confirmed as potent probiotics in terms of biosafety, highly resistant to acidic pH, gastric juice, bile salt, high hydrophobicity to solvents, auto and co-aggregation potential. These four isolates also exhibited virtuous antioxidant activity. Further the isolates, KAF124 and 135 proved their efficiency in growth and survival of fish after challenged againt
Aeromonas hydrophila
. The isolates were identified based on their 16S rRNA gene sequence and the data were submitted to Genbank as
Pseudomonas aeruginosa
KAF121 (MH393516)
, Bacillus cereus
KAF124 (MH393226)
, Bacillus thuringiensis
KAF135 (MH393230)
,
and
Pseudomonas otitidis
KAF136 (MH393230). The results conclude that two isolates, KAF124 and KAF135 are highly safe and potent probiotics which are first time isolated from the marine fish
M. seheli.
The two
Bacillus
strains could be used as better alternatives to antibiotics and other chemical-based drugs to prevent/control infectious diseases in aquaculture.
This study aims to explore novel lactic acid bacteria (LAB) from breast‐fed infants' faeces towards characterizing their antimicrobial compound, bacteriocin. The LAB, Lacticaseibacillus paracasei F9‐02 showed strong antimicrobial activity against clinical pathogens. Their proteinaceous nature was confirmed as the activity was completely abolished when treated with proteinaceous enzymes and retained during neutral pH and catalase treatment. The purified bacteriocin showed antimicrobial activity at the minimum inhibitory concentration (MIC) value of 7.56 μg/ml against vancomycin‐resistant Enterococcus sp. [vancomycin‐resistant enterococcal (VRE)], and methicillin‐resistant Staphylococcus aureus (MRSA), 15.13 μg/ml against Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype typhi and 30.25 μg/ml against Shigella flexneri. Present study also proved the bactericidal, non‐cytotoxic and non‐hemolytic nature of bacteriocin. Additionally, bacteriocin retained their stability under various physico‐chemical conditions, broad range of pH (2–10), temperature (40–121°C), enzymes (amylase, lipase and lysozyme), surfactants [Tween‐20, 80, 100 and sodium dodecyl sulfate (SDS)], metal ions (CaCl2, FeSO4, ZnSO4, MgSO4, MnSO4, CuCl2) and NaCl (2%–8%). The molecular weight of bacteriocin (~28 kDa) was determined by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), functional and active groups were assessed by Fourier Transform‐Infrared (FT‐IR). To our knowledge, this is the first study reporting L. paracasei from breast‐fed infants' faeces and assessing their antimicrobial compound, bacteriocin. The study results furnish the essential features to confirm the therapeutic potential of L. paracasei F9‐02 bacteriocin.
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