Biopreservative Efficacy of Bacteriocin GP1 of Lactobacillus rhamnosus GP1 on Stored Fish Filets.

The bacteriocin based strategy of biopreservation has got wide spread research interests in the recent past for their prospects in reducing usage of chemical preservatives. The bacteriocin GP1 with antibacterial activity and produced by Lactobacillus rhamnosus (L. rhamnosus) GP1 was tested for its effect on sensory (color, odor, and appearance), chemical (pH, Total Volatile Base-Nitrogen (TVB-N), Total Methyl Amine (TMA), Total Free Fatty Acid) and bacteriological (total bacterial count, count of Staphylococcus sp., Aeromonas sp., total coliform, Lactobacillus sp., Pseudomonas sp., and Vibrio sp.) quality attributes of fish filets stored at 4 and 0°C. The sensory attributes of the fish filets treated with the bacteriocin and control from 7 to 28 days of storage in both the storage temperatures varied significantly. The pH of the raw fish increased from the initial 6.8 to 7.91 and 7.43 for the control and bacteriocin GP1, respectively, at the end of storage period (28 days) when stored at 4°C. However, the pH showed a decreasing trend with the increase in period of storage for the samples stored at 0°C. The TVB-N content of the bacteriocin treated samples stored at 4°C remained within the limit of acceptability (35 mg/100 g) at the 21st day. The TMA level also remained within the acceptable limit of 10-15 mg/100 g at the 21st day in the case of bacteriocin-treated samples. The application of bacteriocin GP1 in the stored fish was effective in controlling the growth of coliforms, Aeromonas sp., Lactobacillus sp., and Vibrio sp. in the treated fish samples. The study concluded the prospects of bacteriocin GP1 as a biopreservative in storage of fish and fish products.

Diversity and antagonistic potential of marine microbes collected from south-west coast of India.

The diversity of some of the culturable microorganisms associated with marine flora and fauna collected off Vizhinjam and Mulloor coast of South India was evaluated and their bioactive production potential determined. From a total of 24 bacteria, 4 actinomycetes and 8 fungi isolated from diverse marine sources, five bacterial species-BLM3, BSP2, BCS1, BCS4 and BMA6 showed inhibitory activity against at least one of the tested pathogens viz., Klebsiella pneumonia KU1, Pseudomonas aeruginosa VL3, Salmonella enterica typhimurium MTCC 98, Escherichia coli MTCC 40, Micrococcus luteus MTCC 105, Staphylococcus simulans MTCC 3610, Proteus vulgaris MTCC 426, Vibrio fluvialis, Vibrio sp. P3a and Vibrio sp. P3b. The isolated actinomycetes and fungi did not produce significant inhibition zones against the tested pathogens; however, the macroalgal isolated actinomycetes strain AMA1 produced reddish pigment in Starch Casein medium which remained stable till the stationary phase of growth. The marine sediment isolate BCS4, identified as Bacillus sp. showed wide spectrum of activity against the tested Gram positive bacteria, S. simulans MTCC 3610 and Gram negative bacteria, Proteus vulgaris with zone of inhibitions of 25 and 11 mm respectively. Better extraction of the bioactive compound was obtained with ethyl acetate when compared with methanol, benzene and hexane and TLC analysis revealed the presence of an active compound. The 16SrRNA sequencing confirmed the potent strain belong to Bacillus sp. and hence designated Bacillus sp. BCS4.

Isolation of a bacteriocin-producing lactococcus lactis and application of its bacteriocin to manage spoilage bacteria in high-value marine fish under different storage temperatures.

The bacteriocins of lactic acid bacteria have considerable potential for biopreservation. The Lactococcus lactis strain PSY2 (GenBank account no. JF703669) isolated from the surface of marine perch Perca flavescens produced antibacterial activity against pathogenic and spoilage-causing Gram-positive and Gram-negative bacteria viz. Arthrobacter sp., Acinetobacter sp., Bacillus subtilis, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus and possessed broad inhibitory spectrum. The biopreservative efficacy of the bacteriocin PSY2 was evaluated using fillets of reef cod, Epinephelus diacanthus. The fillets (10 g) were sprayed with 2.0 ml of 1,600 AU/ml bacteriocin, wrapped and kept under different storage temperatures viz., 4, 0 and -18 °C. The biopreservative extended the shelf-life of fillets stored at 4 °C to >21 days as against <14 days observed in the untreated samples. The total count of spoilage bacteria was reduced by 2.5 logarithmic units in the treated sample during the 14th day of storage as against the control. Chemical analysis revealed a significant change (P < 0.05) in the pH value, free fatty acid (as % oleic acid), total volatile base nitrogen and total methyl amine content in the treated samples. The overall acceptability in terms of sensory attributes was significantly higher in the bacteriocin-treated samples stored for 21 days at 4 °C while the untreated samples became unacceptable by the 14th day. The biopreservative gave no significant effect at -18 °C. Thus, the bacteriocin derived from L. lactis PSY2 gave increased protection against spoilage bacteria and offers an alternative for the preservation of high-value sea foods.