Characterization of Bacteriocin from Indigenous Probiotic Lactobacillus with Emphasis on Broad Antibacterial Spectrum

Debashis Halder^1*, Manisha Mandal² and Shyamapada Mandal¹

¹University of GourBanga, India
²MGM Medical College and LSK Hospital, India

Background: Bacteriocins from lactic acid bacteria (LAB) have been excellent biotherapeutic agents to be used against pathogenic bacteria. However, the antibacterial activities of bacteriocins from indigenous LAB have not been validated scientifically from our part of the globe. The current study determines the antibacterial properties and characterizes bacteriocin isolated from local Lactobacillus strains.

Methods: Five commercial curd samples were processed microbiologically, using MRS media, in order to isolate LAB. The LAB was identified following conventionaland molecular methods, and the probiotic features were validated. Antagonistic properties of the isolated LAB were determined against the indicator pathogenic bacteria. Bacteriocin isolated from such probiotic strains were characterized through enzyme treatment, SDS-PAGE analysis and antibacterial property.

Result: The LAB isolates were identified as Lactobacillus Spp. and the isolates showed probiotic features, with tolerance to variable temperature (15°C and 42°C) and acid (pH 2-4), bile salt (0.125%, 0.25% and 0.50 %) and NaCl (2%, 4% and 6.5%). The LAB were γ-hemolytic and did not cause gelatin hydrolysis and mostly were sensitive to the antibiotics tested. Antagonistic activity test revelsa zone diameter of inhibition (ZDI) of 16-46 mm and 7-26 mm in agar-overlay and agar-well techniques, respectively, against the gram positive and gram negative indicator bacterial pathogens. The isolated bacteriocins from probiotic LAB were of 11-14 kDa. The bacteriocin showed antibacterial activity displaying ZDIs 15-30 mm and minimum inhibitory concentration (MICs) 7.12 – 483.12 µg/ml.

Conclusion: The lactobacilli were excellent probiotics, and the bacteriocin from the LAB had a broad spectrum of antibacterial activity. Thus, the indigenous Lactobacillus strains from local niches and the bacteriocin isolated from them might be used as biotherapeutic agents against bacterial infection.

Keywords: Lactic acid bacteria; probiotics; bacteriocin; antibacterial activity; biotherapeutic agent

Biography:
Debashis Halder is involved in Ph.D Research since last three years, under the supervision of Prof. Shyamapada Mandal, Laboratory of Microbiology and Experimental Medicine, Department of Zoology, University of GourBanga, India. He has worked on three projects and published five research articles in four reputed international journals. He is passionate to pursue a career in Medical Microbiology and truly attracted by Molecular Immunology and Phytomedicine. He wishes to continue as a scientist with a dynamic team of sincere researchers along with continuous research in his fields and extend his valuable service towards the scientific community with extensive research work.

Use of Encapsulated B. lactis through Freeze-Drying and Extrusion for Probiotic Yogurt Production

Konstantinos Alexias^1*, Georgia Frakolaki², Tryfon Kekes², Maria Katsouli², Virginia Giannou² and Konstantina Tzia²

¹Technical University of Delft, Netherlands
²National Technical University of Athens, Greece

Probiotic bacteria provide significant health benefits and can be incorporated into foods in order to develop functional products with particular commercial interest. According to IDF, the minimum concentration of probiotic bacteria in the final product should be 10⁷ cfu/g. However, the survival of probiotic bacteria and the maintenance of their functionality during food processing and preservation, and through their passage from the gastrointestinal tract must be ensured. Encapsulation technology ensures the viability and integrity of the cells. Various encapsulation methods have been reported in the literature.

In this study, the encapsulation of Bifidobacterium animalis subsp. Lactiswas achieved through freeze-drying and extrusionusing various encapsulating agents. The encapsulated by freeze-drying bacteria were incorporated in milk (10¹¹cfu/L), while the encapsulated by extrusion bacteria were used (7,5*10¹⁰cfu/L) along with the conventional starter culture. In both cases, the inoculated milk was fermented into yogurt at 45°C. The time required to reach pH=4.5 was recorded as fermentation time. After fermentation was completed the physicochemical (viscosity, texture) and microbiological characteristics of the samples were evaluated.

In the case of encapsulation by freeze-drying, cyclodextrin provided bacterial load values of 9*10⁵cfu/g and exhibited superior physicochemical characteristics amongst the encapsulating agents studied. In the case of encapsulation by extrusion, the highest bacterial load values in the final yogurt product were achieved by the mixtures of alginate-inulin and alginate-maltodextrin (1.54*10⁶cfu/g and 9.6*10⁵cfu/g respectively) as encapsulating agents. The alginate-inulin mixture also provided samples with satisfactory physicochemical characteristics as well.

Biography:
Konstantinos Alexias studied at the National Technical University of Athens, at the School of Chemical Engineering, where he completed his Diploma thesis under the supervision of Professor ConstantinaTzia entitled: “Encapsulation of probiotic bacteria and incorporation of the encapsulated products in yoghurt”. After his graduation on February 2018 (Diploma Grade: 8.01/10), he was offered a position at the Technical University of Delft, Netherlands as a Professional Doctorate in Engineering where he continue to work on up to now.

Indigenous Probiotic Lactobacillus Isolates Presenting Antibiotic like Activity against Human Pathogenic Bacteria

Debashis Halder^1*, Manisha Mandal², Shiv Sekhar Chatterjee³, Nishith Kumar Pal³ and Shyamapada Mandal¹

¹Department of Zoology, University of GourBanga, India
²Department of Physiology, MGM Medical College and LSK Hospital, India
³Department of Microbiology, NRS Medical College and Hospital, India

Background: Indigenous lactic acid bacteria are well known probiotics having antibacterialactivity against potentially pathogenic bacteria. This study aims to characterize the curd lactobacilli for their probiotic potentiality and antagonistic activity against clinical bacteria.

Methods: Four curd samples were processed microbiologically for the isolation of lactic acid bacteria (LAB). The LAB strains obtained were identified by conventional methods: cultural aspect, gram-staining, biochemical and sugar fermentation tests. The probiotic properties were justified with tolerance to low-pH, bile salt and sodium chloride, and the antagonistic activity of the lactobacilli against human pathogenic bacteria (Escherichia coli, Proteus vulgaris, Acinetobacterbaumannii and Salmonella entericaserovarTyphi) was assessed. Hemolytic activity and antibiotic susceptibility were determined for the lactobacilli isolates, and the cumulative probiotic potential (CPP) values were recorded.

Result: Four lactobacilli isolates, L. animalisLMEM6, L. plantarumLMEM7, L. acidophilusLMEM8 and L. rhamnosusLMEM9, procured from the curd samples, survived in low-pH and high bile salt conditions, and showed growth inhibitory activity against the indicator bacteria by agar-well (zone diameter of inhibition; ZDIs: 13.67 ±0.58–29.50 ±2.10 mm) and agar overlay (ZDIs: 11.33 ±0.58–35.67 ±2.52 mm) methods; the average growth inhibitory activity of lactobacilli ranged 233.34 ±45.54–280.56 ±83.67 AU/mL, against the test bacterial pathogens. All the lactobacilli were non-hemolytic and sensitive to most of the test antibiotics. The CPP values of the isolated LAB were recorded as 80–100%.

Conclusion: The curd lactobacilli procured might be used as the valid candidates of probiotics, and bio-therapeutics against bacterial infection to humans.

Keywords: lactobacilli; probiotics; antagonistic activity; indicator bacterial pathogens; antibioticsusceptibility; γ-hemolytic activity; cumulative probiotic potential

Biography:
Debashis Halder is involved in Ph.D Research since last three years, under the supervision of Prof. Shyamapada Mandal, Laboratory of Microbiology and Experimental Medicine, Department of Zoology, University of GourBanga, India. He has worked on three projects and published five research articles in four reputed international journals. He is passionate to pursue a career in Medical Microbiology and truly attracted by Molecular Immunology and Phytomedicine. He wishes to continue as a scientist with a dynamic team of sincere researchers along with continuous research in his fields and extend his valuable service towards the scientific community with extensive research work.