A.K. BEENAJITHU RAPPAI2023-06-172023-06-172022-02-11https://krishikosh.egranth.ac.in/handle/1/5810197631Submitted in partial fulfillment of the requirement for the degree of Master of Technology in Dairy MicrobiologyA potentially probiotic lactic acid bacterium was isolated from human breast milk. Based on biochemical characterization and 16SrRNA sequencing, the isolate was identified as Pediococcus pentosaceus DM101, the sequence of which is deposited in NCBI with accession number MK774704. Acid and bile tolerance studies indicated that Pediococcus pentosaceus DM101 can withstand pH 3.0 and 0.6 % (w/v) bile salt for four hours. The isolate exhibited an auto-aggregation value of 67.9±0.74% and a cell surface hydrophobicity values of 60.7±0.67% with xylene signifying the good adhesion potential for the isolate. Inability to cause haemolysis and liquefy gelatin suggests the possible absence of virulence factors. Antibiogram revealed the isolate to be resistant to Vancomycin, Methicillin, Bacitracin, and Cephalosporin group of antibiotics. Congo red assay confirmed the exopolysaccharide (EPS) producing nature of the isolate. DPPH(2,2-diphenyl picrylhydrazyl) assay of the cell pellet and cell-free supernatant revealed an IC 50 value of 61.57 and 20.78mg/ml, endorsing its radical scavenging potential. Based on survival per cent, encapsulation by extrusion was optimized with 2.0% sodium alginate as gelling agent, 0.1 M CaCl2 as hardening solution and gelling time 20 minutes. The alginate beads so obtained were characterized in terms of swelling ratio and dissolution behavior. The alkaline pH 8.0 facilitated the release of bioactive components by 4h, whereas acidic pH 2.0 did not release the contents even after 8h. When exposed to simulated gastrointestinal conditions, the survival rates for encapsulated and non-encapsulated cells were 86.11% and 15.86% respectively. On 60th day of storage, log reduction of viable cells in encapsulated form at 4°C and -18°C was 1.10 and 3.30 respectively. For the same time period, corresponding values were 9.17 and 9.30 for non-encapsulated cells. The observations endorse encapsulation as an effective tool for sustaining viability when exposed to challenging environment.EnglishThesis