.

Mondal and Aruna

Determination of antibacterial activity of bacteriocin obtained from Lactobacillus casie and

bacteriocins

Streptococcus species was maximum at pH 5 (Table 2).

Table 2 shows results of, antibacterial activity of

The plate counts were obtained on MRS agar for

bacteriocins of G1, G2, G3 and G4 isolated strains

strain isolates of G1, G2, G3 and G4. The counts

at pH 5 and pH 7. An agar well diffusion method were recorded in colony forming units per ml (CFU/

was used for testing the antagonistic property of

ml). No growth was detected on MRS agar at zero

bacteriocins with indicator organisms. Out of the

minutes. At 24hrs the microbial counts were 1.4 x 10 5 ,

six indicator organisms, the antibacterial activity

1.6 x 10 6 , 1.8 x 10 8 , 1.9 x 10 5 CFU/ml for G1, G2, G3 and

of bacteriocins was observed with Escherichia coli,

G4. At 72 hrs the microbial counts were 1.5 x 10 6 , 1.7 x

Pseudomonas aeruginosa, Staphylococcus aureus and

10 7 , 1.9 x 10 9 , 1.9 x 10 9 CFU/ml for G1, G2, G3 and G4.

Klebsiella sps. Inhibitory activity was not observed

against Proteus vulgaris and Bacillus subtilis. The

Biopreservative property of bacteriocin in apple juice

maximum inhibitory activity was shown by G2

against P.aeruginosa and least activity was seen

Table 3: At zero minutes - Biopreservative efficiency of

against E.coli. The maximum inhibition zone was

bacteriocin in apple juice

measured at pH 5 (20 mm) and pH 7 (21 mm) with

P. aeruginosa. . Therefore the effect of pH played

Strain

Bacteriocin concentration in ul

isolates

an important role in the antagonistic activity of

In absence of

25 ul

50 ul

100 ul

bacteriocins. Earlier, the bacteriocin produced by

bacteriocin

Lactococcus lactis D53 and 23 was active over a wide

pH range with the highest activity shown at low pH

range of 3–5 (Schillinger and Lucke, 1989), as was the

case with the bacteriocin from Pediococcus sp. (Jamuna

and Jeevaratnam, 2004). Earlier, the bacteriocin

(+): Indicates presence of microbial colonies, (-): Indicates

produced by a newly isolated Bacillus species

Absence of microbial colonies

strain 8A was found active over a pH range of 5–8

(Bizani and Brandelli, 2002). Liu and Hansen (1990)

The bacteriocins from isolates G1, G2, G3 and G4 were

reported that the Nisin is 228 times more soluble

tested for the preservative effect in apple juice (Table

at pH 2 than at pH 8. The antibacterial activity of

3) at zero time (immediately after the addition of

Table 2. Antibacterial Activity of Bacteriocins at pH 5 and pH 7

Strain

Zone of inhibition (mm)

isolates

E.coli

B.subtilis

P.aeruginos

P.vulgaris

S.aureus

Klebsiella sps

(-): Indicates absence of inhibition

124