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Chapter V Discussion
was dependent on medium pH and incubation temperature, and is inversely correlated with
the specific bacteriocin production.
Leroy et al. (2003) reported in their study that at constant pH 6.5, high bacteriocin
activity was obtained in the temperature range of 20-30°C. Bacteriocin activity was only
found between pH 5.5 and 8.0. Kang and Lee (2005) who optimized bacteriocin produced
from E. faecium GM-1 reported the optimal production of bacteriocin, when the culture pH
was 6.0-6.5 and an incubation temperature of 35-40°C was provided.
The L. casei LAM-1 differed in behavioral pattern, i.e bacteriocin production
occurred in late stage of growth peaking after 18 h. In batch fermentation, L. casei LAM-1
produced bacteriocin at the mid log growth phase, and was maximum for upto 2,300 AU/ml
at the late stationary phase (Yoon et al., 2005).
Optimization of inoculum size revealed the maximum production of bacteriocin and
inhibition of sensitive strain to 1% for all of the isolated strains of L. casei (LAM-1). One
percent (1% v/v) inoculum was used in bacteriocin production experiments by many authors
(Leroy et al., 2003; Moreno et al., 2003; Achemchem et al., 2005).
Plasmid curing revealed that the bacteriocin production genes are mediated by
chromosomal DNA. These findings are in accordance with Franz et al. 1996 and Du Toit et
al. 2000, who reported that no plasmid could be isolated from L. casei LAM-1 indicating that
the gene for bacteriocin production are located on the chromosomal DNA.
The activity of bacteriocins produced by L. casei (LAM-1) was thermo-stable and
retained their activity even after the heat treatment at 121°C for 15 minutes. These results
were consistent with the stability of bacteriocins reported previously. Ying et al. (2011)
observed that pediocin LB-B1 to be relatively heat stable at moderate temperatures of 100 o C