Isolation and Functional Characterization of Lactic Acid Bacteria From Different Sources
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Date
2012
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Publisher
UAS, Dharwad
Abstract
An attempt was made to isolate lactic acid bacteria (LAB) from different
sources and characterize them in terms of agriculturally important functional
characteristics. Totally, 97 isolates of LAB were isolated from different sources such
as dairy products, rhizhosphere soils, fruits, vegetables, sprouted grains and fermented
foods. The isolates were characterized based on morphological and biochemical
characteristics. Cells varied in their shape like, rod and cocci. All the isolates were
Gram-positive, and negative for catalase. Based on acid and gas production tests, the
isolates were grouped into homo and heterofermentative LAB. Further, the isolates
were screened for beneficial characters. The results revealed that the highest indole
acetic acid production was recorded in the isolate LAB 63 (grapes) (73.65 μg/ml),
which was higher than the reference strain. The isolates were also tested for Psolubilization
activity. None of the isolates showed any P-solubilization activity. The
antagonistic activity of the LAB isolates against fungal pathogens like Aspergillus
flavus and Colletotrichum capscici was studied. None of the isolates inhibited the
growth of the fungal pathogens. The antibacterial activity of the LAB isolates against
bacterial pathogens like Xanthomonas axonopodis pv. punicae and Ralstonia
solanacerum was studied. The highest zone of inhibition of 17.25 dia. (in mm) of X.
axonopodis pv. punicae was recorded by the isolate LAB 92 (karadant) which was
higher than the reference strain. All the isolates were subjected for exopolysaccharide
(EPS) production. Although all the isolates produced EPS, LAB 67 (rhizhosphere soil
greengram) produced the highest amount (93.2 μg/ml) of exopolysaccharide. All the
isolates were examined for lactic acid production. The maximum lactic acid
production was observed in the isolate LAB 72 (rhizhosphere soil soybean) (8.2%),
which was significantly higher than that of the reference strain. All the isolates were
tested for methionine production qualitatively through thin layer chromatography
(TLC). Out of 97 isolates, only 12 isolates showed positive for methionine
production, as indicated by their Rf values. With regard to lactic acid production, the
isolate LAB 72 (rhizhosphere soil soybean) was more promising and has potential to
be utilized industrially after thorough investigations including optimization studies.