Purification and characterization of a novel a-D-glucosidase from Lactobacillus fermentum with unique substrate specificity towards resistant starch.

Resistant starch is not digestible in the small intestine
and is fermented by lactic acid bacteria in the
large intestine into short chain fatty acids, such as
acetate, propionate and butyrate, which result in
several health benefits in analogy with dietary fibre
components. The mode and mechanism of resistant
starch degradation by lactic acid bacteria
is still not understood. In the present study, we have
purified a-D-glucosidase from Lactobacillus
fermentum NCDC 156 by employing three sequential
steps i.e. ultra filtration, DEAE-cellulose and
Sephadex G-100 chromatographies. It was found
to be a monomeric protein (~50 kDa). The optimum
pH and temperature of this enzyme were found to
be 5.5 and 37∞C, respectively. Under optimised conditions
with p-nitrophenyl-D-glucopyranoside as the
substrate, the enzyme exhibited a Km of 0.97 mM.
Its activity was inhibited by Hg2+ and oxalic acid.
N-terminal blocked purified enzyme was subjected
to lysyl endopeptidase digestion and the resultant
peptides were subjected to BLAST analysis to understand
their homology with other a-Dglucosidases
from lactobacillus species.