Isolation and Cultivation of a Xylanolytic Bacillus subtilis Extracted from the Gut of the Termite Reticulitermes santonensis

The aim of this work was the isolation of xylanolytic microorganisms from the
digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after
the hydrolysis of xylans can be further fermented to provide bioethanol. A xylanolytic strain
of Bacillus subtilis was isolated from the hindgut of the termite and displayed amylase and
xylanase activities. The bacterium was grown on media containing agricultural residues:
wheat bran, wheat distiller’s grains, and rapeseed oil cake. Wheat bran led to the highest
induction of xylanase activity, although the development of the strain was less fast than in
the other media. It was possible to reach maximal xylanase activities of 44.3, 33.5, and
29.1 I.U./ml in the media containing wheat bran, wheat distiller’s grains, and rapeseed oil
cake, respectively. Mass spectrometry identified a wide range of xylose oligomers,
highlighting an endoxylanase activity. The enzyme was stable up to 45 °C and displayed
an optimal pH close to 8.