Characterization of chitosanase of a deep biosphere Bacillus strain

A chitosanase of deep-biosphere Bacillus thuringiensis strain JAM-GG01 was purified. The optimal pH and temperature for the purified enzyme (Cho-GG) were about pH 6 and 60 °C, but Cho-GG was unexpectedly unstable under incubation at over 40 °C. This discrepancy between higher activity and lower stability in the same range of temperature was abolished by the addition of reaction products, chitotriose and chitotetraose. The Cho-GG gene was amplified by PCR and sequenced. The deduced amino acid sequence of Cho-GG showed more than 98% identity to those of other Bacillus enzymes belonging to GH family 8. Although Cho-GG did not show the definite characteristics of a sub-seafloor ectoenzyme, the thermal stability of many chitosanases of B. turingienesis and other related strains can be improved by adding chitotriose or chitotetraose.