Enhanced degradation of alpha-chitin materials prepared from shrimp processing byproduct and production of N-acetyl-D-glucosamine by thermoactive chitinases from soil mesophilic fungi.

Soil isolates of mesophilic Penicillium
monoverticillium CFR 2, Aspergillus flavus CFR 10
and Fusarium oxysporum CFR 8 were cultivated in
solid state fermentation (SSF) using wheat bran solid
medium supplemented with a-chitin in order to
produce chitinolytic enzyme. Under SSF cultivation,
maximum enzymes (U/g IDS) production was 41.0
(endo-chitinase) and 195.4 (b-N-acetylhexosaminidase)
by P. monoverticillium, 26.8 (endo-chitinase)
and 222.1 (b-N-acetylhexosaminidase) by A. flavus
and 13.3 (endo-chitinase) and 168.3 (b-N-acetylhexosaminidase)
by F. oxysporum after 166 h of
incubation. The crude endo-chitinase and b-N-acetylhexosaminidase
derived from A. flavus and F. oxysporum
revealed optimum temperature at 62 ± 1�C, but
the enzymes from P. monoverticillium showed optimum
temperature at 52 ± 1�C for maximum activity.
Several fold increase in endo-chitinase and b-Nacetylhexosaminidase
activities in the crude enzymes
preparation was achieved after concentrating with
polyethylene glycol. The concentrated crude chitinases
from P. monoverticillium, A. flavus and F. oxysporum,
respectively yielded 95.6, 96.6 and 96.1 mmol/l of
N-acetyl-D-glucosamine (GlcNAc) in 48 h of reaction
from colloidal chitin. While, the crude enzyme
preparations of P. monoverticillium, A. flavus and
F. oxysporum produced 10.11, 6.85 and 10.7 mmol/l of
GlcNAc respectively, in 48 h of reaction from crystalline
a-chitin. HPLC analysis of colloidal chitin
hydrolysates prepared with crude chitinases derived
from P. monoverticillium, A. flavus and F. oxysporum
revealed that the major reaction product was monomeric
GlcNAc (*80%) and a small amount of
(GlcNAc)4 (*20%), indicating the potential of these
enzymes for efficient production of GlcNAc from
a-chitin.