Statistical optimization of solid state fermentation conditions for the enhanced production of thermoactive chitinases by mesophilic soil fungi using response surface methodology and their application in the reclamation of shrimp processing by-products

The mesophilic strains Aspergillus flavus CFR 10
and Fusarium oxysporum CFR 8 are potent producers of
extracellular thermoactive chitinases (endo-chitinase and β-
N-acetylhexosaminidase). Chitinases have a wide range of
applications in many areas including reclamation of seafood
processing chitinous by-products. In the present study, the
interactive effects of four fermentation conditions on
thermoactive chitinase production by solid state fermentation
(SSF) using commercial wheat bran (CWB) was investigated
employing response surface methodology (RSM). Further,
these chitinases were applied for the preparation of N-acetyl
chitooligosaccharides from shrimp chitin. Statistical optimization
resulted in the production (unit/g initial dry substrate,
U/g IDS) of 19.8 endo-chitinase and 649.0 β-N-acetylhexosaminidase
activity by A. flavus CFR 10, and 17.5 endochitinase
and 319.9 β-N-acetylhexosaminidase activity by F.
oxysporum CFR 8. Activity of crude endo-chitinase and β-
N-acetylhexosaminidase were found to be optimum at 62±
1 °C in a wide pH range. Hydrolysis of colloidal chitin with
crude chitinases produced the maximum N- acetyl
chitooligosaccharides yield (mmol/l) of 10.4±0.28 at 6 h
and 10.2±0.01 at 30 h post-reaction initiation, respectively,
by the enzymes of A. flavus CFR 10 and F. oxysporum CFR 8.
HPLC analysis revealed the presence of N- acetyl
chitooligosaccharides with N-acetyl chitotriose as the main
end product of the colloidal chitin hydrolysis. These results
indicate the potential of mesophilic A. flavus CFR 10 and F.
oxysporum CFR 8 in the production of thermoactive
chitinases employing the economical SSF process using
CWB as an ideal substrate, as well as the potential of these
chitinases for the reclamation of abundant shrimp processing
by-products and production of defined N- acetyl
chitooligosaccharides.