Enzymatic hydrolysis of chitin in the production of oligosaccharides using Lecanicillium fungicola chitinases

Lecanicillium fungicola was selected among 15 strains as chitinase producer and it was used to obtain the crude enzyme (UFL) in submerged fermentation (SF) with added chitin. The UFL displayed at pH 6 and 40 degrees C the highest endochitinase (Endo) and N-acetylhexosaminidase (NHase) activities, 747 and 410 U/mg, respectively. Four bands of proteins with molecular weights of 123.1, 85.5, 33.1 and 23 kDa were detected in UFL by SDS-PAGE. In order to increase solubilities of the substrates, alpha and beta-chitins were treated with alkali; degrees of deacetylation (DD) were determined 55 and 50%, respectively. Thereafter, chitin hydrolysis with UFL was carried out at 40 degrees C and pH 5, Endo and NHase at these conditions were 619 and 355 U/mg of protein, respectively. The partial deacetylation as well as the use of acidified reaction media improved significantly the enzyme efficiency in terms of yields of chitin oligosaccharides produced and process time. The maximum chitin oligosaccharides concentration (P-max) obtained from alpha- and beta-deacetylated chitins were 2.77 and 4.44 mmol/l, respectively; whereas for alpha-chitin it was determined a very small amount of product (0.17 mmol/l). Despite of these results, the maximum production rate (V-max 0.0836 mmol/l h) for alpha-deacetylated chitin was significantly higher than beta-deacetylated chitin (0.0363 mmol/l h). (c) 2005 Elsevier Ltd. All rights reserved.