Abstract
Many filamentous fungi are currently considered major plant pathogens in different countries around the world, posing a significant threat to global food security. Chemical fungicides used on crops have actually caused alarming problems for human health and seriously polluted our living environment. Using biological control agents is a potential scientific solution to replace chemical fungicides. Streptomyces flaveus is a potential biocontrol agent capable of producing chitinase enzymes that can be induced in media containing filamentous fungal cells. While the type of chitinase and the chitinase concentration in microbial preparations play an important role in preventing and treating fungal diseases in plants, it remains unclear whether the chitinases produced by this actinomycete are exochitinases or endochitinases. This study investigated the protein precipitation using saturated ammonium sulfate solution and chitinase separation using gel column chromatography. Chitinases in the chromatographic fractions were recognized using colloidal chitin agar and then identified using 4-nitrophenyl N-acetyl-ß-D-glucosaminide, 4-nitrophenyl N,N'-diacetyl-ß-D-chitobioside and 4-nitrophenyl ß-D-N,N',N''-triacetylchitotriose to release p-nitrophenol, which upon ionization in basic pH was measured colorimetrically at 405 nm. The results showed that S. flaveus chitinases were (-N-acetylglucosaminidase, chitobiosidase and endochitinase. These chitinases may be different in their capability of degrading fungal cell wall chitin. S. flaveus culture, thus optimized for high concentrations of these different chitinases, may be more effective when used to control the fungal growth. The chitinases identified in this study will be characterized and their individual concentrations will be optimized in subsequent studies.
