ABSTRACT
Chitinase is one of the important enzymes as it is directly linked to Chitin that has wide applications in industrial, medical and commercial fields for its biocompatibility and biodegradability. Here, we report extracellular chitinase production by Streptomyces violascens NRRL B2700 under submerged fermentation condition. Chitinase production started after 10 h of incubation and reached to maximum level at 72 h of cultivation. Studies on the influence of additional carbon and nitrogen sources on chitinase production revealed that maltose, xylose, fructose, lactose, soybean meal and ammonium nitrate served as good carbon and nitrogen sources to enhance chitinase yield by 1.6 to 6 fold. Medium supplemented with 1% colloidal chitin produced high chitinase concentration (0.1714 U/mg). The enzyme chitinase was purified from the culture broth by 75% ammonium sulphate precipitation, DEAE-cellulose ion-exchange and sephadex G-100 gel filtration. The molecular mass of the purified chitinase was 65 kDa as estimated by SDS-PAGE. The apparent Michaelis constant (Km) and the maximum rate (Vmax) of the enzyme for colloidal chitin were 1.556 mg/mL and 2.680 µM/min/mg, respectively suggested high affinity towards chitin. Possibly, it is the first report on production of chitinase from S. violascens NRRL B2700. The findings were encouraging, especially for cost effective production, and further warrants media and purification optimization studies for enhanced yield.
ABSTRACT
El objetivo de este trabajo fue la selección de cepas nativas del género Bacillus con actividad quitinolíticay proteolítica, en suelo tropical en la costa de Oaxaca, México. Se aislaron 150 cepas, de las cuales 22fueron seleccionadas por presentar actividad quitinolítica y proteolítica. Dicha actividad se evaluó porla formación de halo de hidrólisis alrededor de la colonia en medios de cultivo suplementados con quitinacoloidal al 5% y leche descremada al 1% respectivamente. Las cepas LUM B001, B003, B013, B015y B065 presentaron mayor actividad quitinolítica y proteolítica, por lo que tienen el potencial para serevaluadas en control biológico de hongos fitopatógenos. Se encontró al género Bacillus distribuido ensuelos cultivados y no cultivados, no se encontraron diferencias estadísticas según el cultivo establecido(P<0,05), sin embargo se encontraron diferencias significativas (P<0,05) entre las zonas estudiadas, correspondiendolas menores recuperaciones de cepas a los terrenos del municipio de Tututepec, Oaxaca.
This work was aimed at selecting native strains from the Bacillus genus having chitinolytic and proteolytic activityfrom soil from the tropical coast of Oaxaca, Mexico. 150 strains were isolated, 22 of which were selectedas they presented chitinolytic and proteolytic activity. Such activity was assessed by the formation of a hydrolysishalo around the colony in culture media supplemented with 5% colloidal chitin and 1% skimmed milk.The LUM B001, B003, B013, B015 and B065-chitin strains presented higher quitinolytic and proteolytic activity,thereby having the potential for being evaluated in the biological control of phytopathogenic fungi. TheBacillus genus was found in cultivated and uncultivated soils; no statistical differences were found accordingto established crop (p <0.05); however, significant differences (p <0.05) were found between the areas beingstudied regarding the smaller amount of strains collected from land in the municipality of Tututepec, Oaxaca.