7-77: Screening of alkalophilic microorganisms producer of the cyclodextrin glucanotransferase (CGTase) from Cerrado areas

Cyclodextrins (CD) are cyclic molecules, composed of D-glucose units linked by α-1,4-glicosidic bonds. The most common cyclodextrin are the α-, β- and γ- types consisting of six, seven and eight glucose units, respectively. Cyclodextrins are produced by the action of a unique microbial enzyme, cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19), on starch substrate. These compounds are capable of forming inclusion complexes with a wide variety of chemical molecules. Because these inclusions the cyclodextrin presents a wide variety of use in food, pharmaceutical, cosmetic and toileters industries. In this study forty alcalophilic bacterial strains were isolated from samples of Cerrado vegetation soils, utilizing the CGTase selective medium of PARK et al.,1988 (1.0% soluble starch, 0.5% yeast extracts, 0.5% peptone, 0.1% K₂HPO₄, 0.02% MgSO₄.7H₂O, 0.03% phenolphthalein, 0.01% methyl orange, 1.5% agar, 1.0% Na₂CO₃, separately sterilized, pH10.0). The strains were cultivated until 72 hours in liquid medium, under agitation of 150 cycles per minute. The strains named LD-7, PA-5, LD-18.1, A-2-1 and LD-16 produced high levels of CGTase activity. The enzymatic assays were conducted with crude CGTase by dextrinizing and phenolphthalein methods. Time course of enzymatic production by these alkalophilic strains were determined at submerged fermentation using soluble starch as substrate. The highest yield to CGTase production was observed between 60-84 hours of fermentation. The enzymatic activities obtained by LD-7, PA-5 and LD-18.1 strains were similar that shown by Bacillus sp subgroup alcalophilus E16. The alkalophilic bacterium, Bacillus sp subgroup alcalophilus E16, was studied by this group in pervious studies.