Bacillus lehensis-an alkali-tolerant bacterium isolated from cassava starch wastewater: optimization of parameters for cyclodextrin glycosyltransferase production

Abstract

A Gram-positive, endospore-forming, alkali-tolerant bacterial strain, designated CGII, was isolated from the wastewater of a cassava flour mill in the state of São Paulo, Brazil and submitted to phylogenetic studies and biochemical tests. The 16S rRNA gene sequence indicated the highest degree of genomic similarity with MLB2 strains of Bacillus lehensis (100%). A two-level central composite rotatable design was then employed to optimize the medium composition and culture conditions for the production of the enzyme cyclodextrin glycosyltransferase (CGTase) in shake-flask and bioreactors. CCTase activity was measured under different production conditions, such as culture medium, agitation and aeration. Highest enzyme production by B. lehensis was achieved in 72 h with a maximal activity of 134.05 U mL(-1). The response surface method demonstrated that the proposed model achieved a good level of agreement with experimental data, with a correlation coefficient of 0.910, thereby confirming the adequate reliability of the model.