Production of cyclodextrin glycosyltransferase by alkaliphilic Bacillus circulans in submerged and solid-state cultivation.

Cyclodextrin glycosyltransferase (CGTase; E.C. 2.4.1.19) is an industrially important enzyme, which is used to produce cyclodextrins (CDs). In this research, we report the use of experimental factorial design to find the best conditions of pH and temperature for CGTase production by Bacillus circulans var. alkalophilus. The optimized calculated values for the tested variables were, respectively, pH 9.7 and temperature 36 degrees C, with a CGTase activity of 615 U mL(-1). The CGTase production was further studied with the optimized process parameters on submerged cultivations (SC) and solid-state cultivations (SSC) using soybean industrial fibrous residue (SIFR). The maximum CGTase activity obtained on SC was 1,155 U mL(-1) under aerobic conditions. Cell growth and CGTase synthesis in SSC using SIFR as substrate was excellent, with CGTase activity of 32,776 U g ((SIFR))(-1). These results strongly support the use of SIFR for CGTase production since it is a non-expensive residue.