Development of a novel enzymatic process for the production of cyclodextrins from raw corn starch

Abstract

Bacillus sp. BE101 was isolated from soil and used to obtain the cyclodextrin glycosyltransferase(E.C.3.2.1.19 CGTase). This enzyme has a high activity for producing cyclodextrins. Cyclodextrin glycosyltransferse was purified by acetone precipitation, DEAE-cellulose chromatography, and sephadex G-150 chromatography. The molecular weight of the enxyme was calculated 73,000 by SDS-PAGE. The optimum conditions for CGTase activity were pH 6.0$\sim$6.5 and temperature 45$^\circ$C. CGTase from Bacillus sp. BE101 synthesized mainly $\beta$-cyclodextrin from soluble starch; composition of $\alpha$-, $\beta$-, $\gamma$- cyclodextrin was 1:7:2. An increase in cyclodextrin production by organic solvents such as acetone, propanol, and ethanol was observed. The maximum increase was observed at 10\%(v/v) ethanol, and the enhancement of production yield was about 100\%. The cause of increase in production yield of cyclodextrins by ethanol was due to the increase in hydrosis of starch by CGTase in the presence of ethanol. A novel enzymatic process for the production of cyclodextrins from unliquefied starch was develpoed. Cyclodextrins were produced from unliquefied corn starch in an attrition bioreactor without liquefaction. The effect of milling media size and material on the performance of the attrition bioreactor was investigated, and operational parameters such as agitation speed, volume of milling media, ratio of enzyme to starch, and starch concentration were optimized. Optimum conditions were milling media glass beads of 3 mm diameter, agitation speed 300 rpm, volume of milling media 30\% (v/v), and ratio of enzyme to starch 500 units/g starch. The production yield of cyclodextrins reached 35\% (w/w) (53g/L) from 15\% (w/v) unliquefied corn starch at 24h under optimized conditions. Cyclodextrins were produced from unliquefied corn starch in the presence of water-miscible organic solvents using cyclodextrin glycosyltransferase (CGTase) in an attrition bioreactor. The pro...