New thermostable α-amylase-like pullulanase from thermophilic Bacillus sp. 3183

Abstract

The utility of extracellular pullulanase preparation from thermophilic Bacillus sp. 3183 was evaluated. It (3.2 U g −1 DS) did not increase the saccharification yield of glucose from liquefied starch (35%, w/w, maltodextrin DE 10) with glucoamylase (12.5 U g −1 DS) and also did not decrease the reaction time. However, the enzyme preparation itself was sufficient to saccharify the liquefied starch into mainly DP1 to DP4. The pullulanase and α-amylase were separated and the pullulanase was purified to homogeneity from the culture supernatant by ammonium sulfate treatment, DEAE-Sepharose CL-6B, S-Sepharose, and Octyl-Sepharose column chromatography and finally by preparative disc gel electrophoresis. The purified enzyme cleaved pullulan in α-1,6 linkages making only maltotriose, but it cleaved starch in α-1,4 linkages producing various saccharides (DP2 and higher). The pullulanase of thermophilic Bacillus sp. is a new type of enzyme having an abnormal ability to cleave starch readily at α-1,4 linkages.