A novel maltohexaose-forming ?-amylase from Bacillus caldovelox: patterns and mechanisms of action

Abstract

The acidophilic, thermostable a-amylase of Bacillus caldovelox displays a unique end-product profile and action pattern on starch. Maltohexaose is preferentially produced, with a maximum yield of 40-44% (w/w) from 35% (w/v) starch and dextrins (DE 9 and DE 18). Maltohexaose, the initial product of 1% (w/v) starch and 35% (w/v) dextrin (DE 42) hydrolysis, is subsequently converted into maltopentaose with a maximum yield of 30% (w/w). This reaction does not involve glucose production. Substrates were hydrolysed from the non-reducing end by either a uni-or multimolecular mechanism, with no hydrolysis of maltohexaose or smaller sugars. The Km values for soluble starch and maltoheptaose were 4.68 mg/ml and 2.13 x 10 -2 M, respectively. (Hayashi et al. 1988) and a mutant Klebsiella pneumoniae (Monma et al. 1983) that produce maltohexaose in yields of 25-40% (w/w). However, with the exception of B. amyloliquefaciens, maltohexaose is only an initial hydrolysis product and is subsequently broken down to smaller saccharides. In this respect the a-amylase of B. caldovelox produces a unique and particularly high yield of maltohexaose from starch, 44% (w/w), and cannot hydrolyse maltohexaose (Bealin-Kelly et al. 1990). Studies have shown that this high yield of maltohexaose is due to the selective hydrolysis of only larger oligosaccharides and preferential cleavage of maltohexaose from the non-reducing end of the substrate, linked to the inability of the enzyme to hydrolyse any maltooligosaccharide of less than seven glucose units.

CLONING AND SEQUENCING OF THE α-AMYLASE GENE FROMBACILLUS SUBTILISUS116 STRAIN ENCODING AN ENZYME CLOSELY IDENTICAL TO THAT FROMBACILLUS AMYLOLIQUEFACIENSBUT DISTINCT IN THERMAL STABILITY

“…As for the more selective and multispecific amylases, they have rather become more widely used in bakery industry, particularly for their limited hydrolytic action on starch (Champenois et al 1999;Van Der Maaler et al 2002). Finally, yet more importantly, atypical amylases have become commonly used in the production of the maltodextrins with high content in specific maltosaccharides (Takasaki 1982;Yoshigi et al 1985;Hayashi et al 1988;Fogarty et al 1991;Nigam and Singh 1995;Shaw et al 1995;Nakano et al 1998;Marchal et al 1999;Ben Ali et al 2001).…”

Cloning of Novel Maltooligosaccharide-Producing Amylases as Antistaling Agents for Bread

“…The manufacture of maltooligosaccharides larger than maltotriose had been very difficult, but the discovery of microbial enzymes that produce specific maltooligosaccharides has made it possible to produce syrups containing various maltooligosaccharides (Okada and Nakakuki, 1992). Many amylases producing specific maltooligosaccharide were found: maltohexaose-producing amylases from Bacillus circulans G-6 (Takasaki, 1982) and Bacillus caldovelox (Fogarty et al, 1991); maltopentaose-producing amylases from Pseudomonas sp. (Shida et al, 1992); maltotetraose-producing amylases from Bacillus sp.…”

Hybrid Bacillus amyloliquefaciens X Bacillus licheniformisα‐Amylases

“…The accumulation of Glc, among the hydrolysis products of soluble starch is one of the characteristics of the AmyBA enzyme, while AmyLI belongs in this respect to the a-amylases that hydrolyse Glc, (Fogarty, 1983;Fogarty et al, 1991). We made use of that character in order to compare the hybrid enzymes for either Glc, hydrolysis or accumulation.…”