Purification, characterization and application of thermostable amylopullulanase from Streptomyces erumpens MTCC 7317 under submerged fermentation

An Alkalothermophilic Amylopullulanase from the Yeast Clavispora lusitaniae ABS7: Purification, Characterization and Potential Application in Laundry Detergent

In the present study, α-amylase and pullulanase from Clavispora lusitaniae ABS7 isolated from wheat seeds were studied. The gel filtration and ion-exchange chromatography revealed the presence of α-amylase and pullulanase activities in the same fraction with yields of 23.88% and 21.11%, respectively. SDS-PAGE showed a single band (75 kDa), which had both α-amylase (independent of Ca2+) and pullulanase (a calcium metalloenzyme) activities. The products of the enzymatic reaction on pullulan were glucose, maltose, and maltotriose, whereas the conversion of starch produced glucose and maltose. The α-amylase and pullulanase had pH optima at 9 and temperature optima at 75 and 80 °C, respectively. After heat treatment at 100 °C for 180 min, the pullulanase retained 42% of its initial activity, while α-amylase maintained only 38.6%. The cations Zn2+, Cu2+, Na+, and Mn2+ increased the α-amylase activity. Other cations Hg2+, Mg2+, and Ca2+ were stimulators of pullulanase. Urea and Tween 80 inhibited both enzymes, whereas EDTA only inhibited pullulanase. In addition, the amylopullulanase retained its activity in the presence of various commercial laundry detergents. The performance of the alcalothermostable enzyme of Clavispora lusitaniae ABS7 qualified it for the industrial use, particularly in detergents, since it had demonstrated an excellent stability and compatibility with the commercial laundry detergents.

Microbial starch debranching enzymes: Developments and applications

Starch debranching enzymes (SDBEs) hydrolyze the α-1,6 glycosidic bonds in polysaccharides such as starch, amylopectin, pullulan and glycogen. SDBEs are also important enzymes for the preparation of sugar syrup, resistant starch and cyclodextrin. As the synergistic catalysis of SDBEs and other starch-acting hydrolases can effectively improve the raw material utilization and production efficiency during starch processing steps such as saccharification and modification, they have attracted substantial research interest in the past decades. The substrate specificities of the two major members of SDBEs, pullulanases and isoamylases, are quite different. Pullulanases generally require at least two α-1,4 linked glucose units existing on both sugar chains linked by the α-1,6 bond, while isoamylases require at least three units of α-1,4 linked glucose. SDBEs mainly belong to glycoside hydrolase (GH) family 13 and 57. Except for GH57 type II pullulanse, GH13 pullulanases and isoamylases share plenty of similarities in sequence and structure of the core catalytic domains. However, the N-terminal domains, which might be one of the determinants contributing to the substrate binding of SDBEs, are distinct in different enzymes. In order to overcome the current defects of SDBEs in catalytic efficiency, thermostability and expression level, great efforts have been made to develop effective enzyme engineering and fermentation strategies. Herein, the diverse biochemical properties and distinct features in the sequence and structure of pullulanase and isoamylase from different sources are summarized. Up-to-date developments in the enzyme engineering, heterologous production and industrial applications of SDBEs is also reviewed. Finally, research perspective which could help understanding and broadening the applications of SDBEs are provided.

Biotechnology and bioengineering of pullulanase: state of the art and perspectives

Pullulanase (EC 3.2.1.41) is a starch-debranching enzyme in the α-amylase family and specifically cleaves α-1,6-glycosidic linkages in starch-type polysaccharides, such as pullulan, β-limited dextrin, glycogen, and amylopectin. It plays a key role in debranching and hydrolyzing starch completely, thus bring improved product quality, increased productivity, and reduced production cost in producing resistant starch, sugar syrup, and beer. Plenty of researches have been made with respects to the discovery of either thermophilic or mesophilic pullulanases, however, few examples meet the demand of industrial application. This review presents the progress made in the recent years from the first aspect of characteristics of pullulanases. The heterologous expression of pullulanases in different microbial hosts and the methods used to improve the expression effectiveness and the regulation of enzyme production are also described. Then, the function evolution of pullulanases from a protein engineering view is discussed. In addition, the immobilization strategy using novel materials is introduced to improve the recyclability of pullulanases. At the same time, we indicate the trends in the future research to facilitate the industrial application of pullulanases.