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.