A Bibliometric Analysis and Review of Pullulan-Degrading Enzymes—Past and Current Trends

Abstract

Starch and pullulan degrading enzymes are essential industrial biocatalysts. Pullulan-degrading enzymes are grouped into pullulanases (types I and type II) and pullulan hydrolase (types I, II and III). Generally, these enzymes hydrolyse the α-1,6 glucosidic bonds (and α-1,4 for certain enzyme groups) of substrates and form reducing sugars such as glucose, maltose, maltotriose, panose or isopanose. This review covers two main aspects: (i) bibliometric analysis of publications and patents related to pullulan-degrading enzymes and (ii) biological aspects of free and immobilised pullulan-degrading enzymes and protein engineering. The collective data suggest that most publications involved researchers within the same institution or country in the past and current practice. Multi-national interaction shall be improved, especially in tapping the enzymes from unculturable prokaryotes. While the understanding of pullulanases may reach a certain extend of saturation, the discovery of pullulan hydrolases is still limited. In this report, we suggest readers consider using the next-generation sequencing technique to fill the gaps of finding more new sequences encoding pullulan-degrading enzymes to expand the knowledge body of this topic.

Glycogen degrading activities of catalytic domains of α-amylase and α-amylase-pullulanase enzymes conserved inGardnerellaspp. from the vaginal microbiome

“…This enzyme also included an N-terminal signal peptide domain, C-terminal transmembrane domain and a cell wall anchor LPxTG domain (Figure 3A). This multidomain enzyme is traditionally referred to as Type II amylopullulanase, however, recently it has been suggested that these enzymes are more appropriately classified as Type II α-amylase-pullulanase (27) and so the term ‘α-amylase-pullulanase’ is used throughout this paper. The domain organization of G. leopoldii NR017 α-amylase-pullulanase (RFT33565.1) is shown in Figure 3A.…”

“…Of the two extracellular glycosyl hydrolases identified by dbCAN2, the α-amylase-pullulanase was predicted to contain separate amylase and pullulanase catalytic domains; a conformation historically referred to as Type II amylopullulanase (35). With the availability of more sequence data, these enzymes are now classified as Type II α-amylase-pullulanase and they differ from amylopullulanases which have only one catalytic domain capable of hydrolyzing both a-1,4 and a-1,6 glycosidic bonds (23). The amylase and pullulanase domains of the identified Gardnerella α-amylase-pullulanase flanked 2 - 4 CBMs.…”

“…While type I pullulanases hydrolyze only a-1,6 glycosidic bonds, type II pullulanases are capable of hydrolyzing a-1,4 and a-1,6 glycosidic bonds. Amylopullulanase, a subtype of type II pullulanase, are mainly reported in thermophilic bacteria and have a single catalytic domain, whereas α-amylase-pullulanase has dual catalytic domains (a-amylase: for a-1,4 glycosidic bonds and pullulanase: for a-1,6 glycosidic bonds) and are reported in mesophilic bacteria (23). α-amylase-pullulanases have been characterized in Bifidobacterium breve UCC2003, B. adolescentis P2P3 (39, 41) and a few other species (23).…”

“…Amylopullulanase, a subtype of type II pullulanase, are mainly reported in thermophilic bacteria and have a single catalytic domain, whereas α-amylase-pullulanase has dual catalytic domains (a-amylase: for a-1,4 glycosidic bonds and pullulanase: for a-1,6 glycosidic bonds) and are reported in mesophilic bacteria (23). α-amylase-pullulanases have been characterized in Bifidobacterium breve UCC2003, B. adolescentis P2P3 (39, 41) and a few other species (23). Our results showed that the pullulanase domain of the G. leopoldii α-amylase-pullulanase hydrolyzes a-1,4 as well as a-1,6 glycosidic bonds, which to our knowledge has not been reported before.…”

Genomic Analysis Provides New Insights Into Biotechnological and Industrial Potential of Parageobacillus thermantarcticus M1

“…Pullulanase is known to play a crucial role in starch processing, leading to its widespread use in various applications in food, pharmaceutical, material, and bioenergy industries ( Pang et al, 2020 ). Moreover, the analysis indicated the presence of a gene encoding neopullulanase, a type I pullulan hydrolase ( Kahar et al, 2022 ). These pullulan degrading enzymes can hydrolyze the glycosidic bonds of pullulan and starch, and forms reducing sugars.…”