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

Expression optimization and characterization of a novel amylopullulanase from the thermophilic Cohnella sp. A01

Amylopullulanase (EC. 3.2.1.41/1) is an enzyme that hydrolyzes starch and pullulan, capable of breaking (4 → 1)-α and (6 → 1)-α bonds in starch. Here, the Amy1136 gene (2166 base pairs) from the thermophilic bacterium Cohnella sp. A01 was cloned into the expression vector pET-26b(+) and expressed in Escherichia coli BL21. The enzyme was purified using heat shock at 90 °C for 15 min. The expression optimization of Amy1136 was performed using Plackett-Burman and Box-Behnken design as follows: temperature of 26.7 °C, rotational speed of 180 rpm, and bacterial population of 1.25. The Amy1136 displayed the highest activity at a temperature of 50 °C (on pullulan) and a pH of 8.0 (on starch) and, also exhibited stability at high temperatures (90 °C) and over a range of pH values. Ag+ significantly increased enzyme activity, while Co2+ completely inhibited amylase activity. The enzyme was found to be calcium-independent. The kinetic parameters Km, Vmax, kcat, and kcat/Km for amylase activity were 2.4 mg/mL, 38.650 μmol min-1 mg-1, 38.1129 S-1, and 0.09269 S-1mg mL-1, respectively, and for pullulanase activity were 173.1 mg/mL, 59.337 μmol min-1 mg-1, 1.586 S-1, and 1.78338 S-1mg mL-1, respectively. The thermodynamic parameters Kin, t1/2, Ea#, ΔH#, ΔG# and ΔS# were calculated equal to 0.20 × 10-2 (m-1), 462.09 (min), 16.87 (kJ/mol), 14.18 (kJ/mol), 47.34 (kJ/mol) and 102.60 (Jmol K-1), respectively. The stability of Amy1136 under high temperature, acidic and alkaline pH, surfactants, organic solvents, and calcium independence, suggests its suitability for industrial applications.

Genomic and functional insights of a mucin foraging Rhodopirellula halodulae sp. nov

Nine novel strains were obtained from various algal and seagrass samples. The analysis of the 16S rRNA gene-based phylogenetic tree revealed monophyletic placement of all novel strains within the Rhodopirellula genus. The type strain was identified as JC737T, which shared 99.1 % 16S rRNA gene sequence identity with Rhodopirellula baltica SH1T, while strain JC740 was designated as an additional strain. The genome sizes of strains JC737T and JC740 were 6.6 and 6.7 Mb, respectively, and the G + C content was 56.2 %. The strains cladded distinctly in the phylogenomic tree, and the ANI and dDDH values of the strain JC737T were 75.8-76.1 % and 20.8-21.3 %, respectively, in comparison to other Rhodopirellula members. The strain demonstrated a versatile degradation capability, exhibiting a diverse array of complex polysaccharides, including mucin which had not been previously identified within the members of the phylum Planctomycetota. The phylogenomic, pan-genomic, morphological, physiological, and genomic characterization of the strain lead to the proposal to describe the strain as Rhodopirellula halodulae sp. nov.

Pullulan-1-Ethyl-3-Methylimidazolium Tetrafluoroborate Composite as a Water-Soluble Active Component of a Vibration Sensor

In recent years, the issue of electronic waste production has gained significant attention. To mitigate the environmental impact of e-waste, one approach under consideration involves the development of biodegradable electronic devices or devices that dissolve in the environment at the end of their life cycle. This study presents results related to the creation of a sensor that effectively addresses both criteria. The device was constructed using a composite material formed by impregnating a pullulan membrane (a biodegradable water-soluble biopolymer) with 1-Ethyl-3-Methylimidazolium tetrafluoroborate (a water-soluble ionic liquid) and coating the product with a conductive silver-based varnish. Capitalizing on the piezoionic effect, the device has demonstrated functionality as a vibration sensor with a sensitivity of approximately 5.5 × 10-5 V/mm and a resolution of about 1 mm. The novelty of this study lies in the unique combination of materials. Unlike the use of piezoelectric materials, this combination allows for the production of a device that does not require an external potential difference generator to function properly as a sensor. Furthermore, the combination of a biopolymer, such as pullulan, and an ionic liquid, both readily soluble in water, in creating an active electronic component represents an innovation in the field of vibration sensors.

Isolation, characterization, and cloning of thermostable pullulanase from Geobacillus stearothermophilus ADM-11

This study aimed to identify thermo-stable pullulanase-producing bacteria in soil samples of potato fields and food-producing companies. Pullulan agar medium was used to screen 17 bacterial strains, which were incubated at 65 °C. The isolate with the maximum activity (375U/ml) was selected and recognized as Geobacillus stearothermophilus ADM-11 by morphological, biochemical characterization, and 16S rRNA gene sequencing. The pullulanase production required optimum pH of 7 and temperature of 75 °C, respectively. The electrophoresis of purified pullulanase on SDS-polyacrylamide gel revealed 83 kDa of a molecular weight that is active at 70 °C and pH 7.0. It was also stable at 90 °C but its activity was decreased by 10 % at 100 °C. The action of pullulanase was increased and stabilized by Ca+2 among the metal ions. Beta and gamma-cyclodextrins inhibited enzyme activity while ethylenediaminetetraacetate (EDTA) and phenylmethylsulfonyl fluoride (PMSF) have no significant effect on pullulanase activity. A full-length pullulanase gene was amplified from G. stearothermophilus ADM-11 using genomic DNA 2.1 kb of PCR product which was then purified and ligated in the cloning vector pTZ57R using the TA cloning technique. Colony PCR confirmed cloning on the positive clones after the pullulanase gene had been ligated and subjected to restriction digestion. It revealed 74 % similarity with the reported pullulanase gene from Geobacillus sp. 44C. The thermostability of pullulanase and its ability to degrade raw pullulan may therefore have wide-scale applications in starch processing, the detergent business, and new biotechnological applications.

Pullulanase: unleashing the power of enzyme with a promising future in the food industry

Pullulanases are the most important industrial group of enzymes in family 13 glycosyl hydrolases. They hydrolyze either α-1,6 and α-1,4 or both glycosidic bonds in pullulan as well as other carbohydrates to produce glucose, maltose, and maltotriose syrups, which have important uses in food and other related sectors. However, very less reports are available on pullulanase production from native strains because of low yield issues. In line with the increasing demands for pullulanase, it has become important to search for novel pullulanase-producing microorganisms with high yields. Moreover, high production costs and low yield are major limitations in the industrial production of pullulanase enzymes. The production cost of pullulanase by using the solid-state fermentation (SSF) process can be minimized by selecting agro-industrial waste. This review summarizes the types, sources, production strategies, and potential applications of pullulanase in different food and other related industries. Researchers should focus on fungal strains producing pullulanase for better yield and low production costs by using agro-waste. It will prove a better enzyme in different food processing industries and will surely reduce the cost of products.

Thermostable enzyme research advances: a bibliometric analysis

Thermostable enzymes are enzymes that can withstand elevated temperatures as high as 50 °C without altering their structure or distinctive features. The potential of thermostable enzymes to increase the conversion rate at high temperature has been identified as a key factor in enhancing the efficiency of industrial operations. Performing procedures at higher temperatures with thermostable enzymes minimises the risk of microbial contamination, which is one of the most significant benefits. In addition, it helps reduce substrate viscosity, improve transfer speeds, and increase solubility during reaction operations. Thermostable enzymes offer enormous industrial potential as biocatalysts, especially cellulase and xylanase, which have garnered considerable amount of interest for biodegradation and biofuel applications. As the usage of enzymes becomes more common, a range of performance-enhancing applications are being explored. This article offers a bibliometric evaluation of thermostable enzymes. Scopus databases were searched for scientific articles. The findings indicated that thermostable enzymes are widely employed in biodegradation as well as in biofuel and biomass production. Japan, the United States, China, and India, as along with the institutions affiliated with these nations, stand out as the academically most productive in the field of thermostable enzymes. This study's analysis exposed a vast number of published papers that demonstrate the industrial potential of thermostable enzymes. These results highlight the significance of thermostable enzyme research for a variety of applications.

Glycogen-Degrading Activities of Catalytic Domains of α-Amylase and α-Amylase-Pullulanase Enzymes Conserved in Gardnerella spp. from the Vaginal Microbiome

Gardnerella spp. are associated with bacterial vaginosis in which normally dominant lactobacilli are replaced with facultative and anaerobic bacteria, including Gardnerella spp. Co-occurrence of multiple species of Gardnerella is common in the vagina, and competition for nutrients such as glycogen likely contributes to the differential abundances of Gardnerella spp. Glycogen must be digested into smaller components for uptake, a process that depends on the combined action of glycogen-degrading enzymes. In this study, the ability of culture supernatants of 15 isolates of Gardnerella spp. to produce glucose, maltose, maltotriose, and maltotetraose from glycogen was demonstrated. Carbohydrate-active enzymes (CAZymes) were identified bioinformatically in Gardnerella proteomes using dbCAN2. Identified proteins included a single-domain α-amylase (EC 3.2.1.1) (encoded by all 15 isolates) and an α-amylase-pullulanase (EC 3.2.1.41) containing amylase, carbohydrate binding modules, and pullulanase domains (14/15 isolates). To verify the sequence-based functional predictions, the amylase and pullulanase domains of the α-amylase-pullulanase and the single-domain α-amylase were each produced in Escherichia coli. The α-amylase domain from the α-amylase-pullulanase released maltose, maltotriose, and maltotetraose from glycogen, and the pullulanase domain released maltotriose from pullulan and maltose from glycogen, demonstrating that the Gardnerella α-amylase-pullulanase is capable of hydrolyzing α-1,4 and α-1,6 glycosidic bonds. Similarly, the single-domain α-amylase protein also produced maltose, maltotriose, and maltotetraose from glycogen. Our findings show that Gardnerella spp. produce extracellular amylase enzymes as "public goods" that can digest glycogen into maltose, maltotriose, and maltotetraose that can be used by the vaginal microbiota. IMPORTANCE Increased abundance of Gardnerella spp. is a diagnostic characteristic of bacterial vaginosis, an imbalance in the human vaginal microbiome associated with troubling symptoms, and negative reproductive health outcomes, including increased transmission of sexually transmitted infections and preterm birth. Competition for nutrients is likely an important factor in causing dramatic shifts in the vaginal microbial community, but little is known about the contribution of bacterial enzymes to the metabolism of glycogen, a major food source available to vaginal bacteria. The significance of our research is characterizing the activity of enzymes conserved in Gardnerella species that contribute to the ability of these bacteria to utilize glycogen.

Improved Stability and Hydrolysates of Hyperthermophilic GH57 Type II Pullulanase from the Deep-Sea Archaeon Thermococcus siculi HJ21 by Truncation

Pullulanase (EC 3.2.1.41) belongs to the amylase family and is often used alone or in combination with other amylases in the industrial production of starch-based products. This enzyme is often required in industrial production because of its better stability. We here truncated the pullulanase gene from the deep-sea hydrothermal anaerobic archaeon Thermococcus siculi HJ21 and obtained Pul-HJΔ782, which is a member of the α-amylase family GH57. The results revealed that the optimum temperature for Pul-HJΔ782 was 100 °C, and its thermostability at 100 °C improved after truncation. Less than 15% of its enzyme activity was lost after 1 h of incubation at 100 °C, and 57% activity remained after 5 h of treatment. Truncation significantly improved the overall pH tolerance range of Pul-HJΔ782, and its stability in the pH range 4–8 was over 80% relative activity from an average of 60%. The sequence and structural model of Pul-HJΔ782 was analyzed, and its instability index was reduced significantly. Furthermore, the hydrolysates of the truncated and wild-type pullulanase were analyzed, and the enzymatic digestion efficiency of the truncated Pul-HJΔ782 was higher.

In-Depth Characterization of Debranching Type I Pullulanase from Priestia koreensis HL12 as Potential Biocatalyst for Starch Saccharification and Modification

Pullulanase is an effective starch debranching enzyme widely used in starch saccharification and modification. In this work, the biochemical characteristics and potential application of a new type I pullulanase from Priestia koreensis HL12 (HL12Pul) were evaluated and reported for the first time. Through in-depth evolutionary analysis, HL12Pul was classified as type I pullulanase belonging to glycoside hydrolase family 13, subfamily 14 (GH13_14). HL12Pul comprises multi-domains architecture, including two carbohydrate-binding domains, CBM68 and CBM48, at the N-terminus, the TIM barrel structure of glycoside hydrolase family 13 (GH13) and C-domain. Based on sequence analysis and experimental cleavage profile, HL12Pul specifically hydrolyzes only α-1,6 glycosidic linkage-rich substrates. The enzyme optimally works at 40 °C, pH 6.0, with the maximum specific activity of 181.14 ± 3.55 U/mg protein and catalytic efficiency (kcat/Km) of 49.39 mL/mg·s toward pullulan. In addition, HL12Pul worked in synergy with raw starch-degrading α-amylase, promoting raw cassava starch hydrolysis and increasing the sugar yield by 2.9-fold in comparison to the α-amylase alone in a short reaction time. Furthermore, HL12Pul effectively produces type III-resistant starch (RSIII) from cassava starch with a production yield of 70%. These indicate that HL12Pul has the potential as a biocatalyst for starch saccharification and modification.

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

Parageobacillus thermantarcticus strain M1 is a Gram-positive, motile, facultative anaerobic, spore forming, and thermophilic bacterium, isolated from geothermal soil of the crater of Mount Melbourne (74°22′ S, 164°40′ E) during the Italian Antarctic Expedition occurred in Austral summer 1986–1987. Strain M1 demonstrated great biotechnological and industrial potential owing to its ability to produce exopolysaccharides (EPSs), ethanol and thermostable extracellular enzymes, such as an xylanase and a β-xylosidase, and intracellular ones, such as xylose/glucose isomerase and protease. Furthermore, recent studies revealed its high potential in green chemistry due to its use in residual biomass transformation/valorization and as an appropriate model for microbial astrobiology studies. In the present study, using a systems-based approach, genomic analysis of P. thermantarcticus M1 was carried out to enlighten its functional characteristics. The elucidation of whole-genome organization of this thermophilic cell factory increased our understanding of biological mechanisms and pathways, by providing valuable information on the essential genes related to the biosynthesis of nucleotide sugar precursors, monosaccharide unit assembly, as well as the production of EPSs and ethanol. In addition, gene prediction and genome annotation studies identified genes encoding xylanolytic enzymes that are required for the conversion of lignocellulosic materials to high-value added molecules. Our findings pointed out the significant potential of strain M1 in various biotechnological and industrial applications considering its capacity to produce EPSs, ethanol and thermostable enzymes via the utilization of lignocellulosic waste materials.