A thermophilic fungal GH36 α-galactosidase from Lichtheimia ramosa and its synergistic hydrolysis of locust bean gum

Purification and characterization of α-galactosidase isolated from Klebsiella pneumoniae in the human oral cavity

The enzyme α-Galactosidase (α-D-galactoside galactohydrolase [EC 3.2.1.22]) is an exoglycosidase that hydrolyzes the terminal α-galactosyl moieties of glycolipids and glycoproteins. It is ubiquitous in nature and possesses extensive applications in the food, pharma, and biotechnology industries. The present study aimed to purify α-galactosidase from Klebsiella pneumoniae, a bacterium isolated from the human oral cavity. The purification steps involved ammonium sulfate precipitation (70 %), dialysis, ion exchange chromatography using a DEAE-cellulose column, and affinity monolith chromatography. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis was used to determine the molecular weight of the purified enzyme. The kinetic constants, Michaelis constant (Km) and maximal velocity (Vmax), for this enzyme were determined by using p-nitrophenyl-α-D-galactopyranoside as substrate. The results showed that the purification fold, specific activity, and yield were 126.52, 138.58 units/mg, and 21.5 %, respectively. The SDS-PAGE showed that the molecular weight of the purified enzyme was 75 kDa. The optimum pH and temperature of the purified α-galactosidase were detected at pH 6.0 and 50 °C, respectively. The kinetic constants, Michaelis constant (Km) and maximal velocity (Vmax), for this enzyme were 4.6 mM and 769.23 U/ml, respectively. α-galactosidase from Klebsiella pneumoniae was purified and characterized. (SDS-PAGE) analysis showed that the purified enzyme appeared as single band with a molecular weight of 75 kDa.

Properties of OSA-esterified insoluble fraction of Persian gum and its application in dairy cream

BACKGROUND

In the present study, the insoluble fraction of Persian gum (IFPG) was modified with octenyl succinic anhydride (OSA) and its various properties were assessed. In addition, the effect of OSA-IFPG on the rheological and textural properties of dairy cream was investigated.

RESULTS

Suitable conditions for achieving a degree of substitution (DS) of 0.023 were found at pH 9, IFPG concentration 4 wt%, OSA concentration 10 wt% and a temperature of 40 °C, within 120 min. The carbonyl group attachment in OSA-IFPG was also confirmed via Fourier transform infrared and H-nuclear magnetic resonance spectroscopy (1 H-NMR). While the X-ray diffraction test indicated no significant changes in the structure of the IFPG after modification with OSA, esterification increased the negative charge density, decreased thermal decomposition temperature and increased the emulsifying capacity to 100%, which was obtained for the first time. The use of OSA-modified IFPG in creams augmented the complex viscosity, loss and storage modulus, while also demonstrating the creation of a pseudo-gel network. The hardness and adhesiveness of the texture increased, which can be explained by the formation of a compact structure and reduced particle size.

CONCLUSION

Overall, OSA-IFPG with hydrophilic and hydrophobic sections may function as an emulsifier and be recommended as a safe source of hydrocolloids for emulsion stability. It can also provide a positive physical structure when added to dairy cream, even if the fat concentration is lower than usual. © 2023 Society of Chemical Industry.

Comparative genomics predict specific genes in potential mucorales identification

Mucoralean fungi could cause mucormycosis in humans, particularly in immunodeficient individuals and those with diabetes mellitus or trauma. With plenty of species and genera, their molecular identification and pathogenicity have a large deviation. Reported cases of mucormycosis showed frequent occurrence in Rhizopus species, Mucor species, and Lichtheimia species. We analyzed the whole genome sequences of 25 species of the top 10 Mucorales genera, along with another 22 important pathogenic non-Mucorales species, to dig the target genes for monitoring Mucorales species and identify potential genomic imprints of virulence in them. Mucorales-specific genes have been found in various orthogroups extracted by Python script, while genus-specific genes were annotated covering cellular structure, biochemistry metabolism, molecular processing, and signal transduction. Proteins related to the virulence of Mucorales species varied with distinct significance in copy numbers, in which Orthofinder was conducted. Based on our fresh retrospective analysis of mucormycosis, a comparative genomic analysis of pathogenic Mucorales was conducted in more frequent pathogens. Specific orthologs between Mucorales and non-Mucoralean pathogenic fungi were discussed in detail. Referring to the previously reported virulence proteins, we included more frequent pathogenic Mucorales and compared them in Mucorales species and non-Mucorales species. Besides, more samples are needed to further verify the potential target genes.

Characterization of a fungal α-galactosidase and its synergistic effect with β-mannanase for hydrolysis of galactomannan

An acid stable α-galactosidase was produced and purified from mannolytic fungal strain, Penicillium aculeatum APS1. Enzyme was produced using wheat bran and copra cake moistened with corn steep liquor by solid state fermentation. APS1αgal having molecular weight of 65.4 kDa was purified to electrophoretic homogeneity by three phase partitioning and gel permeation chromatography with high enzyme recovery. APS1αgal was found to be maximally active at 55 °C and pH 4.5, having high stability at acidic pH. Thermal stability and thermal inactivation kinetics of APS1αgal were also studied. APS1αgal was found to effectively hydrolyse oligosaccharides as well as polysaccharides having α-1,6 linked galactose. Abolishment of enzyme activity in N-brommosuccinimide revealed an important role of tryptophan residue in catalysis. APS1αgal had shown outstanding tolerance to NaCl and proteases. MALDI-TOF MS/MS analysis indicated that enzyme is probably a member of family GH27. Synergistic interaction between APS1αgal and β-mannanase for hydrolysis of galactomannan was very clear and maximum 2.0° of synergy was found under simultaneous mode of action. This study reports a new source of α-galactosidase with biochemical properties suitable for applications in food and feed industries.

Biochemical analyses of a novel acidophilic GH5 β-mannanase from Trichoderma asperellum ND-1 and its application in mannooligosaccharides production from galactomannans

In this study, an acidophilic GH5 β-mannanase (TaMan5) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 2.0-fold increase, 67.5 ± 1.95 U/mL). TaMan5 displayed the highest specificity toward locust bean gum (K_m = 1.34 mg/mL, V_max = 749.14 μmol/min/mg) at pH 4.0 and 65°C. Furthermore, TaMan5 displayed remarkable tolerance to acidic environments, retaining over 80% of its original activity at pH 3.0-5.0. The activity of TaMan5 was remarkably decreased by Cu²⁺, Mn²⁺, and SDS, while Fe²⁺/Fe³⁺ improved the enzyme activity. A thin-layer chromatography (TLC) analysis of the action model showed that TaMan5 could rapidly degrade mannan/MOS into mannobiose without mannose via hydrolysis action as well as transglycosylation. Site-directed mutagenesis results suggested that Glu²⁰⁵, Glu³¹³, and Asp³⁵⁷ of TaMan5 are crucial catalytic residues, with Asp¹⁵² playing an auxiliary function. Additionally, TaMan5 and commercial α-galactosidase displayed a remarkable synergistic effect on the degradation of galactomannans. This study provided a novel β-mannanase with ideal characteristics and can be considered a potential candidate for the production of bioactive polysaccharide mannobiose.

Molecular advances in microbial α-galactosidases: challenges and prospects

α-Galactosidase (α-D-galactosidase galactohydrolase; EC 3.2.1.22), is an industrially important enzyme that hydrolyzes the galactose residues in galactooligosaccharides and polysaccharides. The industrial production of α-galactosidase is currently insufficient owing to the high production cost, low production efficiency and low enzyme activity. Recent years have witnessed an increase in the worldwide research on molecular techniques to improve the production efficiency of microbial α-galactosidases. Cloning and overexpression of the gene sequences coding for α-galactosidases can not only increase the enzyme yield but can confer industrially beneficial characteristics to the enzyme protein. This review focuses on the molecular advances in the overexpression of α-galactosidases in bacterial and yeast/fungal expression systems. Recombinant α-galactosidases have improved biochemical and hydrolytic properties compared to their native counterparts. Metabolic engineering of microorganisms to produce high yields of α-galactosidase can also assist in the production of value-added products. Developing new variants of α-galactosidases through directed evolution can yield enzymes with increased catalytic activity and altered regioselectivity. The bottlenecks in the recombinant production of α-galactosidases are also discussed. The knowledge about the hurdles in the overexpression of recombinant proteins illuminates the emerging possibilities of developing a successful microbial cell factory and widens the opportunities for the production of industrially beneficial α-galactosidases.

Heterologous Expression of a Thermostable α-Galactosidase from Parageobacillus thermoglucosidasius Isolated from the Lignocellulolytic Microbial Consortium TMC7

α-Galactosidase is a debranching enzyme widely used in the food, feed, paper, and pharmaceuticals industries and plays an important role in hemicellulose degradation. Here, T26, an aerobic bacterial strain with thermostable α-galactosidase activity, was isolated from laboratory-preserved lignocellulolytic microbial consortium TMC7, and identified as Parageobacillus thermoglucosidasius. The α-galactosidase, called T26GAL and derived from the T26 culture supernatant, exhibited a maximum enzyme activity of 0.4976 IU/ml when cultured at 60°C and 180 rpm for 2 days. Bioinformatics analysis revealed that the α-galactosidase T26GAL belongs to the GH36 family. Subsequently, the pET-26 vector was used for the heterologous expression of the T26 α-galactosidase gene in Escherichia coli BL21 (DE3). The optimum pH for α-galactosidase T26GAL was determined to be 8.0, while the optimum temperature was 60°C. In addition, T26GAL demonstrated a remarkable thermostability with more than 93% enzyme activity, even at a high temperature of 90°C. Furthermore, Ca2+ and Mg2+ promoted the activity of T26GAL while Zn2+ and Cu2+ inhibited it. The substrate specificity studies revealed that T26GAL efficiently degraded raffinose, stachyose, and guar gum, but not locust bean gum. This study thus facilitated the discovery of an effective heat-resistant α-galactosidase with potent industrial application. Meanwhile, as part of our research on lignocellulose degradation by a microbial consortium, the present work provides an important basis for encouraging further investigation into this enzyme complex.

Microbial α-galactosidases: Efficient biocatalysts for bioprocess technology

Galactomannans, abundantly present in plant biomass, can be used as renewable fermentation feedstock for biorefineries working for the production of bioethanol and other value-added products. The complete and efficient bioconversion of biomass to fermentable sugars for the generation of biofuels and other value-added products require the concerted action of accessory enzymes like α-galactosidases, which can work in cohesion with other carbohydrases in an enzyme cocktail. In the paper industry, α-galactosidases enhance the bleaching effect of endo-β-1,4-mannanases on softwood kraft pulp. Microbial α-galactosidases also find applications in the treatment of legume foods, recovery of sucrose from sugar beet syrup, improving the rheological properties of galactomannans, and synthesis of α-galactooligosaccharides to be used as functional food ingredients. Owing to their industrial applications, there is a surge in the research focused on α-galactosidases. The current review illustrates the diverse industrial applications of microbial α-galactosidases and their challenges and prospects.

Identification and Characterization of a Thermostable GH36 α-Galactosidase from Anoxybacillusvitaminiphilus WMF1 and Its Application in Synthesizing Isofloridoside by Reverse Hydrolysis

An α-galactosidase-producing strain named Anoxybacillus vitaminiphilus WMF1, which catalyzed the reverse hydrolysis of d-galactose and glycerol to produce isofloridoside, was isolated from soil. The α-galactosidase (galV) gene was cloned and expressed in Escherichia coli. The galV was classified into the GH36 family with a molecular mass of 80 kDa. The optimum pH and temperature of galV was pH 7.5 and 60 °C, respectively, and it was highly stable at alkaline pH (6.0-9.0) and temperature below 65 °C. The specificity for p-nitrophenyl α-d-galactopyranoside was 70 U/mg, much higher than that for raffinose and stachyose. Among the metals and reagents tested, galV showed tolerance in the presence of various organic solvents. The kinetic parameters of the enzyme towards p-nitrophenyl α-d-galactopyranoside were obtained as Km (0.12 mM), Vmax (1.10 × 10-3 mM s-1), and Kcat/Km (763.92 mM-1 s-1). During the reaction of reverse hydrolysis, the enzyme exhibited high specificity towards the glycosyl donor galactose and acceptors glycerol, ethanol and ethylene glycol. Finally, the isofloridoside was synthesized using galactose as the donor and glycerol as the acceptor with a 26.6% conversion rate of galactose. This study indicated that galV might provide a potential enzyme source in producing isofloridoside because of its high thermal stability and activity.

Engineering a Trypsin-Resistant Thermophilic α-Galactosidase to Enhance Pepsin Resistance, Acidic Tolerance, Catalytic Performance, and Potential in the Food and Feed Industry

α-Galactosidase has potential applications, and attempts to improve proteolytic resistance of enzymes have important values. We use a novel strategy for genetic manipulation of a pepsin-sensitive region specific for a pepsin-sensitive but trypsin-resistant high-temperature-active Gal27B from Neosartorya fischeri to screen mutants with enhanced pepsin resistance. All enzymes were produced in Pichia pastoris to identify the roles of loop 4 (Gal27B-A23) and its key residue at position 156 (Gly156Arg/Pro/His) in pepsin resistance. Gal27B-A23 and Gly156Arg/Pro/His elevated pepsin resistance, thermostability, stability at low pH, activity toward raffinose (5.3-6.9-fold) and stachyose (about 1.3-fold), and catalytic efficiencies (up to 4.9-fold). Replacing the pepsin cleavage site Glu155 with Gly improved pepsin resistance but had no effect on pepsin resistance when Arg/Pro/His was at position 156. Thus, pepsin resistance could appear to occur through steric hindrance between the residue at the altered site and neighboring pepsin active site. In the presence of pepsin or trypsin, all mutations increased the ability of Gal27B to hydrolyze galactosaccharides in soybean flour (up to 9.6- and 4.3-fold, respectively) and promoted apparent metabolizable energy and nutrient digestibility in soybean meal for broilers (1.3-1.8-fold). The high activity and tolerance to heat, low pH, and protease benefit food and feed industry in a cost-effective way.