Sepabeads EC-EP immobilized α-galactosidase: Immobilization, characterization and application in the degradation of raffinose-type oligosaccharides

Complementary Distant and Active Site Mutations Simultaneously Enhance Catalytic Activity and Thermostability of α-Galactosidase

The industrial applications of enzymes are limited due to the activity-stability trade-off, which implies that the improvement of thermostability often accompanies decreased activity. This study presents a dual-strategy approach to simultaneously improve the catalytic efficiency and thermostability of α-galactosidase galV from Anoxybacillus vitaminiphilus WMF1. Our integrated method combines computational analysis with enzyme property prediction to selectively target and modify the catalytic region and residues that are distant from the active site. We identified and experimentally validated mutations that improve activity without compromising stability and further increased thermostability through additional distant-site mutations. The resulting mutant enzyme variant N549Q/T550N/Y634F demonstrated a 6.2-fold increase in catalytic efficiency and a 3.2-fold improvement in the half-life at 65 °C. Molecular dynamics (MD) simulations supported the structural basis for the observed enhancements. This approach offers a refined strategy for engineering α-galactosidases with improved industrial applicability, overcoming the traditional trade-offs between enzyme activity and stability. Hydrolytic activity toward raffinose family oligosaccharides (RFOs) was validated using soymilk as a model substrate, demonstrating significant practical potential.

Purification and characterization of α-galactosidases from Penicillium griseoroseum for efficient soymilk hydrolysis

Soybean utilization is limited by the presence of raffinose oligosaccharides (RFO), which are not digested by humans and cause gastrointestinal discomfort. This study explores the potential of α-galactosidases from Penicillium griseoroseum for RFO hydrolysis in soymilk. Two distinct α-galactosidase enzymes, designated α-Gal1 and α-Gal2, were purified using a combination of ion-exchange chromatography and native polyacrylamide gel electrophoresis. Both enzymes exhibited characteristics of multimeric proteins and displayed similar biochemical properties. Optimal activity was observed at a pH range of 4.5-5.0 and a temperature range of 40-45 °C. Notably, α-Gal1 demonstrated high thermostability with a half-life of 16 h at 40 °C. The α-galactosidases displayed different substrate affinitiesfor the substrates ρ-NP-αGal, o-NP-αGal, rD-raffinose, d-stachyose, and mD-melibiose. The Michaelis-Menten constant (Km) values for α-Gal1 were 1.06, 1.31, 28.74, 19.88, and 4.77 mmol/L, respectively, while those for α-Gal2 were 0.8, 1.26, 30.46, 21.74 and 5.01 mmol/L, respectively. Both α-Gal1 and α-Gal2 were strongly inhibited by metal ions (Ag⁺, Cu2⁺, Fe2⁺, and Hg2⁺) and moderately inhibited by d-melibiose. Importantly, both enzymes efficiently hydrolyzed RFOs, achieving complete d-stachyose elimination from soymilk after a 6-h incubation. These findings propose the promising application of these α-galactosidases in industrial soymilk production, potentially enhancing its nutritional value and alleviating gastrointestinal issues in consumers.

Recent Advances and Perspectives on Food-Grade Immobilisation Systems for Enzymes

The use of enzyme immobilisation is becoming increasingly popular in beverage processing, as this method offers significant advantages, such as enhanced enzyme performance and expanded applications, while allowing for easy process termination via simple filtration. This literature review analysed approximately 120 articles, published on the Web of Science between 2000 and 2023, focused on enzyme immobilisation systems for beverage processing applications. The impact of immobilisation on enzymatic activity, including the effects on the chemical and kinetic properties, recyclability, and feasibility in continuous processes, was evaluated. Applications of these systems to beverage production, such as wine, beer, fruit juices, milk, and plant-based beverages, were examined. The immobilisation process effectively enhanced the pH and thermal stability but caused negative impacts on the kinetic properties by reducing the maximum velocity and Michaelis-Menten constant. However, it allowed for multiple reuses and facilitated continuous flow processes. The encapsulation also allowed for easy process control by simplifying the removal of the enzymes from the beverages via simple filtration, negating the need for expensive heat treatments, which could result in product quality losses.

Immobilization of α-galactosidase in polyvinyl alcohol-chitosan-glycidyl methacrylate hydrogels based on directional freezing-assisted salting-out strategy for hydrolysis of RFOs

Raffinose family oligosaccharides (RFOs) in food are the main factors causing flatulence in Irritable Bowel Syndrome (IBS) patients and the development of effective approaches for reducing food-derived RFOs is of paramount importance. In this study, polyvinyl alcohol (PVA)-chitosan (CS)-glycidyl methacrylate (GMA) immobilized α-galactosidase was prepared by the directional freezing-assisted salting-out technique, aimed to hydrolyze RFOs. SEM, FTIR, XPS, fluorescence and UV characterization results demonstrated that α-galactosidase was successfully cross-linked in the PVA-CS-GMA hydrogels, forming a distinct porous stable network through the covalent bond between the enzyme and the carrier. Mechanical performance and swelling capacity analysis illustrated that α-gal @ PVA-CS-GMA not only had suitable strength and toughness for longer durability, but also exhibited high water content and swelling capacity for better retention of catalytic activity. The enzymatic properties of α-gal @ PVA-CS-GMA showed an improved Km value, pH and temperature tolerance range, anti-enzymatic inhibitor (melibiose) activity compared to the free α-galactosidase and its reusability was at least 12 times with prolonged storage stability. Finally, it was successfully applied in the hydrolysis of RFOs in soybeans. These findings provide a new strategy for the development of α-galactosidase immobilization system to biological transform the RFOs components in the food for diet intervention of IBS.

Biochemical characterization and insights into the potency of the acidic Aspergillus niger NRC114 purified α-galactosidase in removing raffinose family oligosaccharides from soymilk yogurt

BACKGROUND

Because humans lack α-galactosidase, foods containing certain oligosaccharides from the raffinose family, such as soybeans and other legumes, may disrupt digestion and cause flatulence.

RESULTS

Aspergillus niger NRC114 α-galactosidase was purified using protein precipitation, gel filtration, and ion exchange chromatography steps, which resulted in a 123-fold purification. The purified enzyme was found to be 64 kDa using the SDS-PAGE approach. The optimum pH and temperature of the purified α-galactosidase were detected at pH 3.5 and 60 ºC, respectively. The pure enzyme exhibited potent acidic pH stability at pH 3.0 and pH 4.0 for 2 h, and it retained its full activity at 50 ºC and 60 ºC for 120 min and 90 min, respectively. The enzyme was activated using 2.5 mM of K⁺, Mg²⁺, Co²⁺, or Zn²⁺ by 14%, 23%, 28%, and 11%, respectively. The K_m and V_max values of the purified enzyme were calculated to be 0.401 µM and 14.65 μmol min^-1, respectively. The soymilk yogurt showed an increase in its total phenolic content and total flavonoids after enzyme treatment, as well as several volatile compounds that were detected and identified using GC-MS analysis. HPLC analysis clarified the enzymatic action in the hydrolysis of raffinose family oligosaccharides.

CONCLUSION

The findings of this study indicate the importance of A. niger NRC114 α-galactosidase enzyme for future studies, especially its applications in a variety of biological fields.

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.