Isolation of a protease-resistant and pH-stable α-galactosidase displaying hydrolytic efficacy toward raffinose family oligosaccharides from the button mushroom Agaricus bisporus

Properties and applications of α-galactosidase in agricultural waste processing and secondary agricultural process industries

Agriculture products form the foundation building blocks of our daily lives. Although they have been claimed to be renewable resources with a low carbon footprint, the agricultural community is constantly challenged to overcome two post-harvest bottlenecks: first, farm bio-waste, a substantial economic and environmental burden to the farming sector, and second, an inefficient agricultural processing sector, plagued by the need for significant energy input to generate the products. Both these sectors require extensive processing technologies that are demanding in their energy requirements and expensive. To address these issues, an enzyme(s)-based green chemistry is available to break down complex structures into bio-degradable compounds that source alternate energy with valuable by-products and co-products. α-Galactosidase is a widespread class of glycoside hydroxylases that hydrolyzes α-galactosyl moieties in simple and complex oligo and polysaccharides, glycolipids, and glycoproteins. As a result of its growing importance, in this review we discuss the source of the enzyme, production and purification systems, and enzyme properties. We also elaborate on the enzyme's potential in agricultural bio-waste management, secondary agricultural industries like sugar refining, soymilk derivatives, food and confectionery, and animal feed processing. Insight into this vital enzyme will provide new avenues for less expensive green chemistry-based secondary agricultural processing and agricultural sustainability. © 2023 Society of Chemical Industry.

Isolation, Characterization, and Biocompatibility of Bisporitin, a Ribotoxin-like Protein from White Button Mushroom (Agaricus bisporus)

White button mushroom (Agaricus bisporus (J.E. Lange) Imbach) is one of the widely consumed edible mushrooms. Indeed, A. bisporus fruiting bodies are a rich source of nutrients and bioactive molecules. In addition, several enzymes with biotechnological applications are found in A. bisporus (e.g., enzymes for lignocellulose degradation). Here, a novel ribotoxin-like protein (RL-P) from the edible mushroom A. bisporus was purified and characterized. This RL-P, named bisporitin, is a monomeric protein (17-kDa) exhibiting specific ribonucleolytic activity by releasing the α-fragment (hallmark of RL-Ps) when incubated with rabbit ribosomes. In addition, bisporitin shows magnesium-dependent endonuclease activity and displays a similar far-UV CD spectrum as ageritin, the prototype of RL-Ps, isolated from Cyclocybe aegerita fruiting bodies. Interestingly, bisporitin is the first member of RL-Ps to have noticeably lower thermal stability (T_m = 48.59 ± 0.98 °C) compared to RL-Ps isolated in other mushrooms (T_m > 70 °C). Finally, this protein is only partially hydrolyzed in an in vitro digestive system and does not produce adverse growing effects on eukaryotic cell lines. This evidence paves the way for future investigations on possible bioactivities of this RL-P in the digestive system.

Improved Foods Using Enzymes from Basidiomycetes

Within the kingdom of fungi, the division Basidiomycota represents more than 30,000 species, some with huge genomes indicating great metabolic potential. The fruiting bodies of many basidiomycetes are appreciated as food (“mushrooms”). Solid-state and submerged cultivation processes have been established for many species. Specifically, xylophilic fungi secrete numerous enzymes but also form smaller metabolites along unique pathways; both groups of compounds may be of interest to the food processing industry. To stimulate further research and not aim at comprehensiveness in the broad field, this review describes some recent progress in fermentation processes and the knowledge of fungal genetics. Processes with potential for food applications based on lipases, esterases, glycosidases, peptidases and oxidoreductases are presented. The formation and degradation of colourants, the degradation of harmful food components, the formation of food ingredients and particularly of volatile and non-volatile flavours serve as examples. In summary, edible basidiomycetes are foods—and catalysts—for food applications and rich donors of genes to construct heterologous cell factories for fermentation processes. Options arise to support the worldwide trend toward greener, more eco-friendly and sustainable processes.

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.

Good hydrolysis activity on raffinose family oligosaccharides by a novel α-galactosidase from Tremella aurantialba

An α-galactosidase designated as TAG was purified from the dried fruit bodies of Tremella aurantialba with 182.5-fold purification. The purification procedure involved ion exchange chromatography on Q-sepharose, DEAE-Cellulose, and Mono Q and gel filtration by FPLC on Superdex 75. The purified α-galactosidase was a monomeric protein with a molecular mass of 88 kDa. The optimal pH of TAG was 5.0 and more than 60% of the original enzyme activity remained at pH 2.0 and 3.0. Its optimal temperature was 54 °C with good thermo-stability, 30.8% of the original activity was retained after exposure to a temperature of 70 °C for 1 h. The metal ions Hg²⁺, Cu²⁺, Fe³⁺ and Mg²⁺ strongly inhibited the enzyme activity. The enzyme activity was found to be inhibited by N-bromosuccinimide indicating that tryptophan was essential to the catalytic activity of α-galactosidase. The enzyme completely hydrolysed stachyose and partially hydrolysed raffinose to galactose at 50 °C within 6 h as detected by thin layer chromatography and the dinitrosalicylic acid method and the content of reducing sugar reached 4.36 mg/mL.

Mushroom extracts and compounds with suppressive action on breast cancer: evidence from studies using cultured cancer cells, tumor-bearing animals, and clinical trials

This article reviews mushrooms with anti-breast cancer activity. The mushrooms covered which are better known include the following: button mushroom Agaricus bisporus, Brazilian mushroom Agaricus blazei, Amauroderma rugosum, stout camphor fungus Antrodia camphorata, Jew's ear (black) fungus or black wood ear fungus Auricularia auricula-judae, reishi mushroom or Lingzhi Ganoderma lucidum, Ganoderma sinense, maitake mushroom or sheep's head mushroom Grifola frondosa, lion's mane mushroom or monkey head mushroom Hericium erinaceum, brown beech mushroom Hypsizigus marmoreus, sulfur polypore mushroom Laetiporus sulphureus, Lentinula edodes (shiitake mushroom), Phellinus linteus (Japanese "meshimakobu," Chinese "song gen," Korean "sanghwang," American "black hoof mushroom"), abalone mushroom Pleurotus abalonus, king oyster mushroom Pleurotus eryngii, oyster mushroom Pleurotus ostreatus, tuckahoe or Fu Ling Poria cocos, and split gill mushroom Schizophyllum commune. Antineoplastic effectiveness in human clinical trials and mechanism of anticancer action have been reported for Antrodia camphorata, Cordyceps sinensis, Coriolus versicolor, Ganoderma lucidum, Grifola frondosa, and Lentinula edodes.

Microbial production and biotechnological applications of α-galactosidase

α-Galactosidase, (E.C. 3.2.1.22) is an exoglycosidase that target galactooligosaccharides such as raffinose, melibiose, stachyose and branched polysaccharides like galactomannans and galacto-glucomannans by catalysing the hydrolysis of α-1,6 linked terminal galactose residues. The enzyme has been isolated and characterized from microbial, plant and animal sources. This ubiquitous enzyme possesses physiological significance and immense industrial potential. Optimization of the growth conditions and efficient purification strategies can lead to a significant increase in the enzyme production. To boost commercial productivity, cloning of novel α-galactosidase genes and their heterologous expression in suitable host has gained popularity. Enzyme immobilization leads to its greater reutilization, superior thermostability, pH tolerance and increased activity. The enzyme is well explored in food industry in the removal of raffinose family oligosaccharides (RFOs) in soymilk and sugar crystallization process. It also improves animal feed quality and biomass processing. Applications of the enzyme is in the area of biomedicine includes therapeutic advances in treatment of Fabry disease, blood group conversion and removal of α-gal type immunogenic epitopes in xenotransplantation. With considerable biotechnological applications, this enzyme has been vastly commercialized and holds greater future prospects.

Characterization of a highly stable α-galactosidase from thermophilic Rasamsonia emersonii heterologously expressed in a modified Pichia pastoris expression system

Background

Structurally stable α-galactosidases are of great interest for various biotechnological applications. More thermophilic α-galactosidases with high activity and structural stability have therefore to be mined and characterized. On the other hand, few studies have been performed to prominently enhance the AOX1 promoter activity in the commonly used Pichia pastoris system, in which production of some heterologous proteins are insufficient for further study.

Results

ReGal2 encoding a thermoactive α-galactosidase was identified from the thermophilic (hemi)cellulolytic fungus Rasamsonia emersonii. Significantly increased production of ReGal2 was achieved when ReGal2 was expressed in an engineered Pastoris pichia expression system with a modified AOX1 promoter and simultaneous fortified expression of Mxr1 that is involved in transcriptionally activating AOX1. Purified ReGal2 exists as an oligomer and has remarkable thermo-activity and thermo-tolerance, exhibiting maximum activity of 935 U/mg towards pNPGal at 80 °C and retaining full activity after incubation at 70 °C for 60 h. ReGal2 is insensitive to treatments by many metal ions and exhibits superior tolerance to protein denaturants. Moreover, ReGal2 efficiently hydrolyzed stachyose and raffinose in soybeans at 70 °C in 3 h and 24 h, respectively.

Conclusion

A modified P. pichia expression system with significantly enhanced AOX1 promoter activity has been established, in which ReGal2 production is markedly elevated to facilitate downstream purification and characterization. Purified ReGal2 exhibited prominent features in thermostability, catalytic activity, and resistance to protein denaturants. ReGal2 thus holds great potential in relevant biotechnological applications.

Optimization of Saccharomyces cerevisiae α-galactosidase production and application in the degradation of raffinose family oligosaccharides

BACKGROUND

α-Galactosidases are enzymes that act on galactosides present in many vegetables, mainly legumes and cereals, have growing importance with respect to our diet. For this reason, the use of their catalytic activity is of great interest in numerous biotechnological applications, especially those in the food industry directed to the degradation of oligosaccharides derived from raffinose. The aim of this work has been to optimize the recombinant production and further characterization of α-galactosidase of Saccharomyces cerevisiae.

RESULTS

The MEL1 gene coding for the α-galactosidase of S. cerevisiae (ScAGal) was cloned and expressed in the S. cerevisiae strain BJ3505. Different constructions were designed to obtain the degree of purification necessary for enzymatic characterization and to improve the productive process of the enzyme. ScAGal has greater specificity for the synthetic substrate p-nitrophenyl-α-D-galactopyranoside than for natural substrates, followed by the natural glycosides, melibiose, raffinose and stachyose; it only acts on locust bean gum after prior treatment with β-mannosidase. Furthermore, this enzyme strongly resists proteases, and shows remarkable activation in their presence. Hydrolysis of galactose bonds linked to terminal non-reducing mannose residues of synthetic galactomannan-oligosaccharides confirms that ScAGal belongs to the first group of α-galactosidases, according to substrate specificity. Optimization of culture conditions by the statistical model of Response Surface helped to improve the productivity by up to tenfold when the concentration of the carbon source and the aeration of the culture medium was increased, and up to 20 times to extend the cultivation time to 216 h.

CONCLUSIONS

ScAGal characteristics and improvement in productivity that have been achieved contribute in making ScAGal a good candidate for application in the elimination of raffinose family oligosaccharides found in many products of the food industry.

Diversity of potentially exploitable pharmacological activities of the highly prized edible medicinal fungus Antrodia camphorata

Antrodia camphorata, also known as A. cinnamomea, is a precious medicinal basidiomycete fungus endemic to Taiwan. This article summarizes the recent advances in research on the multifarious pharmacological effects of A. camphorata. The mushroom exhibits anticancer activity toward a large variety of cancers including breast, cervical, ovarian, prostate, bladder, colorectal, pancreatic, liver, and lung cancers; melanoma; leukemia; lymphoma; neuroblastoma; and glioblastoma. Other activities encompass antiinflammatory, antiatopic dermatitis, anticachexia, immunoregulatory, antiobesity, antidiabetic, antihyperlipidemic, antiatherosclerotic, antihypertensive, antiplatelet, antioxidative, antiphotodamaging, hepatoprotective, renoprotective, neuroprotective, testis protecting, antiasthmatic, osteogenic, osteoprotective, antiviral, antibacterial, and wound healing activities. This review aims to provide a reference for further development and utilization of this highly prized mushroom.

Purification and characterization of a novel protease-resistant GH27 α-galactosidase from Hericium erinaceus

A novel 57-kDa acidic α-galactosidase designated as HEG has been purified from the dry fruiting bodies of Hericium erinaceus. The isolation protocol involved ion-exchange chromatography and gel filtration on a Superdex75 column. The purification fold and specific activity were 1251 and 46 units/mg, respectively. A BLAST search of internal peptide sequences obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis suggested that the enzyme belonged to the GH27 family. The activity of the enzyme reached its maximum at a pH of 6.0 or at 60 °C. The enzyme was stable within an acidic pH range of 2.2-7.0 and in a narrow temperature range. The enzyme was strongly inhibited by Zn²⁺, Fe³⁺, Ag⁺ ions and SDS. The Lineweaver-Burk plot suggested that the mode of inhibition by galactose and melibiose were of a mixed type. N-bromosuccinimide drastically decreased the activity of the enzyme, whereas diethylpyrocarbonate and carbodiimide strengthened the activity slightly. Moreover, the isolated enzyme displayed remarkable resistance to acid proteases, neutral proteases and pepsin. The enzyme could also hydrolyse oligosaccharides and polysaccharides. In addition, acidic protease promoted the hydrolysis of RFOs by HEG. The K_m values of the enzyme towards pNPGal, raffinose and stachyose were 0.36 mM, 40.07 mM and 54.71 mM, respectively. These favourable properties increase the potential of the enzyme in the food industry and animal feed applications.

A novel α-galactosidase from the thermophilic probiotic Bacillus coagulans with remarkable protease-resistance and high hydrolytic activity

A novel α-galactosidase of glycoside hydrolase family 36 was cloned from Bacillus coagulans, overexpressed in Escherichia coli, and characterized. The purified enzyme Aga-BC7050 was 85 kDa according to SDS-PAGE and 168 kDa according to gel filtration, indicating that its native structure is a dimer. With p-nitrophenyl-α-d- galactopyranoside (pNPGal) as the substrate, optimal temperature and pH were 55 °C and 6.0, respectively. At 60 °C for 30 min, it retained > 50% of its activity. It was stable at pH 5.0–10.0, and showed remarkable resistance to proteinase K, subtilisin A, α-chymotrypsin, and trypsin. Its activity was not inhibited by glucose, sucrose, xylose, or fructose, but was slightly inhibited at galactose concentrations up to 100 mM. Aga-BC7050 was highly active toward pNPGal, melibiose, raffinose, and stachyose. It completely hydrolyzed melibiose, raffinose, and stachyose in < 30 min. These characteristics suggest that Aga-BC7050 could be used in feed and food industries and sugar processing.