Characteristics of yeast lectins and their role in cell–cell interactions

Lectin-glycan interactions: a comprehensive cataloguing of cancer-associated glycans for biorecognition and bio-alteration: a review

This comprehensive review meticulously compiles data on an array of lectins and their interactions with different cancer types through specific glycans. Crucially, it establishes the link between aberrant glycosylation and cancer types. This repository of lectin-defined glycan signatures, assumes paramount importance in the realm of cancer and its dynamic nature. Cancer, known for its remarkable heterogeneity and individualized behaviour, can be better understood through these glycan signatures. The current review discusses the important lectins and their carbohydrate specificities, especially recognizing glycans of cancer origin. The review also addresses the key aspects of differentially expressed glycans on normal and cancerous cell surfaces. Specific cancer types highlighted in this review include breast cancer, colon cancer, glioblastoma, cervical cancer, lung cancer, liver cancer, and leukaemia. The glycan profiles unveiled through this review hold the key to tailor-made treatment and precise diagnostics. It opens up avenues to explore the potential of targeting glycosyltransferases and glycosidases linked with cancer advancement and metastasis. Armed with knowledge about specific glycan expressions, researchers can design targeted therapies to modulate glycan profiles, potentially hampering the advance of this relentless disease.

A single-pass type I membrane protein, mannose-specific L-type lectin, potentially involved in the adhesion and invasion of Cryptosporidium parvum

Cryptosporidium is a globally distributed zoonotic protozoan parasite that can cause severe diarrhea in humans and animals. L-type lectins are carbohydrate-binding proteins involved in multiple pathways in animals and plants, including protein transportation, secretion, innate immunity, and the unfolded protein response signaling pathway. However, the biological function of the L-type lectins remains unknown in Cryptosporidium parvum. Here, we preliminarily characterized an L-type lectin in C. parvum (CpLTL) that contains a lectin-leg-like domain. Immunofluorescence assay confirmed that CpLTL is located on the wall of oocysts, the surface of the mid-anterior region of the sporozoite and the cytoplasm of merozoites. The involvement of CpLTL in parasite invasion is partly supported by experiments showing that an anti-CpLTL antibody could partially block the invasion of C. parvum sporozoites into host cells. Moreover, the recombinant CpLTL showed binding ability with mannose and the surface of host cells, and competitively inhibited the invasion of C. parvum. Two host cell proteins were identified by proteomics which should be prioritized for future validation of CpLTL-binding. Our data indicated that CpLTL is potentially involved in the adhesion and invasion of C. parvum.

Sclerotinia sclerotiorum Agglutinin Modulates Sclerotial Development, Pathogenicity and Response to Abiotic and Biotic Stresses in Different Manners

Sclerotinia sclerotiorum is an important plant pathogenic fungus of many crops. Our previous study identified the S. sclerotiorum agglutinin (SSA) that can be partially degraded by the serine protease CmSp1 from the mycoparasite Coniothyrium minitans. However, the biological functions of SSA in the pathogenicity of S. sclerotiorum and in its response to infection by C. minitans, as well as to environmental stresses, remain unknown. In this study, SSA disruption and complementary mutants were generated for characterization of its biological functions. Both the wild-type (WT) of S. sclerotiorum and the mutants were compared for growth and sclerotial formation on potato dextrose agar (PDA) and autoclaved carrot slices (ACS), for pathogenicity on oilseed rape, as well as for susceptibility to chemical stresses (NaCl, KCl, CaCl₂, sorbitol, mannitol, sucrose, sodium dodecyl sulfate, H₂O₂) and to the mycoparasitism of C. minitans. The disruption mutants (ΔSSA-175, ΔSSA-178, ΔSSA-225) did not differ from the WT and the complementary mutant ΔSSA-178C in mycelial growth. However, compared to the WT and ΔSSA-178C, the disruption mutants formed immature sclerotia on PDA, and produced less but larger sclerotia on ACS; they became less sensitive to the eight investigated chemical stresses, but more aggressive in infecting leaves of oilseed rape, and more susceptible to mycoparasitism by C. minitans. These results suggest that SSA positively regulates sclerotial development and resistance to C. minitans mycoparasitism, but negatively regulates pathogenicity and resistance to chemical stresses.

A roadmap to understanding diversity and function of coral reef-associated fungi

Tropical coral reefs are hotspots of marine productivity, owing to the association of reef-building corals with endosymbiotic algae and metabolically diverse bacterial communities. However, the functional importance of fungi, well-known for their contribution to shaping terrestrial ecosystems and global nutrient cycles, remains underexplored on coral reefs. We here conceptualize how fungal functional traits may have facilitated the spread, diversification, and ecological adaptation of marine fungi on coral reefs. We propose that functions of reef-associated fungi may be diverse and go beyond their hitherto described roles of pathogens and bioeroders, including but not limited to reef-scale biogeochemical cycles and the structuring of coral-associated and environmental microbiomes via chemical mediation. Recent technological and conceptual advances will allow the elucidation of the physiological, ecological, and chemical contributions of understudied marine fungi to coral holobiont and reef ecosystem functioning and health and may help provide an outlook for reef management actions.

Modeling bioaffinity-based targeted delivery of antimicrobials to Escherichia coli biofilms using yeast microparticles. Part II: Parameter evaluation and validation

The design of bioaffinity-based targeted delivery systems for biofilm inactivation may require a comprehensive understanding of physicochemical and biochemical properties of biobased antimicrobial particles and their interactions with biofilm. In this study, Escherichia coli biofilm inactivation by chlorine-charged yeast microparticles was numerically simulated, and the roles of chemical stability, binding affinity, and controlled release of this targeted delivery system were assessed using this numerical simulation. The simulation results were experimentally validated using two different types of yeast microparticles. The results of this study illustrate that chorine stability achieved by yeast microparticles was a key factor for improved biofilm inactivation in an organic-rich environment (>6 additional log reduction in 20 min compared to the free chlorine treatment). Moreover, the binding affinity of yeast microparticles to E. coli biofilms was another key factor for an enhanced inactivation of biofilm, as a 10-fold increase in binding rate resulted in a 4.2-fold faster inactivation. Overall, the mechanistic modeling framework developed in this study could guide the design and development of biobased particles for targeted inactivation of biofilms.

Evolution and Physiology of Amphibious Yeasts

Since the emergence of the first fungi some 700 million years ago, unicellular yeast-like forms have emerged multiple times in independent lineages via convergent evolution. While tens to hundreds of millions of years separate the independent evolution of these unicellular organisms, they share remarkable phenotypic and metabolic similarities, and all have streamlined genomes. Yeasts occur in every aquatic environment yet examined. Many species are aquatic; perhaps most are amphibious. How these species have evolved to thrive in aquatic habitats is fundamental to understanding functions and evolutionary mechanisms in this unique group of fungi. Here we review the state of knowledge of the physiological and ecological diversity of amphibious yeasts and their key evolutionary adaptations enabling survival in aquatic habitats. We emphasize some genera previously thought to be exclusively terrestrial. Finally, we discuss the ability of many yeasts to survive in extreme habitats and how this might lend insight into ecological plasticity, including amphibious lifestyles. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A Comprehensive Phylogenetic and Bioinformatics Survey of Lectins in the Fungal Kingdom

Fungal lectins are a large family of carbohydrate-binding proteins with no enzymatic activity. They play fundamental biological roles in the interactions of fungi with their environment and are found in many different species across the fungal kingdom. In particular, their contribution to defense against feeders has been emphasized, and when secreted, lectins may be involved in the recognition of bacteria, fungal competitors and specific host plants. Carbohydrate specificities and quaternary structures vary widely, but evidence for an evolutionary relationship within the different classes of fungal lectins is supported by a high degree of amino acid sequence identity. The UniLectin3D database contains 194 fungal lectin 3D structures, of which 129 are characterized with a carbohydrate ligand. Using the UniLectin3D lectin classification system, 109 lectin sequence motifs were defined to screen 1223 species deposited in the genomic portal MycoCosm of the Joint Genome Institute. The resulting 33,485 putative lectin sequences are organized in MycoLec, a publicly available and searchable database. These results shed light on the evolution of the lectin gene families in fungi.

S. boulardii Fails to Hold Its Cell Wall Integrity against Nonpathogenic E. coli: Are Probiotic Yeasts Losing the Battle?

Probiotic yeast Saccharomyces boulardii exerts direct probiotic action on pathogenic E. coli by trapping them on surfaces and inactivating toxic lipopolysaccharides. Using optical dark-field microscopy, we show that nonpathogenic E. coli cells also readily bind probiotic S. boulardii. More importantly, the adhered nonpathogenic E. coli progressively damage S. boulardii cell walls and lyse them. Co-cultured methylene blue-supplemented agar-plate assay indicates that rough lipopolysaccharides might be playing a key role in S. boulardii cell wall damage. When experiments are repeated with lipopolysaccharide-depleted E. coli and also lipopolysaccharide-deficient E. coli, adhesion decreases substantially. The co-cultured assay further reveals that free lipopolysaccharides, released from E. coli, are also causing damage to S. boulardii walls like adhered E. coli. These new findings contradict the known S. boulardii-E. coli interaction mechanisms. We confirm that E. coli cells do not bind or damage human erythrocyte cell walls; therefore, they have not developed pathogenicity. The combined results demonstrate the first example of nonpathogenic E. coli being harmful to probiotic yeast S. boulardii. This finding is important because gut microbial flora contain large numbers of nonpathogenic E. coli. If they bind or damage probiotic S. boulardii cell walls, then the probiotic efficiency toward pathogenic E. coli will be compromised.

Lectins purified from medicinal and edible mushrooms: Insights into their antiviral activity against pathogenic viruses

For thousands of years, fungi have been a valuable and promising source of therapeutic agents for treatment of various diseases. Mushroom is a macrofungus which has been cultivated worldwide for its nutritional value and medicinal applications. Several bioactive molecules were extracted from mushroom such as polysaccharides, lectins and terpenoids. Lectins are carbohydrate-binding proteins with non-immunologic origin. Lectins were classified according to their structure, origin and sugar specificity. This protein has different binding specificity with surface glycan moiety which determines its activity and therapeutic applications. A wide range of medicinal activities such as antitumor, antiviral, antimicrobial, immunomodulatory and antidiabetic were reported from sugar-binding proteins. However, glycan-binding protein from mushroom is not well explored as antiviral agent. The discovery of novel antiviral agents is a public health emergency to overcome the current pandemic and be ready for the upcoming viral pandemics. The mechanism of action of lectin against viruses targets numerous steps in viral life cycle such as viral attachment, entry and replication. This review described the history, classification, purification techniques, structure-function relationship and different therapeutic applications of mushroom lectin. In addition, we focus on the antiviral activity, purification and physicochemical characteristics of some mushroom lectins.

Interaction between human mucins and parasite glycoproteins: the role of lectins and glycosidases in colonization by intestinal protozoa

Intestinal mucins are the first line of defense against microorganisms. Although knowledge about the mechanisms involved in the establishment of intestinal protozoa is limited, there is evidence that these parasites produce lectin-like molecules and glycosidases, that exert both, constitutive and secretory functions, promoting the establishment of these microorganisms. In the present review, we analyse the main interactions between mucins of the host intestine and the four main protozoan parasites in humans and their implications in intestinal colonization. There are lectin-like molecules that contain complex oligosaccharide structures and N-acetylglucosamine (GlcNAc), mannose and sialic acid as main components, which are excreted/secreted by Giardia intestinalis, and recognized by the host using mannose-binding lectins (MBL). Entamoeba histolytica and Cryptosporidium spp. express the lectin galactose/N-acetyl-D-galactosamine, which facilitates their adhesion to cells. In Cryptosporidium, the glycoproteins gp30, gp40/15 and gp900 and the glycoprotein lectin CpClec are involved in protozoan adhesion to intestinal cells, forming an adhesion-attack complex. G. intestinalis and E. histolytica can also produce glycosidases such as β-N-acetyl-D-glucosaminidase, α-d-glucosidase, β-d-galactosidase, β-l-fucosidase, α-N-acetyl-d-galactosaminidase and β-mannosidase. In Blastocystis, α-D-mannose, α-D-glucose, GlcNAc, α-D-fucose, chitin and sialic acid that have been identified on their surface. Fucosidases, hexosaminidases and polygalacturonases, which may be involved in the mucin degradation process, have also been described in the Blastocystis secretoma. Similarly, symbiotic coexistence with the intestinal microbiota promotes the survival of parasites facilitating cell invasion and nutrients obtention. Furthermore, it is necessary to identify and characterize more glycosidases, which have been only partially described by in silico analyses of the parasite genome.

Engineered Saccharomyces cerevisiae for lignocellulosic valorization: a review and perspectives on bioethanol production

The biorefinery concept, consisting in using renewable biomass with economical and energy goals, appeared in response to the ongoing exhaustion of fossil reserves. Bioethanol is the most prominent biofuel and has been considered one of the top chemicals to be obtained from biomass. Saccharomyces cerevisiae, the preferred microorganism for ethanol production, has been the target of extensive genetic modifications to improve the production of this alcohol from renewable biomasses. Additionally, S. cerevisiae strains from harsh industrial environments have been exploited due to their robust traits and improved fermentative capacity. Nevertheless, there is still not an optimized strain capable of turning second generation bioprocesses economically viable. Considering this, and aiming to facilitate and guide the future development of effective S. cerevisiae strains, this work reviews genetic engineering strategies envisioning improvements in ^2nd generation bioethanol production, with special focus in process-related traits, xylose consumption, and consolidated bioprocessing. Altogether, the genetic toolbox described proves S. cerevisiae to be a key microorganism for the establishment of a bioeconomy, not only for the production of lignocellulosic bioethanol, but also having potential as a cell factory platform for overall valorization of renewable biomasses.

Structure and properties of the oyster mushroom (Pleurotus ostreatus) lectin

Pleurotus ostreatus Lectin (POL) is a 353 amino acid chain lectin that can be purified from the fruiting bodies of the very well-known and widely diffused edible oyster mushrooms (P. ostreatus). The lectin has been partially characterized by different groups and, although it was crystallized about 20 years ago, its 3D structure and the details of its interactions with carbohydrates are still unknown. This paper reports the 3D structure and ligand-binding properties of POL. We have determined the X-ray structure of the apo-protein purified from the fruiting bodies of the mushroom and that of the recombinant protein in complex with melibiose to a resolution of about 2 Å. The lectin is a homodimer in which the two polypeptide chains are linked by a disulfide bridge. A POL monomer is composed of two highly homologous β-jellyroll domains each of which containing a calcium-dependent carbohydrate-binding site. A high degree of sequence similarity is observed between the two carbohydrate-binding modules present in each monomer. The structure of the lectin in complex with melibiose reveals that a POL dimer has four calcium-dependent carbohydrate-binding sites. The interaction with sugars in solution has been characterized by isothermal titration calorimetry and saturation transfer difference NMR and it sheds new light on the molecular determinants of POL specificity. The lectin exhibits in vitro antiproliferative effects against human cancer cell lines and presents structural similarity with the prototype member of the CBM67 family, the noncatalytic domain of Streptomyces avermitilis α-rhamnosidase.

Development of smart anti-glycan reagents using immunized lampreys

Studies on the expression of cellular glycans are limited by a lack of sensitive tools that can discriminate specific structural features. Here we describe the development of a robust platform using immunized lampreys (Petromyzon marinus), which secrete variable lymphocyte receptors called VLRBs as antibodies, for generating libraries of anti-glycan reagents. We identified a wide variety of glycan-specific VLRBs detectable in lamprey plasma after immunization with whole fixed cells, tissue homogenates, and human milk. The cDNAs from lamprey lymphocytes were cloned into yeast surface display (YSD) libraries for enrichment by multiple methods. We generated VLRB-Ig chimeras, termed smart anti-glycan reagents (SAGRs), whose specificities were defined by microarray analysis and immunohistochemistry. 15 VLRB antibodies were discovered that discriminated between linkages, functional groups and unique presentations of the terminal glycan motif. The development of SAGRs will enhance future studies on glycan expression by providing sequenced, defined antibodies for a variety of research applications.

Tanya McKitrick et al. develop a platform for generating libraries of anti-glycan reagents using immunized lampreys. They identify 15 glycan-specific lymphocyte receptor antibodies that can distinguish between different functional groups of the terminal glycan motif.

Purification and characterisation of a xylose-specific mitogenic lectin from Fusarium sambucinum

A xylose-specific intracellular lectin, showing hemagglutination only with rabbit erythrocytes was purified from mycelium of Fusarium sambucinum which was designated as FSL. An array of anion exchange chromatography on Q-Sepharose and gel-exclusion chromatography on Sephadex G-100 resulted in 84.21% yield and 53.99-fold purification of lectin with specific activity of 169.53 titre/mg. Molecular weight of FSL determined by SDS-PAGE was 70.7 kDa, which was further confirmed by gel-exclusion chromatography. Native-PAGE analysis of FSL showed its monomeric nature. FSL was observed to be a glycoprotein containing 2.9% carbohydrate. Hapten inhibition profile of FSL displayed its strong affinity towards D-xylose (MIC 1.562 mM), L-fucose (MIC 6.25 mM), D-mannose (MIC 3.125 mM), fetuin (MIC 15.62 μg/mL), asialofetuin (MIC 125 μg/mL) and BSM (MIC 3.125 μg/mL). Affinity of FSL towards xylose is rare. FSL was found stable over a pH range 6.0-7.5 and upto 40 °C temperature. Hemagglutination activity of FSL remained unaffected by divalent ions. Lectin concentration of 5 μg/mL was found sufficient to stimulate proliferation of murine spleen cells and its concentration 75 μg/mL exhibited highest mitogenic potential. FSL exhibited maximum mitogenic stimulatory index of 14.35. The purification, characterisation and mitogenicity of F. sambucinum lectin has been reported first time.

Heterologous expression and molecular binding properties of AofleA, a fucose-specific lectin from nematophagous fungus Arthrobotrys oligospora

Lectins are the primary recognition macromolecules for various types of fucosylation, a common eukaryotic post-translational modification. In this study, we report the heterologous expression and molecular binding properties of a fucose-specific lectin, AofleA, isolated from Arthrobotrys oligospora. This is the first reported fucose-specific lectin found in nematophagous fungi. The recombinant AofleA (r-AofleA) was expressed in Escherichia coli with high efficiency, yielding at least 500 mg of soluble and functional r-AofleA per liter of broth. Using hemagglutination inhibition assay and glycan microarray analysis, r-AofleA was found to be broadly specific for fucosylated glycans or oligosaccharides including Fucα(1-2), Fucα(1-3), Fucα(1-4) and Fucα(1-6) linkages, similar to Aleuria aurantia lectin (AAL). Frontal affinity chromatography showed that r-AofleA has high affinity towards PA-L-fucose with an average K_d value of 15 nM. These findings provide a basis for improved understanding of the structure and functions of AofleA during recognition and capture of prey nematodes by nematophagous fungus A. oligospora.

Purification of a potent mitogenic homodimeric Penicillium griseoroseum lectin and its characterisation

Penicillium griseoroseum lectin was 80-fold purified by successive DEAE Sepharose anion exchange and Sephadex G-100 gel permeation chromatography. P. griseoroseum lectin exhibited haemagglutination activity towards protease-treated rabbit erythrocytes. It showed specificity towards various carbohydrates such as d-mannose, N-acetyl-d-glucosamine, mucins, and so forth. P. griseoroseum lectin was found as a glycoprotein with glycan content of 4.33%. Purified P. griseoroseum lectin is homodimeric having a molecular mass of 57 kDa with subunit molecular mass of 28.6 kDa. Haemagglutination activity of purified P. griseoroseum lectin was completely stable from 25°C to 35°C at a pH range of 6-7.5. Lectin activity was not influenced by divalent metal ions and denaturants. P. griseoroseum lectin manifested mitogenicity towards mice splenocytes and activity reached a peak at 75 μg/ml of lectin concentration. P. griseoroseum lectin in microgram concentrations stimulated proliferation of mice splenocytes. Thus, P. griseoroseum lectin exhibits potential mitogenicity, which can be exploited for further biomedical applications.

Lectin biosensors in cancer glycan biomarker detection

Cancer has high incidence and it will continue to increase over the next decades. Detection and quantification of cancer-associated biomarkers is frequently carried out for diagnosis, prognosis and treatment monitoring at various disease stages. It is well-known that glycosylation profiles change significantly during oncogenesis. Aberrant glycans produced during tumorigenesis are, therefore, valuable molecules for detection and characterization of cancer, and for therapeutic design and monitoring. Although glycoproteomics has benefited from the development of analytical tools such as high performance liquid chromatography, two-dimensional gel and capillary electrophoresis and mass spectrometry, these approaches are not well suited for rapid point-of-care (POC) testing easily performed by medical staff. Lectins are biomolecules found in nature with specific affinities toward particular glycan structures and bind them thus forming a relatively strong complex. Because of this characteristic, lectins have been used in analytical techniques for the selective capture or separation of certain glycans in complex samples, namely, in lectin affinity chromatography, or to characterize glycosylation profiles in diverse clinical situations, using lectin microarrays. Lectin-based biosensors have been developed for the detection of specific aberrant and cancer-associated glycostructures to aid diagnosis, prognosis and treatment assessment of these patients. The attractive features of biosensors, such as portability and simple use make them highly suitable for POC testing. Recent developments in lectin biosensors, as well as their potential and pitfalls in cancer glycan biomarker detection, are presented in this chapter.

Fucose-specific lectin of Aspergillus fumigatus: binding properties and effects on immune response stimulation

Aspergillus fumigatus is the major causative fungus of aspergillosis, and many studies have explored the relationship between A. fumigatus and pathogenicity. In the current study, we focused on a fucose-specific lectin, FleA, as a novel molecule which related to the pathogenicity of A. fumigatus. The disruption of the fleA gene did not lead to clear morphological changes compared to parental strain under several stress conditions in culture, but germination become earlier. In comparison with parental strain, the pathogenicity of disruptant was enhanced in a mouse infection model. The pattern of conidial phagocytosis and adhesion to cultured cells did not explain this enhanced pathogenicity. FleA was reported to contain six conserved fucose-binding sites; the analysis of constructed FleA point mutants revealed nonequivalent contribution of the fucose-binding sites to fucose binding. Based on the immune response induced in the cultured cells upon exposure to wild-type and mutant FleA, we propose a model of the FleA molecule in A. fumigatus infection.

Polyporus squamosus Lectin 1a (PSL1a) Exhibits Cytotoxicity in Mammalian Cells by Disruption of Focal Adhesions, Inhibition of Protein Synthesis and Induction of Apoptosis

PSL1a is a lectin from the mushroom Polyporus squamosus that binds to sialylated glycans and glycoconjugates with high specificity and selectivity. In addition to its N-terminal carbohydrate-binding domain, PSL1a possesses a Ca²⁺-dependent proteolytic activity in the C-terminal domain. In the present study, we demonstrate that PSL1a has cytotoxic effects on mammalian cancer cells, and we show that the cytotoxicity is dependent on the cysteine protease activity. PSL1a treatment leads to cell rounding and detachment from the substratum, concomitant with disruption of vinculin complexes in focal adhesions. We also demonstrate that PSL1a inhibits protein synthesis and induces apoptosis in HeLa cells, in a time- and concentration-dependent manner.

Lectin activity in mycelial extracts of Fusarium species

Lectins are non-immunogenic carbohydrate-recognizing proteins that bind to glycoproteins, glycolipids, or polysaccharides with high affinity and exhibit remarkable ability to agglutinate erythrocytes and other cells. In the present study, ten Fusarium species previously not explored for lectins were screened for the presence of lectin activity. Mycelial extracts of F. fujikuroi, F. beomiformii, F. begoniae, F. nisikadoi, F. anthophilum, F. incarnatum, and F. tabacinum manifested agglutination of rabbit erythrocytes. Neuraminidase treatment of rabbit erythrocytes increased lectin titers of F. nisikadoi and F. tabacinum extracts, whereas the protease treatment resulted in a significant decline in agglutination by most of the lectins. Results of hapten inhibition studies demonstrated unique carbohydrate specificity of Fusarium lectins toward O-acetyl sialic acids. Activity of the majority of Fusarium lectins exhibited binding affinity to d-ribose, l-fucose, d-glucose, l-arabinose, d-mannitol, d-galactosamine hydrochloride, d-galacturonic acid, N-acetyl-d-galactosamine, N-acetyl-neuraminic acid, 2-deoxy-d-ribose, fetuin, asialofetuin, and bovine submaxillary mucin. Melibiose and N-glycolyl neuraminic acid did not inhibit the activity of any of the Fusarium lectins. Mycelial extracts of F. begoniae, F. nisikadoi, F. anthophilum, and F. incarnatum interacted with most of the carbohydrates tested. F. fujikuroi and F. anthophilum extracts displayed strong interaction with starch. The expression of lectin activity as a function of culture age was investigated. Most species displayed lectin activity on the 7th day of cultivation, and it varied with progressing of culture age.

Purification, characterization, and mitogenic potential of a mucin-specific mycelial lectin from Aspergillus sparsus

Lectins are carbohydrate binding proteins or glycoproteins that bind reversibly to specific carbohydrates present on the apposing cells, which is responsible for their ability to agglutinate red blood cells, lymphocytes, fibroblasts, etc. Due to their carbohydrate specificity, lectins have been used for purification and characterization of glycoproteins like antibodies, cytokines, tumor-associated glycoproteins, hormones, inhibitors, growth factors, various enzymes, membrane proteins (receptors), or even toxins and viruses. In the present study, a mycelial lectin from Aspergillus sparsus was purified, characterized, and evaluated for its mitogenic potential. Lectin could be effectively purified 17.8-fold in a single-step using affinity chromatography on mucin-sepharose column. Lectin migrated as a single band in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with an apparent molecular mass of 100.2 kDa. Lectin showed pH optima of 6.5-8.0, and optimum temperature was determined to be 20-30 °C. Lectin was stable within a pH range of 5.5-10.0 and showed fairly good thermostability. Lectin activity was unaffected in the presence of EDTA, while activity reduced upon interaction with denaturants. MTT assay revealed strong mitogenic potential of A. sparsus lectin at a concentration up to 100 μg/ml.

Biosorption of Elements

Biosorption is a unique ability of living or dead biomass to interact with substances such as metals where reduction of sorbate concentration can be achieved. Thus, it has been widely proposed as a promising alternative for metal remediation and recovery owing to its low cost and sustainable “green” nature. Despite considerable biosorption‐related research performed in the past few decades, no significant commercial success has been achieved so far. This chapter starts with discussion of the basic science of biosorption and the potential of some selected biomasses such as yeast, algae, agro‐based waste and vermicompost to be used as biosorbent material. Following this, some important issues regarding the practical application of biosorption are highlighted, including the advantages and disadvantages of using dead or living biomass, the availability of biosorption reactors, immobilization techniques, metal recovery and post‐treatment of spent biosorbent. Lastly, current challenges that limit the commercial success of biosorption as well as the direction of future research are discussed.

Algal lectins as promising biomolecules for biomedical research

Lectins are natural bioactive ubiquitous proteins or glycoproteins of non-immune response that bind reversibly to glycans of glycoproteins, glycolipids and polysaccharides possessing at least one non-catalytic domain causing agglutination. Some of them consist of several carbohydrate-binding domains which endow them with the properties of cell agglutination or precipitation of glycoconjugates. Lectins are rampant in nature from plants, animals and microorganisms. Among microorganisms, algae are the potent source of lectins with unique properties specifically from red algae. The demand of peculiar and neoteric biologically active substances has intensified the developments on isolation and biomedical applications of new algal lectins. Comprehensively, algal lectins are used in biomedical research for antiviral, antinociceptive, anti-inflammatory, anti-tumor activities, etc. and in pharmaceutics for the fabrication of cost-effective protein expression systems and nutraceutics. In this review, an attempt has been made to collate the information on various biomedical applications of algal lectins.