Lectins have the ability to bind specific carbohydrates and they have potential applications as medical and pharmacological agents. The unique structure and usefulness of red algal lectin have been reported, but these lectins are limited to a few marine algal groups. In this study, a novel mannose-binding lectin from Grateloupia chiangii (G. chiangii lectin, GCL) was purified using antiviral screens and affinity chromatography. We characterized the molecular weight, agglutination activity, hemagglutination activity, and heat stability of GCL. To determine the carbohydrate specificity, a glycan microarray was performed. GCL showed strong binding affinity for Maltohexaose-β-Sp1 and Maltoheptaose-β-Sp1 with weak affinity for other monosaccharides and preferred binding to high-mannan structures. The N-terminal sequence and peptide sequence of GCL were determined using an Edman degradation method and LC-MS/MS, and the cDNA and peptide sequences were deduced. GCL was shown to consist of 231 amino acids (24.9 kDa) and the N-terminus methionine was eliminated after translation. GCL possessed a tandem repeat structure of six domains, similar to the other red algal lectins. The mannose binding properties and tandem repeat structure of GCL may confer it the potential to act as an antiviral agent for protection against viral infection.

Dinoflagellates are an important group of phytoplanktons, characterized by two dissimilar flagella and distinctive features of both plants and animals. Dinoflagellate-generated harmful algal blooms (HABs) and associated damage frequently occur in coastal areas, which are concomitant with increasing eutrophication and climate change derived from anthropogenic waste and atmospheric carbon dioxide, respectively. The severe damage and harmful effects of dinoflagellate phycotoxins in the fishing industry have been recognized over the past few decades, and the management and monitoring of HABs have attracted much attention, leaving aside the industrial application of their valuable toxins. Specific modes of action of the organisms’ toxins can effectively be utilized for producing beneficial materials, such as Botox and other therapeutic agents. This review aims to explore the potential industrial applications of marine dinoflagellate phycotoxins; furthermore, this review focuses on their modes of action and summarizes the available knowledge on them.

Lectin is an important protein in medical and pharmacological applications. Impurities in lectin derived from natural sources and the generation of inactive proteins by recombinant technology are major obstacles for the use of lectins. Expressing recombinant lectin with a tandem repeat structure can potentially overcome these problems, but few studies have systematically examined this possibility. This was investigated in the present study using three distinct forms of recombinant mannose-binding lectin from Bryopsis plumosa (BPL2)—i.e., the monomer (rD1BPL2), as well as the dimer (rD2BPL2), and tetramer (rD4BPL2) arranged as tandem repeats. The concentration of the inducer molecule isopropyl β-D-1-thiogalactopyranoside and the induction time had no effect on the efficiency of the expression of each construct. Of the tested constructs, only rD4BPL2 showed hemagglutination activity towards horse erythrocytes; the activity of towards the former was 64 times higher than that of native BPL2. Recombinant and native BPL2 showed differences in carbohydrate specificity; the activity of rD4BPL2 was inhibited by the glycoprotein fetuin, whereas that of native BPL2 was also inhibited by d-mannose. Our results indicate that expression as tandem repeat sequences can increase the efficiency of lectin production on a large scale using a bacterial expression system.

Lectins, characterized by their carbohydrate-binding ability, have extensive practical applications. However, their industrial use is limited due to impurity. Thus, quality-controlled production of recombinant lectin is necessary. In this study, the algal lectin BPL3 (Bryopsis plumosa lectin 3) was successfully produced using a bacterial expression system, BL21(DE3), with an artificial repeated structure (dimeric construct). Recombinant dimeric BPL3 (rD2BPL3) was confirmed by LC-MS/MS spectrometry. Expression efficiency was greater for the construct with the repeat structure (rD2BPL3) than the monomeric form (rD1BPL3). Optimal conditions for expression were 1 mM IPTG at 20 °C. Recombinant lectin was purified under denaturing conditions and refolded by the flash dilution method. Recombinant BPL3 was solubilized in 1× PBS containing 2 M urea. rD2BPL3 showed strong hemagglutination activity using human erythrocyte. rD2BPL3 had a similar sugar specificity to that of the native protein, i.e., to N-acetyl-glucosamine (GlcNAc) and N-acetyl-galactosamine (GalNAc). Glycan array results showed that recombinant BPL3 and native BPL3 exhibited different binding properties. Both showed weak binding activity to α-Man-Sp. Native BPL3 showed strong binding specificity to the alpha conformation of amino sugars, and rD2BPL3 had binding activity to the beta conformation. The process developed in this study was suitable for the quality-controlled large-scale production of recombinant lectins.

Background: This study focused on evaluating the physiochemical characteristics and antibacterial activity of Octoprohibitin-encapsulated CNPs (Octoprohibitin-CNPs) against Acinetobacter baumannii. Methods: Octoprohibitin was encapsulated into CNPs via ionotropic gelation with carboxymethyl chitosan (CMC) and low molecular weight chitosan (CS). Octoprohibitin-CNPs were dispersed in phosphate-buffered saline and the release kinetic profile was determined. Then Octoprohibitin-CNPs were examined using field-emission transmission electron microscopy and physicochemical characterization was performed. Antibacterial activity of Octoprohibitin-CNPs against A. baumannii was evaluated. Biofilm inhibition and eradication assays were performed using the crystal violet (CV) staining-based method for biofilm quantification. Results: The average diameter, zeta potential, encapsulation efficiency, and loading capacity of Octoprohibitin-CNPs were 244.5 ± 21.97 nm, +48.57 ± 0.38 mV, and 85.7% and 34.2%, respectively. TEM analysis imaging revealed that Octoprohibitin-CNPs are irregularly shaped, with fewer aggregates than CNPs. Octoprohibitin-CNPs exhibited a biphasic release pattern, characterized by an initial rapid phase followed by a sustained release over time, extending up to 93.68 ± 6.48% total release until 96 h. In vitro, Octoprohibitin-CNPs showed lower cytotoxicity compared to Octoprohibitin alone. Time-kill kinetic and bacterial viability reduction assays showed Octoprohibitin-CNPs exhibited slightly higher antibacterial activity against A. baumannii than Octoprohibitin. Conclusions: Octoprohibitin-CNP-treated A. baumannii exhibited higher levels of morphological deviation, increased membrane permeability, and the production of reactive oxygen species, as well as antibiofilm activity with greater biofilm inhibition and eradication than Octoprohibitin. These findings show that Octoprohibitin-CNPs perform better against A. baumannii compared to Octoprohibitin alone.