► We review extraction procedures for the recovery of fucoidan from brown algae. ► Classical as well as novel extraction procedures are covered. ► Novel techniques are ultrasound-, microwave-, and ...enzyme-assisted extraction. ► It is assumed that these methods will support an improved extraction of fucoidan.
Sulfated polysaccharides, such as the so-called fucoidans, from brown algae exhibit a versatile biological activity, which is thought to be associated with their characteristic sulfated fucose backbone. The extraction of the target compound is one of the most important steps of the purification process. The correct adjustment of parameters, such as temperature, pH, and extraction time, greatly influences the yield and prevents the possible structural alteration of the sulfated polysaccharides. This review includes historical and current extraction procedures for sulfated polysaccharides and illustrates novel extraction techniques, which can effectively improve the extraction process. The use of ultrasound- and microwave-assisted extraction techniques is described, the potential of which has been underestimated to date. Furthermore, the enzyme-assisted extraction of fucoidans is in its infancy. It is assumed that further improvements of these procedures (e.g., by the application of computer-aided techniques) will have a major impact on the economics and the scalability of the extraction process as well as yielding a sugar fraction with a conserved sulfation pattern.
A comparative study concerning the physicochemical, monomeric composition and biological characters among different fucoidan fractions is presented. Common purification techniques for fucoidan ...usually involve many steps. During these steps, the important structural features might be affected and consequently alter its biological activities. Three purified fractions were derived from Fucus vesiculosus water extract which, afterwards, were purified by a recently-developed dye affinity chromatography protocol. This protocol is based on dye-sulfated polysaccharide interactions. The first two fractions were obtained from crude precipitated fucoidan at different pH values of the adsorption phase: pH 1 and 6. This procedure resulted in fucoidan_1 and 6 fractions. The other, third, fraction: fucoidan_M, however, was obtained from a buffered crude extract at pH 1, eliminating the ethanol precipitation step. All of the three fractions were then further evaluated. Results revealed that fucoidan_M showed the highest sulfur content (S%), 12.11%, with the lowest average molecular weight, 48 kDa. Fucose, galactose, and uronic acid/glucose dimers were detected in all fractions, although, xylose was only detected in fucoidan_1 and 6. In a concentration of 10 µg·mL(-1), Fucoidan_6 showed the highest heparin-like anticoagulant activity and could prolong the APTT and TT significantly to 66.03 ± 2.93 and 75.36 ± 1.37 s, respectively. In addition, fucoidan_M demonstrated the highest potency against HSV-1 with an IC50 of 2.41 µg·mL(-1). The technique proved to be a candidate for fucoidan purifaction from its crude extract removing the precipitation step from common purification protocols and produced different fucoidan qualities resulted from the different incubation conditions with the immobilized thiazine toluidine blue O dye.
Cyanobacteria obtain their energy through photosynthesis and live embedded in a matrix of extracellular polymeric substances (EPS) containing valuable products, e.g., polysaccharides, lipids, ...proteins, and antimicrobials. Besides chlorophyll a and carotenoids, they have light-absorbing compounds in the form of light-harvesting complexes, the so-called phycobilisomes, consisting of different phycobiliproteins. Together they close the “green gap” whereby cyanobacteria can use light more effective than higher plants. Cultivation of cyanobacteria on a lab-scale results in small amounts of biomass for their characterization or a comprehensive screening. EPS are, for example, produced as a protection against suboptimal culture conditions. Carotenoids are essential light-harvesting pigments for photosynthesis, play a key role in photoprotective reactions, and are produced for cell wall stabilization. Essentially, the pigment composition of cyanobacteria depends on the available light spectrum, nitrogen content, and temperature. Especially the production of EPS and pigments are indicators for the cell-condition. Therefore, different EPS extraction methods were tested including the determination of inhibitory effects of extracts against
Escherichia coli
. Based on the best EPS extraction method, a new strategy for downstream processing (DSP) was developed to determine EPS, the pigments chlorophyll
a
and carotenoids, and phycobiliproteins from only one sample. As cyanobacterial model organisms
Trichocoleus sociatus
and
Nostoc flagelliforme
were used, and DSP strategy was successfully transferred to four additional cyanobacteria. The final DSP includes the following steps: (i) EPS extraction, (ii) lyophilization of biomass, (iii) extraction of phycobiliproteins, and a final (iv) chlorophyll a and carotenoid extraction. The new strategy allows a comprehensive characterization of cyanobacterial cells.
The cultivation of cyanobacteria with the addition of an organic carbon source (meaning as heterotrophic or mixotrophic cultivation) is a promising technique to increase their slow growth rate. ...However, most cyanobacteria cultures are infected by non-separable heterotrophic bacteria. While their contribution to the biomass is rather insignificant in a phototrophic cultivation, problems may arise in heterotrophic and mixotrophic mode. Heterotrophic bacteria can potentially utilize carbohydrates quickly, thus preventing any benefit for the cyanobacteria. In order to estimate the advantage of the supplementation of a carbon source, it is essential to quantify the proportion of cyanobacteria and heterotrophic bacteria in the resulting biomass. In this work, the use of quantitative polymerase chain reaction (qPCR) is proposed. To prepare the samples, a DNA extraction method for cyanobacteria was improved to provide reproducible and robust results for the group of terrestrial cyanobacteria. Two pairs of primers were used, which bind either to the 16S rRNA gene of all cyanobacteria or all bacteria including cyanobacteria. This allows a determination of the proportion of cyanobacteria in the biomass. The method was established with the two terrestrial cyanobacteria
Trichocoleus sociatus
SAG 26.92 and
Nostoc muscorum
SAG B-1453-12a. As proof of concept, a heterotrophic cultivation with
T. sociatus
with glucose was performed. After 2 days of cultivation, a reduction of the biomass partition of the cyanobacterium to 90% was detected. Afterwards, the proportion increased again.
The original version of this article unfortunately contains mistake introduced during the publishing process. The names of the authors were interchanged in the author group. The corrected author ...group is shown above.
Fucoidan is a sulfated polysaccharide with promising pharmacological applications. Due to its medicinal properties, there is a demand for a separation technique that yields a high purification grade. ...Here, we present a novel purification tool for recovering fucoidan from the marine brown macroalgae Fucus vesiculosus. The developed method is based on amino‐derivatized Sepabeads® EC‐EA. The beads were modified with toluidine blue (TB), a thiazine derivative, to exploit the strong donor acceptor interactions between the cationic dye and the anionic polysaccharide. The adsorption kinetics and the binding capacity of the resin were analyzed. A Sips model was used to approximate the adsorption isotherm, resulting in a maximum capacity of 127.7 mg fucoidan per g adsorbent. Investigation of the effect of adsorption step's pH on purity and chemical structure was performed by TB and Fourier transform infra‐red spectroscopy assays. Results showed that adsorption at pH 1 and 6 had negligible effects on fucoidan's chemical structure. However, purity was actually improved by 1.55‐ and 1.69‐fold at pH 1 and 6, respectively, with an average yield of 5 g/100 g dried algae powder. In contrast, only a 1.46‐fold increment was observed in fucoidan purified by the traditional method at pH 2, with a yield of 7.5 g/100 g dried algae powder. Furthermore, fucoidan purified by this method at pH 6 complies with, or even exceeds the quality of the commercially available (≥95% pure) fucoidan (Sigma‐Aldrich®) with respect to molecular weight and sulfur content. Therefore, dye affinity chromatography provides more advantages than the classically used techniques for fucoidan purification.
Phototrophic biofilms, in particular terrestrial cyanobacteria, offer a variety of biotechnologically interesting products such as natural dyes, antibiotics or dietary supplements. However, ...phototrophic biofilms are difficult to cultivate in submerged bioreactors. A new generation of biofilm photobioreactors imitates the natural habitat resulting in higher productivity. In this work, an aerosol-based photobioreactor is presented that was characterized for the cultivation of phototrophic biofilms. Experiments and simulation of aerosol distribution showed a uniform aerosol supply to biofilms. Compared to previous prototypes, the growth of the terrestrial cyanobacterium Nostoc sp. could be almost tripled. Different surfaces for biofilm growth were investigated regarding hydrophobicity, contact angle, light- and temperature distribution. Further, the results were successfully simulated. Finally, the growth of Nostoc sp. was investigated on different surfaces and the biofilm thickness was measured noninvasively using optical coherence tomography. It could be shown that the cultivation surface had no influence on biomass production, but did affect biofilm thickness.
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•Novel peptide antibiotic from a terrestrial cyanobacterium.•Successful heterologous production with E. coli.•Potent activity against several Gram-positive bacteria.
With regard to ...the emerging health threat by antibiotic resistant bacteria, bacteriocins are considered as a promising way to overcome this urgent problem. In this work, a hitherto unknown bacteriocin from the terrestrial cyanobacterium Chroococcidiopsis cubana was heterologously expressed in Escherichia coli, purified to homogeneity and tested for activity against several bacteria and one yeast species. The compound showed potent bacteriolytic activity against several Gram-positive bacteria and slight activity against one Gram-negative strain. The bacteriocin had no cytotoxic impact on mouse neuroblastoma N2a cells, indicating its potential for treatment against Gram-positive bacterial pathogens in human diseases.
Chloroperoxidase (CPO) is a versatile enzyme, which is secreted by the marine fungus Caldariomyces fumago (Leptoxyphium fumago). However, the application of the enzyme is hampered by its high price, ...which is due to the costly, labor‐intensive purification process. One challenge of the downstream process is the removal of a coproduced black pigment that forms a complex with the active enzyme. While strain development can be considered as an option to reduce the synthesis of the interfering pigment, the metabolism of the microorganism can be altered alternatively by using the biofilm growth mode of the fungus. The aim of this study was to reduce pigment formation during CPO synthesis. We investigated for the first time CPO production during C. fumago biofilm growth initiated through the presence of different microstructured stainless steel surfaces (material number: 1.4571; AISI 316Ti). CPO production by C. fumago was similar when grown as a biofilm or in suspension, whereas pigment formation was drastically reduced by cells grown on moderately structured surfaces (Ra = 0.13 ± 0.02 μm). The possibilities of biofilm growth for changing cell properties and for continuous fermentation are discussed.
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