Navicula sp. Sulfated Polysaccharide Gels Induced by Fe(III): Rheology and Microstructure

A sulfated exopolysaccharide derived from Chlorella sp. exhibiting in vitro anti-α-D-Glucosidase activity

There is a great scientific curiosity to discover all environments sheltering microalgae, especially those with exceptional characteristics from coldest to hottest ones, the purpose remains to explore the potential of the native microalgae flora and the research for new bioactive compounds. This study aimed to isolate a polysaccharide-producing microalga from an extreme ecosystem and to evaluate its capacity to inhibit the α-D-glucosidase enzyme. Chlorella strain is isolated from hypersaline Lake in the Algerian desert. The exopolysaccharide extraction was performed by the concentration of free-cell supernatant in a rotary evaporator. The infrared analysis showed a characteristic footprint of carbohydrates with particular functional groups, such as sulfate. Gas chromatography-mass spectrometry has revealed a hetero-exopolysaccharide composed of galactose 35.75%, glucose 21.13%, xylose 16.81%, fructose 6.96%, arabinose 5.10%, and glucuronic acid 2.68%. The evaluation of the anti-hyperglycemic activity demonstrated a significant α-D-glucosidase inhibition of 80.94 ± 0.01% at 10 mg mL-1 with IC50 equal to 4.31 ± 0.20 mg mL-1. This study opens a vast prospect to use exopolysaccharides as natural nutraceutical or food additive.

Circular economy approaches for the production of high-value polysaccharides from microalgal biomass grown on industrial fish processing wastewater: A review

The discharge of high-strength wastewater from the fish-processing industries, comprising undefined blends of toxic and organic compounds, has always been a subject of great disquiet worldwide. Despite a large number of effluent treatment methodologies known to date, biosorption with the aid of naturally grown microalgae has been recognized recently to possess promising outcomes in eradicating pollutants comprising organic compounds from liquid effluents. Interestingly, the microalgal biomass harvested from phytoremediation of fish effluent was identified to be abundant in bio compounds that exhibited potential application in pharmaceutical, nutraceutical, and, aquaculture feed, generating a circular economy. In this context, the focus of the review is to emphasize the applications of microalgal species as naturally occurring and zero-cost adsorbents for the elimination of organic contaminants from fish liquid effluents. The summary of the literature encompassed in this work is supposed to benefit the readers to comprehend the primary mechanisms by which microalgae uptakes the organic matter from fish processing effluents and converts them into various biological molecules. From the scientific works assessed through this review, the most promising microalgae species regards to nutrient uptake and removal efficiency from fish effluent, were identified as Chlorella sp. > Spirulina sp. > Scenedesmus sp. The review further revealed supercritical fluid extraction as the robust extraction tool for the extraction of targeted bioproducts from microalgal biomass grown within fish effluents. Eventually, the information presented through this review establishes phytoremediation using microalgal biomass to be a natural cost-effective, sustainable circular bio-economy approach that could be robustly applied for the efficient treatment of wastewater discharged from food processing industries.

Sulfated Polysaccharides from Chaetoceros muelleri: Macromolecular Characteristics and Bioactive Properties

Simple Summary

Algae are an important source of bioactive compounds. The interest in microalgae is increasing due to their high-value products and the advantage of biomass cultivation under controlled conditions. Polysaccharides are released by algae and microalgae species and have been reported to have bioactivities found beneficial to human health. Despite the recognized importance of these organisms, the structure of polysaccharides in microalgae has been practically unexplored in contrast to that of macroalgae. Only a few microalgae polysaccharide structures have been solved due to the difficulties in the extraction of pure samples and the complexity of their chemical structures. Reports emphasize how the molecular weight, the content of sulfate groups, and the negative charge may be responsible for their multiple bioactivities. To better understand the uses and potential applications of extracellular polysaccharides, it is necessary to know their structure and physicochemical properties, which include molecular weight and chain conformation, since they are decisive in their biochemical behavior.

Abstract

In the present study, a culture of Chaetoceros muelleri, a cosmopolitan planktonic diatom microalga present in the Sea of Cortez, was established under controlled laboratory conditions. A sulfated polysaccharide (CMSP) extraction was carried out from the biomass obtained, resulting in a yield of 2.2% (w/w of dry biomass). The CMSP sample was analyzed by Fourier transform infrared spectroscopy, showing bands ranging from 3405 to 590 cm⁻¹ and a sulfate substitution degree of 0.10. Scanning electron microscopy with elemental analysis revealed that the CMSP particles are irregularly shaped with non-acute angles and contain sulfur. High-performance liquid chromatography coupled to a dynamic light-scattering detector yielded molecular weight (Mw), polydispersity index (PDI), intrinsic viscosity [η], and hydrodynamic radius (Rh) values of 4.13 kDa, 2.0, 4.68 mL/g, and 1.3 nm, respectively, for the CMSP. This polysaccharide did not present cytotoxicity in CCD-841 colon cells. The antioxidant activity and the glycemic index of the CMSP were 23% and 49, respectively, which gives this molecule an added value by keeping low glycemic levels and exerting antioxidant activity simultaneously.

Effects of monosaccharide composition on quantitative analysis of total sugar content by phenol-sulfuric acid method

Phenol-sulfuric acid method is one of the most common methods applied to the analysis of total sugar content during polysaccharides study. However, it was found that the results obtained from the phenol-sulfuric acid method was generally lower than the real total sugar content, especially when acidic monosaccharides were contained in the polysaccharides samples. Therefore, the present study focused to unveil the proposed problem. Based on the optimization of colorimetric conditions, such as optimal wave length of absorption, linearity range, color reaction time and temperature, it indicated that the phenol-sulfuric acid method was a convenient and accurate way for the total sugar content analysis. In addition, the color-rendering capabilities of 10 common monosaccharides were systematically analyzed to obtain a relative correction factor for each monosaccharide relative to glucose, which was proved to be the main reason for the deviation in the detection of total sugar content. Moreover, the key points during the application of phenol-sulfuric acid method were suggested. This study provides a scientific theoretical basis and a reliable experimental research method for the accurate determination of total sugar content by the phenol-sulfuric acid method, and which will also promote the application of this convenient method in the polysaccharides study.

Total Phenolic Levels, In Vitro Antioxidant Properties, and Fatty Acid Profile of Two Microalgae, Tetraselmis marina Strain IMA043 and Naviculoid Diatom Strain IMA053, Isolated from the North Adriatic Sea

This work studied the potential biotechnological applications of a naviculoid diatom (IMA053) and a green microalga (Tetraselmis marina IMA043) isolated from the North Adriatic Sea. Water, methanol, and dichloromethane (DCM) extracts were prepared from microalgae biomass and evaluated for total phenolic content (TPC) and in vitro antioxidant properties. Biomass was profiled for fatty acid methyl esters (FAME) composition. The DCM extracts had the highest levels of total phenolics, with values of 40.58 and 86.14 mg GAE/g dry weight (DW in IMA053 and IMA043, respectively). The DCM extracts had a higher radical scavenging activity (RSA) than the water and methanol ones, especially those from IMA043, with RSAs of 99.65% toward 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) at 10 mg/mL, and of 103.43% against 2,2-diphenyl-1-picrylhydrazyl (DPPH) at 5 mg/mL. The DCM extract of IMA053 displayed relevant copper chelating properties (67.48% at 10 mg/mL), while the highest iron chelating activity was observed in the water extract of the same species (92.05% at 10 mg/mL). Both strains presented a high proportion of saturated (SFA) and monounsaturated (MUFA) fatty acids. The results suggested that these microalgae could be further explored as sources of natural antioxidants for the pharmaceutical and food industry and as feedstock for biofuel production.

Photosynthetic microorganisms and their bioactive molecules as new product to healing wounds

Wounds are a public health problem due to long periods required to repair damaged skin, risk of infection, and amputations. Thus, there is a need to obtain new therapeutic agents with less side effects, more effective oxygen delivery, and increased epithelial cell migration. Photosynthetic microorganisms, such as microalgae and cyanobacteria, may be used as a source of biomolecules for the treatment of different injuries. The aim of this review article focuses on healing potential using phytoconstituents from photosynthetic microorganisms. Cyanophyte Spirulina and Chlorophyte Chlorella are more promising due to steroids, triterpenes, carbohydrates, phenols, and proteins such as lectins and phycocyanin. However, there are few reports about identification and specific function of these molecules on the skin. In other microalgae and cyanobacteria genus, high contents of pigments such as β-carotene, chlorophyll a, allophycocyanin, and hydroxypheophytin were detected, but their effects on phases of wound healing is absent yet. The development of new topical drugs from photosynthetic microorganisms could be a potential alternative to maximize healing. KEY POINTS: • Conventional treatment to skin injuries has limitations. • Proteins, terpenes, and phenols increase collagen deposition and re-epithelialization. • Microalgae and cyanobacteria may be used as a source of biomolecules to wound healing.

Influence of Carbohydrate Additives on the Growth Rate of Microalgae Biomass with an Increased Carbohydrate Content

Our study focused on investigating the possibilities of controlling the accumulation of carbohydrates in certain microalgae species (Arthrospira platensis Gomont, Chlorella vulgaris Beijer, and Dunaliella salina Teod) to determine their potential in biofuel production (biohydrogen). It was found that after the introduction of carbohydrates (0.05 g⋅L⁻¹) into the nutrient medium, the growth rate of the microalgae biomass increased, and the accumulation of carbohydrates reached 41.1%, 47.9%, and 31.7% for Arthrospira platensis, Chlorella vulgaris, and Dunaliella salina, respectively. Chlorella vulgaris had the highest total carbohydrate content (a mixture of glucose, fructose, sucrose, and maltose, 16.97%) among the studied microalgae, while for Arthrospira platensis and Dunaliella salina, the accumulation of total carbohydrates was 9.59% and 8.68%, respectively. Thus, the introduction of carbohydrates into the nutrient medium can stimulate their accumulation in the microalgae biomass, an application of biofuel production (biohydrogen).

Hydrogel composite of lanthanum and Halorubrum ejinoor sp. cell lysate as an adsorbing material

OBJECTIVES

Although halophilic archaea are rich in natural environments, their biotechnological applications are not as prevalent as those of other extremophiles, such as thermophiles and alkaliphiles. This study presents an simple method to prepare a hydrogel composite using crude cell lysate of a halophilic archaea, Halorubrum ejinoor sp. (H.e.) which was isolated from a saline lake in Inner Mongolia, China. Furthermore, formation mechanism and potential applications of the hydrogel as an adsorbing material are discussed.

RESULTS

Halorubrum ejinoor sp. (H.e.) cell lysate was firstly prepared by adding pure water onto the H.e. cell pellet, followed by a short incubation at 60 °C. The cell lysate was injected into different metal ion (or H⁺) solutions to obtain the hydrogel composite. It was observed that H⁺, Fe³⁺, La³⁺, Cu²⁺, and Ca²⁺ induced gelation of the cell lysate, while Fe²⁺, Co²⁺, Ni²⁺, Mg²⁺, Na⁺, and K⁺ did not. DNA and extracellular polysaccharides (EPS) in the H.e. cell lysate were found to be responsible for the gelation reaction. These results suggest that DNA and EPS should be crosslinked by metal ions (or H⁺) and form a networked structure in which the metal ion (or H⁺) serves as an anchor point. Potential application of the hydrogel as an adsorbing material was explored using La³⁺-induced H.e. hydrogel composite. The hydrogel composite can adsorb the fluoride, phosphate and DNA-binding carcinogenic agents, such as acridine orange.

CONCLUSIONS

The simplicity and cost effectiveness of the preparation method might make H.e. hydrogel a promising adsorbing material. This work is expected to expand the technical applications of haloarchaea.

Optimization of growing conditions for pigments production from microalga Navicula incerta using response surface methodology and its antioxidant capacity

Navicula incerta is a marine microalga distributed in Baja California, México, commonly used in aquaculture nutrition, and has been extended to human food, biomedical, and pharmaceutical industries due to its high biological activity. Therefore, the study aimed to optimize culture conditions to produce antioxidant pigments. A central composite experimental design and response surface methodology (RSM) was employed to analyze the best culture conditions. The medium (nitrogen-deficient concentrations), salinity (PSU = Practical Salinity Unity [g/kg]), age of culture (days), and solvent extraction (ethanol, methanol, and acetone) were the factors used for the experiment. Chlorophyll a (Chl a) and total carotenoids (T-Car), determined spectroscopically, were used as the response variables. The antioxidant capacity was evaluated by DPPH^• and ABTS^•+ radical inhibition, FRAP, and anti-hemolytic activity. According to the overlay plots, the optimum growth conditions for Chl a and T-Car production were the following conditions: medium = 0.44 mol·L^-1 of NaNO₃, salinity = 40 PSU, age of culture: 3.5 days, and solvent = methanol. The pigment extracts obtained in these optimized conditions had high antioxidant activity in ABTS^•+ (86.2-92.1% of inhibition) and anti-hemolytic activity (81.8-96.7% of hemolysis inhibition). Low inhibition (33-35%) was observed in DPPH^•. The highest value of FRAP (766.03 ± 16.62 μmol TE/g) was observed in the acetonic extract. The results demonstrated that RSM could obtain an extract with high antioxidant capacity with potential applications in the biomedical and pharmaceutical industry, which encourages the use of natural resources for chemoprevention of chronic-degenerative pathologies.

Biochemical characterization of Nostoc sp. exopolysaccharides and evaluation of potential use in wound healing

Exopolysaccharides (EPS) produced by cyanobacteria are complex biomolecules of anionic nature with potential biomedical applications. In this study, the EPS produced by the Nostoc sp. strains PCC7936 and PCC7413 were characterized and evaluated as a biomaterial for new wound dressings. The addition of acetate ions to the culture medium slightly stimulated EPS production, achieving 1463.1 ± 16.0 mgL^-1 (PCC7413) and 1372.1 ± 29.0 mgL^-1 (PCC7936). Both EPS presented nine monosaccharide residues and a MW > 1000 kDa. The acetate addition changed the monosaccharide molar percentages. FTIR and DLS results confirmed the anionic nature and the presence of sulfate groups in both EPS, which are determinant features for biomedical applications. Both EPS at 1%(w/v) formed gels in the presence of 0.4%(w/v) FeCl₃. Results obtained for MTT assay and wound healing in vitro scratch assay revealed hydrogels biocompatibility and ability to promote fibroblast migration and proliferation that was greater in PCC7936. The Nostoc EPS hydrogels presented promising properties to be applied in the treatment of skin injuries.

Protective effects of polysaccharides on hepatic injury: A review

Chronic hepatic injury caused by hepatitis B and C virus (HBV and HCV) infection, high fat diet and alcohol intake has increased to be the critical promoter of hepatocellular carcinoma (HCC). These high risk factors set into motion a vicious cycle of hepatocyte death, inflammation and fibrosis that finally results in cirrhosis and HCC after several decades. However, the treatment options for HCC are very limited. Therefore, early treatment of liver injury may reduce the incidence and probability of HCC or delay the progression of HCC. Substantial ongoing research has focused on nontoxic biological macromolecules, mainly polysaccharides, which possess prominent efficacies on hepatoprotective activity. Based on these encouraging observations, a great deal of effort has been devoted to discovering novel polysaccharides for the development of effective therapeutics for hepatic injury. This review focuses on the protective effects of polysaccharides on liver injury, including hepatitis virus infection, nonalcoholic steatohepatitis, alcoholic liver disease and other hepatic injuries, and describes the underlying mechanisms.