Preparation and Characterization of Intracellular and Exopolysaccharides during Cycle Cultivation of Spirulina platensis

Biogel scavenging slows the sinking of organic particles to the ocean depths

One of Earth's largest carbon fluxes is driven by particles made from photosynthetically fixed matter, which aggregate and sink into the deep ocean. While biodegradation is known to reduce this vertical flux, the biophysical processes that control particle sinking speed are not well understood. Here, we use a vertical millifluidic column to video-track single particles and find that biogels scavenged by particles during sinking significantly reduce the particles' sinking speed, slowing them by up to 45% within one day. Combining observations with a mathematical model, we determine that the mechanism for this slowdown is a combination of increased drag due to the formation of biogel tendrils and increased buoyancy due to the biogel's low density. Because biogels are pervasive in the ocean, we propose that by slowing the sinking of organic particles they attenuate the vertical carbon flux in the ocean.

Recent advances in polysaccharide-dominated extracellular polymeric substances from microalgae: A review

Microalgae are an environmentally friendly and sustainable alternative resource for future food and pharmaceutical production. Microalgal extracellular polymeric substances (EPMS) are polymers consisting of polysaccharides, proteins, lipids and nucleic acids secreted by microalgal cells. This review systematically summarizes the research progress of microalgal EPMS, including its composition, structure, formation, biological activity and application. The diversity of structural units and binding modes confers microalgal EPMS with unique structural and biological activity, which is species-specific. In addition to the polysaccharides with antioxidant, antiviral, and antitumor effects, extracellular vesicles isolated from microalgal EPMS are emerging as new drug carriers. However, challenges such as relatively low yields, complex separation techniques, intricate processing-secretion pathways, and unclear mechanisms of action still hinder the industrial application of microalgal EPMS. By scientifically summarizing the research progress and leveraging strategies such as metabolic regulation, genetic modification, and advanced separation and characterization technologies, microalgal EPMS is expected to see widespread applications in the food, cosmetics, and therapeutic industries.

A novel bioactive and functional exopolysaccharide from the cyanobacterial strain Arthrospira maxima cultivated under salinity stress

Cyanobacterial exopolysaccharides (EPS) remain released by cyanobacteria in the surrounding environment with the main purpose of protection against harmful environmental conditions. Recently, they have received significant attention due to their unique structural characteristics, functional properties, and potential applications across various fields. The current study describes the evaluation of EPS production under salinity stress from Arthrospira maxima. The application of high salinity up to 40 g/L enhanced EPS production, which was collected and purified by alcohol precipitation followed by membrane dialysis and lyophilization. A yield of 60 mg/L was obtained. The Size exclusion chromatography gave for the purified EPS an apparent molecular weight of 2.1 × 105 Da. Monosaccharide composition showed that EPS is a heteropolymer, with mannose, xylose, and glucuronic acid identified as the predominant monosaccharides and derivatives. Nuclear magnetic resonance spectroscopy (13C and 1H) confirmed that EPS is a heteropolysaccharide, entirely in α- anomeric configuration, with glucuronic acid as a main monomer that is probably linked to mannose and xylose via α-glycosidic linkages. Bioactivity assessment of EPS revealed that it exhibits antibacterial activity against several strains, notably, Bacillus subtilis (MIC: 0.6 ± 0.05 mg/mL), Bacillus cereus (MIC: 1 ± 0.01 mg/mL), Escherichia coli (MIC: 0.8 ± 0.01 mg/mL) and Klebsiella pneumonia (MIC: 0.8 ± 0.01 mg/mL). Antioxidant activity was measured using the DPPH radical scavenging assay, yielding an IC₅₀ of 6.83 mg/mL. Besides, EPS was also found to exhibit an interesting emulsifying property with several oil types, indicating its potential as a versatile biopolymer for applications in various industrial sectors.

Recent biotechnological applications of value-added bioactive compounds from microalgae and seaweeds

Microalgae and seaweed have been consumed as food for several decades to combat starvation and food shortages worldwide. The most famous edible microalgae species are Nostoc, Spirulina, and Aphanizomenon, in addition to seaweeds, which are used in traditional medicine and food, such as Nori, which is one of the most popular foods containing Pyropia alga as a major ingredient. Recently, many applications use algae-derived polysaccharides such as agar, alginate, carrageenan, cellulose, fucoidan, mannan, laminarin, ulvan, and xylan as gelling agents in food, pharmaceuticals, and cosmetics industries. Moreover, pigments (carotenoids particularly astaxanthins, chlorophylls, and phycobilins), minerals, vitamins, polyunsaturated fatty acids, peptides, proteins, polyphenols, and diterpenes compounds are accumulated under specific cultivation and stress conditions in the algal cells to be harvested and their biomass used as a feedstock for the relevant industries and applications. No less critical is the use of algae in bioremediation, thus contributing significantly to environmental sustainability.This review will explore and discuss the various applications of microalgae and seaweeds, emphasising their role in bioremediation, recent products with algal added-value compounds that are now on the market, and novel under-developing applications such as bioplastics and nanoparticle production. Nonetheless, special attention is also drawn towards the limitations of these applications and the technologies applied, and how they may be overcome.

Engineering strategies and applications of cyanobacterial exopolysaccharides: A review on past achievements and recent perspectives

Cyanobacteria are ideally suited for developing sustainable biological products but are underdeveloped due to a lack of genetic tools. Exopolysaccharide (EPS) is one of the essential bioproducts with widespread industrial applications. Despite their unique structural characteristics associated with distinct biological and physicochemical aspects, EPS from cyanobacteria has been underexplored. However, it is expected to accelerate in the near future due to the utilization of low-cost cyanobacterial platforms and readily available information on the structural data and specific features of these biopolymers. In recent years, cyanobacterial EPSs have attracted growing scientific attention due to their simple renewability, rheological characteristics, massive production, and potential uses in several biotechnology domains. This review focuses on the most recent research on potential new EPS producers and their distinct compositions responsible for novel biological activities. Additionally, nutritional and process parameters discovered recently for enhancing EPS production and engineering strategies applied currently to control the biosynthetic pathway for enhanced EPS production are critically highlighted. The process intensification of previously developed EPS extraction and purification processes from cyanobacterial biomass is also extensively explained. Furthermore, the newly reported biotechnological applications of cyanobacterial exopolysaccharides are also discussed.

Stability and bioactivities evaluation of analytical grade C-phycocyanin during the storage of Spirulina platensis powder

C-phycocyanin (C-PC) is a natural high-value blue phycobiliprotein from Spirulina platensis, which has wide biological applications in food, pharmaceutical, and cosmetics. However, the freshness of S. platensis powder (SPP) materials and C-PC purification play critical roles in evaluating the stability and bioactivities of C-PC, which severely affect its commercial application. This study investigated the effect of spray-dried SPP freshness on the biofunctional activities of analytical grade C-PC (AGC-PC). The yield of AGC-PC extracted from spray-dried SPP could reach 101.88 mg/g (75% recovery ratio) after purification by reversed phase high-performance liquid chromatography (RP-HPLC) system. The half-life period (t1/2 ) of AGC-PC stability at 60°C and 8000 lux light could remain 171.70 min and 176.11 h within 6 months storage of spray-dried SPP. The emulsifying activity index (EAI) and foaming capacity (FC) of AGC-PC from fresh-dried SPP showed maximum values of 68.64 m2 /g and 252.9%, respectively. The EC50 of AGC-PC from fresh spray-dried SPP on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline -6-sulfonic acid (ABTS+·) scavenging activity could reach 63.76 and 92.93 mg/L, respectively. The EC50 of AGC-PC from fresh spray-dried SPP on proteinase inhibition and anti-lipoxygenase activity were 302.96 and 178.8 mg/L, respectively. The stability and biofunctional activities of AGC-PC remained stable within 6 months storage of SPP, and then rapidly decreased after 9 months storage due to the disintegration of the trimeric (αβ)3 and hexameric (αβ)6 forms of C-PC. It is concluded that the optimal storage period of SPP for preparation of AGC-PC in commercial use should be less than 6 months. PRACTICAL APPLICATION: The C-phycocyanin (C-PC) from dried Spirulina platensis powder (SPP) has been widely applied in food nutritional, florescent markers, pharmaceuticals, cosmetics, etc, due to its blue color, fluorescence, and antioxidant properties. However, the effect of dried SPP freshness on the stability and functional activity of C-PC has been rarely reported. This study found that the thermostability, photostability, emulsifying, antioxidant, and anti-inflammatory activities of analytical grade C-PC (AGC-PC) significantly decreased after 6 months storage of SPP. Based on investigations, we have proposed that the suitable storage time of dried SPP for preparation of AGC-PC in commercial application should be within 6 months.

The potential, challenges, and prospects of the genus Spirulina polysaccharides as future multipurpose biomacromolecules

Spirulina has been widely used worldwide as a food and medicinal ingredient for centuries. Polysaccharides are major bioactive constituents of Spirulina and are of interest because of their functional properties and unlimited application potential. However, the clinical translation and market industrialization of the polysaccharides from genus Spirulina (PGS) are retarded due to the lack of a further understanding of their isolation, bioactivities, structure-activity relationships (SARs), toxicity, and, most importantly, versatile applications. Herein, we provide an overview of the extraction, purification, and structural features of PGS; meanwhile, the advances in bioactivities, SARs, mechanisms of effects, and toxicity are discussed and summarized. Furthermore, the applications, potential developments, and future research directions are scrutinized and highlighted. This review may help fill the knowledge gap between theoretical insights and practical applications and guide future research and industrial application of PGS.