Traditional and new trend strategies to enhance pigment contents in microalgae.

Microalgae are a source of a wide variety of commodities, including particularly valuable pigments. The typical pigments present in microalgae are the chlorophylls, carotenoids, and phycobiliproteins. However, other types of pigments, of the family of water-soluble polyphenols, usually encountered in terrestrial plants, have been recently reported in microalgae. Among such microalgal polyphenols, many flavonoids have a yellowish hue, and are used as natural textile dyes. Besides being used as natural colorants, for example in the food or cosmetic industry, microalgal pigments also possess many bioactive properties, making them functional as nutraceutical or pharmaceutical agents. Each type of pigment, with its own chemical structure, fulfills particular biological functions. Considering both eukaryotes and prokaryotes, some species within the four most promising microalgae groups (Cyanobacteria, Rhodophyta, Chlorophyta and Heterokontophyta) are distinguished by their high contents of specific added-value pigments. To further enhance microalgae pigment contents during autotrophic cultivation, a review is made of the main related strategies adopted during the last decade, including light adjustments (quantity and quality, and the duration of the photoperiod cycle), and regard to mineral medium characteristics (salinity, nutrients concentrations, presence of inductive chemicals). In contrast to what is usually observed for growth-related pigments, accumulation of non-photosynthetic pigments (polyphenols and secondary carotenoids) requires particularly stressful conditions. Finally, pigment enrichment is also made possible with two new cutting-edge technologies, via the application of metallic nanoparticles or magnetic fields.

Extraction of Astaxanthin from Haematococcus pluvialis and Preparation of Astaxanthin Liposomes.

Astaxanthin has 550 times more antioxidant activity than vitamin E, so it can scavenge free radicals in vivo and improve body immunity. However, the poor stability of astaxanthin becomes a bottleneck problem that limits its application. Herein, Haematococcus pluvialis (H. pluvialis) as a raw material was used to extract astaxanthin, and the optimal extraction conditions included the extraction solvent (EA:EtOH = 1:6, v/v), extraction temperature (60 °C), and extraction time (70 min). The extracted astaxanthin was then loaded using lecithin to form corresponding liposomes via the ethanol injection method. The results showed that the particle size and zeta potential of the prepared liposomes were 105.8 ± 1.2 nm and -38.0 ± 1.7 mV, respectively, and the encapsulation efficiency of astaxanthin in liposomes was 88.83%. More importantly, the stability of astaxanthin was significantly improved after being embedded in the prepared liposomes.

Photoprotective activities of Capsosiphon fulvescens in UVB-induced SKH-1 mice and human keratinocytes.

Capsosiphon fulvescens (CF) is a green alga widely consumed in East Asian countries, particularly in Korea. It has a rich composition of vitamins, minerals, dietary fibers, and bioactive compounds, which contribute to its multiple therapeutic properties. Its application ranges from acting as an antioxidant and anti-inflammatory agent to supporting the skin system. Despite these benefits of CF, the effects and mechanisms of action related to photoaging of the skin have not yet been elucidated. To investigate the photoprotective effects of CF against photoaging, both animal (SKH-1 mouse) and cell models (HaCaT cell line) were used in this study. As a result, administering the CF extract over a period of 10 weeks, which included times of Ultraviolet B (UVB) exposure, significantly reduced erythema and various UVB-induced skin changes, such as wrinkle formation, and the thickening of the epidermis and dermis, as well as alterations in the length and depth of wrinkles. Furthermore, our investigation into CF extract's antiwrinkle properties revealed its efficacy in enhancing skin hydration and collagen content, counteracting the collagen depletion and moisture loss induced by UVB radiation. Also, the fact that the levels of p-ERK, p-p38, and p-JNK proteins went down shows that the CF extract might have a controlling effect on the MAPK signaling pathways. Our findings suggest that CF holds significant potential for preventing photoaging, providing a foundation for the development of functional foods or botanical drugs targeting skin aging and related skin disorders. PRACTICAL APPLICATION: This research proved that Capsosiphon fulvescen, a green alga widely consumed in East Asian countries, provides photoprotective activities against UV-induced skin aging. Therefore, Capsosiphon fulvescen can be utilized as functional foods or botanical drugs targeting skin aging and related skin disorders.

Dietary algal-sourced zinc nanoparticles promote growth performance, intestinal integrity, and immune response of Nile tilapia (Oreochromis niloticus).

BACKGROUND: Trace elements play a crucial role in fish nutrition, with zinc (Zn) being one of the most important elements. BIO-sourced zinc nanoparticles were synthesized using the green microalga Pediastrum boryanum (BIO-ZnNPs, 29.35 nm). 30 or 60 mg/ kg dry feed of the BIO-ZnNPs (BIO-ZnNPs30 and BIO-ZnNPs60) were mixed with the Nile tilapia (Oreochromis niloticus) basal diet and fed to the fish for 8 weeks to evaluate their impact on fish growth, digestion, intestinal integrity, antioxidative status, and immunity. RESULTS: A significant enhancement was observed in all investigated parameters, except for the serum protein profile. BIO-ZnNPs at 60 mg/kg feed elevated the activities of reduced glutathione (GSH) and catalase (CAT), enzymatic antioxidants, but did not induce oxidative stress as reflected by no change in MDA level. Fish intestinal immunity was improved in a dose-dependent manner, in terms of improved morphometry and a higher count of acid mucin-producing goblet cells. Interleukin-8 (IL-8) was upregulated in BIO-ZnNPs30 compared to BIO-ZnNPs60 and control fish groups, while no significant expressions were noted in tumor necrosis factor-alpha (TNFα), nuclear factor kappa B (NFkB), and Caspase3 genes. CONCLUSION: Overall, BIO-ZnNPs inclusion at 60 mg/kg feed showed the most advantage in different scenarios, compared to BIO-ZnNPs at 30 mg/kg feed. The positive effects on growth and intestinal health suggest that BIO-ZnNPs supplementation of aquafeeds has many benefits for farmed fish.

Enhanced toxicity-free astaxanthin extraction from Haematococcus pluvialis via concurrent cell disruption and demulsification.

The extraction of astaxanthin from Haematococcus pluvialis involves the utilization of petroleum-derived organic solvents or supercritical CO2, beset by safety concerns, high costs, and environmental sustainability limitations. This study, in contrast, employed a method involving the adjustment of salt concentration, propylene glycol, and vegetable oil fraction to disrupt emulsion in aqueous cell lysates for facilitating the separation of astaxanthin. Under optimized conditions, an astaxanthin-containing oil with a content of 1.88% was obtained even with the use of wet biomass, and four rounds of consecutive extraction resulted in a cumulative recovery yield of 66.41%. This process produced astaxanthin-enriched soybean oil with 9.49 times improved antioxidant capacity that satisfies a requirement for health functional application. Omitting the solvent removal and drying processes, which consume tremendous energy, can reduce the production cost by 2.98 times compared to conventional methods. Consequently, this study suggests an effective technique for producing edible oil containing H. pluvialis-derived astaxanthin.

Haematococcus pluvialis polysaccharides improve microbiota-driven gut epithelial and vascular barrier and prevent alcoholic steatohepatitis development.

Algal polysaccharides possess many biological activities and health benefits, such as antioxidant, anti-tumor, anti-coagulant, and immunomodulatory potential. Gut microbiota has emerged as one of the major contributor in mediating the health benefits of algal polysaccharides. In this study we showed that Haematococcus pluvialis polysaccharides (HPP) decreased serum transaminase levels and hepatic triglyceride content, alleviated inflammation and oxidative stress in the liver of chronic and binge ethanol diet-fed mice. Furthermore, HPP reduced endotoxemia, improved gut microbiota dysbiosis, inhibited epithelial barrier disruption and gut vascular barrier (GVB) damage in ethanol diet-fed mice. Co-housing vehicle-fed mice with HPP-fed mice alleviated ethanol-induced liver damage and endotoxemia. Moreover, fecal microbiota transplantation from HPP-fed mice into antibiotic-induced microbiota-depleted recipients also alleviated ethanol-induced liver injury and improved gut epithelial and vascular barrier. Our study demonstrated that HPP ameliorated ethanol-induced gut epithelial and vascular barrier dysfunction through alteration of gut microbiota, therefore preventing alcoholic liver damage.

Chemically modified seaweed polysaccharides: Improved functional and biological properties and prospective in food applications.

Seaweed polysaccharides are natural biomacromolecules with unique physicochemical properties (e.g., good gelling, emulsifying, and film-forming properties) and diverse biological activities (e.g., anticoagulant, antioxidant, immunoregulatory, and antitumor effects). Furthermore, they are nontoxic, biocompatible and biodegradable, and abundant in resources. Therefore, they have been widely utilized in food, cosmetics, and pharmaceutical industries. However, their properties and bioactivities sometimes are not satisfactory for some purposes. Modification of polysaccharides can impart the amphiphilicity and new functions to the biopolymers and change the structure and conformation, thus effectively improving their functional properties and biological activities so as to meet the requirement for targeted applications. This review outlined the modification methods of representative red algae polysaccharides (carrageenan and agar), brown algae polysaccharides (fucoidan, alginate, and laminaran), and green algae polysaccharides (ulvan) that have potential food applications, including etherification, esterification, degradation, sulfation, phosphorylation, selenylation, and so on. The improved functional properties and bioactivities of the modified seaweed polysaccharides and their potential food applications are also summarized.

Quality of cellulose and biostimulant extracts from Oedogonium calcareum cultivated during primary wastewater treatment.

A practical two-product cascading biorefinery was developed to extract a biostimulant and cellulose from the freshwater filamentous macroalga Oedogonium calcareum grown while treating primary wastewater. Biostimulant production provides a valuable extract with production of disinfected residual biomass for further product development. Both Escherichia coli and F-specific RNA bacteriophage, indicators of human pathogens contamination, were absent from the residual biomass. The chemical composition of the biostimulant was complex, consisting of growth-promoting substances, free amino acids, and minerals. The O. calcareum cellulose fractions yielded between 9.5% and 10.1% (w/w) with purities from 84% to 90% and closely resembled microcrystalline cellulose. Biostimulant extraction improved cellulose quality by increasing crystallinity from 59% to 62%. Biomass condition, drying process, and biostimulant production influenced the crystallinity index. This study demonstrates a two-step process of biostimulant and cellulose extraction from wastewater-grown Oedogonium, simultaneously disinfecting biomass and isolating high-quality cellulose as a sustainable alternative to conventional extraction methods.

Impact of the biomass pretreatment and simulated gastrointestinal digestion on the digestibility and antioxidant activity of microalgae Chlorella vulgaris and Tetraselmis chuii.

Chlorella vulgaris and Tetraselmis chuii are two microalgae species already marketed because of their richness in high-value and health-beneficial compounds. Previous studies have demonstrated the biological properties of compounds isolated from both microalgae, although data are not yet available on the impact that pre-treatment and gastrointestinal digestion could exert on these properties. The aim of the present study was to analyze the impact of the biomass pre-treatment (freeze/thaw cycles plus ultrasounds) and simulated gastrointestinal digestion in the bioaccessibility and in vitro antioxidant activity (ABTS, ORAC, Q-FRAP, Q-DPPH) of the released digests. The cell wall from microalgae were susceptible to the pre-treatment and the action of saliva and gastric enzymes, releasing bioactive peptides and phenolic compounds that contributed to the potent antioxidant activity of digests through their radical scavenging and iron reduction capacities. Our findings suggest the potential of these microalgae against oxidative stress-associated diseases at both, intestinal and systemic level.

Antimicrobial Activity of Arthrospira (Former Spirulina) and Dunaliella Related to Recognized Antimicrobial Bioactive Compounds.

With the increasing rate of the antimicrobial resistance phenomenon, natural products gain our attention as potential drug candidates. Apart from being used as nutraceuticals and for biotechnological purposes, microalgae and phytoplankton have well-recognized antimicrobial compounds and proved anti-infectious potential. In this review, we comprehensively outline the antimicrobial activity of one genus of cyanobacteria (Arthrospira, formerly Spirulina) and of eukaryotic microalgae (Dunaliella). Both, especially Arthrospira, are mostly used as nutraceuticals and as a source of antioxidants for health supplements, cancer therapy and cosmetics. Their diverse bioactive compounds provide other bioactivities and potential for various medical applications. Their antibacterial and antifungal activity vary in a broad range and are strain specific. There are strains of Arthrospira platensis with very potent activity and minimum inhibitory concentrations (MICs) as low as 2-15 µg/mL against bacterial fish pathogens including Bacillus and Vibrio spp. Arthrospira sp. has demonstrated an inhibition zone (IZ) of 50 mm against Staphylococcus aureus. Remarkable is the substantial amount of in vivo studies of Arthrospira showing it to be very promising for preventing vibriosis in shrimp and Helicobacter pylori infection and for wound healing. The innovative laser irradiation of the chlorophyll it releases can cause photodynamic destruction of bacteria. Dunaliella salina has exhibited MIC values lower than 300 µg/mL and an IZ value of 25.4 mm on different bacteria, while Dunaliella tertiolecta has demonstrated MIC values of 25 and 50 µg/mL against some Staphylococcus spp. These values fulfill the criteria for significant antimicrobial activity and sometimes are comparable or exceed the activity of the control antibiotics. The bioactive compounds which are responsible for that action are fatty acids including PUFAs, polysaccharides, glycosides, peptides, neophytadiene, etc. Cyanobacteria, such as Arthrospira, also particularly have antimicrobial flavonoids, terpenes, alkaloids, saponins, quinones and some unique-to-them compounds, such as phycobiliproteins, polyhydroxybutyrate, the peptide microcystin, etc. These metabolites can be optimized by using stress factors in a two-step process of fermentation in closed photobioreactors (PBRs).

Inhibitory effects of algal polysaccharide extract from Cladophora spp. against herpes simplex virus infection.

Herpes simplex virus (HSV) is a causative agent of fever blister, genital herpes, and neonatal herpes. Nowadays, edible algae are recognized as health food due to high nutrition content and their many active compounds that are beneficial to health. The purpose of this study is to investigate the inhibitory effects of algal polysaccharide extract from Cladophora spp. against herpes simplex virus type 1 and type 2 on Vero cells. In this study, the structure of polysaccharide extract is presented as S=O and C-O-S of the sulfate group, as identified by the FT-IR technique. The toxicity of algal polysaccharide extract on Vero cells was determined by MTT assay. The algal extract showed low toxicity on the cells, with 50% cytotoxic concentration (CC50) value greater than 5000 µg mL-1. The inhibition of HSV infection by the algal extract was then evaluated on Vero cells using plaque reduction assay. The 50% effective concentration (EC50) values of algal extract exhibited antiviral activity against HSV-1 upon treatment before, during, and after viral adsorption with and without removal of the extract were 70.31, 15.17, > 5000 and 9.78 µg mL-1, respectively. Additionally, the EC50 values of algal extract against HSV-2 upon treatment before, during and after viral adsorption with, and without removal of the extract were 5.85, 2.57, > 5000 and 26.96 µg mL-1, respectively. Moreover, the algal extract demonstrated direct inactivation of HSV-1 and HSV-2 virions as well as inhibitory effect against HSV replication. Accordingly, algal polysaccharide extract containing sulfated polysaccharides showed strong activity against HSV. Therefore, it is proved to be useful to apply Cladophora spp. polysaccharide extract as an anti-HSV agent.

Supercritical CO2 extraction increases the recovery levels of omega-3 fatty acids in Tetraselmis chuii extracts.

Tetraselmis chuii is a microalgae marketed as ingredient meeting the acceptance criteria for novel foods established by the European Union and can be an important source of healthy fatty acids (FA). The aim of this research was to characterize the FA profile of T. chuii fractions obtained by supercritical carbon dioxide (SCCO2) extraction operating with two sequential co-solvents and to evaluate the effect of biomass pretreatment (freeze/thaw cycles followed by ultrasounds). T. chuii biomass was confirmed to be an important source of omega-3 FA, mainly due to the abundance of α-linolenic acid, and pre-treatment significantly improved the lipid yield. Other omega-3 FA, such as 16:3, 16:4, 18:4, 18:5, 20:3 and 20:5, were also detected in different proportions. When SCCO2 extraction of pretreated and un-pretreated T. chuii was compared with conventional solvent extraction, the nutritional quality indices of the extracts were improved by the use of SCCO2.

Functional Characterization of a CruP-Like Isomerase in Dunaliella.

Dunaliella bardawil is a marine unicellular green algal that produces large amounts of ß-carotene and is a model organism for studying the carotenoid synthesis pathway. However, there are still many mysteries about the enzymes of the D. bardawil lycopene synthesis pathway that have not been revealed. Here, we have identified a CruP-like lycopene isomerase, named DbLyISO, and successfully cloned its gene from D. bardawil. DbLyISO showed a high homology with CruPs. We constructed a 3D model of DbLyISO and performed molecular docking with lycopene, as well as molecular dynamics testing, to identify the functional characteristics of DbLyISO. Functional activity of DbLyISO was also performed by overexpressing gene in both E. coli and D. bardawil. Results revealed that DbLyISO acted at the C-5 and C-13 positions of lycopene, catalyzing its cis-trans isomerization to produce a more stable trans structure. These results provide new ideas for the development of a carotenoid series from engineered bacteria, algae, and plants.

Semisynthesis of new sulfated heterorhamnan derivatives obtained from green seaweed Gayralia brasiliensis and evaluation of their anticoagulant activity.

Marine green algae produce sulfated polysaccharides with diverse structures and a wide range of biological activities. This study aimed to enhance the biotechnological potential of sulfated heterorhamnan (Gb1) from Gayralia brasiliensis by chemically modifying it for improved or new biological functions. Using controlled Smith Degradation (GBS) and O-alkylation with 3-chloropropylamine, we synthesized partially water-soluble amine derivatives. GBS modification increase sulfate groups (29.3 to 37.5 %) and α-l-rhamnose units (69.9 to 81.2 mol%), reducing xylose and glucose, compared to Gb1. The backbone featured predominantly 3- and 2-linked α-l-rhamnosyl and 2,3- linked α-l-rhamnosyl units as branching points. Infrared and NMR analyses confirmed the substitution of hydroxyl groups with aminoalkyl groups. The modified compounds, GBS-AHCs and GBS-AHK, exhibited altered anticoagulant properties. GBS-AHCs showed reduced effectiveness in the APTT assay, while GBS-AHK maintained a similar anticoagulant activity level to Gb1 and GBS. Increased nitrogen content and N-alkylation in GBS-AHCs compared to GBS-AHK may explain their structural differences. The chemical modification proposed did not enhance its anticoagulant activity, possibly due to the introduction of amino groups and a positive charge to the polymer. This characteristic presents new opportunities for investigating the potential of these polysaccharides in various biological applications, such as antimicrobial and antitumoral activities.

The production of FAHFA is enhanced when Haematococcus pluvialis is grown in CO2.

Microalgae are considered as a potential source of bioactive compounds to be used in different fields including food and pharmaceutical industry. In this context, fatty acid esters of hydroxy-fatty acids (FAHFA) are emerging as a new class of compounds with anti-inflammatory and anti-diabetic properties. An existing gap in the field of algal research is the limited knowledge regarding the production of these compounds. Our research questions aimed to determine whether the microalga H. pluvialis can synthesize FAHFA and whether the production levels of these compounds are increased when cultivated in a CO2-rich environment. To answer these questions, we used a LC-QTOF/MS method for the characterization of FAHFA produced by H. pluvialis while an LC-MS/MS method was used for their quantitation. The cultivation conditions of H. pluvialis, which include the utilization of CO2, can result in a 10-50-fold increase in FAHFA production.

A Complex-Type N-Glycan-Specific Lectin Isolated from Green Alga Halimeda borneensis Exhibits Potent Anti-Influenza Virus Activity.

Marine algal lectins specific for high-mannose N-glycans have attracted attention because they strongly inhibit the entry of enveloped viruses, including influenza viruses and SARS-CoV-2, into host cells by binding to high-mannose-type N-glycans on viral surfaces. Here, we report a novel anti-influenza virus lectin (named HBL40), specific for complex-type N-glycans, which was isolated from a marine green alga, Halimeda borneensis. The hemagglutination activity of HBL40 was inhibited with both complex-type N-glycan and O-glycan-linked glycoproteins but not with high-mannose-type N-glycan-linked glycoproteins or any of the monosaccharides examined. In the oligosaccharide-binding experiment using 26 pyridylaminated oligosaccharides, HBL40 only bound to complex-type N-glycans with bi- and triantennary-branched sugar chains. The sialylation, core fucosylation, and the increased number of branched antennae of the N-glycans lowered the binding activity with HBL40. Interestingly, the lectin potently inhibited the infection of influenza virus (A/H3N2/Udorn/72) into NCI-H292 cells at IC50 of 8.02 nM by binding to glycosylated viral hemagglutinin (KD of 1.21 × 10-6 M). HBL40 consisted of two isolectins with slightly different molecular masses to each other that could be separated by reverse-phase HPLC. Both isolectins shared the same 16 N-terminal amino acid sequences. Thus, HBL40 could be useful as an antivirus lectin specific for complex-type N-glycans.

Dietary supplementation with Dunaliella salina microalga promotes quail growth by altering lipid profile and immunity.

The goals of the current research are to ascertain the impacts of Dunaliella salina (DS) on quail growth, carcass criteria, liver and kidney functions, lipid profile, and immune response. Two hundred and forty 7-day-old quail chicks were divided equally into 4 separate groups with 6 replicates with 10 birds each. The groups were as follows: 1) control diet (the basal feed without DS), 2) control diet enriched with 0.25 g DS/kg, 3) control diet enriched with 0.50 g DS/kg, and 4) control diet enriched with 1.00 g DS/kg. Results elucidated that the birds which consumed 0.5 and 1 g DS/kg diet performed better than other birds in terms of live body weight (LBW), body weight gain (BWG), and feed conversion ratio (FCR). There were no significant changes in feed intake (FI) and carcass characteristics due to different dietary DS levels. Compared to the control group, DS-treated groups had better lipid profile (low total cholesterol and LDL values and high HDL values) and immune response (complement 3 values). The quails consumed feeds with different levels of DS had greater (P < 0.038) C3 compared to control. Adding 0.5 and 1 g DS/kg lowered blood concentrations of triglycerides and total protein (TP) values. The high level of DS (1 g/kg) had higher albumin values and lower AST values than other groups (P < 0.05). The creatinine values were at the lowest levels in the group consumed 0.50 g DS/kg feed. No changes (P > 0.05) were demonstrated among experimental groups in the ALT, urea, and lysozyme values. In conclusion, adding D. salina to growing quail diets enhanced growth, immune system, blood lipid profile, and kidney and liver function.

Extraction of chlorophyll a from Tetradesmus obliquus-a method upgrade.

Nowadays, the use of algae is prevalent for both industrial and agricultural purposes. The determination of chlorophyll (Chl) content is a commonly used method for estimating the phytoplankton abundance in different water bodies or biomass density of algal cultures. The aim of the present work is to optimise the efficiency of the Chl extraction from the green alga Tetradesmus obliquus using methanol as extracting solvent. The extraction efficiency was estimated by measuring the Chl a concentration of the extracts using fluorescence spectroscopy. To increase the extraction yield, glass fibre filters with algal cells on top were treated with 10% (v/v) formalin prior to the extraction. We found that this pretreatment significantly enhanced the extraction yield of Chl without its chemical decomposition. We also found that the optimal cell concentration for Chl determination ranged from 1.44 × 104 to 3.60 × 105 cells/mL and the extraction efficiency was lower when the cell density of the culture was out of this range. These results highlight the importance of the optimization of the pigment extraction for the studied algal species.

Structural and biofunctional diversity of sulfated polysaccharides from the genus Codium (Bryopsidales, Chlorophyta): A review.

It is believed that polysaccharides will become a focal point for future production of food, pharmaceuticals, and materials due to their ubiquitous and renewable nature, as well as their exceptional properties that have been extensively validated in the fields of nutrition, healthcare, and materials. Sulfated polysaccharides derived from seaweed sources have attracted considerable attention owing to their distinctive structures and properties. The genus Codium, represented by the species C. fragile, holds significance as a vital economic green seaweed and serves as a traditional Chinese medicinal herb. To date, the cell walls of the genus Codium have been found to contain at least four types of sulfated polysaccharides, specifically pyruvylated ß-d-galactan sulfates, sulfated arabinogalactans, sulfated ß-l-arabinans, and sulfated ß-d-mannans. These sulfated polysaccharides exhibit diverse biofunctions, including anticoagulant, immune-enhancing, anticancer, antioxidant activities, and drug-carrying capacity. This review explores the structural and biofunctional diversity of sulfated polysaccharides derived from the genus Codium. Additionally, in addressing the impending challenges within the industrialization of these polysaccharides, encompassing concerns regarding scale-up production and quality control, we outline potential strategies to address these challenges from the perspectives of raw materials, extraction processes, purification technologies, and methods for quality control.

Cellulose nanocrystals from marine algae Cladophora glomerata by using microwave-assisted extraction.

Algae of the order Cladophorales are the source of a unique nanocellulose with high crystallinity and a large aspect ratio, enabling broad surface modification. Cellulose nanocrystals (CNCs) are obtained via acid hydrolysis of nanocellulose, which is highly crystalline. However, the production of CNCs from Cladophorales algae is limited and still uses a conventional heating method. Thus, this study aimed to develop a microwave-assisted extraction (MAE) method for fast and efficient extraction of CNCs from Cladophora glomerata algae. Additionally, we replaced the use of hypochlorite with H2O2, which is more environmentally friendly, and compared the CNCs obtained from the conventional methods with our new method. The functional structure of CNCs was confirmed by Fourier-transform infrared spectroscopy. Single-step H2O2 bleaching with MAE yielded the smallest-sized CNCs. Our developed method resulted in the production of CNCs with a high crystallinity index, high thermal stability, and high purity of native cellulose. Additionally, none of the CNCs were toxic to primary normal human dermal fibroblasts. The properties of the isolated CNCs may make them useful materials in pharmaceutical and cosmetic formulations.