The bioactivities and biotechnological production approaches of carotenoids derived from microalgae and cyanobacteria.

Microalgae and cyanobacteria are a rich source of carotenoids that are well known for their potent bioactivities, including antioxidant, anti-cancer, anti-proliferative, anti-inflammatory, and anti-obesity properties. Recently, many interests have also been focused on the biological activities of these microalgae/cyanobacteria-derived carotenoids, such as fucoxanthin and ß-carotene potential to be the salutary nutraceuticals, on treating or preventing human common diseases (e.g., cancers). This is due to their special chemical structures that demonstrate unique bioactive functions, in which the biologically active discrepancies might attribute to the different spatial configurations of their molecules. In addition, their abundance and bioaccessibilities make them more popularly applied in food and pharmaceutical industries, as compared to the macroalgal/fungal-derived ones. This review is focused on the recent studies on the bioactivities of fucoxanthin and some carotenoids derived from microalgae and cyanobacteria in relationship with human health and diseases, with emphasis on their potential applications as natural antioxidants. Various biotechnological approaches employed to induce the production of these specific carotenoids from the culture of microalgae/cyanobacteria are also critically reviewed. These well-developed and emerging biotechnologies present promise to be applied in food and pharmaceutical industries to facilitate the efficient manufacture of the bioactive carotenoid products derived from microalgae and cyanobacteria.

Attenuation of inflammatory bowel disease by oral administration of mucoadhesive polydopamine-coated yeast ß-glucan via ROS scavenging and gut microbiota regulation.

Treatment for inflammatory bowel disease (IBD) is challenging since current anti-inflammatory and immunosuppressive therapies do not address the underlying causes of the illness, which include increased levels of reactive oxygen species (ROS) and dysbiosis of the gut commensal microbiota. Additionally, these treatments often have systemic off-target effects and adverse side effects. In this study, we have developed a prebiotic yeast ß-glucan nanocomplex coated with bio-adhesive polydopamine (YBNs@PDA) to effectively prolong their retention time in the gastrointestinal (GI) tract. The oral administration of YBNs@PDA restored the epithelium barriers, reduced ROS levels, and minimized systemic drug exposure while improved therapeutic efficacy in an acute colitis mouse model. Furthermore, 16S ribosomal RNA genes sequencing demonstrated a higher richness and diversity in gut microflora composition following the treatments. In particular, YBNs@PDA markedly augmented the abundance of Lachnospiraceae NK4A136 and Bifidobacterium, both of which are probiotics with crucial roles in relieving colitis via retaining gut homeostasis. Cumulatively, these results demonstrate that the potential of YBNs@PDA as a novel drug-free, ROS-scavenging and gut microbiota regulation nanoplatform for the treatment of GI disorders.

Enzyme-Responsive Double-Locked Photodynamic Molecular Beacon for Targeted Photodynamic Anticancer Therapy.

An advanced photodynamic molecular beacon (PMB) was designed and synthesized, in which a distyryl boron dipyrromethene (DSBDP)-based photosensitizer and a Black Hole Quencher 3 moiety were connected via two peptide segments containing the sequences PLGVR and GFLG, respectively, of a cyclic peptide. These two short peptide sequences are well-known substrates of matrix metalloproteinase-2 (MMP-2) and cathepsin B, respectively, both of which are overexpressed in a wide range of cancer cells either extracellularly (for MMP-2) or intracellularly (for cathepsin B). Owing to the efficient Förster resonance energy transfer between the two components, this PMB was fully quenched in the native form. Only upon interaction with both MMP-2 and cathepsin B, either in a buffer solution or in cancer cells, both of the segments were cleaved specifically, and the two components could be completely separated, thereby restoring the photodynamic activities of the DSBDP moiety. This PMB could also be activated in tumors, and it effectively suppressed the tumor growth in A549 tumor-bearing nude mice upon laser irradiation without causing notable side effects. In particular, it did not cause skin photosensitivity, which is a very common side effect of photodynamic therapy (PDT) using conventional "always-on" photosensitizers. The overall results showed that this "double-locked" PMB functioned as a biological AND logic gate that could only be unlocked by the coexistence of two tumor-associated enzymes, which could greatly enhance the tumor specificity in PDT.

Enhanced In Vitro Anti-Photoaging Effect of Degraded Seaweed Polysaccharides by UV/H2O2 Treatment.

The high molecular weight and poor solubility of seaweed polysaccharides have limited their function and application. In this study, ultraviolet/hydrogen peroxide (UV/H2O2) treatment was used to prepare low-molecular-weight seaweed polysaccharides from Sargassum fusiforme. The effects of UV/H2O2 treatment on the physicochemical properties and anti-photoaging activity of S. fusiforme polysaccharides were studied. UV/H2O2 treatment effectively degraded polysaccharides from S. fusiforme (DSFPs), reducing their molecular weight from 271 kDa to 26 kDa after 2 h treatment. The treatment did not affect the functional groups in DSFPs but changed their molar percentage of monosaccharide composition and morphology. The effects of the treatment on the anti-photoaging function of S. fusiforme polysaccharides were investigated using human epidermal HaCaT cells in vitro. DFSPs significantly improved the cell viability and hydroxyproline secretion of UVB-irradiated HaCaT cells. In particular, DSFP-45 obtained from UV/H2O2 treatment for 45 min showed the best anti-photoaging effect. Moreover, DSFP-45 significantly increased the content and expression of collagen I and decreased those of pro-inflammatory cytokines, including interleukin-1ß, interleukin-6, and tumor necrosis factor-α. Thus, UV/H2O2 treatment could effectively improve the anti-photoaging activity of S. fusiforme polysaccharides. These results provide some insights for developing novel and efficient anti-photoaging drugs or functional foods from seaweed polysaccharides.

Genome-wide mRNA and miRNA analysis in the early stages of germ tube outgrowth in Coprinopsis cinerea.

Coprinopsis cinerea is a model mushroom-forming basidiomycete which produces basidiospores during sexual reproduction. This fungus is widely used to study fruiting body formation and development. Molecular mechanisms controlling its growth from vegetative mycelium to multicellular mature fruiting body have been studied extensively. However, little is known about the underlying biological processes during germ tube outgrowth or the transition from basidiospores to multinucleate hyphae. To better understand sexual spore germination in fungi, here we examined the time-dependent cellular events at resting, germinating and fully germinated basidiospores of C. cinerea by genome-wide transcriptional and post-transcriptional analyses and by carbohydrate composition analysis. Our results revealed a high demand of protein degradation, and biosynthesis of various compounds at the early stage of basidiospore gemination and dynamic changes of carbohydrate metabolism throughout the germination process. Seven microRNA-like RNAs (milRNAs) were identified in the resting basidiospores of C. cinerea, six of which were basidiospore-specific. Glycogen and trehalose were shown to be the carbon sources supporting the initiation of germ tube outgrowth. One basidiospore-specific milRNA, cci-milR-37, was found to be a potential regulator of glycogen metabolic pathways related to vegetative hyphal growth. Our results demonstrated the mRNA and miRNA-mediated regulation on energy production, protein and carbohydrate metabolisms at the early developmental stages of germ tube to form totipotent hyphae. To our knowledge, this is the first study to show the roles of miRNAs in mushroom basidiospore germination and out-growth.

In Vitro Infant Faecal Fermentation of Low Viscosity Barley ß-Glucan and Its Acid Hydrolyzed Derivatives: Evaluation of Their Potential as Novel Prebiotics.

Barley contains high level of ß-1,3-1,4-glucans (BBGs) which can be fermented by microbes and are a potential prebiotic. In the present study, native BBG with low viscosity and a MW of 319 kDa was depolymerized by acid hydrolysis to produce a series of four structurally characterized fragments with MWs ranging from 6⁻104 kDa. In vitro fermentation of these BBG samples by infant faecal microbiome was evaluated using a validated deep-well plate protocol as parallel miniature bioreactors. Microbial taxa were identified using 16S amplicon sequencing after 40 h of anaerobic fermentation. Bioinformatics analysis including diversity indexes, predicted metagenomic KEGG functions and predicted phenotypes were performed on the sequenced data. Short chain fatty acids and dissolved ammonia were quantified and the SCFAs/NH3 ratio was used to evaluate the eubiosis/dysbiosis potential. Correlation analysis showed that most of the parameters investigated showed a parabolic function instead of a monotonous function with the BBG samples having different MWs. Among the five BBGs, it was concluded that BBG with an intermediate MW of 28 kDa is the most promising candidate to be developed as a novel prebiotic.

Mechanistic Study of Utilization of Water-Insoluble Saccharomyces cerevisiae Glucans by Bifidobacterium breve Strain JCM1192.

Bifidobacteria exert beneficial effects on hosts and are extensively used as probiotics. However, due to the genetic inaccessibility of these bacteria, little is known about their mechanisms of carbohydrate utilization and regulation. Bifidobacterium breve strain JCM1192 can grow on water-insoluble yeast (Saccharomyces cerevisiae) cell wall glucans (YCWG), which were recently considered as potential prebiotics. According to the results of 1H nuclear magnetic resonance (NMR) spectrometry, the YCWG were composed of highly branched (1→3,1→6)-ß-glucans and (1→4,1→6)-α-glucans. Although the YCWG were composed of 78.3% ß-glucans and 21.7% α-glucans, only α-glucans were consumed by the B. breve strain. The ABC transporter (malEFG1) and pullulanase (aapA) genes were transcriptionally upregulated in the metabolism of insoluble yeast glucans, suggesting their potential involvement in the process. A nonsense mutation identified in the gene encoding an ABC transporter ATP-binding protein (MalK) led to growth failure of an ethyl methanesulfonate-generated mutant with yeast glucans. Coculture of the wild-type strain and the mutant showed that this protein was responsible for the import of yeast glucans or their breakdown products, rather than the export of α-glucan-catabolizing enzymes. Further characterization of the carbohydrate utilization of the mutant and three of its revertants indicated that this mutation was pleiotropic: the mutant could not grow with maltose, glycogen, dextrin, raffinose, cellobiose, melibiose, or turanose. We propose that insoluble yeast α-glucans are hydrolyzed by extracellular pullulanase into maltose and/or maltooligosaccharides, which are then transported into the cell by the ABC transport system composed of MalEFG1 and MalK. The mechanism elucidated here will facilitate the development of B. breve and water-insoluble yeast glucans as novel synbiotics.IMPORTANCE In general, Bifidobacterium strains are genetically intractable. Coupling classic forward genetics with next-generation sequencing, here we identified an ABC transporter ATP-binding protein (MalK) responsible for the import of insoluble yeast glucan breakdown products by B. breve JCM1192. We demonstrated the pleiotropic effects of the ABC transporter ATP-binding protein in maltose/maltooligosaccharide, raffinose, cellobiose, melibiose, and turanose transport. With the addition of transcriptional analysis, we propose that insoluble yeast glucans are broken down by extracellular pullulanase into maltose and/or maltooligosaccharides, which are then transported into the cell by the ABC transport system composed of MalEFG1 and MalK. The mechanism elucidated here will facilitate the development of B. breve and water-insoluble yeast glucans as novel synbiotics.

Water extract from Pleurotus pulmonarius with antioxidant activity exerts in vivo chemoprophylaxis and chemosensitization for liver cancer.

Chemoprophylaxis and chemosensitization are promising strategies to combat human cancers. Natural antioxidant agents show great promise in cancer therapy, and the use of edible mushrooms against cancer is receiving more interest globally. In this study, the radical scavenging activities including diphenyl-1-picrylhydrazyl, superoxide anion radical, hydroxyl radical, and hydrogen peroxide were compared among hot water extracts from 3 edible mushrooms, among which Pleurotus pulmonarius (Pp) possessed the highest antioxidant potential. Oral administration of Pp 2 wk in advance could markedly inhibit the incidence and size of tumor (Huh7 liver cancer cells) with an inhibition rate of 93.1% in nude mice. No obvious side effect was observed in the Pp-treated mice as indicated by their body weight and histological analysis of major organs. The cancer prevention by Pp treatment might be explained by the inhibition of cancer cell proliferation indicated by reduction of ki-67 staining and the inactivation of phosphoinositide 3-kinase (PI3K)/AKT signaling pathway in the Pp-treated mice. Furthermore, a significant synergistic effect was observed when the mice were treated with a combination of low dose of cisplatin and Pp. Taken together, these results suggest the potential application of Pp as an adjuvant in the chemotherapy of liver cancer.

Effects of Oat ß-Glucan and Inulin on Alleviation of Nonalcoholic Steatohepatitis Aggravated by Circadian Disruption in C57BL/6J Mice.

This was the first study that examined the effects of oat ß-glucan and inulin on diet-induced nonalcoholic steatohepatitis (NASH) in circadian-disrupted (CD)-male C57BL/6J mice. CD intensified NASH, significantly increasing alanine aminotransferase and upregulating hepatic tumor necrosis factor α (TNFα) and transforming growth factor ß 1 (TGFß1). However, these observations were significantly alleviated by oat ß-glucan and inulin treatments. Compared to CD NASH mice, oat ß-glucan significantly decreased the liver index, aspartate aminotransferase (AST), and insulin. In prebiotic-treated and CD NASH mice, significant negative correlations were found between enrichment of Muribaculaceae bacterium Isolate-036 (Harlan), Muribaculaceae bacterium Isolate-001 (NCI), and Bacteroides ovatus after oat ß-glucan supplementation with TNFα and TGFß1 levels; and enrichment of Muribaculaceae bacterium Isolate-110 (HZI) after inulin supplementation with AST level. In conclusion, oat ß-glucan and inulin exhibited similar antiliver injury, anti-inflammatory, and antifibrotic activities but had no effect on cecal short-chain fatty acids and gut microbiota diversity in CD NASH mice.

Fungal ß-Glucan-Based Nanotherapeutics: From Fabrication to Application.

Fungal ß-glucans are naturally occurring active macromolecules used in food and medicine due to their wide range of biological activities and positive health benefits. Significant research efforts have been devoted over the past decade to producing fungal ß-glucan-based nanomaterials and promoting their uses in numerous fields, including biomedicine. Herein, this review offers an up-to-date report on the synthetic strategies of common fungal ß-glucan-based nanomaterials and preparation methods such as nanoprecipitation and emulsification. In addition, we highlight current examples of fungal ß-glucan-based theranostic nanosystems and their prospective use for drug delivery and treatment in anti-cancer, vaccination, as well as anti-inflammatory treatments. It is anticipated that future advances in polysaccharide chemistry and nanotechnology will aid in the clinical translation of fungal ß-glucan-based nanomaterials for the delivery of drugs and the treatment of illnesses.

A Tetrazine-Caged Carbon-Dipyrromethene as a Bioorthogonally Activatable Fluorescent Probe.

A water-soluble 1,2,4,5-tetrazine-substituted carbon-dipyrromethene (C-DIPY) was synthesized from the previously reported carbonyl pyrrole dimer through a two-step procedure. Owing to the presence of a tetrazine moiety, the fluorescence emission of this compound was largely quenched in phosphate-buffered saline at pH 7.4. Upon addition of a bicyclo[6.1.0]non-4-yne (BCN) derivative, the tetrazine-based quenching component of the compound was disrupted through the inverse electron-demand Diels-Alder reaction to restore the fluorescence in up to 6.6-fold. This bioorthogonal activation was also demonstrated using U-87 MG human glioblastoma cells, in which the fluorescence intensity of this C-DIPY could be enhanced by 8.7-fold upon post-incubation with the BCN derivative. The results showed that this tetrazine-caged C-DIPY can serve as a bioorthogonally activatable fluorescent probe for bioimaging. The compound, however, was found to reside preferentially in the lysosomes instead of the mitochondria of the cells as predicted based on its cationic character, which could be attributed to its energy-dependent endocytic cellular uptake pathway, for which lysosomes are the end station.

Utilization of Food-Derived ß-Glucans to Prevent and Treat Non-Alcoholic Fatty Liver Disease (NAFLD).

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease nowadays. Currently, there is no officially approved drug to treat NAFLD. In view of the increasing global prevalence of NAFLD and an absence of treatments, the development of effective treatments is of utmost importance. ß-glucan, a natural bioactive polysaccharide, has demonstrated hepatoprotective effects in NAFLD prevention and treatment. This review solely focuses on gathering the published preclinical animal studies that demonstrated the anti-liver injury, anti-steatotic, anti-inflammatory, anti-fibrotic, and antioxidant activities of ß-glucan. The impact of ß-glucan on gut microbiota and its metabolites including short-chain fatty acids and bile acids as the underlying mechanism for its bioactive beneficial effect on NAFLD is also explored. Given the limited knowledge of ß-glucan on anti-fibrotic activity, bile acid metabolism, and gut microbiota function, additional relevant research is highly encouraged to lay a solid foundation for the use of food-derived ß-glucan as a functional food for NAFLD. It is envisaged that further investigation of food-derived ß-glucan in human clinical studies should be carried out for its wider utilization.

Partially Acid-Hydrolyzed Porphyran Improved Dextran Sulfate Sodium-Induced Acute Colitis by Modulation of Gut Microbiota and Enhancing the Mucosal Barrier.

The pharmacological values of marine algal polysaccharides on gut health are being recognized in recent research. However, the protective effect of degraded polysaccharides from Porphyra haitanensis (PHP-D) on the colonic mucosal barrier damaged in ulcerative colitis is poorly understood. The purpose of this study was to investigate how PHP-D could maintain the integrity of colonic mucosal layer mediated by microbiota in a dextran sulfate sodium (DSS)-induced colitis mouse model. Structural analysis revealed that PHP-D had a typical porphyran structure having a backbone of alternating (1 → 3)-linked ß-d-galactopyranose units linked to either (1 → 4)-3,6-anhydro-α-l-galactopyranose units or (1 → 4)-linked α-l-galactose-6-sulfate units. An in vivo study demonstrated that PHP-D treatment reduced the severity of DSS-induced ulcerative colitis. 16S rRNA phylogenetic sequencing revealed that PHP-D affected the diversity of gut microbiota with an increase of Bacteroides, Muribaculum, and Lactobacillus species. Similarly, PHP-D increased levels of short-chain fatty acids. Furthermore, PHP-D restored mucus thickness and improved the expression of tight junction proteins. This work demonstrates that PHP-D is capable of enhancing a colonic mucosal barrier. These outcomes offer unique perspectives on the potential application of P. haitanensis as a promising natural product for the management of ulcerative colitis.

In Vitro Fermentation Characteristics of Fungal Polysaccharides Derived from Wolfiporia cocos and Their Effect on Human Fecal Microbiota.

Gut microbiota has been described as a new 'organ' that interferes with host physiology by its metabolites produced from the utilization and biotransformation of undigested food components. Fu Ling (FL), the sclerotia of fungi Wolfiporia cocos, contains ß-glucan, which is a known natural polysaccharide with strong medicinal efficacy. This study endeavors to evaluate the fermentability of FL and polysaccharides extracted from its sclerotia. An in vitro fermentation of structurally characterized FL and its ß-glucan by human fecal microbiota was conducted. Total bacterial count, pH change, short-chain fatty acid profile and microbiota profile were assessed post-fermentation. FL containing over 70% of ß-(1 → 3) and (1 → 6)-glucans with a low degree of branching of 0.24 could enhance acetic acid (a major microbial metabolite) production. Both FL and its extracted ß-glucan had similar modulation on microbial composition. They enriched Phascolarctobacterium faecium, Bacteroides dorei and Parabacteroides distasonis, all of which are shown to possess anti-inflammatory effects. FL polysaccharide can be utilized as a natural whole food for its potential health benefits to human gut bacteria.

Effects of Synbiotic Supplementation on Metabolic Syndrome Traits and Gut Microbial Profile among Overweight and Obese Hong Kong Chinese Individuals: A Randomized Trial.

In view of the limited evidence showing anti-obesity effects of synbiotics via modulation of the gut microbiota in humans, a randomized clinical trial was performed. Assessment of the metabolic syndrome traits and profiling of the fecal gut microbiota using 16S rRNA gene sequencing in overweight and obese Hong Kong Chinese individuals before and after dietary intervention with an 8-week increased consumption of fruits and vegetables and/or synbiotic supplementation was conducted. The selected synbiotic contained two probiotics (Lactobacillus acidophilus NCFM and Bifidobacterium lactis HN019) and a prebiotic (polydextrose). Fifty-five overweight or obese individuals were randomized and divided into a synbiotic group (SG; n = 19), a dietary intervention group (DG; n = 18), and a group receiving combined interventions (DSG; n = 18). DSG showed the greatest weight loss effects and number of significant differences in clinical parameters compared to its baseline values-notably, decreases in fasting glucose, insulin, HOMA-IR, and triglycerides and an increase in HDL-cholesterol. DSG lowered Megamonas abundance, which was positively associated with BMI, body fat mass, and trunk fat mass. The results suggested that increasing dietary fiber consumption from fruits and vegetables combined with synbiotic supplementation is more effective than either approach alone in tackling obesity.

ProBioQuest: a database and semantic analysis engine for literature, clinical trials and patents related to probiotics.

The use of probiotics to improve health via the modulation of gut microbiota has gained wide attention. The growing volume of investigations of probiotic microorganisms and commercialized probiotic products has created the need for a database to organize the health-promoting functions driven by probiotics reported in academic articles, clinical trials and patents. We constructed ProBioQuest to collect up-to-date literature related to probiotics from PubMed.gov, ClinicalTrials.gov and PatentsView. More than 2.8 million articles have been collected. Automated information technology-assisted procedures enabled us to collect the data continuously, providing the most up-to-date information. Statistical functions and semantic analyses are provided on the website as an advanced search engine, which contributes to the semantic tool of this database for information search and analyses. The semantic analytical output provides categorized search results and functions to enhance further analysis. A keyword bank is included which can display multiple tables of contents. Users can select keywords from different displayed categories to achieve easily filtered searches. Additional information on the searched items can be browsed via the link-out function. ProBioQuest is not only useful to scientists and health professionals but also to dietary supplement manufacturers and the general public. In this paper, the method we used to build this database-web system is described. Applications of ProBioQuest for several literature-based analyses of probiotics are included as examples of the various uses of this search engine. ProBioQuest can be accessed free of charge at http://kwanlab.bio.cuhk.edu.hk/PBQ/. Database URL: http://kwanlab.bio.cuhk.edu.hk/PBQ/.

+UVA treatment increases the degree of unsaturation in microalgal fatty acids and total carotenoid content in Nitzschia closterium (Bacillariophyceae) and Isochrysis zhangjiangensis (Chrysophyceae).

The production of metabolites by microalgae is affected by environmental conditions in which they are living. The metabolic responses of two marine microalgae, Nitzschia closterium and Isochrysis zhangjiangensis, to a 3-day UVA-stress and 3-day UVA-recovery treatment were compared, based on their growth, fatty acid profiles and content of total carotenoids. When cultured under photosynthetically active radiation, coupled with UVA treatment, both microalgae underwent a significant increase in their growth during the UVA-recovery period compared to the control. The proportions of polyunsaturated fatty acids, including linoleic acid and eicosapentaenoic acid, as well as total carotenoids, were significantly increased in both microalgae, mainly in the UVA-stress period, but not the UVA-recovery period. The metabolic responses of the two microalgae to UVA treatment were species-dependent and could be utilised to produce microalgal biomass rich in polyunsaturated fatty acids and carotenoids for use as functional food ingredients.

Gene expression profile analysis of gallic acid-induced cell death process.

Gallic acid is a natural phenolic compound that displays anti-cancer properties in clinically relevant cell culture and rodent models. To date, the molecular mechanism governing the gallic acid-induced cancer cell death process is largely unclear, thus hindering development of novel therapeutics. Therefore, we performed time-course RNA-sequencing to reveal the gene expression profiles at the early (2nd hour), middle (4th and 6th hour), and late (9th hour) stages of the gallic acid-induced cell death process in HeLa cells. By Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, we found significant changes in transcription of the genes in different types of cell death pathways. This involved the ferroptotic cell death pathway at the early stage, apoptotic pathway at the middle stage, and necroptotic pathway at the late stage. Metabolic pathways were identified at all the stages, indicating that this is an active cell death process. Interestingly, the initiation and execution of gallic acid-induced cell death were mediated by multiple biological processes, including iron and amino acid metabolism, and the biosynthesis of glutathione, as targeting on these pathways suppressed cell death. In summary, our work provides a dataset with differentially expressed genes across different stages of cell death process during the gallic acid induction, which is important for further study on the control of this cell death mechanism.

Vitamins D and D2 in Cultivated Mushrooms under Ultraviolet Irradiation and Their Bioavailability in Humans: A Mini-Review.

Vitamin D deficiency is a public health issue that not only results in skeletal disorders but is also linked to several chronic diseases. Several studies have shown that ultraviolet (UV)-treated mushrooms are a potential dietary source of vitamin D, as these mushrooms have a high rate of conversion of ergosterol to vitamin D2. However, there are gaps in knowledge about the most appropriate irradiation conditions, including the source, dose, intensity, and duration of irradiation, for maximizing vitamin D2 content in mushrooms. UVB seems to be most effective in transforming ergosterol to vitamin D2 in both fresh and dried mushrooms. Effects of drying, storage, and thermal treatments on vitamin D content in UV-treated fresh mushrooms have been reported. This knowledge is important for the mushroom industry in order to provide the market with vitamin D2-enhanced mushrooms in a safe and affordable manner. Recent studies in humans focused on the bioavailability of vitamin D2 from mushrooms. The study results showed that UV-treated mushrooms were effective in increasing serum 25-hydroxyvitamin D levels, as they contain high vitamin D2. However, other reports indicate that there are no significant changes in serum 25(OH)D levels and suggest that vitamin D2 is not as effective as vitamin D2 in increasing serum 25(OH) D levels. Vitamin D2 bioavailability is still unclear, and there is an urgent need to investigate the effectiveness, safety, and adequate amount of vitamin D2-enhanced mushrooms for reducing vitamin D deficiency and maintaining vitamin D levels.

Cold stress treatment enhances production of metabolites and biodiesel feedstock in Porphyridium cruentum via adjustment of cell membrane fluidity.

Porphyridium cruentum, a cell-wall-free marine Rhodophyta microalga was cultured under a 5-day cold stress at 0 °C and 15 °C, after reaching the late logarithmic growth phase. Compared with the control at 25 °C, the cold stress treatment significantly (p < 0.05) increased the microalgal biomass (1.21-fold); the amounts of total polyunsaturated fatty acids (1.22-fold); individual fatty acids including linoleic acid (1.50-fold) and eicosatrienoic acid (1.85-fold), and a major carotenoid zeaxanthin (1.53-fold). Furthermore, production of biodiesel feedstock including total C16 + C18 fatty acids was significantly enhanced (p < 0.05) by 1.18-fold after the cold stress treatment. Principal component analysis further indicated that the biosynthetic pathways of fatty acids and carotenoids in this microalga were correlated with the cold stress treatment. These results suggested that P. cruentum had adjusted its cellular membrane fluidity via an 'arm-raising and screw-bolt fastening' mechanism mediated by the synergistic roles of cis-unsaturated fatty acids and carotenoids. The insight obtained from the responses to cold stress in P. cruentum could be a novel technological approach to enhance the production of microalgal metabolites and biodiesel feedstock.