Journal of Applied Phycology最新文献

Fucoidan is a fucose-rich sulfated polysaccharide found mainly in brown seaweeds. Fucoidan has recently gained much attention due to its bioactive and medicinal properties, hence its high potential to be utilized in the pharmaceutical industry. Therefore, an accurate, reliable, and simple method for the specific determination of fucoidan would be a useful tool when looking to recover this valuable polysaccharide. This research focused on developing an assay utilizing the thiazine dye, methylene blue, for the quantification of fucoidan, with a specific application for fucoidan found in algal extracts. Fucoidan could be specifically determined at pH 1, to maximum concentrations of 4 g L^-1 in solution without the interference of alginate and other seaweed extract contaminants. At pH 7 and 11, quantification of fucoidan led to interference from alginate and gallic acid. A conversion factor of 1.8 allowed the quantification of fucoidan from Ecklonia maxima extracts using a commercial standard from Fucus vesiculosis. An Ecklonia maxima extract was found to contain 5.47 ± 0.061 g L^-1 of fucoidan. Measuring the fucoidan and L-fucose concentration in crude seaweed extract through the methylene blue assay and modified Dische and Shettles J Biol Chem 175:595–603, (1948) method, respectively, confirmed the accuracy and specificity of the method. The limit of quantification of the methylene blue assay at pH 1 was 0.62 g L^-1 of fucoidan.

Although established biotechnological applications of microalgae e.g., the production of high-value metabolites is based on axenic cultures, exploitation of the mutualistic consortia of microalgae and bacteria quickly comes to foreground, especially in bioremediation and wastewater treatment. This trend shifts the focus from genomic research of certain microalgal species to metagenomic studies of interactions between microalgae and bacteria in natural communities and in artificial consortia. Dissection of the genetic determinants of the robustness and productivity of the consortia become a hot research direction, too. Admirable contribution to this topic had been made by high-throughput sequencing (HTS), while recent breakthrough in this field was entailed by the advent and rapid development of the 3rd generation nanopore sequencing which becomes increasingly accurate while providing unprecedented sequencing performance. Recent progress of the Oxford Nanopore Technologies (ONT) enabled both classical metagenomic analysis of microalgal-bacterial communities based on whole metagenome sequencing as well as taxonomic and genetic profiling based on the amplicon sequencing. The parallel emergence of novel bioinformatic algorithms for processing the metagenomic datasets opened new opportunities for the analysis of structure and physiology of microalgal-bacterial communities. From the practical perspective, the new HTS techniques became a time- and labor-savers in discovery of new microalgae with a high potential for the accumulation of valuable metabolites, biodegradation of hazardous micropollutants, and biosequestration of nutrients from waste streams. Search for prokaryotic species boosting the biotechnological potential of eukaryotic microalgae via mutualistic interactions with them is another important goal. The insights from the both short-read and long-read metagenomics will form a solid foundation for the rational design of microalgal-bacterial consortia for biotechnology. In this review, we briefly outline the benefits of the long-read sequencing for structural and functional investigation of algal-bacterial consortia and summarize recent reports on using this approach for achieving the biotechnology-related goals.

Eisenia (order Laminariales) is a genus of warm-tolerant kelps found in the Northern and Southern Hemispheres of the East Pacific, as well as in the North West Pacific, where species form beds in rocky bottoms along the sea coast from the intertidal and subtidal zones. There are seven recognized species in the genus, including the endemic and vulnerable E. galapagensis. Despite some remarkable morphological variations, Eisenia species are characterized by two twisted stipe-like parts arising from the main stipe. Genetic data have recently contributed to the understanding of Eisenia systematics; however, additional studies on E. desmarestioides, E. cokeri, and E. gracilis are needed. Aside from economic benefits, Eisenia farming has various other essential benefits, such as resource sustainability and ecosystem benefits, which are especially important in climate change scenarios. Spore-based cultivation has been reported only for E. arborea, E. bicyclis, and E. nipponica (formerly known as E. arborea sensu Arasaki). This kelp is widely consumed in Korea and Japan and utilized as a raw material for alginate production and feed for abalone cultures. Because of its nutritional composition and mineral concentration, Eisenia is also a potential food source outside Asia. Moreover, various pharmacological applications of Eisenia have been reported, particularly those related to antioxidant, antidiabetic, and anti-inflammatory properties. Phlorotannins (brown algal polyphenols) derived from E. bicyclis are linked to these bioactivities. In this work, we present a comprehensive synthesis of the current state of knowledge on Eisenia, offering insights into its taxonomy, distribution, ecology, cultivation, and various applications.

Nori is a dried edible seaweed sheet made from Porphyra, a genus of red algae that thrivesprimarily in subtropical waters. Nori-like products have been developed from tropical seaweed species but they are still considered undesirable due to their astringent taste and lower protein content compared to the original nori. This investigation aimed to produce a nori-like product by utilizing a combination of locally sourced seaweeds, Ulva lactuca and Gracilaria changii, with the addition of anchovy flour to enhance its protein content. To obtain the optimal formulation of the product, we employed a design expert software application to analyze sensory data collected from a hedonic scale assessment involving 25 trained panelists. We evaluated sensory characteristics, including appearance, aroma, texture, taste, and overall satisfaction. Additionally, we considered parameters such as crispness and colour to determine the nori-like product quality. The best-selected product, determined through sensory evaluation, underwent further analysis of its proximate and amino acids profile, as well as mineral content. The results were compared to those of commercial nori from Porphyra. The highest-quality product was found to be the nori-like product with a formula consisting of 25.40% Ulva lactuca, 7.98% Gracilaria changii, 1.50% glycerin, 4.12% anchovy powder and the remainder water.

The unceasing rise in human population has provoked large environmental damage, essentially in air and water habitats. Microalgae have been deeply investigated regarding wastewater treatment as well as a suitable biofuel feedstock. Nevertheless, process optimization and the search for new local strains are imperative to overcome the cost-effectiveness bottleneck that persist in large-scale technology. Linked to this, micro-diversity studies in landfill leachates have been done. However, there has been no study which analysed specifically the microalgal diversity outside of this less-explored environment to see their biotechnological potential. Hence, a specific study of microalgal diversity present in leachates produced by a non-hazardous waste landfill (mainly for municipal solid waste MSW) located in Asturias (Spain) was done. The new strain Chlorella vulgaris DSAF was isolated and identified based on both morphological and molecular methods. Some parameters based on site-climate conditions were studied to understand C. vulgaris DSAF behaviour. The modification in the lipid content and FAMEs profile in response to the stress caused by the addition of NaCl and nutrient deprivation were also studied. The stress induction produced significant morphological changes when compared to control group (e.g., bigger cell sizes). Specifically, the addition of 25 g L^-1 of NaCl achieved an increase of 25% of biomass. Total lipids increased under nutrient deprivation (N, P and NP) from 13 to 34% (w/w). Oleic acid was the most abundant fatty acid, reaching 50% of total FAMEs under NP deprivation conditions. Linoleic acid and α-linolenic acid also showed a moderate increase during NaCl stress. The positive results during calculation of the main biodiesel properties determined that C. vulgaris DSAF would be a potential biodiesel feedstock under different cultivation conditions.

Fucoidans are a heterogenous class of fucose-rich sulfated carbohydrates which have attracted increasing attention in cancer and inflammation research due to their bioactive properties. There are reports that fucoidans may have direct antibacterial effects and synergy with antibiotics. However, the literature is conflicting, potentially due to the limited reporting of origin, characteristics, and extraction methods of the fucoidans tested. Here we report the results of 18 defined fucoidans screened for direct, indirect, and synergistic antibacterial effects. 15 distinct fucoidan fractions, isolated from Laminaria hyperborea using a solvent-free extraction process, were characterised for molecular weight, pH, viscosity, and sulfur content. These, together with three commercially available crude fractions, were assessed at concentrations from 0.03125-24 mg mL^-1 for minimum inhibitory concentration against Staphylococcus aureus, Streptococcus mutans and Streptococcus sanguinis. Furthermore, we tested a selection of fucoidans for antibacterial synergy with vancomycin and indirect antibacterial effects in whole blood survival assays. Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) was performed to assess the stress response in fucoidan-treated S. aureus cultures. We have identified one fucoidan fraction with bactericidal activity against diverse bacteria. This effect is dose-, fucoidan fraction- and bacteria-specific, and furthermore, not related to osmotic stress. No synergistic effects were observed with fucoidan in combination vancomycin. Fucoidans have exciting potential as antimicrobial agents. Further analysis is required to establish the precise molecular characteristics responsible for their potent bactericidal activity.

Seasonal changes in the size of the herbal drug red alga Chondria armata (Rhodomelaceae, Ceramiales) were investigated in Kagoshima, Japan, which is near the northern distributional limit in the western Pacific. Additionally, its photosynthetic response to irradiance and temperature was examined using dissolved oxygen sensors and a pulse amplitude modulation (PAM)-chlorophyll fluorometer. This alga was observed in tidepools throughout the year; its height and weight were greatest in December and the lowest in April and May. The net photosynthesis of the photosynthesis–irradiance (P–E) curve determined at 28°C quickly saturated at 113 µmol photons m^-2 s^-1, with minimal inhibition even at 1000 µmol photons m^-2 s^-1. The gross photosynthesis of the photosynthesis–temperature (P–T) curved over 8 to 40°C, measured at 500 µmol photons m^-2 s^-1, peaked at 30.1°C and decreased rapidly below 20°C and above 36°C, respectively. Similarly, the effective quantum yield (ΔF/F_m') after a 3-day culture during 4–40°C at 50 µmol photons m^-2 s^-1 remained stable between 16°C and 32°C but decreased outside of this range. The combined effect of irradiance (200 [low] and 1000 [high] µmol photons m^-2 s^-1) and temperature (28, 22, and 16°C) revealed that ΔF/F_m' declined during exposure to high irradiance at all temperature treatments. However, it mostly recovered after a subsequent 12-hour period of dim-light acclimation at 28°C and 22°C. In contrast, those at 16°C could not recover, indicating the occurrence of low-temperature light stress. This alga appears to be well-adapted to the irradiance and temperature environment at the study site. However, the winter temperature appears to approach its threshold level, and the occurrence of strong light during the winter might adversely affect the abundance of this alga near its northern distributional limit.

High expectations are placed on microalgae as a sustainable source of valuable biomolecules. Robust methods to control microalgae cultivation processes are needed to enhance their efficiency and, thereafter, increase the profitability of microalgae-based products. To meet this need, a non-invasive monitoring method based on a hyperspectral imager was developed for laboratory scale and afterwards tested on industrial scale cultivations. In the laboratory experiments, reference data for microalgal biomass concentration was gathered to construct 1) a vegetation index-based linear regression model and 2) a one-dimensional convolutional neural network model to resolve microalgae biomass concentration from the spectral images. The two modelling approaches were compared. The mean absolute percentage error (MAPE) for the index-based model was 15–24%, with the standard deviation (SD) of 13-18 for the different species. MAPE for the convolutional neural network was 11–26% (SD = 10–22). Both models predicted the biomass well. The convolutional neural network could also classify the monocultures of green algae by species (accuracy of 97–99%). The index-based model was fast to construct and easy to interpret. The index-based monitoring was also tested in an industrial setup demonstrating a promising ability to retrieve microalgae-biomass-based signals in different cultivation systems.

Since 2012 the Moroccan Atlantic coast has witnessed the introduction of the brown alien seaweed Sargassum muticum with a high invasive potential presenting environmental and economic risks. This study evaluates the effect of seasons and location on the biochemical composition of S. muticum. Proteins, carbohydrates, lipids, pigments, minerals, and heavy metals were studied during four seasons from spring 2019 to autumn 2020 at four sites along the Moroccan Atlantic coast: El Jadida, Saada (SA), Sidi Bouzid (SB), Moulay Abdallah (MA) and Jorf Lasfar (JL). MA presents the highest protein content (12.5% dw) during spring and the highest level of lipid and carbohydrate content during summer (1.8% dw and 41.5% dw respectively). The highest chlorophyll a content was found in JL and MA sites with (21.6 and 21.45 mg mL^-1, respectively) during winter. Maximum chlorophyll c and carotenoids were found at SA with (2.27 and 9.71 mg mL^-1, respectively) during winter. In all locations and during all seasons, the mineral profile was rich in essential minerals such as magnesium, manganese, zinc, iron, selenium, and lithium. Levels of toxic metals Al and Pb were lower than in previous studies whereas Cd and As were slightly higher than the legislation limits for dry seaweeds. Therefore, in this context, some strategies of S. muticum valorisation should be favoured such as bioenergy, bioplastic or biostimulant over others such as human food and animal feed.

A type III polyketide synthase (SfuPKS2) from the edible seaweed Sargassum fusiforme was cloned and biochemically characterized. SfuPKS2 can only accept octanoyl-CoA (C8) and neither other long-chain fatty acyl-CoAs, nor non-fatty acyl-CoAs synthesized in this study as the substrate. In addition, in incubation with octanoyl-CoA, only a single product peak was observed, giving rise to the triketide α-pyrone derivative. To understand the substrate specificity of SfuPKS2, we constructed a structural model and performed docking analysis to reveal amino acid residues critical for enzyme-substrate binding. Putative key residues were then mutated experimentally and the impact on protein function was assessed by incubating the mutant with octanoyl-CoA. We found that key amino acids governing enzyme activity and specificity included Ser171, His236, Phe254, and Ile377. Mutations on these amino acids generally resulted in altered interactions with the substrate and thus the enzyme activity. In summary, our work provided mechanistic insight on how the selectivity toward the substrate is achieved in SfuPKS2.