Chlorella sorokiniana is a microalgae with high amounts of carotenoids, but the extraction methods need to be improved. This work hypothesized that the combination of ionic liquids (ILs) and ultrasound would provide a fast and efficient process for carotenoid extraction, allowing for the reuse of ILs in several extractive cycles. This study aimed to develop an improved ILs/ultrasound-based method for extracting carotenoids from C. sorokiniana. The potential reuse of ILs in five consecutive extraction cycles and the recovery of carotenoids was also examined. Moreover, the antioxidant activity of the carotenoid extracts and their effects on metabolic cell viability and cell death were investigated using HT22 neuronal cells. Initial tests with four ILs and acetone as a control were carried out in an ultrasonic probe. The ILs (1-butyl-3-methylimidazolium chloride [BMIM][Cl]; 1-hexyl-3-methylimidazolium chloride [HMIM][Cl]) were selected for the 25−1 fractional experimental design. The maximized parameters obtained in the experimental design were the following: IL ([HMIM][Cl]), a 1:10 solid-liquid ratio, a 1:4 IL-cosolvent ratio, and two repetitions of extraction with 7.5 min (with an extraction yield of 1.29 mg·g−1 of dry matter). A total of 11 carotenoids were separated, and nine were identified, the major ones being lutein and β-carotene. [HMIM][Cl] recyclability using resin Amberlite XAD-7HP was efficient for at least five cycles. On average, 91 % of the IL was recovered, and the pigment yield increased by 40 %. The antioxidant activities of the extracts obtained using [HMIM][Cl] and acetone were 1.65 μmol and 2.32 μmol of α-tocopherol, respectively. Both extracts (≤ 4.0 μg·mL−1) exhibited no significant toxicity to HT22 cells. The proposed method is an innovative and improved approach for carotenoid extraction from C. sorokiniana due to its short extraction times and high process yield. [HMIM][Cl] demonstrated stability in reuse cycles and proved to have the potential for obtaining carotenoids from C. sorokiniana.

In recent years, the proliferation of industrial effluents has posed significant challenges. In comparison to traditional physical and chemical methods, biological approaches have gained prominence among researchers due to their cost-effectiveness, abundant sources, ease of operation, and minimal secondary pollution. Moreover, employing microalgae for bioremediation offers the added advantage of concurrent production of diverse sustainable resources and biofuels. Nevertheless, challenges pertaining to recovery and reaction conditions continue to impede its large-scale implementation. Thus, exploration of improved solutions, such as enhanced reaction conditions, is imperative to maximize efficiency. In this review, we elucidate the mechanisms and pivotal factors involved in the removal of heavy metals by microalgae. Notably, we highlight innovative bioreactor technologies, including immobilization carriers, modified microalgae, and symbiotic systems, as focal points of this discussion. This comprehensive overview underscores the potential of microalgae-based bioremediation and paves the way for future advancements in this critical field.

Microalgae are widely distributed in the ocean, and some species are prone to causing harmful algal blooms that threaten the marine ecological environment. At present, microscopy is the most common method for microalgae analysis, and the combination of computer vision and microscopy is the mainstream trend in algae morphology classification. However, most methods only focus on the species and quantities of algae, without obtaining contour information that can further analyze their survival status and biomass. Therefore, this article proposes a convolutional neural network (AlgaeSeg-YOLO), which can recognize the species, quantities, and contours of algae. Firstly, a dataset of microalgae microscopic images in microfluidic chips was constructed, which includes a total of 2799 annotated images of 6 harmful microalgae, including 3916 instances. Secondly, the AlgaeSeg-YOLO was constructed with stronger feature fusion and pixel-level spatial information modeling capabilities based on YOLOv8n-seg. Finally, compared to other common methods, the experimental results show that the mAP (mean Average Precision) of AlgaeSeg-YOLO reaches 95.61 %, which is 1.64 %, 1.76 %, 5.28 %, 3.34 %, and 5.39 % higher than YOLOv8n-seg, YOLOv5n-seg, Mask R-CNN, Cascade Mask R-CNN, and SOLOv2, respectively, achieving real-time and accurate segmentation of microalgae in complex backgrounds. Meanwhile, the parameters and computation remain relatively low. This work helps to achieve fully automated analysis of microalgae, reduce labor costs, and provide technical support for long-term monitoring of the ecological environment and further research.

The presence of cyanobacteria in water for drinking and recreational purposes is considered problematic due to their bloom-forming and toxigenic potential. While most cyanotoxins are produced by extensively studied cyanobacteria, little is known about other abundant genera not usually assessed for their toxic potential. Here, a newly isolate of Limnothrix redekei from an Italian drinking water reservoir was cultured and investigated per means of biological, chemical, and genomic methods. Compared to other Limnothrix spp., the isolate yielded high biomass productivity and was mainly constituted by proteins. The isolate had similar genomic features to the other 10 genomes of Limnothrix spp. published so far, regardless of their geographical distribution. Most of genes were implicated in primary metabolism (e.g. photosynthesis, nutrients transport, cell division), while <1 % of the genome was dedicated to secondary metabolism. Two regions encoding for a cyanobactin and a polyketide were found, whereas those for known cyanotoxins were not present. Toxicological investigations based on the crustacean Artemia sp. bioassay revealed potential toxicity of Limnothrix aqueous extracts (mortality >90 %). The highest toxicity was observed in a single fraction of the extract, whose UV spectrum presented carotenoid-like characteristics. Although the structure of the putative toxin was not yet elucidated, these findings pose the basis for further investigations on Limnothrix spp. toxicity, for which the observed toxic aqueous extracts could not exclude possible implications for ecosystems and humans through drinking water resources.

The motive of this study is to predict the concentration of C-phycocyanin (CPC) from Spirulina platensis by adapting several colour models along with machine learning (ML) and deep learning (DL) techniques. Initially, three different culture mediums such as Zarrouk, BG-11, and AF6 were compared, and the BG-11 medium was chosen due to its overall best biomass growth, least amount of chemical usage, and CPC production. The performance of the convolutional neural network (CNN) without the input parameters of ‘Abs’ and ‘Day’ results in a higher R2 of 0.7269 as compared to both support vector machine (SVM) and artificial neural network (ANN) with R2 of 0.2725 and 0.2552, respectively. The absence of regularisation techniques has caused the scenario of model overfitting, showing results of R2Train = 0.9891 and R2Val = 0.5170 (without image augmentation) and R2Train = 0.9710 and R2Val = 0.5521 (including 20 % dropout but without image augmentation). Meanwhile, both SVM and ANN models were observed to show significantly high accuracy when including extra parameters of ‘Abs’ and ‘Day’ as compared to the CNN model with R2 of 0.9903 and 0.9827, respectively. We aim to establish a high precision and real-time assessment of microalgae biomolecule intelligent system that requires low cost, less time consumption, and is widely applicable, addressing the challenges associated with conventional microalgae quantification and identification.

Isoprene from marine emissions significantly influences the atmospheric oxidative capacity and secondary pollutants in the marine boundary layer. While marine algae are recognized as primary contributors to marine emissions of isoprene, the long-term and dark-phase isoprene production from these organisms remains underexplored, potentially lead to inaccuracies in estimating marine isoprene emissions. In this study, we conducted a time series investigation of isoprene emission from Chaetoceros curvisetus with a growth cycle duration of 19 days and examined the influence of environmental factors. Our findings revealed that C. curvisetus emits isoprene during its whole growth cycle, with peak emissions (2.82 × 10−11 μmol cells−1 h−1) recorded in the stationary phase. Under nitrogen, light and temperature stress, significant release of isoprene is found. During both the light and dark phases, isoprene emission was observed with comparable intensities. Transcriptome analysis showed that 41 differentially expressed transcripts were involved in the synthesis of volatile organic compounds. Notably, downregulation of genes associated with pyruvate synthesis in the glycolysis pathway suggests its importance for dark isoprene release. The study also highlighted downregulation of isopentenyl phosphate kinase and Gene Ontology enrichment in organelles housing mevalonate (MVA) pathways, suggesting that exchange involving the transport of intermediate metabolites between MVA and methylerythritol phosphate (MEP) pathway may contribute to the released isoprene in dark phase. Furthermore, the synthesis of substrates and downstream products is related to the dark release of isoprene. In conclusion, our study illuminates the pivotal roles of substrate availability, interplay between MVA and MEP pathways, and glycolysis pathway in governing isoprene emissions under light/dark cycles.

Microalgae and cyanobacteria are photosynthetic and unicellular organisms that contain considerable amounts of proteins, lipids, carbohydrates, and polyunsaturated fatty acids, among others, with applications in the cosmetic, pharmaceutical, and food industries. These microorganisms can accumulate protein up to 70 % of total biomass depending on the microalgal strain, hence they have been regarded as an alternative protein source for the future. Microalgal proteins have important applications such as emulsifying, foaming, and gelation properties, which are important for the determination of quality and texture of foods. Some microalgal peptides possess important bioactivity with many health-benefit effects. Therefore, to maximize the production of proteins from microalgae and cyanobacteria, many protein extraction procedures have been studied to increase the economic return. They have been tested towards higher protein yields at low energy cost, the preservation of protein native properties, and lower cell debris. This later is fundamental to facilitate the subsequent purification processes so that the overall cost can be reduced. The aim of this work is to review some cell disruption processes for the extraction of protein from microalgae and cyanobacteria, considering that this step is crucial for the overall process due to the high rigidness of microalgal cell covering, which can hamper the release of proteins. It also aims at reviewing the purification techniques after cellular disruption, from conventional to more recent approaches, and finally addresses the antioxidant, antidiabetic, antihypertensive, antibacterial and other bioactive properties of microalgal protein hydrolysates and peptides.

Trivalent iron ions (Fe(III)) have important effects on aquatic ecosystems, especially on the functional diversity and stability of microorganisms and ecosystems. Here, a cultivable microalgae (Chlorococcum sp. GD) from the natural environment (Shanxi, China) were isolated and identified. A combined high-throughput 16S rRNA gene amplicon sequencing/excitation-emission matrix coupled with parallel factor (EEM-PARAFAC) analysis was used to integrated the results of Fe(III) influence on Chlorococcum sp. GD bacterial community and dissolved organic matter (DOM) characteristics through laboratory experiments. Due to the addition of Fe(III) in the form of ferric nitrate (Fe(NO3)3·9H2O), complexed with EDTA to maintain solubility and bioavailability, the bacterial community was altered. This led to a decrease in the relative abundance of Proteobacteria and Actinobacteria and an increase in the relative abundance of Cyanobacteria, especially under excessive Fe(III) treatment. In addition, the relative contribution of bacterial community dispersal limitation and homogenizing dispersal was 100 %, which may lead to differences in their local adaptation and ecological processes with homogenization of bacterial diversity and loss of function. Excessive Fe(III) caused a significant increase in the abundance of genes involved in the carbon cycle (p < 0.01) and a significant decrease in genes involved in the nitrogen cycle (p < 0.01), further affecting the overall regulatory network of gene expression. This led to an increase in the abundance of genes involved in metabolism, cellular processes, environmental information processing, genetic information processing, and human diseases. The moderate amount of Fe(III) promoted the production of microbial components and accelerated the degree of DOM humification. It is also worth mentioning that excessive Fe(III) inhibited DOM degradation. Overall, this work explored the characteristics of bacterial community and DOM changes in Fe(III)-stressed Chlorococcum sp. GD as an example, which contributes to an in-depth understanding of microbial community diversity and element cycling in aquatic ecosystems.

Spirulina platensis and its extracts possess positive benefits for human health indications from malnutrition, antioxidant properties, and therapeutic properties. This study investigates the antioxidant activity of Spirulina platensis extracts and their cytotoxicity against the breast cancer cell line (MCF-7). The antioxidant and cytotoxicity properties of C- phycocyanin (C-PC) were directly compared with the diethyl ether extract of S. platensis (DEE). Results indicated that C-PC exhibited superior antioxidant activity compared to DEE extract. The observed values for C-PC are 1.453 μg/mL (IC50-value), 299.6 μM AA eq/mL, 86.68 μM TE eq/mL, and 179 μg/g for ABTS assay, DPPH, FRAP and total antioxidant activity, respectively. Moreover, C-PC also demonstrated enhanced cytotoxic activity against MCF-7 tumor cells with IC50 values of 100 μg/mL and 630 μg/mL for C-PC and DEE; respectively. C-PC treatment downregulated the expression of PI3K, Akt, mTOR, and Wnt. C-PC treatment to MCF-7 cells significantly induced caspase 3, caspase 8, and caspase 9. Similar effects, with lower tendency, were also observed for DEE extracts of S. platensis. Molecular docking studies suggest that S. platensis' bioactive constituents can induce apoptosis through intrinsic pathways. The current findings provide evidence for the medical importance of Spirulina platensis active constituents as promising natural anticancer drugs.

In the present investigation, fucoidan isolated from Nizamuddinia zanardinii was hydrolysed using 0.01 N HCl at boiling temperature for 10, 20, 40 and 60 min. Native and hydrolysed fucoidans contained a close chemical compositions, most importantly constituted of sulfates and uronic acids as well as fucose, galactose and mannose. Hydrolysis and cross-flow ultrafiltration produced fucoidan hydrolysates having different weight average molecular weights. The FH20 fucoidan was the most potent polysaccharide hydrolysate to stimulate NO-release from RAW264.7 macrophage cells. After cross-flow ultrafiltration of FH20, 100 < kDa fucoidan, polysaccharide with high branching degree consisting mainly of (1 → 2)-Fucp, (1 → 2,3)-Fucp, (1 → 3)-Galp, (1 → 2,3)-Galp, (1 → 2)-Manp and (1 → 3)-Manp residues, exerted the highest stimulation effect on RAW264.7 macrophage cells, secreting considerable NO, TNF-α, IL-1β, IL-6 and IL-12 proinflammatory mediators. Also, 100 < kDa fucoidan activated NK-92 cells to release TNF-α, INF-γ, granzyme-B, perforin, NKG2D and FasL. Both RAW264.7 and NK-92 cells were activated through NF-κB and MAPKs signalling pathways and the degree of stimulation capacity in fucoidan from N. zanardinii was in close correlation with the molecular weight.