Algal Research-Biomass Biofuels and Bioproducts最新文献

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.

The carotenoid productivity of a euryhaline Synechococcus sp. was studied in indoor and outdoor conditions. Indoor experiments revealed that the strain could maintain growth and carotenoid accumulation within a salinity range of 2.5–8.0 % NaCl. In an indoor two phase semi-continuous cultivation in PBRs, every three days, 50 % of the culture was replaced with fresh growth media in phase one, whereas the removed culture was grown for another three days in the second phase to enhance the carotenoid yield. Biomass and carotenoid productivity of the strain in the second phase were similar in five consecutive cultivation cycles. Next, the same two-phase cultivation experiment was conducted in 5 sq. m outdoor raceway tanks. However, for the outdoor experiment, carotenoid-rich biomass was harvested from the second phase by membrane filtration, and the growth media was recycled for cultivating in the first phase. The salinity of the culture continued to increase as the evaporated water was balanced by seawater. The semi-continuous cultivation of the first phase continued for 20 days before the culture salinity reached 7.4 % NaCl. For Synechococcus sp., the growth and carotenoid productivities were not affected within this salinity range.

The present study innovatively explores the impact of adding agricultural mixed plant hormones (gibberellin acid-indole-3-acetic acid-brassinolide, GIB) on simultaneously removing nutrients and antibiotics out of aquaculture wastewater within different four microalgae-bacteria-fungus symbionts. The results indicated that under the optimal symbiotic technology (Chlorella vulgaris+S395-2+Clonostachys rosea) and the best hormone GIB (20 mg L⁻¹) addition, both growth characteristics and photosynthetic performance of microalgae-bacteria-fungus symbionts were optimal. Under optimal treatment conditions, the average nutrient removal efficiency (TN and TP) reached 93.71 ± 5.02 % and 93.56 ± 4.07 %, separately, whereas the average removal efficiency of antibiotics (oxytetracycline, ciprofloxacin and sulfadiazine) were 99.46 ± 0.17 %, 89.53 ± 5.41 %, and 85.68 ± 6.82 %, respectively. This study offers a promising new direction for algal treatment technology, particularly in the concurrent removal of antibiotics and nutrients.

Offshore macroalgae production offers the potential to provide valuable biomass for food, energy, and higher value products without the use of land or freshwater while using excess nutrients and carbon dioxide. To realize this potential, the Macroalgae Research Inspiring Novel Energy Resources program of the Advanced Research Projects Agency-Energy has initiated projects to develop advanced cultivation technologies that enable the cost- and energy-efficient production of macroalgal biomass. This study addresses the life-cycle greenhouse gas emissions and energy return on investment for five U.S. offshore macroalgae production systems designed for deployment at the thousand-hectare scale using a detailed module developed within the GREET life-cycle analysis model for this study.

The carbon intensity of macroalgae production system designs, expressed as kg of carbon dioxide equivalent per dry metric ton of algae harvested, vary widely from 49 to 220 and confirm that biomass productivity has the highest degree of sensitivity across the model parameters tested. Regardless of the system designs, the upstream and combustion emissions from fuel use are the key contributor (over 45 %) to carbon intensity, indicating that the use of low-carbon fuels (e.g., renewable diesel) could further reduce greenhouse gas emissions. Further studies need to specify the market opportunity and specific product slates for macroalgae to provide a complete picture of the environmental impacts of macroalgal feedstock.

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.

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.

The polysaccharides from green algal Caulerpa lentillifera (CLP) have shown strong positive effects on terrestrial animal immunity. However, little is known about their function in aquatic animals. Here, we fed shrimp with diets containing different CLP contents (0, 0.1 %, 0.2 %, and 0.4 %). Our results indicated that the increase of 0.1 % CLP could significantly enhance shrimp growth rate, weight gain, and hepatopancreas index, and all doses of CLP could greatly increase the shrimp crude protein content compared to the control. In addition, 0.1 % CLP significantly enhanced the shrimp phagocytic activity, hepatopancreatic acid phosphatase (ACP) activity, hepatopancreatic alkaline phosphatase (AKP) activity, and plasma superoxide dismutase (SOD) activity, while reducing plasma malondialdehyde (MDA) activity compared to the controlled diet. The 16S rDNA sequence of shrimp intestine microbiota indicated that the intestinal microbiota diversity in shrimp fed with 0.2 % CLP diets was higher than that in the control, including an increase in beneficial microbial groups (Proteobacteria, Actinobacteria, Firmicutes, and TM7) and a decrease in harmful ones (Shewanella and Vibrio). Feeding with CLP could enrich carbohydrate and amino acid metabolism. Correlation analysis indicated that peroxidase (POD) had the widest correlation with communities, being inversely correlated with seven distinct microbial taxa. Moreover, four distinct microbial taxa were significantly associated with weight. These data indicate that CLP is a potential shrimp forage supplement and recommend the optimum dose of CLP inclusion to be 0.1 %–0.2 % in shrimp diets.

The efficient operation of large-scale microalgae cultivation facilities requires continuous awareness of the culture condition. Although many conventional methods can be implemented in the laboratory, this goal can only be accomplished with non-invasive techniques such as spectral imaging based on the measurement of light backscattering of the culture surface. Several imaging methods are available, but we argue that developments in spectral approach will be among the essential breakthroughs for future advanced industrial-scale cultivation of microalgae.

The spectral methods initially developed for long-range (satellite and airborne) remote sensing of large water bodies are now increasingly employed for close-range monitoring of phytoplankton in natural ecosystems and large-scale microalgal cultures in open ponds and in closed photobioreactors. Similarly to high-throughput phenotyping which is now central to the progress of plant sciences, accelerated breeding, and precision farming, spectral imaging is gaining attention in microalgal biotechnology. Its power stems from the automated, rapid, non-invasive collection of large datasets, and the current advances in Machine Learning (ML). Their benefits include affordability, high information payload, and simplicity.

This review briefly presents imaging methods currently used in microalgal research, then focuses on spectral imaging. The background and biophysical foundation of remote sensing of communities and artificial monocultures is presented. Then, we elaborate on the methods for extracting relevant information from spectral images for monitoring of biomass accumulation, culture health, and target metabolites. Special attention was given to novel, trendy applications of ML to processing images and spectral data for the inference of actionable insights into the culture condition.

This study aimed to evaluate the effect of microalgal photoautotrophic treatment on estrogenic activity (EA) and removal process of two emerging contaminants (ECs), bisphenol-A (BPA) and triclosan (TCS), in synthetic wastewater (SWW). The concentration used for BPA (17 mg/L) and TCS (325 μg/L) is the median effective concentration (EC₅₀). Two conditions were evaluated, using a microalgae inoculum of ≈300 and ≈500 mg TSS/L (Total Suspended Solids per liter). For BPA, biodegradation was found to be the removal process contributing to the highest percentage removal, reaching >40 % for both initial microalgae inoculum (≈300 and ≈500 mg TSS/L). For TCS, the highest removal process was photodegradation, with >28 % (sum of direct and indirect removal). However, for TCS it was observed that for TSS ≈ 500 mg/L TSS, sorption (adsorption and absorption) increased by ≈17 % with respect to that determined for TSS ≈ 300 mg/L. Microalgae photoautotrophic treatment, using ≈500 mg TSS/L, resulted in a reduction of EA for TCS (by 33 %); but a 1.13-fold increase of EA for BPA. No EA effect of BPA and TCS was observed at ≈300 mg TSS/L. Both treatments resulted in a removal of >95 % of BPA and ≈86 % of TCS. For direct photodegradation, removals of both BPA and TCS were quantified as 3.8 % and 14.4 %, respectively. However, an increase in EA was observed for both ECs (1.79-fold for BPA and 1.23-fold for TCS). Indirect photodegradation resulted in removals of 26.2 % and 14.1 %, respectively. Additionally, EA showed a 2.4-fold increase for BPA, whilst a 17.99 % decrease was observed for TCS. In conclusion, no linear correlation was observed between EA and EC removals. Microalgae photoautotrophic treatment resulted in high removal efficiencies of TCS and BPA, as well as a decreased EA of TCS.

Microalgae are an underutilized biomass source of nutritionally valuable extracts with promising texturizing capacities that can be used for food applications. This also requires the development of environmentally friendly extraction technologies. Hydrothermal processing was used in this study to investigate the effects of temperature (up to 225 °C) on the extracts from the diatom Phaeodactylum tricornutum. The relationship between protein and polysaccharides' presence and functionality was assessed, based on structure, composition, bioactivity, and rheological behavior. An optimal condition of non-isothermal processing at 120 °C resulted in the extract with gelling capacity (at 20 % w/w extract concentration). This extract is rich in carbohydrates in oligosaccharide form (9 g per 100 g extract) and protein (16 g per 100 g extract), which indicates nutritional relevance and possible prebiotic effects. Moreover, after an additional purification step with food-grade solvents, this extract was able to gel at 5 % w/w concentration. These combined with its significant antioxidant activity (over 100 μmol Trolox equivalents per gram of extract in all studied conditions, using the ABTS method) point towards new possibilities for the application of Phaeodactylum tricornutum extracts in novel clean-label vegan foods. Overall, these findings suggest that the novel approach proposed in this work, based on hydrothermal processing, is feasible and compatible with the need for the application of simple purification steps with food-grade solvents. Furthermore, it reinforced the relevance of the carbohydrate fractions and carbohydrate-protein interactions from microalgae.