Microalgal Biomass Research Articles

Photobioreactor Systems for Mitigating Ammonia and Carbon Dioxide from a Broiler House

This study investigated the effectiveness of photobioreactor (PBR) systems in reducing air pollutants emitted from broiler houses. It focused on two microalgae species and one cyanobacterium grown under different media conditions and investigated their ability to mitigate ammonia (NH3) and carbon dioxide (CO2) in the exhaust air of a broiler house. Ankistrodesmus sp. achieved the highest cell concentrations across all experiments, with maximum dry biomass concentration observed under Nitrogen-free Bold’s Basal Medium (BBM−N) culture conditions. Scenedesmus sp. showed the highest NH3 mitigation efficiency (52.3%) with BBM−N culture, while Synechococcaceae species exhibited the highest CO2 mitigation efficiency (70.8%) with DI-water culture condition. Operating costs for producing 1.0 g L-1day-1 of dry microalgal biomass ranged from 0.10-0.35 USD L-1day-1. The cost of removing 1 g of NH3 ranged from $3.53-7.16, while for CO2, it ranged from $0.04-0.59. The study also evaluated the economic feasibility of this approach, demonstrating significant cost savings in biomass and protein production. These findings highlight the potential of PBR systems as a sustainable solution for reducing air pollutants in broiler house environments.

“Antimicrobial and antioxidant capacity of Dunaliella salina, Tetraselmis chuii and Isochrysis galbana and their potential use in food.” a systematic review

AbstractThe main compounds extracted from the biomass of marine microalgae have antioxidant, antimicrobial, antifungal, anti-inflammatory and antitumor effects, making the possibility of using these properties in the development of foods feasible. Despite the proven biological activity of microalgae, there are still challenges regarding the production and use of microalgal biomass or its derivatives in food industries that are related to high production costs, and there is little research regarding the evaluation of their safety and the search for their application in food development. Therefore, this research aimed to collect information regarding the biological activities of marine microalgae, which allows their use as a natural antimicrobial additive in food matrices and as an ingredient in the development of functional foods with antioxidant capacity. The search interval for the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines was five years. Different methods for the extraction of antioxidant and antimicrobial compounds from the marine microalgae Dunaliella salina, Tetraselmis chuii and Isochrysis galbana were compared and discussed, and the viability of their use and application in food matrices and in the food industry in general were analyzed. It was concluded that there are research gaps in the use of microalgae biomass as an extract, the identification of bioactive molecules for use in the food industry as antimicrobial agents and for the development of functional foods with antioxidant capacity.

Biomass Accumulation, Contaminant Removal, and Settling Performance of Chlorella sp. in Unsterilized and Diluted Anaerobic Digestion Effluent

Microalgae demonstrate significant efficacy in wastewater treatment. Anaerobic digestion effluent (ADE) is regarded as an underutilized resource, abundant in carbon, nitrogen, phosphorus, and other nutrients; however, the presence of inhibitory factors restricts microalgal growth, thereby preventing its direct treatment via microalgae. The purpose of this study was to dilute ADE using various dilution media and subsequently cultivate Chlorella sp. to identify optimal culture conditions that enhance microalgal biomass and water quality. The effects of various dilution conditions were assessed by evaluating the biomass, sedimentation properties, and nutrient removal efficiencies of microalgae. The results demonstrate that microalgal biomass increases as the dilution ratio increased. The microalgae biomass in the treatments diluted with simulated wastewater was significantly higher than that with deionized water, but their effluent quality failed to meet discharge standards. The treatment diluted with deionized water for 10 times exhibited abundant microbial biomass with strong antioxidant properties. The corresponding total phosphorus concentration in the effluent (6.96 mg/L) adhered to emission limits under the Livestock and Poultry Industry Pollutant Emission Standards (8 mg/L), while ammonia nitrogen concentration (90 mg/L) was near compliance (80 mg/L). The corresponding microbial biomass, with a sludge volume index (SVI30) of 72.72 mL/g, can be recovered economically and efficiently by simple precipitation. Its high protein (52.07%) and carbohydrate (27.05%) content, coupled with low ash (10.75%), makes it a promising candidate for animal feed and fermentation. This study will aid in understanding microalgal growth in unsterilized ADE and establish a theoretical foundation for cost-effective ADE purification and microalgal biomass production.

Effects of the use of acetone as co-solvent on the financial viability of bio-crude production by hydrothermal liquefaction of CO2 captured by microalgae

Hydrothermal Liquefaction (HTL) is a promising technology to produce biocrude from microalgal biomass that has captured gaseous CO2. However, several problems of this technology must still be solved to make it economically and technically feasible. One of the main problems in the financial viability of the HTL process is the low yield obtained when only water is used as a solvent, with results close to or lower than 30 wt%. This, in turn, increases the production cost to over 120 USD/BBL. In recent years, some authors have focused their efforts on increasing biocrude production through the extensive use of organic solvents, without considering the effects on economic viability. The present work evaluated the financial effect of using acetone as an organic co-solvent, finding that high acetone contents increased operating costs of the process, mainly due to losses in its handling and recovery. On the contrary, very low acetone contents had very little effect on the biocrude yield. It was possible to establish that concentrations close to 5 wt% of acetone, mixed with water, resulted in a yield of about 60 wt% and a production cost of 50 USD/BBL of biocrude, with an energetic densification of 30.25 MJ/kg and 8.60∘ API, classifying it as heavy crude, which makes it necessary to include refining processes for heteroatom removal. Chemical characterization of biocrude revealed a high content of nitrogenous compounds (23.6 wt%) and oxygenated compounds (10.7 wt%), which have to be removed for the subsequent production of commercial liquid fuels. It is concluded that the use of a water-acetone mixture allows for obtaining positive operating profits, which helps to the high capital costs involved in this type of technology, making it more financially comparable with the conventional petroleum industry.

Adaptation of Chlorella vulgaris immobilization on rice straw with liquid manure to create a sustainable feedstock for biogas production and potential feed applications

Rice straw (RS) is a widely available agricultural residue with significant potential for biogas production and feed applications; however, its poor digestibility and nutritional value limit its utilization. This study explores an innovative approach to enhance the digestibility and nutritional value of RS by cultivating Chlorella vulgaris through immobilization technology on RS, using liquid manure (LM) as an alternative to the traditional BG11 medium. The results showed an increase in chlorophyll a (Chl a) after 12 days for both the BG11 medium and LM-based treatments, from 0.13 to 0.34 and 0.24 mg Chl a/g product (DM), respectively. Additionally, the immobilized microalgal biomass increased to 284.18 and 170.14 mg algal biomass/g product (DM), respectively. Soaking under microaerobic conditions during cultivation led to the partial degradation of RS. This, combined with the formed microalgal biofilm, contributed to an improved digestibility of the dry matter, reaching 69.1% and 65.9% for the final products based on the BG11 medium and LM mediums, respectively, compared to 52.1% for the raw RS. Furthermore, the crude protein and lipids contents were significantly improved with the potential for applications in feed, reaching 21.4% and 4.1% for the BG11 medium-based product, while they were observed to be 12.8% and 3.0%, respectively, for the LM-based product. Additionally, carbon-to-nitrogen ratio was significantly reduced compared to the raw RS. The higher digestibility and improved nutritional value contributed to increased biogas production, reaching 129.3 and 118.7 mL/g (TS) for the products based on the traditional medium and LM medium, respectively, compared to 86.7 mL/g (TS) for the raw RS. The immobilization mechanism and biofilm development could be attributed to the roughness of the RS and extracellular polymer substances. This study demonstrates that integrating C. vulgaris cultivation on RS with LM as a nutrient source not only enhances the digestibility and nutritional value of RS but also offers a sustainable waste management solution with potential applications in biogas production and animal feed.

Innovative Approach in Sustainable Agriculture: Harnessing Microalgae Potential via Subcritical Water Extraction

Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 ºC) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation.The best germination was achieved by To-B extracts at 170 ºC (1:10: 148% at 0.2g/L, 1:80: 145% at 0.5g/L). Only To-PWW extracts at 0.2g/L had a significant germination effect (120 ºC: 120-123% for both loads; 170 ºC: 115% for 1:80). To-PWW extract at 120 ºC and 1:10 significantly affected cucumber and mung bean root formation (224 and 268%, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139-181%). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.

Optimization of the marine microalgae Nannochloropsis oculata harvesting by flocculation: Effects on biomass quality and residual medium reuse for a new cycle

ABSTRACT Flocculation using natural plant-based biopolymers from Moringa oleifera seeds and Acacia mearnsii flocculant as Tanfloc® (TSG) has emerged as an efficient strategy for microalgae biomass harvesting. This study optimized the recovery process of Nannochloropsis oculata by varying flocculant concentration, sedimentation time, and culture pH. Results revealed that 1.2 mg.L−1 of TSG at pH 8.9 achieved optimal conditions, although TSG proved effective across different pH ranges. Alkaline flocculation (ALK) also enhanced microalgae harvesting, yielding a high harvesting efficiency (>96%) within 30 minutes of sedimentation. Both methods achieved a concentration factor exceeding 20. However, the use of ALK resulted in reduced lipid and carbohydrate content compared to the control condition. Carotenoid levels showed no significant difference. TSG influenced lipid extraction but not fatty acid quality or carbohydrate extraction. Importantly, the residual medium from TSG flocculation could sustain subsequent cultivation cycles without nutrient supplementation, presenting a cost-effective solution for microalgae cultivation and harvesting.

Distinct exposure impact of non-degradable and biodegradable microplastics on freshwater microalgae (Chlorella pyrenoidosa): Implications for polylactic acid as a sustainable plastic alternative

Microplastics (MPs) are increasingly recognized as significant sources of harm to biota in various environments. However, the detrimental impacts of aged MPs with different structures and degradability remain poorly understood. In this study, aged MPs from polylactic acid (PLA), polyethylene (PE), and polystyrene (PS), representing biodegradable, aliphatic, and aromatic plastics, respectively, were prepared to examine their effects on microalgae (Chlorella pyrenoidosa). Structural and property analyses indicated the presence of aging and oxygen-containing functional groups on the surfaces of the MPs, which correlated with an increase in negative electrical charge (i.e., aged PLA > aged PE ≈ aged PS). Aged PLA MPs affected microalgae biomass, promoted protein synthesis, and elevated mild oxidative stress. In contrast, aged PE and PS MPs not only affected biomass, protein, and carbohydrate synthesis but also inhibited photosynthetic pigment production and activity, resulting in intracellular oxidative stress. Excitation-emission-matrix spectra analysis showed that PLA induced microalgae to secrete large amounts of humic acid-like extracellular polymers, whereas aged PE and aged PS groups contained only small amounts of them and proteins. This study addresses critical knowledge gaps in the toxicology of various aged MPs on microalgae and provides valuable insights into the potential of PLA as a sustainable alternative to conventional plastics in microalgae culture industry.

Sweet sorghum as alternative carbon sources for Chlorella sp. valued-added compounds production: A mechanistic insight using transcriptomics

Substituting agricultural by-products for glucose as a carbon source is an effective strategy for reducing the cultivation cost of Chlorella sp. However, the response mechanism of Chlorella sp. to variations in carbon sources remains unclear, and the potential of microalgal biomass for food development warrants further exploration. This study used hydrolysate of sweet sorghum stem juice (HSJ) for the mixotrophic cultivation of Chlorella sp. And transcriptomic analysis was performed to investigate the physiological and metabolic mechanisms as well as the biosynthesis of value-added compounds (e.g., pigments and proteins) of Chlorella sp. in response to changes in carbon sources. The HSJ + NM group (HSJ supplemented with nitrogen and minerals) significantly increased total chlorophyll, carotenoids, lutein, and protein levels by 18.02 %, 13.34 %, 35.95 %, and 20.36 %, respectively, compared to the control (adjusted BG-11 medium supplemented with 10 g/L glucose). Notably, transcript levels of genes for multiple key enzymes involved in glycolysis/gluconeogenesis, TCA cycle, oxidative phosphorylation pathway, and photosynthesis pathways were significantly up-regulated. The activity of these pathways promoted the pigments and proteins synthesis in Chlorella sp. Encouragingly, the cost of cultivating Chlorella sp. with HSJ + NM (0.495 USD/kg) was 43.35 % of glucose (1.142 USD/kg). Further, by fermenting Chlorella sp. cultures with Saccharomyces cerevisiae and further homogenizing and blending the fermentation broth, we developed a nutritious and palatable Chlorella sp. fermented beverage, addressing the common issue of algal odor in such products. This study provides theoretical and practical foundations for the mixotrophic cultivation of microalgae and the application of microalgal biomass in food innovation.

Cell Disruption and Hydrolysis of Microchloropsis salina Biomass as a Feedstock for Fermentation

Microalgae are a promising biomass source because of their capability to fixate CO2 very efficiently. In this study, the potential of Microchloropsis salina biomass as a feedstock for fermentation was explored, focusing on biomass hydrolysis by employing various mechanical and chemical cell disruption strategies in combination with enzymatic hydrolysis. Among the mechanical cell disruption methods investigated on a lab scale, namely ultrasonication, bead milling, and high-pressure homogenization, the most effective was bead milling using stainless-steel beads with a diameter of 2 mm. In this way, 87–97% of the cells were disrupted in 40 min using a mixer mill. High-pressure homogenization was also effective, achieving 86% disruption efficiency after four passes on a 30–200 L scale using biomass with 15% (w/w) solids content. Enzymatic hydrolysis of the disrupted cells using a mixture of cellulases and mannanases yielded up to 25% saccharification efficiency after 72 h. Acidic hydrolysis of undisrupted cells followed by enzymatic treatment yielded around 30% saccharification efficiency but was coupled with significant dilution of the resulting hydrolysate. Microalgal biomass hydrolysate produced was determined to have ~8.1 g L−1 sugars and 2.5% (w/w) total carbon, as well as sufficient nitrogen and phosphorus content as a fermentation medium.

Environmental impact assessment in microalgal lipid production: carbon footprint and net emissions

This study focuses on analyzing the role of microalgae in mitigating climate change through CO2 capture and lipid production, which can be used in the development of energy products and commercially relevant products. The objective was to evaluate the net CO2 emissions in three lipid production scenarios from microalgae, in addition to analyzing the impact of various biomass pretreatment technologies before lipid extraction. For this purpose, only the emissions directly generated by energy consumption in the process and the amount of CO2 that can be captured by microalgae cultivation were considered. In all three scenarios, CO2 capture during biomass cultivation and emissions associated with maintaining the process in operation were evaluated. The results show that the emissions generated by energy consumption were 3.56 kg-CO2/kg-oil, 2.19 kg-CO2/kg-oil, and 2.36 kg-CO2/kg-oil in scenarios 1, 2, and 3, respectively, while the CO2 emissions captured in microalgae cultivation were three to four times higher, ultimately resulting in negative emissions in all scenarios. The efficiency of CO2 capture per kilogram of oil produced varies between scenarios, suggesting that the choice of technology and process conditions significantly influence the overall environmental impact. This analysis identifies areas of opportunity to improve microalgal biomass utilization processes, highlighting the stages of the process with the greatest impact on the carbon footprint and enabling the comparison of different technologies on the same basis.

Anaerobic Co-Digestion of Coffee Processing Wastewater and Microalgal Biomass After Protein Extraction

Anaerobic Co-Digestion of Coffee Processing Wastewater and Microalgal Biomass After Protein Extraction

The Emissions of a Compression-Ignition Engine Fuelled by a Mixture of Crude Oil and Biodiesel from the Lipids Accumulated in the Waste Glycerol-Fed Culture of Schizochytrium sp.

Microalgae are considered to be a promising and prospective source of lipids for the production of biocomponents for conventional liquid fuels. The available sources contain a lot of information about the cultivation of biomass and the amounts and composition of the resulting bio-oils. However, there is a lack of reliable and verified data on the impact of fuel blends based on microalgae biodiesel on the quality of the emitted exhaust gas. Therefore, the main objective of the study was to present the emission characteristics of a compression-ignition engine fuelled with a blend of diesel fuel and biodiesel produced from the lipids accumulated in the biomass of a heterotrophic culture of Schizochytrium sp. The final concentrations of microalgal biomass and lipids in the culture were 140.7 ± 13.9 g/L and 58.2 ± 1.1 g/L, respectively. The composition of fatty acids in the lipid fraction was dominated by decosahexaenoic acid (43.8 ± 2.8%) and palmitic acid (40.4 ± 2.8%). All parameters of the bio-oil met the requirements of the EN 14214 standard. It was found that the use of bio-components allowed lower concentrations of hydrocarbons in the exhaust gas, ranging between 33 ± 2 ppm and 38 ± 7 ppm, depending on the load level of the engine. For smoke opacity, lower emissions were found in the range of 50–100% engine load levels, where the observed content was between 23 ± 4% and 53 ± 8%.

Changing climate intensifies downstream eutrophication by enhancing nitrogen availability from tropical forests

The contribution of diffuse nutrient exports from forests to downstream water bodies is significant owing to their extensive spatial distribution across watersheds. However, the intricacies of coupling mechanism between diffuse nutrient exports and meteorological factors driving downstream eutrophication remain poorly understood. Multiple methods involving field sampling, laboratory analysis, and model simulation were utilized to investigate the impact of diffuse nutrient exports from tropical forests on chlorophyll a concentration dynamic in the downstream reservoir. A strong positive correlation was observed between air temperature and chlorophyll a concentration, indicating the direct influence of climatic factors on microalgal biomass. The significant positive linear relationship was also observed between diffuse nitrate exports and chlorophyll a concentration, with a regression coefficient of 0.36 (P < 0.001), underscoring the role of nitrogen inputs in stimulating microalgal growth. The interplay between diffuse nitrate exports and meteorological factors was shown to regulate chlorophyll a concentration fluctuation. Additionally, the structural equation model revealed that increasing temperature and decreasing precipitation could elevate chlorophyll a concentration by enhancing nitrogen availability. Monte Carlo simulation results further revealed that temperature and precipitation were the most influential factors affecting chlorophyll a concentration during dry and rainy seasons, with sensitivity values of 0.94 and − 0.76, respectively. Notably, the eutrophication status was projected to deteriorate from light to moderate under diminishing precipitation conditions. These findings underscore the urgency of addressing eutrophication risks in reservoirs surrounded by tropical forests and the implementation of effective nitrate mitigation strategies is imperative, which offers theoretical guidance for the management of eutrophic water restoration within tropical rainforest regions under changing climate conditions.

24-Epibrassinolide promoted growth and organic compounds accumulation in Dunaliella parva by enhancing photosynthesis

As a commonly used type of the sixth class of phytohormones brassinosteroids (BRs), 24-epibrassinolide (EBL) plays the important roles in plant growth and development. Dunaliella parva (D. parva) is an important lipid-producing microalga, and its growth and accumulation of organic compounds need to be further improved for higher application value. However, the effects of EBL on D. parva are still unclear now. In this study, D. parva was treated with different concentrations of 24-epibrassinolide (EBL) to evaluate its influence. Cell density of 0.5 mg/L EBL treated group was 1.28-fold of control at 18 d. The contents of chlorophyll, carotenoid, carbohydrate, starch, protein of 0.5 mg/L EBL treated group were 1.31-, 1.18-, 1.49-, 1.35-, and 1.54-fold of control. The highest mRNA levels of rbcS, rbcL, RuPE, PRK, TPI, FBPA, FBPase, SBPase, DpME, CA in EBL treated group were 1.94-, 2.43-, 2.14-, 1.76-, 1.97-, 2.21-, 1.48-, 1.96-, 2.06-, and 1.89-fold of control. The highest enzymatic activities of ME, CA and RuBisCO in EBL-treated group were 1.27-, 1.23-, and 1.37-fold of control. Lipid content of 0.4 mg/L EBL treated group was 1.44-fold of control. This study demonstrated the great potential of EBL to obtain higher biomass and organic compounds accumulation. Our study indicates that EBL treatment is valuable for the subsequent commercial production of biofuel and other high-value metabolites using microalgal biomass as raw material.

Response and adaptation of Chlorella pyrenoidosa to 6PPD: Physiological and genetic mechanisms

The extensive contamination of the tire antidegradant N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) in aquatic environments have raised concerns about its potential threats to aquatic organisms. Here, the responses of green algae Chlorella pyrenoidosa (C. pyrenoidosa) to 6PPD exposure were investigated for the first time. The growth of C. pyrenoidosa experienced three sequential phases, including inhibition, recovery and stimulation. Physiological and transcriptome analysis suggested that the growth inhibition was associated with the suppressed nitrogen assimilation and amino acid biosynthesis pathways, among which nitrate transporter (NRT) 2.1 was a key target of 6PPD. Molecular docking revealed the steadily binding of 6PPD to the substrate entry region of NRT 2.1 via hydrogen bonds and π − cation interaction, blocking the acquisition of extracellular inorganic nitrogen. Along with the removal of 6PPD through abiotic processes and biodegradation, an adaptive metabolic shift in cells not only facilitated growth recovery but also triggered a compensatory stimulation phase. With regard to microalgal adaptation, upregulated DNA replication and repair pathways served to maintain the integrity of the genetic information, enhanced photosynthesis cascades and central carbon metabolism improved carbon flux and energy conversion to microalgal biomass, recovered amino acid biosynthesis produced essential proteins for multiple metabolisms. The results provide new insights into microalgal molecular responses to 6PPD exposure, facilitating a better understanding of ecological consequences of 6PPD in the environment.

Mixotrophic cultivation of microalgae-bacteria consortia enhances dark fermentation effluent treatment

Dark fermentation (DF) is a waste treatment bioprocess which produces biohydrogen and volatile fatty acids (VFAs) such as acetate or butyrate. DF can be coupled with microalgae cultivation, allowing VFA conversion into valuable biomass. Nevertheless, the process is hindered by slow butyrate consumption. In this study, novel artificial microalgae-bacteria consortia were used as a strategy to accelerate butyrate removal. Three microalgal strains with various trophic metabolisms, Chlorella sorokiniana, Euglena gracilis and Ochromonas danica, were cultivated on DF effluent that was either sterile or contained endogenous bacteria. Bacteria did not impact microalgal biomass production of C. sorokiniana or E. gracilis while accelerating butyrate removal rates 2 to 10-fold. O. danica greatly impacted microbial diversity, probably due to its phagotrophic metabolism. These results show that bacteria in organic rich effluents can greatly aid in substrate removal while allowing microalgal growth, inspiring bioprocesses coupling raw fermentation effluents with microalgae biomass production and valorization.

Microalgae as feed additives in poultry: A review on the health-promoting effects

This review explores the effects of the inclusion of microalgal biomass in feed on the health of poultry (broilers and laying hens). Microalgae have emerged as a promising feed additive, valued not only for their rich nutritional profile, but also for their bioactive substances. Bioactive compounds, such as phenolics, polyunsaturated fatty acids, oligosaccharides and carotenoids, exhibit antioxidant, anti-inflammatory, antibacterial, and antiviral functions, which hold promise for promoting poultry health. With the ban on prophylactic antibiotic use in feed, microalgal biomass emerges as an innovative feed additive to enhance growth performance and prevent health issues in poultry. This review extensively explains the critical health parameters of poultry, including histology of the intestinal tract, intestinal permeability, immunity, antioxidant status and prebiotic effects on the intestinal microbiome. Furthermore, it offers valuable insights into the inclusion of microalgae in poultry feed, promoting these health parameters. It concludes with suggestions for further research and practical recommendations on how to improve poultry health using microalgal biomass.

A Novel Algal–Algal Microbial Fuel Cell for Enhanced Chemical Oxygen Demand Removal

To enhance the removal of COD (Chemical Oxygen Demand) by microalgae, this study constructed a novel microalgae–microalgae microbial fuel cell system (AA-MFC). It investigated the coupling relationship between the COD treatment efficiency at the anode and the production of high-value microalgal products at the cathode, as well as explored the effects of different initial inoculum densities and light–dark cycles. The experiment first measured the operational performance of the newly constructed AA-MFC in open-circuit and closed-circuit modes, demonstrating that this novel AA-MFC could start up rapidly within 32 h and operate stably. The results showed that the AA-MFC enhanced the removal of COD and the growth of microalgae biomass at the anode while maintaining stable power generation. When the initial inoculation density of the anode was 1.2 × 108 cell/cm2 and the light–dark cycle time was 18:6 h, the AA-MFC had the most obvious promoting effect on the COD removal of the anode. Compared with normal culture conditions, the COD removal rate increased by 26.0% to 96.1%. These results indicate that the AA-MFC can not only effectively remove pollutants, but also promote the accumulation of high-value microalgae biomass.

The antibacterial activity of the copper for Staphylococcus aureus 124 and Pseudomonas aeruginosa 18 depends on its state: metalized, chelated and ionic

The hypothesis that the antibacterial effect of copper depends on its state was tested. It was studied the antibacterial effect of copper applied to the fabric, copper in chelated and free (ionic) forms on the growth intensity of Staphylococcus aureus 124 and Pseudomonas aeruginosa 18 in the in vitro system after a single or “primary” contact. Classical microbiology methods were used. Copper was applied to the fabric by magnetron and arc planar discharge systems, and the culture of microalgae Dunaliella viridis, resistant to the action of high concentrations of copper, was used to obtain copper in chelated form. It was shown that a thin layer of copper (3 μm) applied to the fabric showed pronounced antibacterial activity against Staphylococcus (85 % compared to the antibiotic meropenem) and less pronounced activity against Pseudomonas, which is resistant to meropenem. Copper in ionic form inhibited the growth of Staphylococcus aureus 124 as well as the antibiotic, and also effectively inhibited the growth of Pseudomonas aeruginosa 18 i.e., copper ions did not have species specificity like the antibiotic. Components of Dunaliella viridis microalgae cells had weakly expressed antibacterial effect to these types of bacteria, and supplementary addition of copper sulfate to the biomass of microalgae led to an increase of their antibacterial activity and this is more pronounced for microalgae culture in which the ratio « chelated/ionic » forms of copper is shifted to the ionic form. It was shown that the antibacterial activity of microalgae biomass after the first introduction into the tested bacterial cultures depends on the amount of free or “weakly bound” with cell components copper ions. It is suggested that the antibacterial effect of fabric with a thin layer of copper may be determined by two mechanisms: the action of copper ions and mechano-bactericidal effects, while chelated forms of copper may have a prolonged effect on bacterial cultures.