Water Microalgae Research Articles

Study on Lipid and Pigment Contents of Microalgae Cultivated in Water from Litopenaeus vannamei Shrimp Farm

This study aimed to cultivate microalgae in water from Litopenaeus vannamei shrimp farm to be used as supplement for shrimp. The study focused on its growth, lipid and pigment contents and effects of urea addition as nitrogen source and scale-up of microalgae cultivation. Microalga Chlorella sp. SHP isolated from shrimp farm showed higher pigment content and antioxidant activity than other two isolated strains. Chlorella sp. SHP grew best in effluent from treatment pond compared to water from reservoir pond and shrimp pond. The addition of urea at 2 g/L and the scale up in 50 L microalgae cultivation pond gave the maximum biomass of 0.19±0.03 g/L, the lipid content of 44.96±2.79%, and the contents of chlorophyll ab and carotenoids of 11.65 mg/g and 5.45 mg/g, respectively. The antioxidant activity based on radical scavenging activity of 1 g microalgal biomass was 66.71±0.02%. The findings from this study could be an alternative for producing microalgae with high lipid and pigment contents, and further utilization as low-cost supplements for shrimp cultivation.

Widefield Super-Resolution Infrared Spectroscopy and Imaging of Autofluorescent Biological Materials and Photosynthetic Microorganisms Using Fluorescence Detected Photothermal Infrared (FL-PTIR).

We have demonstrated high-speed, super-resolution infrared (IR) spectroscopy and chemical imaging of autofluorescent biomaterials and organisms using camera-based widefield photothermal detection that takes advantage of temperature-dependent modulations of autofluorescent emission. A variety of biological materials and photosynthetic organisms exhibit strong autofluorescence emission under ultraviolet excitation and the autofluorescent emission has a very strong temperature dependence, of order 1%/K. Illuminating a sample with pulses of IR light from a wavelength-tunable laser source causes periodic localized sample temperature increases that result in a corresponding transient decrease in autofluorescent emission. A low-cost light-emitting diode-based fluorescence excitation source was used in combination with a conventional fluorescence microscopy camera to detect localized variations in autofluorescent emission over a wide area as an indicator of localized IR absorption. IR absorption image stacks were acquired over a range of IR wavelengths, including the fingerprint spectral range, enabling extraction of localized IR absorption spectra. We have applied widefield fluorescence detected photothermal IR (FL-PTIR) to an analysis of autofluorescent biological materials including collagen, leaf tissue, and photosynthetic organisms including diatoms and green microalgae cells. We have also demonstrated the FL-PTIR on live microalgae in water, demonstrating the potential for label-free dynamic chemical imaging of autofluorescent cells.

Toxic mechanisms of the antiviral drug arbidol on microalgae in algal bloom water at transcriptomic level

Increasing antivirals in surface water caused by their excessive consumption pose serious threats to aquatic organisms. Our recent research found that the input of antiviral drug arbidol to algal bloom water can induce acute toxicity to the growth and metabolism of Microcystis aeruginosa, resulting in growth inhibition, as well as decrease in chlorophyll and ATP contents. However, the toxic mechanisms involved remained obscure, which were further investigated through transcriptomic analysis in this study. The results indicated that 885–1248 genes in algae were differentially expressed after exposure to 0.01–10.0 mg/L of arbidol, with the majority being down-regulated. Analysis of commonly down-regulated genes found that the cellular response to oxidative stress and damaged DNA bonding were affected, implying that the stress defense system and DNA repair function of algae might be damaged. The down-regulation of genes in porphyrin metabolism, photosynthesis, carbon fixation, glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation might inhibit chlorophyll synthesis, photosynthesis, and ATP supply, thereby hindering the growth and metabolism of algae. Moreover, the down-regulation of genes related to nucleotide metabolism and DNA replication might influence the reproduction of algae. These findings provided effective strategies to elucidate toxic mechanisms of contaminants on algae in algal bloom water.

STUDI KEANEKARAGAMAN MIKROALGA DI SUNGAI MARGASATWA RAGUNAN SEKITAR KANDANG BUAYA

Microalgae are microscopic unicellular organisms that have varying sizes, shapes, and types, have photosynthetic pigments, are photoautotrophic, and are found in aquatic environments. Microalgae have certain limits of tolerance to water chemical physics factors. The presence of microalgae in water can be used as an indicator of the state of the water. This study aims to identify the diversity of microalgae as an indicator of the water quality present in the river around the Ragunan Margasatwa crocodile cage. Sampling was done in the Ragunan Margasatwa Park river near the crocodile cage. Samples of macroalgae are visually identified and include morphology, color, shape, and other characteristics. Based on the observations, it can be concluded that the river ecosystems around the crocodile cages are under low ecosystem pressure. The diversity index generally has a range of values between 1.5 and 4, and lower values reflect increasing ecosystem instability. The lowest microalgae density was found at station 1, which is 120 ind/ml. Individuals with the highest density at station 2, the species Aphanothece sp. with a density value of 293.3 ind/mL.

Performance of Chlorella vulgaris in Phycoremediation of Livestock Effluent

Livestock effluent is known to contain significantly higher concentrations of organic matter and challenging-to-degrade organic compounds compared to urban wastewater. This makes the effluent treatment challenging and adversely affects nearby aquatic environments if improperly treated. Phycoremediation uses microalgae in water and wastewater treatment. This research aim was to evaluate pollutant removal efficiencies, including chemical oxygen demand (COD), total suspended solids (TSS), nitrate (NO₃-N), turbidity, and phosphate (P), using microalgae Chlorella vulgaris (C. vulgaris) cultivation systems for livestock effluent treatment. The biomass weight of C. vulgaris in the cultivation systems was also observed. In this study, C. vulgaris was cultivated in closed cultivation systems in 5 L water bottles with different dilutions (100%, 75%, 50%, and 25%). The water effluent was compared to permissible values using the National Water Quality Standard (NWQS) class II for recreational water use. TSS was significantly removed by 61.97%, while COD and P were removed by 39.1% and 36.4%, respectively. The biomass growth was observed through the dry weight of the C.vulgaris. Therefore, the removal of nutrients from cattle farm effluent by phytoremediation using C. vulgaris demonstrates potential for treatment efficacy.

An attached microalgae platform for recycling phosphorus through biologically mediated fertilizer formation and biomass cultivation

Nutrient management is a global challenge for protecting water bodies from eutrophication and for retaining and sustainably recycling phosphorus within the biosphere. This challenge is especially important for water resource recovery facilities (WRRFs) in jurisdictions that limit nutrient loads in plant effluent. A microalgae-based biofilm platform has been designed, constructed, and tested to remove phosphorus and nitrogen from anaerobic digester (AD) effluent filtrate through cultivating biomass and inducing the precipitation of a mineral called struvite (NH₄MgPO₄ · 6H₂O) using a rotating algae biofilm reactor (RABR). RABRs function by rotating a growth substratum through nutrient rich water and then into the atmosphere, immersing microalgae in both sunlight and water. Photosynthesis is utilized in RABR operation to enhance struvite formation by increasing the pH value within the biofilm through the uptake of carbon dioxide from solution. Measurements of pH trended higher with depth through the biofilm when exposed to light confirming the function of photosynthesis in increasing pH and, as a consequence, struvite formation. In addition, reducing RPM allows more time for water to evaporate through exposure of the biofilm to the atmosphere and provides a management option to exceed struvite solubility product. Struvite precipitation was predicted based on chemical analysis and MINTEQ modeling of ADE, was confirmed using Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy, and quantified by determining ash content. Increase in pH within the biofilm was confirmed as photosynthetic photon flux density increased. While struvite precipitation and removal from wastewater is conventionally accomplished through physicochemical methods, this research is the first report of struvite enhanced formation through algae biofilm-based photosynthesis processes.

Cultivation of Brackish Water Microalgae for Pig Manure Liquid Digestate Recycling

Sustainability and recycling of agricultural and animal husbandry waste are important. Pig manure contains relatively high concentrations of organic matter, such as nitrate-nitrogen, ammonia nitrogen, and phosphate, and a direct discharge can cause environmental pollution. This study successfully culturing four brackish water microalgae, including Tetraselmis chuii, Isochrysis galbana, Chlorella vulgaris, and Proteomonas sulcata, by using a diluted digestate solution of pig manure (NH3 concentration is lower than 10 mg/L). These microalgae can reach their highest cell concentration within 3–7 days of cultivation. The small microalgae, C. vulgaris and I. galbana, reached a cell density of 2.5 × 107 and 1.5 × 107, respectively, whereas lower cell densities were documented for large microalgae T. chuii (1.4 × 106) and P. sulcata (1.6 × 106). Our findings highlight the feasibility of sustainable treatment of animal manure using brackish water microalgae. These results provide opportunities to reduce freshwater usage and environmental pollutions, and support microalgae production for further aquaculture application.

Accurate detection of microalgae in ship ballast water: An innovative computer vision strategy

Microalgae play a crucial role in marine ecological preservation, especially in the management of ship ballast water, where accurate microalgae detection is essential for preventing biological invasions. However, when extracting and observing microalgae from ship ballast water samples, the intricate water quality background and cell adhesion phenomena present substantial interferences for precise microalgae detection, posing significant challenges for existing microalgae detection methods. To address these issues, this paper proposes an innovative microalgae detection method based on efficient omnidimensional dynamic convolution (EOD) and adhesion loss. The novelty of our study lies in the unique loss strategy for detecting adhesive microalgae cells for the first time and its combination with EOD to address the challenges of microalgae detection in complex environments. First, a large number of microalgae images are generated using an enhanced StyleGAN3, supplementing the dataset in complex scenarios to improve the model's robustness. Second, the proposed EOD is applied to mitigate the interference from the complex background and enhance the capability of microalgae feature extraction. Finally, our newly designed adhesion loss strategy imposes penalties on adhered cells based on intersection over union (IOU) and Gaussian distance, effectively tackling the cell adhesion issue. The experimental results indicate that this method achieves a mAP@[0.5:0.95] of 82.1% for microalgae detection in complex environments, meeting real-time microalgae detection requirements. This study provides an innovative perspective for marine ecological preservation, while its highly accurate and real-time microalgae detection method also pioneers new possibilities in microalgae detection research.

An Integrated Approach for the Environmental Characterization of a Coastal Area in the Southern Atacama Desert

Desert areas in northern Chile are highly valuable ecosystems. While human activities are impacting the area in different ways, there are few environmental studies available. The current study analysed the ecological health status (water, sediment, biota) of a northern coastal area in the Atacama Region, including a national park (with a protected marine area), a tourist and benthic management area, and an industrial area. Results from the physical–chemical characterization and physiological state of organisms of ecological importance (macroalgae and microalgae) were integrated to determine pollution and toxic responses. The results identified high and moderate pollution levels for Bi, Ca, As, Ag and Cd in sediments. The As concentration in sediments is the leading environmental problem, with average values above the threshold effect level, associated with fine sediments. The stations showed increasing contamination and stress from north to south (national park > tourist and benthic management area > industrial area), associated with the proximity to the discharge of mining waste from the Salado River. The national park registered the poorest health status as demonstrated by high Cu bioaccumulation and high photosynthetic stress in the macroalgae and the lowest biomass concentration of the microalgae in water. The tourist and benthic management area demonstrated high As concentrations in sediments and Cd bioaccumulation. The industrial area was the least contaminated area, exhibiting lower photosynthetic stress and bioaccumulation.

Life cycle analysis of biodiesel derived from fresh water microalgae and Karanja

Biodiesel is regarded as a feasible substitute for fossil fuel; thus, to fulfil the tremendous need for energy, potential non-edible feedstocks must be identified and assessed in terms of their environmental consequences and energy requirements for biodiesel production. Cradle to Grave life cycle approach (LCA) is currently being used to compare the environmental impacts and energy requirements of biodiesel obtained from two types of biodiesel feedstock i.e., Karanja (Pongamia Pinnata) and Microalgae. Sensitivity analysis was also performed to explore the influence of elements such as agricultural systems and energy sources on LCA systems in the given conditions. Karanja feedstock and microalgae have energy ratios of 3.57 and 0.45, respectively. GHG emissions from well to wheel for oil methyl esters derived from Karanja feedstock are estimated to be 63.81 gCO2eq/MJ, while microalgae feedstock emissions are 85.37 gCO2eq/MJ. According to the sensitivity study, both emission and energy estimates were significantly sensitive to biodiesel output. Karanja excelled in all GHG-emitting processes, with reduced GHG emissions and a greater energy ratio. Microalgae, on the other hand, would be the preferable feedstock in the long run since it has demonstrated competitive performance in terms of carbon dioxide emissions, and energy ratio, and has no detrimental influence on the food cycle.

UV-LEDs combined with persulfate salts as a method to inactivate microalgae in ballast water

The Ballast Water Management Convention (BWMC) establishes limits for viable organisms in discharged ballast water. UV-based ballast water management systems (BMWS) are among the most common, especially those with low pressure (LP) and medium pressure (MP) mercury lamps. An interesting alternative to mercury lamps could be UV LEDs that have been developing over recent years. UVA, UVB, and UVC LEDs have been tested as a method to inactivate microalgae in ballast water. For this study, the diatom Phaeodactylum tricornutum was selected as a target organism. Comparing the D2 (dose required to achieve two log reductions) for P. tricornutum from different UV treatments, it was observed that UVC LEDs were 74.2 % more efficient than UVB LEDs and, compared with previous studies, 48.1 % more efficient than UVC LP mercury lamps. If a five day dark post-treatment was combined with the UV irradiation to avoid photoreactivation, UVC LEDs were 90 % more efficient than UVB LEDs and, compared with previous studies, 36.8 % more efficient than UVC LP mercury lamps. No damage with or without photoreactivation was caused by UVA irradiation with doses up to 4·104 mJ cm−2. The combination of peroxymonosulfate (PMS) with UVA, UVB and UVC LEDs did not significantly increase the inactivation, and the combination of the peroxydisulfate (PDS) with UVC LEDs slightly decreases the inactivation compared with UVC irradiation alone. In conclusion, UVC LEDs were the most efficient for inactivating P. tricornutum, and the combination of PMS and PDS with UV LEDs did not notably improve it.

Development of sustainable bioproducts from microalgae biomass: Current status and future perspectives

Population and pollution make notable contributions to introducing novel sophisticated techniques. From vehicles to industries, the release of CO2 into the atmosphere and wastewater into the running water streams are key concerns. On the other hand, the population is responsible for the rapid manufacturing of all commercial goods. Microalgae are the only answer accessible for the aforementioned difficulties. Similar to plants, microalgae need CO2 and light to thrive and produce a variety of bioproducts such as carbohydrates, protein, lipids, vitamins, sterols, pigments, and silica. Physical (light, temperature, CO2, and UV), chemical (nutrient addition or depletion), enzymatic, and metabolic pathway reconfiguration, as well as indoor or outdoor growing, are highly regarded among the several optimization strategies to make desired products. Wastewater pollution is rectified by growing microalgae in nutrient-rich organic water for their growth, which is used to accelerate bioproducts. This review considers the use of bioproducts in food, animal and aquatic feed, fertilizer, biofuel, medicinal and nutraceutical sectors. This paper also provides different optimization strategies, which include physical and chemical means of extraction methods for enhancing bioactive products. Challenges and future recommendations for enhancing target bioproducts are discussed to overcome environmental issues.

Effects of Two Quinolone Antibiotics on Growth of Four Species of Planktonic Algae

Quinolone antibiotics, especially enrofloxacin and ciprofloxacin, are currently found to be at high levels commonly in natural waters. Studying the effects of these two quinolones on the growth of common microalgae in water is valuable for understanding the ecological effects of quinolones in the aquatic environment. Therefore, the effects of different concentrations of enrofloxacin and ciprofloxacin hydrochloride on the population growth of four species of planktonic microalgae (Chlorella vulgaris, Tetradesmus obliquus, Scenedesmus quadricauda, and Microcystis aeruginosa) were studied. The results showed that there was a significant effect-dose regression relationship between the concentration of nofantibiotic and the growth inhibitory rate of the algae population. The 96h half maximal inhibitory concentration (96h-IC50) of enrofloxacin on T. obliquus, S. quadricauda, M.aeruginosaI and C. vulgaris were 195.6, 88.8, 56.1, and 22.6 mg/L respectively, and the order of sensitivity of the four microalgae to enrofloxacin was T. obliquus＜S. quadricauda＜M. aeruginosa＜C. vulgaris. Another 96h-IC50 of ciprofloxacin hydrochloride to S. quadricauda, T. obliquus, M. aeruginosa, and C. vulgaris were 588.6, 546.3, 49.8, and 44.7 mg/L respectively. The sensitivity of the four microalgae to ciprofloxacin hydrochloride was ranked as follows: S. quadricauda＜T. obliquus＜M. aeruginosa＜C. vulgaris. Among the four species of planktonic microalgae, two species of Scenedesmus were less sensitive to the quinolone antibiotics. Therefore, these two species of Scenedesmus were more resistant to the two quinolone antibiotics, while C. vulgaris was the most sensitive to them. According to the data of IC50, the toxicity of enrofloxacin to three green microalgae was higher than that of ciprofloxacin, while the toxicity of enrofloxacin to M. aeruginosa was lower than that of ciprofloxacin. The population growth of the four planktonic microalgae was inhibited in the first 4 days after being treated by these two quinolone antibiotics, but the microalgae could gradually detoxify and restore their population growth after 96 h. Moreover, the toxicity of enrofloxacin to the four algae increased with time. The toxicity of ciprofloxacin hydrochloride to T. obliquus and S. quadricauda increased, and the toxicity to M. aeruginosa and C. vulgaris decreased. The recovery degree of ciprofloxacin hydrochloride was at least 39% higher than that of enrofloxacin. Low concentrations of enrofloxacin (<36mg/L) provoked a higher density of M. aeruginosa than that of the control group after 10 days of exposure. In this case, the algal density of M. aeruginosa could be more than 107 cells/L when the concentration of enrofloxacin was below 36mg/L.

Process intensification for the enhancement of growth and chlorophyll molecules of isolated Chlorella thermophila: A systematic experimental and optimization approach

In our current work, we have optimized six physicochemical parameters (light intensity, light period, pH, inoculum size, culture period, and salt concentration) toward growth and chlorophyll synthesis using isolated fresh water microalgae Chlorella thermophila [contains ∼6% (w/w on dry biomass basis) chlorophyll]. Here, both experimental and computational [Taguchi orthogonal array (TOA), artificial neural network (ANN), and genetic algorithm (GA)] approaches were employed for the process intensification. Results revealed that the content of biomass and chlorophyll were enhanced by 118% and 95%, respectively, with productivity enhancement of 30% for biomass and 61% for chlorophyll from the optimization of physicochemical parameters. Further, optimum light intensity was found to be 128 µmol m−2 s−1 after conducting experiments in optimized chemical and physicochemical conditions, contributing to the enhancement of productivity of 46% for biomass and 106% for chlorophyll. Urea was found to be the most effective nitrogen source with an increase of 70% and 160% biomass and chlorophyll productivity, respectively. Moreover, sucrose as a carbon source contributed to an increase of 97% and 264% biomass and chlorophyll productivity.

Levulinic Acid Is a Key Strategic Chemical from Biomass

Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are currently produced in fossil based refineries. LA is a key strategic chemical, as fuel grade chemicals and plastic substitutes can be produced by its catalytic conversion. LA derivatisation to various product streams, such as alkyl levulinates via esterification, γ-valerolactone via hydrogenation and N-substituted pyrrolidones via reductive amination and many other transformations of commercial utility are possible owing to the two oxygen functionalities, namely, carbonyl and carboxyl groups, present within the same substrate. Various biomass feedstock, such as agricultural wastes, marine macroalgae, and fresh water microalgae were successfully converted to LA in high yields. Finding a substitute to mineral acid catalysts for the conversion of biomass to LA is a challenge. The use of an ultrasound technique facilitated the production of promising nano-solid acid catalysts including Ga salt of molybophosphoric acid and Ga deposited mordenite zeolite, with optimum amounts of Lewis and Bronsted acidities needed for the conversion of glucose to LA in high yields, being 56 and 59.9 wt.% respectively. Microwave irradiation technology was successfully utilized for the accelerated production of LA (53 wt.%) from glucose in a short duration of 6 min, making use of the unique synergistic catalytic activity of ZnBr2 and HCl.

A Mini Review of Antibacterial Properties of Al2O3 Nanoparticles.

Bacterial antibiotic resistance is one of the most serious modern biomedical problems that prioritizes the search for new agents to combat bacterial pathogens. It is known that nanoparticles of many metals and metal oxides can have an antibacterial effect. However, the antibacterial efficacy of aluminum oxide nanoparticles has been studied little compared to the well-known antimicrobial properties of nanoparticles of oxides of metals such as zinc, silver, iron, and copper. In this review, we have focused on the experimental studies accumulated to date demonstrating the antibacterial effect of aluminum oxide nanoparticles. The review discusses the main ways of synthesis and modification of these nanoparticles, provides the proposed mechanisms of their antibacterial action against gram-positive and gram-negative bacteria, and also compares the antibacterial efficacy depending on morphological characteristics. We have also partially considered the activity of aluminum oxide nanoparticles against water microalgae and fungi. In general, a more detailed study of the antibacterial properties of aluminum oxide nanoparticles is of great interest due to their low toxicity to eukaryotic cells.

Semicontinuous and batch ozonation combined with peroxymonosulfate for inactivation of microalgae in ballast water

The Ballast Water Management Convention (BWMC) establishes limits regarding the permissible number of viable organisms in discharged ballast water. Ozone as a ballast water treatment is interesting because it can be generated in-situ and has strong oxidant power. Additionally, some oxidants can be formed in reaction with seawater, especially brominated compounds, that assist in inactivating microorganisms. The objective of this study is to assess the efficacy of semicontinuous and batch ozonation as well as their combination with peroxymonosulfate salt (PMS) as methods to be used to ensure compliance with regulation D2 of the BWMC using Tetraselmis suecica as a standard microorganism. Growth modeling method was employed to determine the inactivation achieved by the treatments. The results show that ozone is an effective treatment for accomplishing the D2 of the BWMC. Batch ozonation is more efficient than semicontinuous ozonation probably because of the brominated compounds formed during the ozone saturation of the water. The oxidants that are developed during the ozonation of seawater prolong the residual effect of the treatment throughout the days of storage with practically no presence of them in the ballast tanks at 72 h. The addition of the PMS increases the inactivation in the semicontinuous ozonation, but a threshold concentration of ozone is needed to observe the synergistic effect of both oxidants. No increase is associated with the combination of O3 and PMS in the case of batch ozonation.

Environmental factors of rearing water and growth performance of shrimp (Penaeus vannamei) in a microalgal monoculture system

Microalgal ecological regulation technology uses beneficial planktonic microalgae in water their physiological and ecological characteristics, and then to regulate and optimize the water ecological environment. To identify high-quality algal strains suitable for microalgal ecological regulation technology and analyse the ecological regulation mechanism of microalgae in shrimp culture, Nannochloropsis oculata and Thalassiosira sp. preliminarily were used as the research objects. A 60-day feeding trial was conducted to evaluate the effects of N. oculata and Thalassiosira sp. monocultures on the growth performance (survival rate, yield, food coefficient, and specific growth rate) of shrimp and the physicochemical factors (DO, pH, NO2−-N, NO3−-N, NH4+-N, PO43−-P, COD and EI) and biotic factors (content of Vibrio Spp., Vibrio parahaemolyticus and bacteria) of the rearing water. The results showed that different microalgae had significant effects on the growth performance of shrimp and the environmental factors of rearing water. On the one hand, among the groups, the Thalassiosira sp. group (TG) had the highest survival rate, SGR and yield. On the other hand, similar to the nitrogen and phosphorus contents, the eutrophication index was significantly lower in the N. oculata group (NG) and TG than in control group (CG). Furthermore, of the groups, TG had the lowest Vibrio parahaemolyticus content. In summary, the Thalassiosira sp. monoculture in the rearing water absorbed nitrogen and phosphorus, reduced eutrophication, regulated the water environment, inhibited the growth of V. parahaemolyticus and increased the survival and yield of shrimp. This research provides an important theoretical basis and a representative demonstration for constructing a more efficient monoculture technology for microalgae and a new model for ecologically friendly and healthy shrimp cultivation and management.

Conception and Development of a Pulsed Microwave Applicator for Exposure of Fresh Microalgae Biomass

This study presents the conception and development of a microwave (MW) applicator based on a TM010 cavity and a pulsed MW source, both custom-designed for evaluation of MW disruption of microalgae. The objective is the selective heating of microalgae immersed in their environment. The applicator enables exposing microalgae suspension to MW in continuous flow mode and monitoring the energy absorbed by the sample. The design was based on dielectric characteristics of microalgae in water, but other solvents might be considered. A tuning element ensures efficient MW coupling into the samples whose relative permittivity ranges from 10 to 80. The applicator includes a customized power supply operating a commercial magnetron source in pulse mode. The MW pulses are in the range of multiple kilowatts with adjustable duration in the microseconds range. The applicator enables to reach a power density in the microalgae sample beyond 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Preliminary proof-of-principle experiments of MW disruption on fresh microalgae biomass <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Auxenochlorella protothecoides</i> followed by lipid extraction enabled almost complete lipid recovery, while yields were negligible on untreated samples. Total energy consumption was below 4.2 MJ per kg of dry microalgae. Finally, the applicator characteristics are promising for future upscaling and deployment in the industry.

Simultaneous Detection of Viability and Concentration of Microalgae Cells Based on Chlorophyll Fluorescence and Bright Field Dual Imaging.

Ship ballast water contains high concentration of plankton, bacteria, and other microorganisms. If the huge amount of ballast water is discharged without being inactivated, it will definitely spell disaster to the marine environment. Microalgae is the most common species exiting in ballast water, so the detection of the concentration and viability of microalgae is a very important issue. The traditional methods of detecting microalgae in ballast water were costly and need the help of bulky equipment. Herein, a novel method based on microalgae cell intracellular chlorophyll fluorescence (CF) imaging combines with cell bright field (BF) microscopy was proposed. The geometric features of microalgae cells were obtained by BF image, and the cell viability was obtained by CF image. The two images were fused through the classic image registration algorithm to achieve simultaneous detection of the viability and concentration of microalgae cells. Furthermore, a low-cost, miniaturized CF/BF microscopy imaging prototype system based on the above principles was designed. In order to verify the effectiveness of the proposed method, four typical microalgae in ballast water (Platymonas, Pyramimonas sp., Chrysophyta, and Prorocentrum lima) were selected as the samples. The experimental results show that the self-developed prototype can quickly and accurately determine the concentration and the viability of microalgae cells in ship ballast water based on the dual images of BF and CF, and the detection accuracy is equivalent to that of commercial microscope. It was the first time to simultaneously detect the viability and concentration of microalgae cells in ship ballast water using the method that combining the fluorescence and bright field images; moreover, a miniaturized microscopic imaging prototype was developed. Those findings expected to contribute to the microalgae detection and ship ballast water management.