Viable Algae Research Articles

Global estimates of suitable areas for marine algae farming

Marine algae, both macro and micro, have gained increasing attention for their numerous ecosystem service functions, such as food and raw materials provision and climate change mitigation. Currently, the practice of large-scale algae farming is limited to Asian waters, but significant interest has arisen from other continents. However, there is a lack of knowledge about the areas with suitable environmental conditions for expanding algae farming on a global scale. Previous studies have primarily focused on nutrient availability and thermal constraints when assessing the potential for algae culture. This study uses species distribution models based on an ensemble consensus approach to determine the extent of suitable areas and takes into account multiple environmental factors that may affect the feasibility of algae culture. Our results show that approximately 20.8 million km2 of the ocean (∼13.8% of the economic exclusive zones) is suitable for farming marine algae species, with most potential areas located near the coastline. Surprisingly, four out of the top five countries with the largest area suitable for seaweed farming, including Australia, Russia, Canada, and the US, account for 30% of the total suitable areas, yet they currently produce less than 1% of the global seaweed. Several species show promising characteristics for large-scale cultivation, but their viability for commercial production remains uncertain and subject to further assessment of economic feasibility and social acceptance. Further research on the ecological benefits of seaweed farming could also promote the development of an ecologically friendly and financially viable algae mariculture industry. This study provides a scientific basis for decision-makers to understand potential expansion areas and feasible pathways for seaweed farming, with the ultimate goal of ensuring the sustainable utilization of marine resources.

Analytical Method of Viable Algae Cells in Water Based on Variable Fluorescence Statistical Distribution

Analytical Method of Viable Algae Cells in Water Based on Variable Fluorescence Statistical Distribution

Development of Microalgae-based Biofuels as a Viable Green Energy Source: Challenges and Future Perspectives

This paper presents a comprehensive account of the harvesting and processing technologies of microalgae and their applications in developing biofuels such as biodiesel, ethanol, biogas, syngas, and hydrogen. Microalgae have been reflected as an environmental pollution controlling agent due to their faster growth rate, making them a viable alternative to replace the current uses of non-renewable sources. The significantly large volumes of microalgae culture required for bio products are highlighted as a major concern of the complexity at the harvesting stage. At present, there are hardly any single methods that could generally be applied for processing the broad range of microalgae species with varying characteristics. Improvements are also required to effectively minimize the energy and cost required for the microalgae processing methods to be applicable at a commercial scale. By improving the techniques used at the harvesting stage, the costs associated with further processing steps to produce microalgae-based bio products and biofuels could be reduced. Future studies should also focus on identifying better algae strains that produce a high yield of good quality biofuel to economically viable algae biofuel.

基于叶绿素荧光动力学的压载水活体藻细胞数表征参数选择研究

基于叶绿素荧光动力学的压载水活体藻细胞数表征参数选择研究

Raman spectroscopy as a tool for viability assessment of planktonic organisms in UV treated ballast water

To comply with regulations stated by the United Nation’s International Maritime Organization, ballast water discharged by ships must be treated to avoid the spread of invasive organisms including algae. In this study, Raman spectroscopy and multivariate data analysis was used to make a Partial Least Squares Discriminant Analysis (PLS-DA) classification model for discrimination between viable (potential invasive) and UV exposed non-viable organisms. UV exposure is commonly used as a ballast water treatment strategy and a UV based exposure method was developed such that non-viable (and dying) algae consistently could be obtained. Raman spectra from both viable and UV treated algae of Rhodomonas salina and Tetraselmis suecica were measured. A PLS-DA model was obtained to form the normalized dataset, and Cross-Validated using Venetian blinds. Based on their individual Raman spectra, it was possible to obtain 100 % discrimination between the two algal species. The model classified 92 and 91 % of the viable algae correctly for R. salina and T. suecica, respectively, as opposed to 82 and 94 % for non-viable algae. In conclusion, in this proof of concept study, Raman spectroscopy was found to have a potential for algae species identification as well as discrimination between viable and non-viable algae.

An automated 3D-printed smartphone platform integrated with optoelectrowetting (OEW) microfluidic chip for on-site monitoring of viable algae in water

A sudden increase of algae and their associated toxins in aquatic ecosystems can detrimentally affect the quality of the water, causing serious socio-economic and public health problems. To prevent the spread of harmful algae in aquatic ecosystems, it is essential to track the water’s quality through rapid and in-situ monitoring systems. Conventional methods of algae quantification such as microscopy, hemocytometry, and UV–vis spectroscopy, however, are often unsuitable or inconvenient for in-situ assessment as they require skilled labor and expensive equipment. In this study, we developed a three-dimensional (3D)-printed smartphone platform integrated with a light-driven microfluidic chip operated by optoelectrowetting (OEW). This OEW-driven microfluidic chip not only allows multiplexed drop-wise functions such as droplet transportation, merging, mixing, immobilization on a detection zone, for on-chip water sample preparation but also fluorescent detection and counting of target algae cells using a commercially-available smartphone. Two freshwater algae (C. reinhardtii and M. aeruginosa) and two marine water algae (Amphiprora sp and C. closterium) were employed to validate the 3D-printed smartphone platform in this study. The fluorescence images of viable algae and the cell counting from the microfluidic chip were comparable to the results from a hemocytometer (P > 0.05). We have further conducted tests with spiked samples using freshwater and marine water that were directly collected from environmental samples, showing the same order of magnitude of cell numbers in the spiked and control cultures of algae cells (106 cell/mL, P > 0.05). Unlike traditional quantification methods, the 3D-printed smartphone platform integrated with the OEW offers a highly portable, user-friendly, low-cost tool that enables simple on-chip sample preparation and detection of viable algae. Thus, this stand-alone technology has the potential for rapid and in-situ monitoring of water quality, while using the smartphone’s wireless communication capabilities to report the quality of the water in real-time.

Detailed design and optimization of a sustainable micro-algal biofuel process plant

A sustainable micro-algal biofuel process plant was hypothetically and detailed-designed for the production of value products from algae. The process plant cultures algae through controlled growth and processes: production of biomass, extraction of lipids and biofuels and refinement into finished products. The start-off feedstock was Nannochloropsis spp. and the four end products produced were bio-kerosene, methane, biomass slurry and CO₂. The algae were grown to maturity within the least allowable possible time under controlled conditions. From an in-depth analysis of the customer specifications, concept development and selection, the study defines an overall depiction of the end products from the concepts evaluated by using the Pugh matrix and Six sigma methodologies. DMADV approach was implemented.The process finally generated an economically viable algae biomass for conversion to biofuels and other viable products. This paper focuses on the process planning, criteria/concept selection, design optimization with necessary characterizations which were filtered into measurable characteristics for the design of an operable, sustainable functioning plant.

Hydrodynamic design of an enclosed Horizontal BioReactor (HBR) for algae cultivation

Modeling and optimization of key design parameters of bioreactors are critical for development of economically and technically viable algae technologies. The objective of this study is to use computational fluid dynamics (CFD) modeling to design a novel enclosed Horizontal BioReactor (HBR) equipped with a paddle wheel that incurs low capital and operating costs like raceway ponds, but achieves high productivities like enclosed photobioreactors. For the HBR the aspect ratio (length-to-width), paddle wheel diameter and positioning, culture depth, and baffle spacing can be manipulated to achieve adequate flow of the culture that minimizes the formation of low-velocity areas, below 20cm/s, termed “dead zones”. The CFD procedure focused on minimizing dead volume and power consumption. A small-scale HBR (3m2 of surface area) was used for development and validation of the hydrodynamic model, whose parameters were calculated using experimental data. The model was then applied to a pilot-scale HBR (40m2) that is operated outdoors. Placing the paddle wheel at either end of the reactor or incorporating baffles minimized the dead volume. The same effect was also achieved by increasing the size of the paddle wheel or the number of paddle wheels or the depth of the culture. On the other hand, increasing the reactor's aspect ratio resulted in more dead volume, although it decreased power consumption. These findings will be incorporated into the design of large-scale HBRs (200m2) for commercial deployment.

Microalgal-biochar immobilized complex: A novel efficient biosorbent for cadmium removal from aqueous solution

The feasibility of the bioremediation of cadmium (Cd) using microalgal-biochar immobilized complex (MBIC) was investigated. Major operating parameters (e.g., pH, biosorbent dosage, initial Cd(II) concentration and microalgal-biochar ratio) were varied to compare the treatability of viable algae (Chlorella sp.), biochar and MBIC. The biosorption isotherms obtained by using algae or biochar were found to have satisfactory Langmuir predictions, while the best fitting adsorption isotherm model for MBIC was the Sips model. The maximum Cd(II) adsorption capacity of MBIC with a Chlorella sp.: biochar ratio of 2:3 (217.41mgg−1) was higher than that of Chlorella sp. (169.92mgg−1) or biochar (95.82mgg−1) alone. The pseudo-second-order model fitted the biosorption process of MBIC well (R2>0.999). Moreover, zeta potential, SEM and FTIR studies revealed that electrostatic attraction, ion exchange and surface complexation were the main mechanisms responsible for Cd removal when using MBIC.

Temporal changes in the suitability of claywater as a greenwater substitute for rearing larval sablefish (Anoplopoma fimbria)

For some species, marine aquaculture facilities increase turbidity to improve larval feeding, growth, and survival, typically by mixing algae with seawater to make “greenwater.” Clay is a less expensive and inorganic potential algae substitute that has been shown to reduce bacterial levels relative to algae and promote equal or better growth and survival in some species. Sablefish (Anoplopoma fimbria) is a prime candidate species for aquaculture but the rearing of sablefish larvae has not yet been experimentally tested with clay. This study tested whether clay is a viable algae substitute for rearing sablefish, and whether the relative performance of clay versus algae varies as a function of time. In the first week of larval rearing, algae (Nannochloropsis) produced more than three times greater survival than clay (Kentucky Ball Clay OM4). However, switching from algae to clay at the beginning of the second week led to 1.5 times greater larval growth compared to tanks where algae was used in both weeks. The performance difference between clay and algae, despite equal turbidity, suggests that clay and algae have potentially harmful and beneficial effects in addition to turbidity effects, and that these effects change through time. However, because the first experiment was a replacement study, it was not possible to know whether algae produced better survival in week one because 1) clay, which might be harmful, was not present, 2) algae, which might be beneficial, was present, or 3) both. A further additive study was conducted to test the second possibility. The experiment found that adding algae to clay in the first week of larval rearing leads to greater growth and survival, suggesting that algae has beneficial effects beyond turbidity. We discuss some possible mechanisms for potential harmful and beneficial effects of algae and clay.

Contrasting response of a plankton community to two filter-feeding fish and their feces: An in situ enclosure experiment

The responses of plankton communities and nutrient loads to different biomass levels of silver carp and tilapia (0, 25, 70, 130g/m3) were evaluated in situ, using enclosures in Lake Taihu, and the effects of fish feces on algal biomass were assessed using in situ dialysis culture. Both silver carp and tilapia significantly suppressed zooplankton biomass, after which zooplankton grazing was too low to suppress algal populations. Both fish also played an important role in accelerating nutrient circulation, and their feces directly contributed to algal growth. In fact, after passing through the digestive tract of silver carp, the cyanobacteria Microcystis remained viable, and their photosynthetic activity was even stimulated; however, no viable algae were detected in the tilapia feces. Overall, algal biomass increased with increasing biomass levels of the tilapia, whereas the medium biomass level of silver carp (70g/m3) was most effective in controlling cyanobacteria. Our results indicate that stocking with silver carp, rather than with tilapia, is an appropriate strategy for reducing summer cyanobacteria blooms in eutrophic lakes that lack large crustaceous zooplankton, such as Lake Taihu. In addition, stocking with 70g/m3 of silver carp was most effective for suppressing cyanobacteria blooms and improving water quality, which suggests that this moderate biomass level can be used to achieve a beneficial balance between the positive effects of filter feeding and negative effects of feces-derived nutrients on the growth of algae. Statement of relevanceGood for algae control and aquaculture yields increase.

Evaluation of the utility of six measures for algal (Microcystis aeruginosa, Planktothrix agardhii and Pseudokirchneriella subcapitata) viability

Standard algal toxicity tests are used to discern responses of algae to a variety of exposures including pesticides, personal care products and complex mixtures such as runoff and effluents. There are concerns regarding the accuracy, precision and utility of algal viability measures used as endpoints in algal toxicity test protocols. To definitively evaluate six algal viability measures, algae were heat-treated to produce known live:dead cell ratios. Cultures of two prokaryotic algae (Microcystis aeruginosa and Planktothrix agardhii) and a eukaryotic alga (Pseudokirchneriella subcapitata) were boiled for five minutes and mixed after cooling with untreated cultures to produce suspensions of 0%, 25%, 50%, 75% and 100% live algal cells. Optical microscopy was used to assess the viability of algae on a cell-by-cell basis by measuring cell density, uptake of a vital stain (neutral red) and exclusion of a mortal stain (erythrosin b). Aggregate measures of algal cell viability included chlorophyll a concentrations, pheophytin a concentrations and respiration (measured as 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium formazan absorbance (INT)). Cell densities, erythrosin b stained cells and chlorophyll a concentrations correlated with viable M. aeruginosa, P. agardhii and P. subcapitata cells (R2=0.97–0.78, 0.98–0.85 and 0.99–0.97 respectively). Pheophytin a concentrations and neutral red stained cells did not correlate with viable algae (R2=0.41–0.01 and 0.15–0.03 respectively). For INT formazan absorbance, 50%, 75% and 100% viable algae had greater variances and did not strongly correlate (R2=0.75–0.54). This result was likely confounded by respiration associated with resident bacteria. Three of the six methods provided accurate and precise information regarding the viability of both prokaryotic and eukaryotic algae. These methods also have a relatively low initial expense and can be used widely.

Extraction of lipids from microalgae by ultrasound application: Prospection of the optimal extraction method

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20–50% of dry weight) of lipids. A successful and economically viable algae based oil industry will depend on the selection of appropriate microalgal strains and the selection of the most suitable lipid extraction method. In this paper, five extraction methods were evaluated regarding the extraction of lipids from Chlorella vulgaris: Bligh and Dyer, Chen, Folch, Hara and Radin, and Soxhlet. Furthermore, the addition of silica powder was studied to evaluate the introduction of more shear stress to the system as to increase the disruption of cell walls. Among the studied methods, the Bligh and Dyer method assisted by ultrasound resulted in the highest extraction of oil from C. vulgaris (52.5% w/w). Addition of powder silica did not improve the extraction of oil.

Resource demand implications for US algae biofuels production scale-up

Photosynthetic microalgae with the potential for high biomass and oil productivities have long been viewed as a promising class of feedstock for biofuels to displace petroleum-based transportation fuels. Algae offer the additional benefits of potentially being produced without using high-value arable land and fresh water, thereby reducing the competition for those resources between expanding biofuels production and conventional agriculture. Algae growth can also be enhanced by the use of supplemental CO 2 that could be supplied by redirecting concentrated CO 2 emissions from stationary industrial sources such as fossil-fired power plants, cement plants, fermentation industries, and others. In this way, algae may offer an effective means to capture carbon emissions for reuse in renewable fuels and co-products, while at the same time displacing fossil carbon fuels to help bring about a net reduction in overall carbon emissions. Significant displacement of petroleum fuels will require that algae feedstock production reach large volumes that will put demands on key resources. This scenario-based analysis provides a high-level assessment of land, water, CO 2 and nutrient (nitrogen, phosphorus) demands resulting from algae biofuel feedstock production reaching target levels of 10 billion gallons per year (BGY), 20 BGY, 50 BGY, and 100 BGY for four different geographical regions of the United States. Different algae productivities are assumed for each scenario region, where relative productivities are nominally based on annual average solar insolation. The projected resource demands are compared with data that provide an indication of the resource level potentially available in each of the scenario regions. The results suggest that significant resource supply challenges can be expected to emerge as regional algae biofuel production capacity approaches levels of about 10 BGY. The details depend on the geographic region, the target feedstock production volume, and the level of algae productivity that can be achieved. The implications are that the supply of CO 2, nutrients, and water, in particular, can be expected to severely limit the extent to which US production of algae biofuel can be sustainably expanded unless approaches are developed to mitigate these resource constraints in parallel to emergence of a viable algae technology. Land requirements appear to be the least restrictive, particularly in the Western half of the country where larger quantities of potentially suitable classes of land exist. Within the limited scope and assumptions of this analysis, sustainable photosynthetic microalgae biofuel feedstock production in the US in excess of about 10 BGY will likely be a challenge due to other water, CO 2 and nutrient resource limitations. Developing algae production approaches that can effectively use non-fresh water resources and minimize both water and nutrient requirements will help reduce resource constraints. Providing adequate CO 2 resources for enhanced algae production appears the biggest challenge, and could emerge as a constraint at oil production levels below 10 BGY.

Bioprospecting for oil producing microalgal strains: Evaluation of oil and biomass production for ten microalgal strains

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20–50% of dry weight) of lipids. A successful and economically viable algae based oil industry depends on the selection of appropriate algal strains. In this study ten species of microalgae were prospected to determine their suitability for oil production: Chaetoceros gracilis, Chaetoceros mulleri, Chlorella vulgaris, Dunaliella sp., Isochrysis sp., Nannochloropsis oculata, Tetraselmis sp., Tetraselmis chui, Tetraselmis tetrathele and Thalassiosira weissflogii. The study was carried out in 3L glass flasks subjected to constant aeration and controlled artificial illumination and temperature at two different salinities. After harvesting, the extraction of oil was carried out using the Bligh and Dyer method assisted by ultrasound. Results showed that C. gracilis presented the highest oil content and that C. vulgaris presented the highest oil production.

Bioprospecting for hyper-lipid producing microalgal strains for sustainable biofuel production

Global petroleum reserves are shrinking at a fast pace, increasing the demand for alternate fuels. Microalgae have the ability to grow rapidly, and synthesize and accumulate large amounts (approximately 20-50% of dry weight) of neutral lipid stored in cytosolic lipid bodies. A successful and economically viable algae based biofuel industry mainly depends on the selection of appropriate algal strains. The main focus of bioprospecting for microalgae is to identify unique high lipid producing microalgae from different habitats. Indigenous species of microalgae with high lipid yields are especially valuable in the biofuel industry. Isolation, purification and identification of natural microalgal assemblages using conventional techniques is generally time consuming. However, the recent use of micromanipulation as a rapid isolating tool allows for a higher screening throughput. The appropriate media and growth conditions are also important for successful microalgal proliferation. Environmental parameters recorded at the sampling site are necessary to optimize in vitro growth. Identification of species generally requires a combination of morphological and genetic characterization. The selected microalgal strains are grown in upscale systems such as raceway ponds or photobireactors for biomass and lipid production. This paper reviews the recent methodologies adopted for site selection, sampling, strain selection and identification, optimization of cultural conditions for superior lipid yield for biofuel production. Energy generation routes of microalgal lipids and biomass are discussed in detail.

Zostera marina seagrass beds enhance the attachment of the invasive alga Sargassum muticum in soft sediments

The first reports of Sargassum muticum occurring in British waters coincided with a warning that this invasive alga may replace seagrass beds, particularly those of Zostera marina. Initial fears were allayed when subsequent research suggested that both species required different attachment substrata, and, therefore, S. muticum would be unable to replace Zostera beds on soft sediments. Here, however, we present evidence supporting the original warning: contrary to previous research we found that S. muticum is able to successfully colonise soft sediments and, furthermore, that the presence of Z. marina may aid attachment. The majority of S. muticum plants within Zostera beds studied at Salcombe, SW England, were found attached within the soft sediment; outside of the seagrass bed, however, this occurred in greatly reduced numbers. Therefore, we suggest that the presence of Z. marina may actually enhance S. muticum colonization of soft sediments, trapping drifting fragments and allowing viable algae to settle on the seagrass matrix in an otherwise unfavorable environment. The consequences for the invasion of seagrass beds by S. muticum may therefore be more severe than previously thought.

Water-network percolation transition in hydrated blue-green algae in vivo

We found that dc conductivity percolation process typical for low hydrated porous materials shows up in bulk viable blue-green algae, Arthrospira (Spirulina) platensis (strain Laporte 1963/M-132/2b) at unusually low hydrations, more than an order of magnitude lower than in, e.g., hydrated yeast [D. Sokolowska, A. Krol-Otwinowska, J.K. Moscicki, Phys. Rev. E 70 (2004) 052901]. The critical exponent is characteristic for two-dimensional network. Comparison with results for yeast and other similar materials shows that the hydration percolation threshold is a sensitive indicator of wettability of water accessible surface in porous bio- and abiotic materials.

Spectral properties of viable ancient green algae from Arctic permafrost

Spectral properties of viable ancient green algae from Arctic permafrost

Viable algae released by the seastar Dermasterias imbricata feeding on the symbiotic sea anemone Anthopleura elegantissima

Echinoderms are major predators of anemones in temperate ecosystems. The fate of two algae, zooxanthellae and zoochlorellae, after their host anemone (Anthopleura elegantissima Brandt) was consumed by the leather star Dermasterias imbricata Grube was determined in experiments conducted in July and August 2004. Productivity, photosynthetic pigments, and mitotic index (percent of cells dividing) were used as indicators of algal health; algae released after leather stars consumed their host were compared with algae freshly isolated from anemones. Two types of waste products contained algae: pellets resulting from extraoral digestion, and feces. Zooxanthellae and zoochlorellae isolated from these waste products were photosynthetic, although to different extents. For algae from feces and pellets, light-saturated photosynthetic rates (Pmax) were 85 and 13%, respectively, of Pmax of freshly isolated zooxanthellae; and were 20 and 46%, respectively, for zoochlorellae. The photosynthetic pigments and mitotic index (percent of dividing cells) were not altered by the feeding activities of the leather star. These results show that algae released by seastar predation on their hosts remain viable, and are hence available for establishing symbioses in A. elegantissima and other potential hosts.