Production of sustainable thermoplastic composites from waste nitrogen fertilizer-grown marine filamentous cyanobacterium Geitlerinema sp.

The global demand for petroleum-derived plastics continues to increase, as does pollution caused by plastic consumption and landfilling plastic waste. Recycling waste plastics by thermomechanical molding may be advantageous, but it alone cannot address the challenges associated with plastic demand and its widespread pollution. A more sustainable and cleaner approach for recycling plastic waste could be to produce thermoplastic composite blends of waste plastic and biobased alternative materials such as marine algal biomass. In this study, Geitlerinema sp., a marine cyanobacterium, was cultivated with waste nitrogen fertilizer as a nitrogen source, resulting in phycocyanin content and biomass density of 6.5% and 0.7 g/L, respectively. The minimum and maximum tensile strengths of thermoplastic blends containing Geitlerinema sp. biomass, recycled glycerol plasticizer, and waste plastic were 0.29-23.2 MPa, respectively. The tensile strength and Young's modulus of thermoplastic composites decreased as the Geitlerinema sp. biomass concentration increased. Furthermore, thermal analysis revealed that thermoplastics containing Geitlerinema sp. biomass have lower thermal onset and biomass degradation temperatures than waste polyethylene. Nevertheless, 35-50% of Geitlerinema sp. biomass could be a sustainable biobased alternative feedstock for producing thermoplastic blends, making the recycling of waste plastics more sustainable and environmentally friendly.

A comprehensive review on versatile microalga Tetraselmis: Potentials applications in wastewater remediation and bulk chemical production.

Microalgae are considered sustainable resources for the production of biofuel, feed, and bioactive compounds. Among various microalgal genera, the Tetraselmis genus, containing predominantly marine microalgal species with wide tolerance to salinity and temperature, has a high potential for large-scale commercialization. Until now, Tetraselmis sp. are exploited at smaller levels for aquaculture hatcheries and bivalve production. However, its prolific growth rate leads to promising areal productivity and energy-dense biomass, so it is considered a viable source of third-generation biofuel. Also, microbial pathogens and contaminants are not generally associated with Tetraselmis sp. in outdoor conditions due to faster growth as well as dominance in the culture. Numerous studies revealed that the metabolite compositions of Tetraselmis could be altered favorably by changing the growth conditions, taking advantage of its acclimatization or adaptation ability in different conditions. Furthermore, the biorefinery approach produces multiple fractions that can be successfully upgraded into various value-added products along with biofuel. Overall, Tetraselmis sp. could be considered a potential strain for further algal biorefinery development under the circular bioeconomy framework. In this aspect, this review discusses the recent advancements in the cultivation and harvesting of Tetraselmis sp. for wider application in different sectors. Furthermore, this review highlights the key challenges associated with large-scale cultivation, biomass harvesting, and commercial applications for Tetraselmis sp.

Microalgae: A potential bioagent for treatment of emerging contaminants from domestic wastewater.

Water crisis around the world leads to a growing interest in emerging contaminants (ECs) that can affect human health and the environment. Research showed that thousands of compounds from domestic consumers, such as endocrine disrupting chemicals (EDCs), personal care products (PCPs), and pharmaceuticals active compounds (PhAcs), could be found in wastewater in concentration mostly from ng L-1 to µg L-1. However, generally, wastewater treatment plants (WWTPs) are not designed to remove these ECs from wastewater to their discharge levels. Scientists are looking for economically feasible biotreatment options enabling the complete removal of ECs before discharge. Microalgae cultivation in domestic wastewater is likely a feasible approach for removing emerging contaminants and simultaneously removing any residual organic nutrients. Microalgal growth rate and contaminants removal efficiency could be affected by various factors, including light intensity, CO2 addition, presence of different nutrients, etc., and these parameters could greatly help make microalgae treatment more efficient. Furthermore, the algal biomass harvests could be repurposed to produce various bulk chemicals such as sustainable aviation fuel, biofuel, bioplastic, and biochar; this could significantly enhance the economic viability. Therefore, this review summarizes the microalgae-based bioprocess and their mechanisms for removing different ECs from different wastewaters and highlights the different strategies to improve the ECs removal efficiency. Furthermore, this review shows the role of different ECs in biomass profile and the relevance of using ECs-treated microalgae biomass to produce green products, as well as highlights the challenges and future research recommendations.

Microalgal bioremediation of brackish aquaculture wastewater.

Rapid aquaculture industry development contributed to a major increase in aquaculture wastewater generation. In the context of a circular economy, aquaculture wastewater treatment should simultaneously recover nutrients from the wastewater. Among many treatment methods, bioremediation using microalgae could be a cost-effective and environmentally friendly system that can be applied to treat aquaculture wastewater and simultaneously produce high-value microalgal biomass. This study explored the feasibility of treating brackish wastewater (0.8 % NaCl) generated from a Qatari commercial tilapia farm by microalgae. At first, 10 strains were grown using wastewater from the local farm in an indoor experiment. Based on nitrogen assimilation, biomass yield, biomass quality, and ease of harvesting, 4 candidate strains (Haematococcus sp., Neochloris sp., Monoraphidium sp., and Nostoc sp.) were shortlisted for outdoor growth experiments. Although Nostoc sp. could not grow outdoor in the wastewater, the other three strains were able to assimilate at least 70.5 % of the total nitrogen in the wastewater. Haematococcus sp. and Neochloris sp. could be harvested using self-settling, whereas Monoraphidium required an energy-intensive tangential flow filtration membrane process. Hence, the overall energy requirement for bioremediation, including biomass dewatering, for Haematococcus sp., Neochloris sp., and Monoraphidium sp. were determined as 0.64, 0.78, and 5.68 MJ/m3, respectively. Neochloris sp. had almost twice the biomass yield compared to Haematococcus sp. - suggesting that Neochloris sp. could be a potential candidate for aquaculture wastewater treatment.

A comparative physicochemical property assessment and techno-economic analysis of biolubricants produced using chemical modification and additive-based routes.

Several edible and non-edible oil sources are currently being developed as renewable basestocks for biolubricant production. However, these feedstocks possess undesirable physicochemical properties limiting their lubricant applications. Chemical modification and additive-based routes could be used to modify their properties -suitable for different biolubricant applications. The first part of this study compares how the selected modifications affect the properties of the basestocks. Next, the techno-economic analysis (TEA) was conducted to study 4 selected biolubricants and a potential biolubricant derived from marine microalgae biomass. Oxidative stabilities of chemically modified biolubricants followed the order of epoxidation> triesterification> estolide. Pour points of triesters showed minimal increments and reduced for estolides, whereas epoxidation increased pour points. Estolides exhibit maximum kinematic viscosity increment among chemical modification routes, followed by TMP-transesterification and epoxidation. The oxidative stability of chemically modified biolubricants was higher than additized biolubricants; conversely, the viscosity increments and pour point reductions for additized biolubricants were higher than chemically modified biolubricants. TEA results show that the unit cost for producing 1-kg estolide was the highest among the chemical modification routes. The unit cost per kilogram of jatropha biolubricant produced using the additive-based route was lower than chemically modified biolubricants. Due to a high microalgal oil feedstock cost, the unit cost per kilogram of additized microalgae oil biolubricant was more than the unit cost of additized Jatropha oil. The techno-economic feasibility of biolubricant production from marine microalgal oil could be improved by adopting a biorefinery approach.

Haematococcus pluvialis Microalgae Extract Inhibits Proliferation, Invasion, and Induces Apoptosis in Breast Cancer Cells.

Breast cancer (BC) is the most common malignant cancer in females worldwide. Drug resistance, toxicity, and the failure of current therapies to completely cure BC has challenged conventional medicine. Consequently, complementary alternative medicine has become popular due to its safety and efficacy. Haematococcus pluvialis (H. pulvialis) is a green microalga living in fresh water, and its crude extract is rich of bioactives, including carotenoids, known to inhibit cancer cell growth. In the present study, we investigated the effects of a methanol crude extract called "T1" of H. pulvialis on cell growth and migration/invasion of the BC cell line MDA-MB-231 in comparison to the fibroblast control cells. TI significantly suppressed BC cell growth, inhibited migration and invasion and induced apoptosis. Interestingly, apoptosis was mediated by a significant loss of mutant p53 protein, and increased Bax/Bcl2 ratio. Our findings support our hypothesis that T1 exerts its anti-cancer effects by inhibiting BC invasion and inducing apoptosis mediated, at least, via the p53/Bax/Bcl2 pathway. Ongoing experiments aim to identify the molecular mechanisms underpinning T1-inhibited BC cell invasion using pre-designed metastasis gene-based array method.

Solar cultivation of microalgae in a desert environment for the development of techno-functional feed ingredients for aquaculture in Qatar.

The demand for aquaculture feed will increase in the coming years in order to ensure food security for a growing global population. Microalgae represent a potential fish-feed ingredient; however, the feasibility of their sustainable production has great influence on its successful application. Geographical locations offering high light and temperature, such as Qatar, are ideal to cultivate microalgae with high productivities. For that, the environmental and biological interactions, including field and laboratory optimization, for solar production and application of two native microalgae, Picochlorum maculatum and Nannochloris atomus, were investigated as potential aquaculture feed ingredients. After validating pilot-scale outdoor cultivation, both strains were further investigated under simulated seasonal conditions using a thermal model to predict light and culture temperature cycles for the major climatic seasons in Qatar. Applied thermal and light variations ranged from 36 °C and 2049 µmol/m2/s in extreme summer, to as low as 15 °C and 1107 µmol/m2/s in winter, respectively. Biomass productivities of both strains varied significantly with maximum productivities of 32.9 ± 2.5 g/m2/d and 17.1 ± 0.8 g/m2/d found under moderate summer conditions for P. maculatum and N. atomus, respectively. These productivities were significantly reduced under both extreme summer, as well as winter conditions. To improve annual biomass productivities, the effect of implementation of a simple ground heat exchanger for thermal regulation of raceway ponds was also studied. Biomass productivities increased significantly, during extreme seasons due to respective cooling and heating of the culture. Both strains produced high amounts of proteins during winter, 54.5 ± 0.55% and 44 ± 2.25%, while lipid contents were high during summer reaching up to 29.6 ± 0.75 and 28.65 ± 0.65%, for P. maculatum and N. atomus respectively. Finally, using acute toxicity assay with zebra fish embryos, both strains showed no toxicity even at the highest concentrations tested, and is considered safe for use as feed ingredient and to the environment.

Potential of microalgae as a sustainable feed ingredient for aquaculture.

An increase in fish consumption, combined with a decrease in wild fish harvest, is driving the aquaculture industry at rapid pace. Today, farmed seafood accounts for about half of all global seafood demand for human consumption. As the aquaculture industry continues to grow, so does the market for aquafeed. Currently, some of the feed ingredients are coming from low-value forage fishes (fish meal) and terrestrial plants. The production of fish meal can't be increased as it would affect the sustainability and ecosystem of the ocean. Similarly, increasing the production of terrestrial plant-based feed leads to deforestation and increased freshwater use. Hence, alternative and environmentally sustainable sources of feed ingredients need to be developed. Microalgae biomasses represent potential feed source ingredients as the cell metabolites of these microorganisms contain a blend of essential amino acids, healthy triglycerides as fat, vitamins, and pigments. In addition to serving as bulk ingredient in aquafeed, their unique array of bioactive compounds can increase the survivability of farmed species, improve coloration and quality of fillet. Microalgae has the highest areal biomass productivities among photosynthetic organisms, including fodder crops, and thus has a high commercial potential. Also, microalgal production has a low water and arable-land footprint, making microalgal-based feed environmentally sustainable. This review paper will explore the potential of producing microalgae biomass as an ingredient of aquaculture feed.

Outdoor scale-up of Leptolyngbya sp.: Effect of light intensity and inoculum volume on photoinhibition and -oxidation.

The effect of light intensity and inoculum volume on the occurrence of photooxidation for Leptolyngbya sp. QUCCCM 56 was investigated, to facilitate the transition from small-scale laboratory experiments to large-scale outdoor cultivation. Indoor, the strain was capable of growing at light intensities of up to 5600 µmol photons/m2 /s, at inoculation densities as low as 0.1 g/L (10% inoculation volume vol/vol). Levels of chlorophyll and phycocyanin showed a significant decrease within the first 24 h, indicating some level of photooxidation, however, both were able to recover within 72 h. When cultivated under outdoor conditions in Qatar during summer, with average peak light intensities 1981 ± 41 µmol photons/m2 /s, the strain had difficulties growing. The culture recovered after an initial adaptation period, and clear morphological differences were observed, such as an increase in trichome length, as well as coiling of multiple trichomes in tightly packed strands. It was hypothesized that the morphological changes were induced by UV-radiation as an adaptation mechanism for increased self-shading. Furthermore, the presence of contaminating ciliates could have also affected the outdoor culture. Both UV and contaminants are generally not simulated under laboratory environments, causing a mismatch between indoor optimizations and outdoor realizations.

Potential utilization of waste nitrogen fertilizer from a fertilizer industry using marine microalgae.

This study investigated the feasibility of microalgal biomass production using waste nitrogen fertilizers (WNFs) generated by the Qatar Fertiliser Company (QAFCO). From the plant, three types of WNFs (WNF1, WNF2, and WNF3) were collected; WNF1 and WNF2 had high solubility (e.g., 1000 g/L) whereas WNF3 had low solubility (65 g/L). For a lower dosage (i.e., 100 mg N/L) of these WNFs, >98% of nitrogen was soluble in water for WNF1 and WNF2; however, 52 mg N/L was soluble for WNF3. Nitrogen content in these wastes was 44, 43, and 39% for WNF1, WNF2, and WNF3, respectively. As these WNFs were used as the sole nitrogen source to grow Tetraselmis sp., Picochlorum sp., and Synechococcus sp., Tetraselmis sp. could utilize all the three WNFs more efficiently than other two strains. The biomass yield of Tetraselmis sp. in a 100,000 L raceway pond was 0.58 g/L and 0.67 g/L for mixed WNFs (all WNF in equal ratio) and urea, respectively. The metabolite profiles of Tetraselmis sp. biomass grown using mixed WNFs were very similar to the biomass obtained from urea-added culture - suggesting that WNFs produced Tetraselmis sp. biomass could be used as animal feed ingredients. Life cycle impact assessment (LCIA) was conducted for six potential scenarios, using the data from the outdoor cultivation. The production of Tetraselmis sp. biomass in QAFCO premises using its WNFs, flue gas, and waste heat could not only eliminate the consequences of landfilling WNFs but also would improve the energy, cost, and environmental burdens of microalgal biomass production.

Energy recovery and nutrients recycling from municipal sewage sludge.

Hydrothermal Liquefaction (HTL) could be a promising and better alternative to other techniques for energy recovery from municipal sewage sludge (MSS). However, the nutrients (i.e., N, and P) recovery potential from the byproducts, generated in the HTL of MSS, needs to be studied so that a comprehensive sludge management practice could be adopted. In this study, HTL process temperature (275-400 °C), and reaction time (30-120 min) were first investigated for biocrude yield and release of the nutrients to the aqueous phase liquid (APL) and biochar. The maximum energy recovery (i.e., 59%) and maximum energy return on investment (i.e., 3.5) were obtained at 350 °C and 60 min of holding time. With the increase in HTL reaction time, the concentration of nitrogen in the APL increased (5.1 to 6.8 mg/L) while the concentration of phosphorus decreased (0.89 to 0.22 mg/L); the opposite was observed for the biochar. The nutrient recycling efficiency from the APL using microalgae was found to be strain-specific; nitrogen recycling efficiency by Picochlorum sp. and Chlorella sp. were 95.4 and 58.6%, respectively. The APL, derived from 1 kg MSS, could potentially produce 0.49 kg microalgal biomass. Since the concentrations of various metals in the biochar samples were substantially lower compared to their concentrations in raw MSS, the application of biochar as a soil conditioner could be very promising. Overall, net positive energy could be recovered from MSS using the HTL process, while the nutrients in the APL could be used to cultivate specific microalgae, and biochar could be applied to enhance the soil quality.

Effect of the induced dielectrophoretic force on harvesting of marine microalgae (Tetraselmis sp.) in electrocoagulation.

In this study, a new electrocoagulation electrode configuration has been investigated in order to induce dielectrophoretic (DEP) force for the enhanced harvesting of marine microalgae (Tetraselmis sp.). Asymmetrical aluminum electrodes with an alternative current power supply were used. The impact of electrode configuration, current density and electrolysis time were evaluated. A maximum algal harvesting efficiency of 90.9% was achieved using 7.1 mA/cm2 current density and 10 min electrolysis time. The energy consumption was found to be 4.62 kWh/kg of microalgae. The major significance of using the new electrode configuration was found in the aluminum content in the harvested biomass which decreased by 52% compared to the conventional symmetrical electrocoagulation electrodes.

A feasibility study of utilizing hydrothermal liquefaction derived aqueous phase as nutrients for semi-continuous cultivation of Tetraselmis sp.

The feasibility of substituting 50% nutrients by aqueous phase liquid (APL), derived from hydrothermal liquefaction of Tetraselmis sp. biomass, in a semi-continuous cultivation of Tetraselmis sp. was studied. Growth experiments were conducted in indoor photobioreactor and outdoor raceway tank for three consecutive cycles. At the end of exponential growth pahse, 75% of the culture was harvested, and the supernatant was returned to the cultivation system. For control cultures, fresh nutrients were added; however, for the experimental cultures, an appropriate volume of APL was added to replace half of the nutrients. Either indoor or outdoor, the growth rate and biomass yield in APL-added cultures were either equal or slightly better compared to control culture; although APL had little to no effect on the metabolite content of Tetraselmis sp., metabolites profile of Tetraselmis sp. varied between APL-added and control cultures. Nevertheless, 50% nutrients requirements for microalgae cultivation could be replaced by APL.

The effect of culture salinity on the harvesting of microalgae biomass using pilot-scale tangential-flow-filter membrane.

In this study, the effect of culture salinity (4-6% NaCl) on the harvesting of two microalgal strains (i.e., Picochlorum sp., and Tetraselmis sp.) was investigated using pilot-scale TFF membranes. The cultures of these two strains were collected from their respective continuous cultivation in 2, 25,000 L raceway ponds. For both strains, an increase in culture salinity aggravated the membrane fouling and hence negatively influenced the permeate flux rate, biomass concentrating factor, and energy requirement in biomass harvesting. For the TFF membranes, an increase in 1% NaCl salinity, the volume of processed permeate reduced by 30-44 %, the energy consumption per unit volume of permeate increased by 3-63%, and the biomass concentrating factor reduced by 47-61%.

Effect of harvesting methods on the energy requirement of Tetraselmis sp. biomass production and biocrude yield and quality.

A halo-tolerant Tetraselmis sp. was grown in a 100,000 L raceway pond in the Qatari desert environment. As the biomass density reached 0.679 g/L, after 7 days, five different harvesting methods (i.e., cross-flow filtration, electrocoagulation, and coagulation-flocculation by FeCl3, NaOH, and alum) were applied to harvest the biomass. Hydrothermal liquefaction, for all the harvested biomass, was conducted at 350 °C for 30 mins in 10 mL Swagelok unions. The biocrude yield from cross-flow processed biomass (i.e., control) was 50.8%. Biocrude yield from electrocoagulation and alum processed biomass were 62.7% and 60.4% respectively where aluminum could have a catalytic effect. Biocrude yield from FeCl3 and NaOH processed biomass were 42.9% and 19.8% respectively. The total fraction of alkenes and alkanes was higher in the biocrude obtained from alum-harvested biomass, compared to other biocrude samples. However, the transition of metal species from biomass to biocrude was very low in all the biocrudes.

Long-term semi-continuous cultivation of a halo-tolerant Tetraselmis sp. using recycled growth media.

In this study, a halotolerant Tetraselmis sp. was selected for 11-month outdoor semi-continuous cultivation in one sq. m raceway tank in the Qatari desert. A fraction of the culture was harvested using ferric chloride, and the growth media was returned to the tank. The recycling of culture media continued till the culture salinity reached 8% NaCl; 90% culture was then harvested, and the remaining culture fraction was used as inoculum for a new cultivation cycle. The growth of Tetraselmis sp. was not affected by incremental salinity although the intracellular metabolites varied; the average biomass productivity was 17.8 g/m2/d. Harvesting efficiency was slightly affected by the increase in salinity. Iron content in the harvested biomass was in the range of 1.5-3.3%, and acidic solution (pH = 1.48) was able to recover 91.3% iron from the harvested biomass. Nonetheless, Tetraselmis sp. could be grown continuously throughout the year in Qatar's climate condition.

Microalgae harvesting by pH adjusted coagulation-flocculation, recycling of the coagulant and the growth media.

Coagulation-flocculation can be considered as one of the least energy intensive microalgae biomass harvesting processes. However, cost of the coagulant and biomass contamination are two critical issues that need to be considered. In this study, ferric chloride (72-96mg/L) was used to effectively harvest Scenedesmus sp. (530mg/L) - grown in BG-11 media and wastewater. Reducing the culture pH below 6.5, greatly improved the harvesting efficiency. Acidic solution (pH 1.0) was very effective to recover (almost 90%) the associated iron from the harvested biomass. Scenedesmus sp. was able to grow in the supernatant and utilize the residual iron in it. Iron extracted solution, with a supplementation of 9.8mg/L ferric chloride, was able to achieve similar harvesting efficiency. The potential recovery of iron from the harvested biomass and its reuse in the harvesting can improve the biomass quality for subsequent downstream processing while reducing the cost.

A comparative study of the growth of Tetraselmis sp. in large scale fixed depth and decreasing depth raceway ponds.

In this study, an alternative approach was proposed where excess seawater would be added only during inoculation (DD) rather than daily addition (FD). Growth and metabolite contents of Tetraselmis sp. weren't affected for daily increase of 2% NaCl salinity. Tetraselmis sp. was then cultured in DD and FD pond. In DD pond, initial culture depth was 23.5cm and its depth reduced as no water was added; for FD pond, everyday sterilized seawater was added to maintain 20cm depth. DD pond had higher biomass productivity compared to FD pond, until DD pond was deeper than FD pond; metabolite content and FAME profile of Tetraselmis sp. were also similar in both cultures. Therefore, considering the simplicity in operation, halo tolerant microalgae can be grown in DD pond method.

Sustainable production of toxin free marine microalgae biomass as fish feed in large scale open system in the Qatari desert.

Mass cultivation of microalgae biomass for feed should be cost effective and toxin free. Evaporation loss in Qatar can be as high as 2 cm/d. Hence, production of marine microalgae biomass in Qatar would also require mitigating water loss as there was only very limited groundwater reserve. To address these issues, a combination of four growth conditions were applied to a 25,000 L raceway pond: locally isolated microalgae strain was selected which could grow in elevated salinity; strain that did not require silica and vitamins; volume of the culture would increase over time keeping denser inoculum in the beginning, and evaporation water loss would be balanced by adding seawater only. A local saline tolerant Nannochloropsis sp. was selected which did not require silica and vitamins. When the above conditions were combined in the pond, average areal biomass productivities reached 20.37 g/m(2)/d, and the culture was not contaminated by any toxic microalgae.