Although microalgal biomass and environmental benefits of microalgae surpass those of many other feedstocks, the costs associated with up- and downstream technologies still hinder their further ...development. Membrane technology is an emerging technology that has been applied in the microalgae industry for cultivation, harvesting, and biorefinery, and that has contributed to achieving the economic sustainability of microalgal cultivation and reducing energy input. In the most studied field (microalgae harvesting), the lowest energy consumption is currently 0.67 Wh/m3 when using vibrating, negatively charged, patterned PSf membranes with flocculation prior to filtration in an MMV system. However, the operational flux (95 L/m2 h) is not the highest, leaving room for optimization. Cost calculations indicated that the total electrical cost is only a very small fraction (3.05%) of the total production cost (using the energy costs of that period, i.e., 0.1 €/kWh), with CO2 and labor suggested to be the key factors contributing to high production cost. Membrane-based microalgal biofilm systems recently gained a lot of attention as they offer a win-win strategy for low-cost simultaneous microalgae cultivation and harvesting. In addition, they can be used in other fields, such as wastewater treatment and the production of biochemicals. This review suggests that further studies should not only focus on developing new technologies but combine the existing technologies and find their synergistic effects to realize high performance and low costs.
•Harvesting does not significantly influence the final production cost.•The reported lowest energy consumption for harvesting is currently 0.67 Wh/m3.•Patterned membranes can be used to improve microalgal biomass harvesting performance.•More focus on the synergistic effect of the existing membrane technologies is needed.•Membrane-microalgae technology can be used for wound healing.
•There are changes in physical and chemical properties in the aging of microplastics.•Aged microplastics pose a stronger inhibition on the growth of microalgae than that of virgin ...microplastics.•single microplastics and copper significantly inhibit the growth of microalgae and cause serious oxidative stress.•The interaction of microplastics and copper alleviates the negative effect of single microplastics and copper to microalgae.
Microplastics (MPs) could pose potential risks to microalgae, the primary producer of marine ecosystems. Currently, few studies focus on the interaction of aged MPs with other pollutants and their toxic effects to microalgae. Therefore, the present study aimed to investigate i) the aging of microplastics polyvinyl chloride (mPVC) in simulated seawater and the changes in physical and chemical properties; ii) the effects of single mPVC (virgin and aged) and copper on microalgae Chlorella vulgaris; and iii) the interaction of aged mPVC and copper and the oxidative stress towards C. vulgaris. In this study, some wrinkles, rough and fractured surface textures can be observed on the aged mPVC, accompanying with increased hydroxyl groups and aromatic carbon-carbon double bond but decreased carbon hydrogen bond. It was found that single virgin or aged mPVC at low concentration (10 mg/L) had significant inhibition on the growth of C. vulgaris but no inhibition at higher concentration (100, 1,000 mg/L), which can be reasonably explained by the aggregation and precipitation of mPVC at high concentration. The aging of mPVC inhibited the growth of C. vulgaris with the maximum growth inhibition ratio (IR) of 35.26% as compared with that of virgin mPVC (IR = 28.5%). However, the single copper could significantly inhibit the growth of C. vulgaris and the inhibitory effects increased with concentration (0.2, 0.5, 1.0 mg/L). Furthermore, both the single aged mPVC (10 mg/L) and copper (0.5 mg/L) caused serious cell damage, although the concentration of superoxide dismutase (SOD) and the intracellular malonaldehyde (MDA) increased. In contrast to single treatment, the growth of C. vulgaris can be enhanced by the combined group with copper (0.5 mg/L) and aged mPVC (10 mg/L).
Graphical abstract Highlights ► Triacylglycerol assembly in microalgae might occur at plastid envelopes. ► Starch-less mutants provide clues for the engineering of carbon partitioning in algae. ► New ...algal species emerge as models for lipid and biofuel research.
•Magnetic separation method on harvesting tiny marine microalgae was developed.•Recovery efficiency of Nannochloropsis maritima reached above 95% within 4min.•Reuse of culture medium from magnetic ...separation was realized for algal culture.
An efficient magnetic separation technology using Fe3O4 nanoparticles was developed for harvesting marine microalgae Nannochloropsis maritima from culture broth. Recovery capacity of these nanoparticles was affected by microalgal growth phase and reached the peak value when the microalgal growth reached its maximal biomass after 18days. The recovery efficiency of microalgal cells from the culture medium reached more than 95% at the particle dosage of 120mg/L within 4min. Electrostatic attraction at acidic pH and cell aggregation under neutral and alkaline conditions was beneficial for harvesting the algal cells. Higher operation temperature resulted in higher adsorption capacity of these nanoparticles for microalgawl cells. Reuse of the culture medium obtained from magnetic separation gave similar biomass production in comparison with that from centrifugation separation after 5 recycles. Together with these results provide a great potential in high-efficient and economical harvesting of tiny marine microalgae using magnetic separation technology in practice.
A greater insight on the control of the interactions between microalgae and other microorganisms, particularly bacteria, should be useful for enhancing the efficiency of microalgal biomass production ...and associated valuable compounds. Little attention has been paid to the controlled utilization of microalgae-bacteria consortia. However, the studies of microalgal-bacterial interactions have revealed a significant impact of the mutualistic or parasitic relationships on algal growth. The algal growth, for instance, has been shown to be enhanced by growth promoting factors produced by bacteria, such as indole-3-acetic acid. Vitamin B12 produced by bacteria in algal cultures and bacterial siderophores are also known to be involved in promoting faster microalgal growth. More interestingly, enhancement in the intracellular levels of carbohydrates, lipids and pigments of microalgae coupled with algal growth stimulation has also been reported. In this sense, massive algal production might occur in the presence of bacteria, and microalgae-bacteria interactions can be beneficial to the massive production of microalgae and algal products. This manuscript reviews the recent knowledge on the impact of the microalgae-bacteria interactions on the production of microalgae and accumulation of valuable compounds, with an emphasis on algal species having application in aquaculture.
While research and development of algal biofuels are currently receiving much interest and funding, they are still not commercially viable at today’s fossil fuel prices. However, a niche opportunity ...may exist where algae are grown as a by-product of high rate algal ponds (HRAPs) operated for wastewater treatment. In addition to significantly better economics, algal biofuel production from wastewater treatment HRAPs has a much smaller environmental footprint compared to commercial algal production HRAPs which consume freshwater and fertilisers. In this paper the critical parameters that limit algal cultivation, production and harvest are reviewed and practical options that may enhance the net harvestable algal production from wastewater treatment HRAPs including CO
2 addition, species control, control of grazers and parasites and bioflocculation are discussed.
A review of allelopathy on microalgae Tan, Kaiting; Huang, Ziqi; Ji, Ruibo ...
Microbiology (Society for General Microbiology),
06/2019, Letnik:
165, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Algal blooms have severe impacts on the utilization of water resources. The discovery of allelopathy provides a new dimension to solving this problem due to its high efficiency, safety and economy. ...Allelopathy can suppress the growth of microalgae by impairing the structure, photosynthesis and enzyme activity of algal cells. In the current work, we first demonstrate the allelopathy and allelochemicals derived from both plants and algae. We then expound the potential mechanisms of allelopathy on microalgae. Next, the potential application of allelochemicals in water environment is proposed. Finally, the key challenge and future perspective are presented.
Modern life is intimately linked to the availability of fossil fuels, which continue to meet the world's growing energy needs even though their use drives climate change, exhausts finite reserves and ...contributes to global political strife. Biofuels made from renewable resources could be a more sustainable alternative, particularly if sourced from organisms, such as algae, that can be farmed without using valuable arable land. Strain development and process engineering are needed to make algal biofuels practical and economically viable.
•EC50 procainamide growth rate/chlorophyll (mg/l): 104/143 (alone).•EC50 procainamide growth rate/chlorophyll (mg/l): 125/31 (with microplastics).•EC50 doxycycline growth rate/chlorophyll (mg/l): ...39/24 (alone).•EC50 doxycycline growth rate/chlorophyll (mg/l): 21/13 (with microplastics).•Microplastics presence increased pharmaceuticals toxicity.
Microplastics and pharmaceuticals are considered ubiquitous and emergent pollutants of high concern but the knowledge on their effects on primary producers is still limited, especially those caused by mixtures. Thus, the goal of the present study was to investigate if the presence of microplastics (1–5 μm diameter) influences the toxicity of the pharmaceuticals procainamide and doxycycline to the marine microalga Tetraselmis chuii. Bioassays (96 h) to investigate the toxicity of those substances individually and in mixtures (i.e. microplastics-procainamide mixtures and microplastics-doxycycline mixtures) were carried out. Effect criteria were the average specific growth rate (growth rate) and chlorophyll a concentration (chlorophyll). EC10, EC20 and EC50 were determined. Microplastics alone had no significant effects on growth rate up to 41.5 mg/l, whereas chlorophyll was significantly reduced at 0.9 and 2.1 mg/l of microplastics, but not at higher concentrations. The 96 h EC50 (growth rate and chlorophyll, respectively) determined for the other bioassays were: 104 and 143 mg/l for procainamide alone; 125 and 31 mg/l for procainamide in the presence of microplastics; 22 and 14 mg/l for doxycycline alone; 11 and 7 mg/l for doxycycline in the presence of microplastics. Significant differences (p < 0.001) between the toxicity curves of each pharmaceutical alone and in mixture with microplastics were found for procainamide (chlorophyll), and doxycycline (both parameters). Thus, both pharmaceuticals were toxic to T. chuii in the low ppm range, and microplastics-pharmaceutical mixtures were more toxic than the pharmaceuticals alone. Very high decreases of doxycycline concentrations in test media were found, indicating degradation of the antibiotic. Thus, although the biological results are expressed in relation to doxycycline concentration, the effects were likely caused by a mixture of the parental compound and its degradation products. The concentrations of microplastics and pharmaceuticals tested (low ppm range) are higher than those expected to be found in waters of the most part of marine ecosystems (ppt or ppb ranges). However, considering the widespread contamination by microplastics and pharmaceuticals, the concentrations already found in waters, sediments and/or organism of heavily polluted areas, the long-term exposure (over generations) of wild populations to such substances in polluted ecosystems and the possibilities of bioaccumulation and toxicological interactions, these findings are of concern and further research on microplastics-pharmaceuticals toxicological interactions is needed.
Microalgae have been considered as alternative sustainable resources for high-value bioproducts such as lipids (especially triacylglycerides TAGs), polyunsaturated fatty acids (PUFAs), and ...carotenoids, due to their relatively high photosynthetic efficiency, no arable land requirement, and ease of scale-up. It is of great significance to exploit microalgae for the production of high-value bioproducts. How to improve the content or productivity of specific bioproducts has become one of the most urgent challenges. In this review, we will describe high-value bioproducts from microalgae and their biosynthetic pathways (mainly for lipids, PUFAs, and carotenoids). Recent progress and strategies for the enhanced production of bioproducts from microalgae are also described in detail, and these strategies take advantages of optimized cultivation conditions with abiotic stress, chemical stress (addition of metabolic precursors, phytohormones, chemical inhibitors, and chemicals inducing oxidative stress response), and molecular approaches such as metabolic engineering, transcriptional engineering, and gene disruption strategies (mainly RNAi, antisense RNA, miRNA-based knockdown, and CRISPR/Cas9).
PDF
