Adaptation Of Microalgae Research Articles

Effect of urban wastewater ratio in the influent of a membrane photobioreactor for microalgae cultivation and nutrient removal

Microalgae are increasingly attracting attention for the wastewater regeneration, removing nutrients, and obtaining a high-value product. These nutrients are essential for the growth of algae and aquatic plants, but an overabundance of them in aquatic ecosystems can cause eutrophication, so it is very important to control the concentration of these nutrients in wastewater discharges to the environment. In this study, we have carried out the adaptation of microalgae by gradually changing the influent from a culture medium to treated urban wastewater in membrane photobioreactors, analysing the consortium of microalgae and bacteria present and evaluating the removal of nutrients such us nitrogen and phosphorus. A satisfactory adaptation was observed, reaching concentrations of 0.164 g/L at the end of the study. In the case of the chlorophyte communities studied, it was found that the predominant species was the same in all adaptation phases (unclassified environmental Eukaryota), as well as in the photobioreactors that worked in parallel under extreme conditions. Regarding nitrogen and phosphorus removal during the adaptation phases, the values increased in both cases, reaching 96.99% and 48.10%, respectively. Following the microbiological study, bacterial families have been detected that show symbiotic activity during the growth of microalgae. Multidimensional scaling revealed positive correlations between the detected microalgae and nitrogen removal in the membrane photobioreactor. Our data suggest that MPBRs are a potential tertiary treatment that can produce microalgae biomass from real treated wastewater by utilising its nitrogen and phosphorus content, resulting in a higher quality effluent that is less harmful to the environment.

Microalgae adaptation as a strategy to recycle the aqueous phase from hydrothermal liquefaction

Hydrothermal liquefaction (HTL) produces bio-crude oil from wet algae along with an aqueous phase (AP). This effluent contains minerals that can be reused for cultivating new microalgae but whose utility remains limited due to the presence of inhibitors. Reduced photosynthetic performance, growth, and null lipid accumulation were observed in wild-type Chlorella vulgaris NIES 227 cultivated in AP (1/200). Adaptive laboratory evolution was studied by batch transfers and turbidostat mode. Both methods effectively counterbalanced AP toxicity and restored the fitness of the microalgae. After adaptation, a higher AP addition was achieved, from 1/600 to 1/200, without inhibition. As compared with the wild typein control medium (0.261 g/L/d), both adapted-strains maintained competitive productivity (0.310 and 0.258 g/L/d) of lipid-rich biomass (37 %–56 %). The improved tolerance of the adapted strains persisted after the removal of AP and under axenic conditions. Adaptive laboratory evolution is suggested for AP reutilization in the algae production process.

Microalgae for saline wastewater treatment: a critical review

Saline wastewater contains numerous pollutants such as nutrients, heavy metals, micropollutants, and organic pollutants. This kind of wastewater needs to be treated prior to discharging. Compared to other technologies for saline wastewater treatment, the microalgae process is considered to be ‘green’ or environmentally friendly as it generates no secondary pollutants and creates profit. To elucidate the issue, this review investigated the following: (1) the nature of saline wastewater; (2) adaptation of microalgae in saline wastewater; (3) pollutants’ remediation by microalgae in saline wastewater; (4) comparisons with other technologies; and (5) future perspectives. Most importantly, during microalgae process, the saline wastewater is transformed from a waste into a source for biofuel and pigment production. This trend implies to heal the environment, cut remediation expenses and raise revenue.

Microalgae as embedded environmental monitors

In marine ecosystems, microalgae are an important component as they transform large quantities of inorganic compounds into biomass and thereby impact environmental chemistry. Of particular relevance is phytoplankton's sequestration of atmospheric CO2, a greenhouse gas, and nitrate, one cause of harmful algae blooms. On the other hand, microalgae sensitively respond to changes in their chemical environment, which initiates an adaptation of their chemical composition. Analytical methodologies were developed in this study that utilize microalgae's adaptation as a novel approach for in-situ environmental monitoring. Longterm applications of these novel methods are investigations of environmental impacts on phytoplankton's sequestration performance and their nutritional value to higher organisms feeding on them.In order to analyze the chemical composition of live microalgae cells (Nannochloropsis oculata), FTIR-ATR spectroscopy has been employed. From time series of IR spectra, the formation of bio-sediment can be monitored and it has been shown that the nutrient availability has a small but observable impact. Since this bio-sediment formation is governed by several biological parameters of the cells such as growth rate, size, buoyancy, number of cells, etc., this enables studies of chemical environment's impact on biomass formation and the cells' physical parameters.Moreover, the spectroscopic signature of these microalgae has been determined from cultures grown under 25 different CO2 and NO3− mixtures (200 ppm-600 ppm CO2, 0.35 mM-0.75 mM NO3−). A novel, nonlinear modeling methodology coined ‘Predictor Surfaces’ is being presented by means of which the nonlinear responses of the cells to their chemical environment could reliably be described. This approach has been utilized to measure the CO2 concentration in the atmosphere over the phytoplankton culture as well as the nitrate concentration dissolved in their growing environment. The achieved precision of concentration predictions were a few percent of the measurement range. Moreover, the Predictor Surface itself allows for a chemical interpretation of the cells' response to a shift in their chemical environment. This will open new approaches to study the link between concentration levels in an ecosystem and the biological consequences for this ecosystem.

Biological constraints in algal biotechnology

In the past decade, considerable progress has been made in developing the appropriate biotechnology for microalgal mass cultivation aimed at establishing a new agro-industry. This review points out the main biological constraints affecting algal biotechnology outdoors and the requirements for making this biotechnology economically viable. One of them is the availability of a wide variety of algal species and improved strains that favorably respond to varying environmental conditions existing outdoors. It is thus just a matter of time and effort before a new methodology like genetic engineering can and will be applied in this field as well. The study of stress physiology and adaptation of microalgae has also an important application in further development of the biotechnology for mass culturing of microalgae. In outdoor cultures, cells are exposed to severe changes in light and temperature much faster than the time scale required for the cells to acclimate. A better understanding of those parameters and the ability to rapidly monitor those conditions will provide the growers with a better knowledge on how to optimize growth and productivity. Induction of accumulation of high value products is associated with stress conditions. Understanding the physiological response may help in providing a better production system for the desired product and, at a later stage, give an insight of the potential for genetic modification of desired strains. The potential use of microalgae as part of a biological system for bioremediation/detoxification and wastewater treatment is also associated with growing the cells under stress conditions. Important developments in monitoring and feedback control of the culture behavior through application of on-line chlorophyll fluorescence technique are in progress. Understanding the process associated with those unique environmental conditions may help in choosing the right culture conditions as well as selecting strains in order to improve the efficiency of the biological process.

Mutation of algae from sensitivity to resistance against environmental selective agents: the ecological genetics of Dictyosphaerium chlorelloides (Chlorophyceae) under lethal doses of 3-(3,4-dichlorophenyl)-1, 1-dimethylurea herbicide

Residues contribute to water pollution and pose a challenge to microalgal populations because numerous contaminants are toxic to microalgae, even in the micromolar range. Adaptation of microalgae from herbicide sensitivity to herbicide resistance was analysed by an ecological genetic approach, using the unicellular alga Dictyosphaerium chlorelloides (Chlorophyceae) as an experimental model. A dose–effect study showed that the Malthusian parameter under conditions of r selection in an uncrowded environment and the carrying capacity under conditions of K selection in an crowded environment were both restricted even by low concentrations (< 1 μM) of 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) herbicide. When a culture was treated with 50 μM DCMU, it cleared after a few days, as a result of destruction of sensitive cells by the herbicide. However, after further incubation for several days, the culture sometimes regained colour, owing to the growth of cell variants resistant to the herbicide. A fluctuation analysis was carried out to distinguish between (1) herbicide-resistant cells arising by direct and specific acquired adaptation in response to the herbicide and (2) herbicide-resistant cells arising by rare spontaneous mutations occurring randomly during replication of organisms prior to the incorporation of the herbicide. The fluctuation analysis unequivocally demonstrated that DCMU is not facilitating the development of DCMU-resistant cells; rather, we found that DCMU-resistant cells occur spontaneously by mutation in nonselective conditions prior to the incorporation of the herbicide (preselective mutations). The rate of spontaneous mutation from DCMU sensitivity to DCMU resistance was ∼ 2.2 × 10−6 mutants per cell division. Mutation was recurrent from a normal wild-type DCMU-sensitive allele to an DCMU-resistant allele, but such herbicide-resistant alleles were detrimental in terms of fitness in the absence of the herbicide. A competition experiment between wild-type DCMU-sensitive cells and DCMU-resistant mutants showed that, in small populations, the DCMU-resistant mutants are driven to extinction. The resistant variants are maintained in the absence of the herbicide as the result of a balance between new resistant cells arising by rare spontaneous mutation and resistant cells eliminated by natural selection. In our case, the average frequency of DCMU-resistant mutants in the absence of the DCMU is about five DCMU-resistant mutants per million cells. The results of our experimental model suggest that spontaneous mutation from herbicide sensitivity to herbicide resistance is sufficient in itself to assure the survival of microalgae populations in herbicide-contaminated environments when the population size is large.