This work shows the results of the biosynthesis of silver nanoparticles using the microalga Chlorella sp, using growth media with different concentrations of glycerol, between 5%–20%, and different light and temperature conditions. The synthesis of nanoparticles was studied using supernatants and pellets from autotrophic, heterotrophic and mixotrophic cultures of the microalga. The presence of nanoparticles was verified by ultraviolet-visible spectroscopy and the samples showing the highest concentration of nanoparticles were characterized by scanning electron microscopy. The mixotrophic growth conditions favored the excretion of exopolymers that enhanced the reduction of silver and thus the formation of nanoparticles. The nanoparticles obtained presented predominantly ellipsoidal shape with dimensions of 108 nm × 156 nm and 87 nm × 123 nm for the reductions carried out with the supernatants of the mixotrophic cultures with 5% and 10% glycerol, respectively.
The Carthamus tinctorius, commonly known as safflower, is an annual plant with numerous branches and thorns from the Asteraceae family. For this experiment, three treatments were applied to the pots: humic acid, spirulina microalgae, and a mixture of both to analyze their bioactivation effects. These treatments were applied three times per week over the course of two weeks, with irrigation taking place every other day. The wet weight of the aerial parts of the harvested plants was measured and placed in liquid nitrogen, then stored in a freezer. Chlorophyll, carotenoids, proline, protein, phenol, antioxidants, and malondialdehyde were measured. The results show that several bioactivators significantly increased the growth, chlorophyll, carotenoids, protein, and proline of safflower plants when compared to the control. The three treatments reduced the antioxidant and malondialdehyde content significantly. In contrast to the control condition, the mixture of humic acid and spirulina microalgae, as well as humic acid alone, decreased the phenolic content. The findings demonstrated that humic acid and spirulina microalgae can serve as positive plant bioactivators for safflower by boosting its growth and reducing stress.
Modern agricultural production technologies based on the widespread use of pesticides and mineral fertilizers have largely solved the problem of providing the population with food, and at the same time have generated multiple ecological, medical and environmental problems, problems of environmentally friendly and biologically valuable food products, land rehabilitation, restoration of their fertility, etc. Therefore, the emergence of new classes of pesticides with different mechanisms of action, high selectivity and low toxicity for warm-blooded animals is very modern. Currently, the development and application of new plant protection products that are not toxic to humans and animals is of global importance. Priority is given to research aimed at creating plant protection products based on microorganisms and their metabolites, as well as the search for plant substances with potential pesticide activity. In this regard, the question arose of finding new safe fertilizers that can also be economically profitable for production on an industrial scale. One of the current trends in this industry is the use of green microalgae. In this regard, the purpose of our research is the possibility of cultivating green microalgae on phosphorus production waste. During the work, traditional and modern research methods in biology were used. As a result of the work, several problems can be solved, such as the disposal of industrial waste and the production of safe biological fertilizer.
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