The dynamic increase in the commercial application of antimicrobial derivatives of boronic acids, and potential impact of their presence in aquatic systems, supports the necessity to study the toxicity of these substances towards microorganisms of crucial meaning in the environment. One example of the mentioned derivatives is tavaborole (5-fluoro-substituted benzoxaborole), a pharmaceutical agent with antifungal activity. Cyanobacteria were used as model organisms, which are photoautotrophic prokaryotes, as representative aquatic bacteria and photoautotrophs associated with the plant kingdom. To the best of our knowledge, we investigated this issue for the first time. In order to recognize the under-stress response of those microorganisms, the concentration of photopigments—a key factor in the activity of photosynthetic apparatus—was measured spectrophotometrically. We found that the 3-piperazine bis(benzoxaborole) significantly suppressed the growth of halophilic and freshwater cyanobacteria, at a concentration 3.0 mM and 0.3 mM, respectively. Our results also showed that the tested substances at micromolar concentrations stimulated the growth of cyanobacteria, particularly in the freshwater strain Chroococcidiopsis thermalis. The tested substances acted with various strengths, depending on their structure and concentration; nevertheless, they had a greater influence on the synthesis of phycobiliproteins (e.g., lowered their concentration) than on the formation of chlorophyll and carotenoids.

Phycobiliproteins - colorful proteins produced by microalgae and cyanobacteria, owe their unique properties to prosthetic groups, which are open-chain tetrapyrroles. As they are produced in the biosynthesis process, phycobiliproteins possess special biotechnological potential also due to their useful physicochemical properties. A classic example is the use of these proteins - especially phycocyanin with an intense blue color - as natural dyes in the food, cosmetic and pharmaceutical industries. In the products to which they are added, they are responsible not only for color, but also for various biological activities, providing these products with additional values. In this category, the most frequently mentioned are the antioxidant properties of phycobiliproteins, which may be used in the treatment of neurodegenerative diseases, and the fluorescent properties, especially of phycoerythrin, which also predispose these proteins to use in biomedical research. The results of contemporary work on the acquisition and use of phycobiliproteins indicate that the key to the wider use of these substances is to understand the process of biosynthesis of individual groups of these colored proteins, as well as developing ways to effectively control their production. Due to the different physicochemical properties and biological activity of individual, structurally diverse phycobiliproteins, the specificity of the actions taken is extremely important in this case. Since there are real reasons to increase the scale of production of these substances by modifying the conditions of microalgae cultivation, we believe that obtaining larger amounts of specific phycobiliproteins in pure form will intensify the current use and open up new possibilities for the use of these valuable proteins.

Drug overuse harms the biosphere, leading to disturbances in ecosystems’ functioning. Consequently, more and more actions are being taken to minimise the harmful impact of xenopharmaceuticals on the environment. One of the innovative solutions is using biosorbents—natural materials such as cells or biopolymers—to remove environmental pollutants; however, this focuses mainly on the removal of metal ions and colourants. Therefore, this study investigated the biosorption ability of selected pharmaceuticals—paracetamol, diclofenac, and ibuprofen—by the biomass of the cyanobacteria Anabaena sp. and Chroococcidiopsis thermalis, using the LC-MS/MS technique. The viability of the cyanobacteria was assessed by determining photosynthetic pigments in cells using a UV–VIS spectrophotometer. The results indicate that both tested species can be effective biosorbents for paracetamol and diclofenac. At the same time, the tested compounds did not have a toxic effect on the tested cyanobacterial species and, in some cases, stimulated their cell growth. Furthermore, the Anabaena sp. can effectively biotransform DCF into its dimer.