The aim of this study was evaluate the effect of bioaugmentation by free and immobilized strains of microbial consortium on the phytoremediation of polychlorinated biphenyl (PCB)-contaminated soil using the Avena sativa, Brachiaria decumbens, Brassica juncea, and Medicago sativa plants. Alginate and biochar were used as carrier materials and free cells were used as the control. PCBs 44, 66, 118, 138, 153, 170, and 180 were chosen as indicator PCB congeners. After 60 days of plant growth, the concentration of each congener and the survival of the microbial inoculum were evaluated. The removal of the PCB congener was greater in B. juncea planted treatments and using biochar as a carrier material. PCB 66 was the congener with the highest removal percentage in all using biochar and alginate-immobilized microorganisms and free microorganisms, while PCB 170 had the lowest removal percentage in all treatments. The largest removal percentage for all congeners was obtained using biochar as a carrier material (7.2–30.3%) and the lowest with planted treatments using free microorganisms (2.3–6.8%). Real-time polymerase chain reaction (PCR) showed that the microbial inoculum survived when it was immobilized using both alginate and biochar without any significant differences between treatments; however, PCB removal percentages were obtained with biochar, which demonstrated that this carrier material has a positive effect on microbial activity.

In this work, we evaluate the abilities of the plants Brassica juncea, Avena sativa, Brachiaria decumbens, and Medicago sativa to uptake polychlorinated biphenyls (PCBs) and induce degradation of soil microorganisms from contaminated soil. Removal of PCBs 44, 66, 118, 153, 170, and 180 was evaluated in both rhizospheric and nonrhizospheric soils. Microbial and bphA1 gene quantifications were performed by real-time PCR. The PCB concentrations in plant tissues and soil were determined, and a fluorescein diacetate (FDA) hydrolysis assay was used to measure microbial activity in soil. The removal percentages for all PCB congeners in planted soil versus unplanted control soil were statistically significant and varied between 45% and 63%. PCBs 118, 153, 138, and 170 were detected in Brachiaria decumbens roots at different concentrations. In planted soil, an increase in the concentration of bacteria was observed compared to the initial concentration and the concentration in unplanted control soil; however, no significant differences were identified between plants. The number of copies of the bphA1 gene was higher in rhizospheric versus non- rhizospheric soil for all plants at the end of the experiment. However, alfalfa and oat rhizospheric soil showed significant differences in the copy number of the bphA1 gene. In general, the concentration of fluorescein in the rhizospheric soil was greater than that in the nonrhizospheric soil. Although the plants had a positive effect on PCB removal, this effect varied depending on the type of PCB, the plant, and the soil.

Polychlorinated biphenyls (PCBs) are toxic and persistent compounds that are difficult to break down and biodegrade. Plant secondary metabolites (PSMs) on root exudates can act as inducers of the biphenyl catabolic pathway, enhancing PCB biodegradation. In this study, the authors evaluated the effect of root exudates and PSMs obtained from Avena sativa, Brachiaria decumbens, Medicago sativa, and Brassica juncea on the biodegradation of PCB 44, PCB 66, PCB 118, PCB 138, PCB 153, PCB 170, and PCB 180 by a microbial consortium isolated from the rhizosphere of plants grown on soil contaminated with Aroclor 1260. Microorganisms were identified as Pseudomonas sp. and Stenotrophomonas sp. based on their 16S rRNA sequence. The plant root exudates increased the degradation percentage of PCB 44, PCB 66, and PCB 118, which were used as carbon source by the microorganisms. Flavanone, flavone, isoflavone, 7-hydroxyflavanone, 7-hydroxyflavone, and 6-hydroxyflavone were the PSMs identified in the root exudates, which increased the degradation percentage of all seven PCB congeners; they were also used as growth substrates by microbial consortium. These results showed the importance of the interaction between plants and microorganisms for achieving the removal of persistent pollutants such as PCBs from soil.

The textile industry is a generator of high volumes of waste water with a high content of pollutants such as azo dyes, which are recalcitrant and persistent in the environment, these ones have been of interest in the last decades for the entities in charge of the care of the environment. This study evaluated the ability to discolor of reactive black 5 (NR5) by a consortium and the microorganisms that constitute Rhodotorula mucilaginosa, Galactomyces pseudocandidum and Escherichia coli free and immobilized in calcium alginate, coffee husks and bagasse of sugar cane. The results show discoloration was evidenced, where the highest percentage corresponds to G. pseudocandidum (90,05%) and the lowest to R. mucilaginosa (79,31%). When comparing the percentages of discoloration between the free microorganisms and the immobilization matrices, it is observed that the former exhibit the highest percentages of discoloration. In addition, there are no significant differences between using cane bagasse or coffee husks as immobilization matrix.

Chlorpyrifos (CP) is a widely used organophosphorus insecticide that poses significant risks to soil health and ecosystem stability due to its persistence and toxicity. While traditional bioremediation using free-living bacteria has shown limitations, the immobilization of microbial consortia in biochar presents a promising solution. This study investigates the influence of biochar shape on CP degradation efficiency in contaminated soil using immobilized bacteria. Biochar in pellet (PL-BC) and chip (CH-BC) forms was used to immobilize two bacterial strains, Stenotrophomonas maltophilia (C4) and Xanthomonas sintii (C8), known for their CP-degrading capabilities. Results demonstrated that biochar in pellet form significantly enhanced the degradation efficiency, achieving a maximum removal rate of 82.61% when the bacterial consortium was immobilized in PL-BC, compared to 34.55% in CH-BC. The improved performance of the pellet biochar is attributed to its higher surface area and porosity, facilitating better microbial colonization and activity. These findings underscore the importance of biochar morphology in optimizing bioremediation processes and provide insights into sustainable approaches for managing pesticide-contaminated soils.

Cyanobacterial harmful algal blooms (CyanoHABs) in lentic, low tidal water bodies with high concentrations of easily assimilated nutrients have generated worldwide concern. However, CyanoHABs often formed from a variety of lesser-known taxa, such as nanocyanobacteria and picocyanobacteria, which are characterized as numerous and ubiquitous in diverse environments. Studies indicate that some taxa of picocyanobacteria can produce toxins. However, their identification through conventional methods is limited by their size and physiological plasticity, recently molecular methods have been chosen for more reliable results. this systematic review aims to summarize the results of original research articles on predominant picocyanobacteria in surface water bodies collected in indexed journal articles and gray literature. The methodology used consisted of searching for original publications in 3 specific databases and one general, using thesauri and free terms; the articles were filtered by previously defined inclusion and exclusion criteria. Thirty-four articles were selected and analyzed. The results show that the predominant picocyanobacteria in freshwater systems belong to the genus Synechococcus, reported in oligotrophic systems and capable of producing cyanotoxins. Likewise, from 2015 to 2019, the largest number of publications on this topic was obtained, mainly in countries such as China and the United States, which invest in research resources.