Atrazine is a triazine organochlorine herbicide used commonly in some countries like Mexico, however it is hazardous for human, vegetable and animal life. Atrazine reaches groundwater drinking sources, causing serious illnesses in the population. Understanding the mineralized atrazine biodegradation process is a crucial issue in dealing with soils containing atrazine. Bioremediation of soil and water contamination involves a complex interplay between mass transport and biological processes. Soil adsorption, solubility, and interfacial transport limit the availability of contaminants to microorganisms. This review summarizes the recent studies about metabolic pathways and enzymes to degrade atrazine to carbon dioxide, ammonia, water and biomass carried out by some bacteria and fungi species. The biodegradation of atrazine was analyzed, considering the different metabolic pathways of bacteria and fungi. Biodegradation of atrazine by bacteria is well studied, but the fungal metabolism of this compound remains less clear. Some species of white-rot fungi can naturally biodegrade complex compounds, such as lignin, an aromatic polymer that is a major component of plant cell walls. The lignin has a polyphenolic structure that presents similarities with many aromatic pollutants and herbicides like atrazine. A deep understanding of the mechanisms involved is a successful tool for the design of new strategies for biodegrading. A comparison of the rates of degradation between physicochemical and biological processes is included, and some recommendations for the microorganism species and conditions.

Cellulose can be used to produce biofuels and many other products like pharmaceutical goods, food supplements, cosmetics, bio-plastics, etc. Lignocellulosic materials, like O . ficus indica residuals, are a heterogeneous biopolymer formed mainly by lignin, hemicellulose and cellulose. Lignin provides protection to the plants against chemical and microbial degradation, but it can be degraded by white rot fungi species, like Pycnoporus cinnabarinus . Since cellulose molecules are arranged in regular bundles enveloped by hemicellulose and lignin molecules, it is necessary to brake lignin and hemicellulose molecules to recover cellulose for its use in bioprocess. In this work, a biotechnological process for cellulose recovery from cactus waste through depolymerization of lignin by P . cinnabarinus , is presented. The delignification is carried out by aerobic culture in batch stirred bioreactors, with a liquid culture medium enriched with nutrients and minerals with O . ficus indica residuals as the unique carbon source, during eight-day span under continuous feeding of oxygen. A factorial design of experiments (DOE) for eight sets of factor values was selected for this study. The factors were: particle size, pH level, and process temperature. For each experiment, biomass, total reducing carbohydrates (TRC) and dissolved oxygen (DO) concentrations were measured every 24 h. At the end of each experiment, the percentage of delignification, and cellulose recovery was measured by Infrared (IR) spectroscopy. Up to 67% of delignification and 22% of cellulose recovery were obtained by the process. These results were analyzed by a factorial DOE in order to maximize each response individually and to optimize both responses together. The delignification of Opuntia ficus indica thorns has not been previously reported to our knowledge.