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Biodecolorization and biodegradation of azo dyes are a challenge due to their recalcitrance and the characteristics of textile effluents. This study presents the use of Halomonas sp. in the decolorization of azo dyes Reactive Black 5 (RB5), Remazol Brilliant Violet 5R (RV5), and Reactive Orange 16 (RO16) under high alkalinity and salinity conditions. Firstly, the effect of air supply, pH, salinity and dye concentration was evaluated. Halomonas sp. was able to remove above 84% of all dyes in a wide range of pH (6-11) and salt concentrations (2-10%). The decolorization efficiency of RB5, RV5, and RO16 was found to be ≥ 90% after 24, 13 and 3 h, respectively, at 50 mg L-1 of dyes. The process was monitored by HPLC-DAD, finding a reduction of dyes along the time. Further, Halomonas sp. was immobilized in volcanic rocks and used in a packed bed reactor for 72 days, achieving a removal rate of 3.48, 5.73, and 8.52 mg L-1 h-1, for RB5, RV5 and RO16, respectively, at 11.8 h. The study has confirmed the potential of Halomonas sp. to decolorize azo dyes under high salinity and alkalinity conditions and opened a scope for future research in the treatment of textile effluents.

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Background Osmolytes with their effective stabilizing properties are accumulated as protectants not only against salinity but also against denaturing harsh environmental stresses such as freezing, drying, high temperatures, oxygen radicals and radiation. The present work seeks to understand how Halomonas sp. AAD12 cells redirect carbon flux specifically to replenish reactions for biomass and osmolyte synthesis under changing salinity and temperature. To accomplish this goal, a combined FBA-PCA approach has been utilized. Results Experimental data were collected to supply model constraints for FBA and for the verification of the model predictions, which were satisfactory. With restrictions on the various combinations of selected anaplerotic paths (reactions catalyzed by phosphoenolpyruvate carboxylase, pyruvate carboxylase or glyoxylate shunt), two major phenotypes were found. Moreover, under high salt concentrations, when the glucose uptake rate was over 1.1 mmoL DCW- 1 h- 1, an overflow metabolism that led to the synthesis of ethanol caused a slight change in both phenotypes. Conclusions The operation of the glyoxylate shunt as the major anaplerotic pathway and the degradation of 6-phosphogluconate through the Entner-Doudoroff Pathway were the major factors in causing a distinction between the observed phenotypes.

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Este trabajo tuvo como propósito contribuir al conocimiento de la interacción entre la cianobacteria alcalófila Arthrospira platensis y las bacterias que crecen asociadas a su mucilago. Se desarrolló un medio de cultivo heterotrófico en el cual se aislaron cinco cepas bacterianas asociadas a un monocultivo de A. platensis. Se determinó la capacidad de estas cinco cepas para producir ácido 3- indol acético (AIA). La tipificación molecular de los aislamientos bacterianos permitió identificarlos como Exiguobacterium aurantiacum str. DSM 20416, Xanthomonas sp. ML-122, Halomonas sp. Ap-5, Bacillus okhensis str. Kh10-101, Indibacter alkaliphilus, type str. LW1T; todas las cepas bacterianas obtenidas son halotolerantes, alcalófilas y productoras de AIA. Los resultados aportan evidencia para sugerir una interacción benéfica entre A. platensis y sus bacterias asociadas, quizá como estrategia evolutiva de cooperación para desarrollarse en un ambiente hipersalino.

The aim of this study was contribute to knowledge over alkalophilic cianobacteryum Arthrospira platensis and their interaction with some associated bacteria growing in their mucilage. Heterotrophic culture medium was designed, in this medium were isolated five bacterial strains associated to single culture of A. platensis. It was measured the 3-indol acetic acid (IAA) production by these bacterial strains. Molecular typing allowed identify these bacterial strains like Exiguobacterium aurantiacum str. DSM 20416, Xanthomonas sp. ML-122, Halomonas sp. Ap-5, Bacillus okhensis str. Kh10-101, Indibacter alkaliphilus, type str. LW1T; all these bacteria are halotolerant, alkalophilic and IAA producer. The findings allow suggest a beneficial interaction between A. platensis and their associated bacteria, maybe as evolutionary strategy of cooperation to grow and develop in hypersaline environments.

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