Motivación:  ferrous  iron  oxidation  can  take  place  in  partly  controlled  biological  reactors  inoculated  with  mixed  cultures  of  acidophilic  microorganisms.  In  these  bioreactors,  liquor  pH  can affect  productivity.  We  aimed  at  determining  whether  productivity changes are directly due to the chemistry of iron precipitation or due to microbial population changes

Mazuelos Rojas, Alfonso

Villalobo Polo, Eduardo

English

idUS. Depósito de Investigación Universidad de Sevilla

Biosaia (revista de los másteres de Biotecnología Sanitaria y Biotecnología Ambiental, Industrial y Alimentaria de la UPO) nº4 (march de 2016) http://www.bioinfocabd.upo.es/biosaia/  @Biosaia 1 Talk Microbial Populations in Ferrous Iron Oxidation Bioreactors Eduardo Villalobo (1) y Alfonso Mazuelos(2) (1) Departmento de Microbiología/Universidad de Sevilla, Av Reina Mercedes, 41012 Sevilla. (2) Departmento de Ingeniería Química/Universidad de Sevilla, Av Reina Mercedes, 41012 Sevilla. Keywords: ferrous iron biooxidation, bioreactor, acidophiles   ABSTRACT Motivación: ferrous iron oxidation can take place in partly controlled biological reactors inoculated with mixed cultures of acidophilic microorganisms. In these bioreactors, liquor pH can affect productivity. We aimed at determining whether productivity changes are directly due to the chemistry of iron precipitation or due to microbial population changes. Methods: flooded (with 9K standard medium) packed-bed (randomly packed with siliceous stone particles between 6 and 8 mm in size; 0.42 porosity) bioreactors (cylinders 4.32 cm in diameter and 10 cm in height) were operated in continuous mode, with controlled temperature (310C), fed at constant liquid flow rate (100 mL/h), and constantly aerated with two different air-flow rates (250 and 500 mL/min). Liquor inlet pH in bioreactors was change in the range 1.9-0.8. Outlet pH was measured with a standard pH-meter and ferric iron productivities (g/h) were measured in an automatic titrator using the standard potassium dichromate method. Microbial identification was done by phylogenetic analyses of 16S rRNA sequences obtained after PCR, cloning, transformation, and sequencing. Results and conclusions: Operation pH does not affect bioreactor productivity in the range from 1 to 2.3. Falls in productivity are essentially due to ferric iron precipitation chemistry. If upper pH limit is exceed, productivity can be recovered lowering pH; conversely, if lower pH limit is exceed, productivity never recovers though pH is increased. The microbial population of the bioreactor changes with changes in pH, being 1.3 the pH transition value. Above pH 1.3 acidithiobacilli are the dominant microorganisms, while below pH 1.3 leptospirilli are the dominant ones. Thus, we conclude that the microbial population inside the bioreactor behave in a highly versatile manner, allowing productivity to remains virtually unchanging. The versatility turns this kind of bioreactor into a highly flexible platform for ferrous iron oxidation; stepwise pH changes can result into perfectly adapted microbial populations, the basis to treat industrial influent liquor at different pHs. This kind of bioreactor and operation mode has been successfully applied at semi-industrial scale. REFERENCES Mazuelos,A. et al. (2012) Biotic factor does not limit operational pH in packed-bed bioreactor for ferrous iron biooxidation. J. Ind. Microbiol. Biotechnol., 39, 1851–1. Mazuelos,A. et al. (2010) Operational pH in packed-bed reactors for ferrous ion bio-oxidation. Hydrometallurgy, 104, 186–192. Rawlings,D.E. (2002) Heavy metal mining using microbes. Annu. Rev. Microbiol., 56, 65–91 Norris,P.R. et al. (2000) Acidophiles in bioreactor mineral processing. Extremophiles, 4, 71–76    

Microbial Populations in Ferrous Iron Oxidation Bioreactors

Motivación: ferrous iron oxidation can take place in partly controlled biological reactors inoculated with mixed cultures of acidophilic microorganisms. In these bioreactors, liquor pH can affect productivity. We aimed at determining whether productivity changes are directly due to the chemistry of iron precipitation or due to microbial population changes.Methods: flooded (with 9K standard medium) packed-bed (randomly packed with siliceous stone particles between 6 and 8 mm in size; 0.42 porosity) bioreactors (cylinders 4.32 cm in diameter and 10 cm in height) were operated in continuous mode, with controlled temperature (310C), fed at constant liquid flow rate (100 mL/h), and constantly aerated with two different air-flow rates (250 and 500 mL/min). Liquor inlet pH in bioreactors was change in the range 1.9-0.8. Outlet pH was measured with a standard pH-meter and ferric iron productivities (g/h) were measured in an automatic titrator using the standard potassium dichromate method. Microbial identification was done by phylogenetic analyses of 16S rRNA sequences obtained after PCR, cloning, transformation, and sequencing.Results and conclusions: Operation pH does not affect bioreactor productivity in the range from 1 to 2.3. Falls in productivity are essentially due to ferric iron precipitation chemistry. If upper pH limit is exceed, productivity can be recovered lowering pH; conversely, if lower pH limit is exceed, productivity never recovers though pH is increased. The microbial population of the bioreactor changes with changes in pH, being 1.3 the pH transition value. Above pH 1.3 acidithiobacilli are the dominant microorganisms, while below pH 1.3 leptospirilli are the dominant ones. Thus, we conclude that the microbial population inside the bioreactor behave in a highly versatile manner, allowing productivity to remains virtually unchanging. The versatility turns this kind of bioreactor into a highly flexible platform for ferrous iron oxidation; stepwise pH changes can result into perfectly adapted microbial populations, the basis to treat industrial influent liquor at different pHs. This kind of bioreactor and operation mode has been successfully applied at semi-industrial scale

Villalobo, Eduardo

Mazuelos, Alfonso

Revistas UPO (Universidad Pablo de Olivade)

https://idus.us.es/bitstream/11441/96826/1/B_mazuelos-rojas_2016_microbial.pdf

Microbial Populations in Ferrous Iron Oxidation Bioreactors

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