ABSTRACT
Cobalt is an essential element, but its wide use in industry generates important environmental and biological problems. The present study explores theoretical and empirical models of a green process for cobalt {Co2+} bioaccumulation from aqueous solutions. Two Gram-positive Bacillus subtilis species, strains CECT 4522 and LMM (the latter a former laboratory isolate from wastewater samples, which was phylogenetically characterized for the present work), were selected among others as the best Co2+ accumulation systems. Mathematical models representing kinetic and steady-state conditions for discrete and large amounts of bacterial biomass were expanded. In this way, it was possible to theoretically calculate the amount of Co2+ retained on the outer cell wall layer and incorporated inside the cell at any time. Theoretical and empirical hyperbolic-type models were suitable to fit the experimental bioaccumulation data for discrete amounts of bacteria biomass. In addition, kinetic relationships between the amount of Co2+ accumulated and the time before (or after) reaching steady state were established for large amounts of bacterial biomass. Other kinetic approaches were also satisfactorily tested. The two Gram-positive bacteria assayed are promising agents for developing heavy metal removal systems from industrial waste.
Subject(s)
Biodegradation, Environmental , Cobalt , Green Chemistry Technology/methods , Models, Theoretical , Wastewater/chemistry , Water Pollutants, Chemical , Biomass , Cobalt/analysis , Cobalt/chemistry , Cobalt/isolation & purification , Gram-Positive Bacteria/chemistry , Gram-Positive Bacteria/metabolism , Water Pollutants, Chemical/analysis , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/isolation & purification , Water PurificationABSTRACT
Cocoa is naturally fermented in the field before the cocoa seeds are removed for processing. We assessed the dynamics of lactic acid bacteria during cocoa fermentation in Bahia, Brazil. During five days of fermentation, temperature and pH were measured and beans were collected for genomic DNA extraction every 12 h. The DNA was used as a template for amplification with Lac1-Lac2 and Lac3-Lac2 for denaturing gradient gel electrophoresis analyses. pH values ranged from 3.34 to 4.98, while the temperature varied from 23° to 50°C. Lac1-Lac2 primers permitted detection of 11 operational taxonomic units. Twenty-eight operational taxonomic units were obtained with the primer pair Lac3-Lac2. It was observed that there were variations between the numbers of operational taxonomic units throughout the process, probably because of changes in pH and temperature. The greatest similarity in amplified samples was obtained with the primers Lac3-Lac2.
