RESUMO
The inclusion of S0 hydrolysis in a kinetic model of autotrophic denitrification has been recently proposed; however the model has not been calibrated or validated yet. Thus, a new methodology was developed and applied to calibrate and validate this kinetic model for the first time. An inoculum adapted from a poultry wastewater treatment plant at stoichiometric S0/NO3- ratio was used. The model was calibrated with batch data (initial nitrate concentrations of 50 and 6.25 mg NO3--N/L) at an S0/N ratio = 2.29 mg S/mg N and validated with seven different batch data. The sensitivity analysis showed that the most sensitive parameters are related to S0 hydrolysis. The kinetic model was successfully calibrated with the new methodology and validated, with Theil inequality coefficient values lower than 0.21. Thus, the proposed model and methodology were proved to be well suited for the simulation of elemental sulfur-based autotrophic denitrification in batch systems.
Assuntos
Reatores Biológicos , Desnitrificação , Processos Autotróficos , Calibragem , Nitratos , EnxofreRESUMO
We have cloned a cDNA that encodes a novel Xenopus laevis oocyte adenylyl cyclase (xlAC) using oligonucleotides against conserved mammalian adenylyl cyclase regions. The isolated cDNA is 4372 bp long with an open reading frame of 4065 nucleotides which encodes a protein of 1355 amino acids. Comparison of the deduced amino acid sequence with previously cloned mammalian adenylyl cyclases shows a low identity, 19.7% with type 2 rat adenylyl cyclase and 24.2% with type 4 rat adenylyl cyclase, indicating that this Xenopus isoform represents a new member of this protein family. Gene expression studies of the xlAC by reverse PCR showed that this gene is expressed in all oogenesis stages but not during early embryogenesis. Expression of the xlAC in COS-7 cells resulted in increased basal AC activity, that was stimulated by forskolin, Gpp(NH)p and aluminium fluoride, and was insensitive to calcium and calcium-calmodulin (Ca2(+)-CaM).
