Ruben Ferreira Jorge

Extraction and characterisation of apatite- and tricalcium phosphate-based materials from cod fish bones

Apatite- and tricalcium phosphate-based materials were produced from codfish bones, thus converting a waste by-product from the food industry into high added-valued compounds. The bones were annealed at temperatures between 900 and 1200 °C, giving a biphasic material of hydroxyapatite and tricalcium phosphate (Ca10(PO4)6(OH)2 and β-Ca(PO4)3) with a molar proportion of 75:25, a material widely used in biomedical implants. The treatment of the bones in solution prior to their annealing changed the composition of the material. Single phase hydroxyapatite, chlorapatite (Ca10(PO4)6Cl2) and fluorapatite (Ca10(PO4)6F2) were obtained using CaCl2 and NaF solutions, respectively. The samples were analysed by several techniques (X-ray diffraction, infrared spectroscopy, scanning electron microscopy and differential thermal/thermogravimetric analysis) and by elemental analyses, to have a more complete understanding of the conversion process. Such compositional modifications have never been performed before for these materials of natural origin to tailor the relative concentrations of elements. This paper shows the great potential for the conversion of this by-product into highly valuable compounds for biomedical applications, using a simple and effective valorisation process.

Enrichment of microbial cultures able to degrade 1,3-dichloro-2-propanol : a comparison between batch and continuous methods

Microbial cultures able to degrade xenobiotic compounds are the key element for biological treatment of waste effluents and are obtained from enrichment processes. In this study, two common enrichment methods, suspension batch and immobilized continuous, were compared. The main selection factor was the presence of 1,3-dichloro-2-propanol (1,3-DCP) as the single carbon source. Both methods have successfully enriched microbial consortia able to degrade 1,3-DCP. When tested in batch culture, the degradation rates of 1,3-DCP by the two consortia were different, with the consortia obtained by batch enrichment presenting slightly higher rates. A preliminary morphological and biochemical analysis of the predominant colonial types present in each degrading consortia revealed the presence of different constituting strains. Three bacterial isolates capable of degrading 1,3-DCP as single strains were obtained from the batch enrichments. These strains were classified by 16S rRNA analysis as belonging to the Rhizobiaceae group. Degradation rates of 1,3-DCP were lower when single species were used, reaching 45 mg l-1 d-1, as compared to 74 mg l-1 d-1 of the consortia enriched on the batch method. Mutualistic interactions may explain the better performance of the enriched consortia.

Microbial dynamics in a continuous stirred tank bioreactor exposed to an alternating sequence of organic compounds

Microbial dynamics during aerobic biodegradation of an alternating mixture of organic compounds was investigated experimentally in a continuous stirred tank bioreactor (CSTB). A mathematical model describing this system was developed and tested using the experimental results. A model microbial culture consisting of Pseudomonas sp. JS150, a monochlorobenzene (MCB) degrader, and Xanthobacter autotrophicus GJ10, a 1,2-dichloroethane (DCE) degrader, each with exclusive degradation capabilities, was used. The CSTB was inoculated with both microbial strains and exposed to an alternating sequence of the two compounds at noninhibitory concentrations. Concentrations of each microbial strain, of each organic compound, and of degradation product evolved, as well as specific microbial activities via oxygen uptake tests, were monitored. Reduction of the residual DCE discharged from the bioreactor after an MCB to DCE transition was successfully achieved by continuously feeding a low flow of a concentrated solution of both compounds.

Biological treatment of an alternating source of organic compounds in a single tube extractive membrane bioreactor

The performance of a single tube extractive membrane bioreactor (STEMB) exposed to an alternating sequence of toluene (TOL) and dichloromethane (DCM) was investigated. These compounds are two of the most commonly used solvents in the chemical and pharmaceutical industries, and so were used to simulate the scenario of sequentially alternating pollutants. Undefined microbial cultures were used. During experiments, no TOL accumulation was detected in the STEMB. It may be possible that a commensal microbial relationship developed in the system, which maintained the microbial culture responsible for TOL degradation active throughout experiments. On the other hand, accumulation of DCM was detected whenever this compound was introduced. These accumulations resulted in a transient decrease in the removal efficiency of the STEMB. The influence of the membrane-attached biofilm in decreasing DCM discharges was shown. Investigations into the use of an additional carbon source to improve the system response were carried out during critical periods of operation, eg start-up and starvation periods. This strategy proved a successful tool in reducing DCM discharges.