Biomedical subjects

M A M Reis

Publications and source records attributed to M A M Reis.

12 recordsLinked to original sources

PubMed2006

Microbial community analysis with a high PHA storage capacity.

Activated sludge was submitted to aerobic dynamic substrate feeding for the production of biodegradable plastics. Two sequencing batch reactors were operated with acetate or propionate as sole carbon substrates. With acetate a homopolymer of polyhydroxybutyrate (PHB) was obtained and with propionate a copolymer of hydroxybutyrate and hydroxyvalerate P(HB/HV) was produced. Three main morphotypes were identified in both sludges: two belong to the Alphaproteobacteria class and the third to the Betaproteobacteria class. Bacilli belonging to Betaproteobacteria were shown by FISH analysis, applied in combination with Nile Blue post-staining, to be the main responsible for PHAs storage. The latter were affiliated to Azoarcus genus within Betaproteobacteria.

Alkanes↗

PubMed2005

Biodegradation of thiomersal containing effluents by a mercury resistant Pseudomonas putida strain.

Thiomersal, a toxic organomercurial with a strong bactericidal effect, is the most widely used preservative in vaccine production. As a result, vaccine production wastewaters are frequently polluted with thiomersal concentrations above the European limit for mercury effluent discharges for which there is, presently, no remediation technology available. This work proposes a biotechnological process for the remediation of vaccine production wastewaters based on the biological degradation of thiomersal to metallic mercury, under aerobic conditions, by a mercury resistant bacterial strain. The kinetics of thiomersal degradation by a pure culture of Pseudomonas putida spi3 was firstly investigated in batch reactors using a thiomersal amended mineral medium. Subsequently, a continuous stirred tank reactor fed with the same medium was operated at a dilution rate of 0.05 h(-1), and the bioreactor performance and robustness was evaluated when exposed to thiomersal shock loads. In a second stage, the bioreactor was fed directly with a real vaccine wastewater contaminated with thiomersal and the culture ability to grow in the wastewater and remediate it was evaluated for dilution rates ranging from 0.022 to 0.1 h(-1).

Biodegradation, Environmental↗

PubMed2005

Modelling of the extractive membrane bioreactor process based on natural fluorescence fingerprints and process operation history.

A method for non-mechanistic and non-linear modelling of complex biological processes is presented, using the example of the extractive membrane bioreactor (EMB). The model is based on artificial neural networks (ANN), which are able to predict the state of the process from a combination of reactor operational parameters and natural fluorescence fingerprints. Current as well as historic process operation is included in the ANN input vector, in order to account for lag-times within the reactor system and for biofilm dynamics that are dependent on process history. The model is especially relevant for practitioners, as it does not require assumptions on underlying process mechanisms, and it relies on routinely available operational data and on an easy-to-install, non-invasive, in-situ, on-line monitoring method. Moreover, it focuses on the prediction of overall process performance parameters, which are of immediate relevance in practice. The developed model was able to predict the process state very well. Sensitivity analysis revealed that the main impact on process performance stems from process operation rather than the physiological state of the biological culture, and that in the EMB configuration employed process operation history decisively impacts on the process outcome.

Biofilms↗

PubMed2004

Fuzzy expert system in the prediction of neonatal resuscitation.

In view of the importance of anticipating the occurrence of critical situations in medicine, we propose the use of a fuzzy expert system to predict the need for advanced neonatal resuscitation efforts in the delivery room. This system relates the maternal medical, obstetric and neonatal characteristics to the clinical conditions of the newborn, providing a risk measurement of need of advanced neonatal resuscitation measures. It is structured as a fuzzy composition developed on the basis of the subjective perception of danger of nine neonatologists facing 61 antenatal and intrapartum clinical situations which provide a degree of association with the risk of occurrence of perinatal asphyxia. The resulting relational matrix describes the association between clinical factors and risk of perinatal asphyxia. Analyzing the inputs of the presence or absence of all 61 clinical factors, the system returns the rate of risk of perinatal asphyxia as output. A prospectively collected series of 304 cases of perinatal care was analyzed to ascertain system performance. The fuzzy expert system presented a sensitivity of 76.5% and specificity of 94.8% in the identification of the need for advanced neonatal resuscitation measures, considering a cut-off value of 5 on a scale ranging from 0 to 10. The area under the receiver operating characteristic curve was 0.93. The identification of risk situations plays an important role in the planning of health care. These preliminary results encourage us to develop further studies and to refine this model, which is intended to implement an auxiliary system able to help health care staff to make decisions in perinatal care.

Adolescent↗

PubMed2004

Polyhydroxyalkanoates production by activated sludge in a SBR using acetate and propionate as carbon sources.

In this work, sludge was submitted to aerobic dynamic substrate feeding. Two sequencing batch reactors were operated, with acetate or propionate as carbon substrates. When acetate was used the system only produced a homopolymer of polyhydroxybutyrate (PHB). In order to maximize the PHB production, tests with different concentrations of acetate and ammonia were preformed. The best results (67.2% of PHB by cell dry weight) were obtained for 0.7 Nmmol/l of ammonia and 180 Cmmol/l of acetate. The PHB cell content was further improved by pulse addition of substrate, three times 60 Cmmol/l of acetate, reaching a value of 78.5%. Propionate can be used as a precursor for hydroxyvalerate. In conjunction with other substrates, it allows for the formation of copolymers, which present better processing properties on commercial applications. Tests with different concentrations of propionate and ammonia were performed. Under the operating conditions used, the maximum PHA accumulated inside cells was 34.8%, with 30 Cmmol/l of propionate and no ammonia.

Acetates↗

PubMed2003

Production of polyhydroxyalkanoates by mixed microbial cultures.

Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics formed from renewable resources, like sugars, with similar characteristics of polypropylene. These bioplastics are industrially produced by pure cultures using expensive pure substrates. These factors lead to a much higher selling price of PHAs compared to petroleum-based plastics, like polypropylene. The use of mixed cultures and cheap substrates (waste materials) can reduce costs of PHA production by more than 50%. Storage of PHAs by mixed populations occurs under transient conditions mainly caused by discontinuous feeding and variation in the electron donor/acceptor presence. In the last years the mechanisms of storage, metabolism and kinetics of mixed cultures have been studied. The maximum capacity of PHA storage and production rate is dependent on the substrate and on the operating conditions used. In this paper an overview and discussion of various mechanisms and processes for PHA production by mixed cultures is presented.

Journal Article↗

PubMed2003

Monitoring of biofilm reactors using natural fluorescence fingerprints.

Natural fluorescence as a method to monitor biofilm processes was studied, using the example of an extractive membrane bioreactor for the degradation of 3-chloro-4 methylaniline and 1,2-dichloroethane. Non-invasive, on-line, in-situ 2D fluorometry monitoring was employed to elicit biofilm process status. The fluorescence fingerprints were deconvoluted in a pattern recognition approach using artificial neural networks (ANN) through association with key process performance parameters.

Biofilms↗

PubMed2003

Nutrient removal in a sequencing batch reactor operated with short anaerobic/aerobic cycles.

A single sequencing batch reactor operated with short intermittent aeration cycles was used to simultaneously remove carbon, nitrogen and phosphorus. The complete cycle, comprising feeding, anaerobiosis, aerobiosis, settling and decanting, was only 36 minutes long. The system has shown high and stable nutrient removal at 30 degrees C with acetate as carbon source and it has proved to be rather robust and dynamic, efficiently adapting to most of the changes in operating parameters tested: presence of nitrate in the feeding medium, different substrates (propionate and butyrate), temperature and nutrient shock loads. For the optimum conditions used, a removal efficiency of over 90% was obtained for each nutrient. Description of the population kinetics was obtained for each operating condition, by performing batch tests. Kinetic and stoichiometric parameters were used to infer the relative contribution of each group of microorganisms on SBR performance. Compared to the traditional SBR operated with cycles of 6 hours, the use of short intermittent aeration cycles of 36 minutes corresponds to a 40% reduction on aeration time.

Aerobiosis↗

PubMed2003

Production of polyhydroxyalkanoates by a mixed culture in a sequencing batch reactor: the use of propionate as carbon source.

In this work, sludge adapted to anaerobic/aerobic conditions, AN/AE, showing a high capacity of P accumulation, was submitted to aerobic dynamic substrate feeding (ADF). The fermenter was operated as a Sequencing Batch Reactor, with propionate as carbon substrate. Propionate is an important waste product from several industrial processes that can be valued, using it as a precursor for hydroxyvalerate in PHA production. Under the operational conditions used, apart from 3-hydroxyvalerate as its major component, 3-hydroxy-2-methylvalerate, 2-hydroxyisovalerate and 4-oxovalerate were also produced. A second reactor operated under the same conditions was adapted for the use of acetate as carbon substrate. The global metabolism of the organisms involved on PHA production, utilizing acetate or propionate, was studied using in vivo 13C Nuclear Magnetic Resonance (NMR).

Alkanes↗

PubMed2002

Hydrogen metabolism in Desulfovibrio desulfuricans strain New Jersey (NCIMB 8313)--comparative study with D. vulgaris and D. gigas species.

This article aims to study hydrogen production/consumption in Desulfovibrio (D.) desulfuricans strain New Jersey, a sulfate reducer isolated from a medium undergoing active biocorrosion and to compare its hydrogen metabolism with two other Desulfovibrio species, D. gigas and D. vulgaris Hildenborough. Hydrogen production was followed during the growth of these three bacterial species under different growth conditions: no limitation of sulfate and lactate, sulfate limitation, lactate limitation, pyruvate/sulfate medium and in the presence of molybdate. Hydrogen production/consumption by D. desulfuricans shows a behavior similar to that of D. gigas but a different one from that of D. vulgaris, which produces higher quantities of hydrogen on lactate/sulfate medium. The three species are able to increase the hydrogen production when the sulfate became limiting. Moreover, in a pyruvate/sulfate medium hydrogen production was lower than on lactate/sulfate medium. Hydrogen production by D. desulfuricans in presence of molybdate is extremely high. Hydrogenases are key enzymes on production/consumption of hydrogen in sulfate reducing organisms. The specific activity, number and cellular localization of hydrogenases vary within the three Desulfovibrio species used in this work, which could explain the differences observed on hydrogen utilization.

Journal Article↗

PubMed2002

Change in metabolism of PHA accumulation by activated sludge modifying operating conditions.

In the present work, sludge from a stable and efficient phosphorus removal process was used to evaluate the change in the metabolism when the reactor operation was modified from anaerobic/aerobic to aerobic dynamic substrate feeding. The change in operational conditions allowed the population to modify the metabolism of phosphorus and polyhydroxyalkanoates (PHA) accumulation. Under aerobic dynamic feeding, phosphorus accumulation was almost hindered while the amount of PHA accumulation increased significantly. After ten days of operation under dynamic substrate feeding, the reactor operation turned back to anaerobic/aerobic cycles and the metabolism of phosphorus was progressively recovered.

Bacteria, Aerobic↗

PubMed2002

Effect of pH control on EBPR stability and efficiency.

Biological phosphorus removal from water surfaces is an important process for the control of eutrophication. Even though much attention has been devoted to understanding the metabolism of bacteria and the effect of operational parameters on the efficiency of the phosphorus removal process, certain aspects are still unclear. The aim of this work was to evaluate the influence of pH control on the stability and efficiency of two sequenced batch reactors (SBR): one operated with pH control (pH 7.0) and the other without pH control (pH raised from around 7.8 to 8.5). The reactor operated without pH control showed higher efficiency on phosphorus removal and stability than the reactor with pH control. Based on the kinetics of both reactors it could be inferred that a different population developed in both systems.

Bacteria↗