Biomedical subjects

José C Menezes

Publications and source records attributed to José C Menezes.

5 recordsLinked to original sources

PubMed2006

Fourier transform infrared (FT-IR) spectroscopy in bacteriology: towards a reference method for bacteria discrimination.

Rapid and reliable discrimination among clinically relevant pathogenic organisms is a crucial task in microbiology. Microorganism resistance to antimicrobial agents increases prevalence of infections. The possibility of Fourier transform infrared (FT-IR) spectroscopy to assess the overall molecular composition of microbial cells in a non-destructive manner is reflected in the specific spectral fingerprints highly typical for different microorganisms. With the objective of using FT-IR spectroscopy for discrimination between diverse microbial species and strains on a routine basis, a wide range of chemometrics techniques need to be applied. Still a major issue in using FT-IR for successful bacteria characterization is the method for spectra pre-processing. We analyzed different spectra pre-processing methods and their impact on the reduction of spectral variability and on the increase of robustness of chemometrics models. Different types of the Enterococcus faecium bacterial strain were classified according to chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis (PFGE). Samples were collected from human patients. Collected FT-IR spectra were used to verify if the same classification was obtained. In order to further optimize bacteria classification we investigated whether a selected combination of the most discriminative spectral regions could improve results. Two different variable selection methods (genetic algorithms (GAs) and bootstrapping) were investigated and their relative merit for bacteria classification is reported by comparing with results obtained using the entire spectra. Discriminant partial least-squares (Di-PLS) models based on corrected spectra showed improved predictive ability up to 40% when compared to equivalent models using the entire spectral range. The uncertainty in estimating scores was reduced by about 50% when compared to models with all wavelengths. Spectral ranges with relevant chemical information for Enterococcus faecium bacteria discrimination were outlined.

Bacterial Typing Techniques↗

PubMed2006

Improving drug manufacturing with process analytical technology.

Within the process analytical technology (PAT) framework, as presented in the US Food and Drug Administration guidelines, the aim is to design, develop and operate processes consistently to ensure a pre-defined level of quality at the end of the manufacturing process. Three PAT implementation scenarios can be envisaged. Firstly, PAT could be used in its most modest version (in an almost non-PAT manner) to simply replace an existing quality control protocol (eg, using near-infrared spectroscopy for an in-process quality control, such as moisture content). Secondly, the use of in-process monitoring and process analysis could be integrated to enhance process understanding and operation for an existing industrial process. Thirdly, PAT could be used extensively and exclusively throughout development, scale-up and full-scale production of a new product and process. Although the first type of implementations are well known, reports of the second and third types remain scarce. Herein, results obtained from PAT implementations of the second and third types are described for two industrial processes for preparing bulk active pharmaceutical ingredients, demonstrating the benefits in terms of increased process understanding and process control.

Calibration↗

PubMed2005

Monitoring complex media fermentations with near-infrared spectroscopy: comparison of different variable selection methods.

Near-infrared spectroscopy (NIRS) is known to be a suitable technique for rapid fermentation monitoring. Industrial fermentation media are complex, both chemically (ill-defined composition) and physically (multiphase sample matrix), which poses an additional challenge to the development of robust NIRS calibration models. We investigated the use of NIRS for at-line monitoring of the concentration of clavulanic acid during an industrial fermentation. An industrial strain of Streptomyces clavuligerus was cultivated at 200-L scale for the production of clavulanic acid. Partial least squares (PLS) regression was used to develop calibration models between spectral and analytical data. In this work, two different variable selection methods, genetic algorithms (GA) and PLS-bootstrap, were studied and compared with models built using all the spectral variables. Calibration models for clavulanic acid concentration performed well both on internal and external validation. The two variable selection methods improved the predictive ability of the models up to 20%, relative to the calibration model built using the whole spectra.

Algorithms↗

PubMed2005

Evaluation of a new annular capacitance probe for biomass monitoring in industrial pilot-scale fermentations.

The four-pin electrode capacitance probe has already shown to be a valuable tool for on-line monitoring viable biomass concentration in industrial-type fermentations. A new prototype annular probe was developed and its performance in real-time monitoring the concentration of viable cells during industrial pilot-scale fermentation for the production of an Active Pharmaceutical Ingredient (API) was investigated and compared to the four-pin probe. A set of 14 fermentations was monitored on-line: four of them with the four-pin probe, the remaining with the annular probe. The performance of both the annular and the four-pin electrode probe were compared against each other and against off-line measurements (viscosity and packed mycelial volume). The prototype annular probe showed to have higher signal intensity and sensitivity than the standard four-pin probe, with higher signal-to-noise ratio. Furthermore, its new design and construction proved to be easier to handle in an industrial environment.

Bioreactors↗

PubMedDate not supplied

Monitoring a complex medium fermentation with sample-sample two-dimensional FT-NIR correlation spectroscopy.

The possibility of monitoring state transitions during the time course of a fermentation through the analysis of the on-line collected near-infrared (NIR) spectra with sample-sample two-dimensional correlation spectroscopy (SS-2DCoS) was investigated. SS-2DCoS has proved to be useful for extracting process information directly from the spectra collected on-line. The complexity of the system studied prevented the extraction of concentration profiles, but nevertheless, the application of SS-2DCoS enables the identification of fermentation state transitions due to metabolic and morphological changes of the microorganism.

Cells, Cultured↗