Autor(es):
Silva, J. S. 
; Castro, C. C. ; Mendes, Inês ; Duarte, Ricardo Franco ; Vicente, A. A. ; Schuller, Dorit ; Martins, Rui C.
Data: 2011
Identificador Persistente: http://hdl.handle.net/1822/16001
Origem: RepositóriUM - Universidade do Minho
Assunto(s): Spectroscopy; Fiber optics; Fermentation; Wine
Descrição
Spectroscopy is widely used in biological sciences, being applied to liquids, pastes, powders, films, fibers, gases and surfaces. It makes possible to characterize proteins, peptides, lipids, membranes and carbohydrates in pharmaceuticals, foods, plants or animal tissues. It can also provide detailed information about the structure and mechanism of action of molecules.
UV-VIS-SWNIR spectroscopy has not been used for fermentations characterization. This is possibly attributed to the fact that UV-VIS spectroscopy records transmissions between electron energy levels from molecular orbitals, which do not have a direct relationship with the presence/concentration of compounds, instead of vibrational or structural oscillation of molecular groups as in the infrared region, where such relationship is more straightforward. UV-VIS-SWNIR spectroscopy registers many features such as fluorescence and vibrational resonances due to energy decay of exited electrons, which may provide highly accurate fingerprinting of metabolites and metabolic state of the fermentation, provided that an adequate data treatment and interpretation system is available.
In this work we explore the use of fiber optics UV-VIS-SWNIR spectroscopy to characterize wine fermentations of a Saccharomyces cerevisiae collection. This collection comprises 114 strains (among which almost 40 are sequenced strains), between industrial strains used for winemaking, brewing, bakery, distillery (sake, cachaça) and ethanol production, natural isolates obtained in winemaking environments, and also strains from particular environments (e.g. pathogenic strains, isolates from insects, fruits and oak exudates).
Individual fermentations were carried out in 100 mL wine (cv. Loureiro) must for each of the 114 strains, and the growth rate, CO2 release and glucose concentration were followed throughout fermentation. When glucose concentration was below 5 g/L, cells were collected and immediately frozen and stored for fiber optics spectroscopy analysis.
Transmittance fiber optics UV-VIS-SWNIR spectroscopy was used to record the spectra between 200 and 1200 nm, using a highly sensitive scientific-grade spectrometer (Ocean Optics, QE65000) for maximum resolution. The procedure was performed in a special probe container designed to isolate the environmental light and maintain the probe horizontally, to prevent the deposition of debris in the mirrored surface. The following experimental procedure was performed: spectra were obtained at room temperature at previously stabilized (20 min) light sources; dark spectra were recorded and measurements were taken with linear and electric dark correction. Light spectra were statistically monitored, assessing the reproducibility of the light source by regular light measurements. Twenty spectra replicates were recorded for each fermentation.
Results show that after appropriate preprocessing and signal classification, fiber optics UV-VIS-SWNIR spectroscopy is a robust technique for characterize different wine fermentations, being able to characterize and differentiate the fermentation of different strains of S. cerevisiae based on their origins, by each spectroscopic fingerprinting.
This technique associated with other physico-chemical information can benefit the creation of an information system capable of providing extremely detailed information about physical processes and molecular biology that will aid both scientists and engineers to study and develop new biotechnological products.
