Growth model and metabolic activity of brewing yeast biofilm on the surface of spent grains : a biocatalyst for continuous beer fermentation

In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate (Q_im) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble-column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (X_im_act) of the total immobilized biomass (X_im) was subsequently estimated at approximately X_im_act = 0.12 g_IB g_Cˉ¹ (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell-to-carrier adhesion and cell-to-cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (X_im_act) and the maximum attainable biomass load (X_im_max) was included into the model. Since the average biofilm thickness was estimated at ca. 10 μm, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble-column reactor. Good agreement between model simulations and experimental data was achieved.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/3541/2000

Bioresorbable phosphate glass microstructured optical fiber for simultaneous light and drug delivery

Biomedical needs have recently boosted the development of brand-new multifunctional and bioresorbable optical fibers, especially in the field of theranostics. Biocompatible fibers represent great tools for in-body monitoring, diagnostics, and photo-dynamic therapy, thanks to their ability to carry light and act as a drug delivery system in capillary form. Optical fibers are also convenient because of their production scalability since they can be drawn into kilometers starting from a single preform, thus limiting production costs. Furthermore, biocompatible optical fibers can be easily adapted to different applications since they can be well integrated into catheters and other medical instrumentations. In this scenario, calcium-phosphate glass (CPG) optical fibers are promising candidates, thanks to their enhanced thermo-mechanical features and biocompatibility. Moreover, their resorbability, as well as mechanical and optical properties, can be finely tuned by tailoring the specific glass composition. In the present work, we report on our latest results in this field starting from the full characterization of CPG optical fibers by means of in-vitro dissolution tests and in-vivo experiments. Dissolution tests in simulated body fluid revealed that a high amount of MgO can effectively decrease the dissolution time, while in-vivo experiments showed no inflammatory response in the tested animals. The possibility of tailoring the resorption time of the CPG fiber is a key factor in several applications where different operational times are needed, e.g. from few days to few months. In addition, we will show the application of a CPG-based multifunctional fiber to deliver a photosensitive drug and its activation by light carried with the same fiber. Finally, we will report on the design and fabrication of a bioresorbable microstructured CPG fiber by properly combining rotational casting and extrusion techniques

Active optical fibers doped with ceramic nanocrystals

Erbium-doped active optical fiber was successfully prepared by incorporation of ceramic nanocrystals inside a core of optical fiber. Modified chemical vapor deposition was combined with solution-doping approach to preparing preform. Instead of inorganic salts erbium-doped yttrium-aluminium garnet nanocrystals were used in the solution-doping process. Prepared preform was drawn into single-mode optical fiber with a numerical aperture 0.167. Optical and luminescence properties of the fiber were analyzed. Lasing ability of prepared fiber was proofed in a fiber-ring set-up. Optimal laser properties were achieved for a fiber length of 20~m. The slope efficiency of the fiber-laser was about 15%. Presented method can be simply extended to the deposition of other ceramic nanomaterials

Diagenesis of archaeological bone and tooth

An understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis. Here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date. Environmental factors such as soil pH, soil hydrology and ambient temperature, which influence the preservation of skeletal tissues are assessed, while the different diagenetic pathways such as microbial degradation, loss of organics, mineral changes, and DNA degradation are surveyed. Fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction. Diagenetic mechanisms are found to work in conjunction with each other, altering the biogenic composition of skeletal material. This illustrates that researchers must examine multiple diagenetic pathways to fully understand the post-mortem interactions of archaeological skeletal material and the burial environment

Optické senzory pro monitorování bioprocesů

The contribution presents results of the research of an optical glucose sensor. The detection of oxygen depletion caused by glucose oxidation under glucoseoxidase catalysis was used in the glucose sensors. Fluorescence quenching of ruthenium complexes by oxygen was used for the oxygen detection. The complexes and enzyme were immobilized in inorganic-organic ORMOCER membranes. Developed fiber-optic sensors enable to detect glucose in concentrations up to 3 mmol/L and with response times of about 20s