Near-infrared spectroscopy: a tool for monitoring submerged fermentation processes using an immersion optical-fiber probe

Near-infrared (NIR) spectroscopy has been developed as a noninvasive tool for the direct, real-time monitoring of glucose, lactic acid, acetic acid, and biomass in liquid cultures of microrganisms of the genera Lactobacillus and Staphylococcus. This was achieved employing a steam-sterilizable optical- ber probe immersed in the culture (In-line Interactance Systemt ). Second-derivative spectra obtained were subjected to partial least-squares (PLS) regression and the results were used to build predictive models for each analyte of interest. Multivariate regression was carried out on two different sets of spectra, namely whole broth minus the spectral subtraction of water, and raw spectra. A comparison of the two models showed that the rst cannot be properly applied to real-time monitoring, so this work suggests calibration based on non-difference spectra, demonstrating it to be suf ciently reliable to allow the selective determination of the analytes with satisfactory levels of prediction (standard error of prediction (SEP) , 10%). Direct interfacing of the NIR syst em to the bioreactor control system allowed the implementation of completely automated monitoring of different cultivation strategies (continuous, repeated batch). The validity of the in-line analyses carried out was found to depend crucially on maintaining constant hydrodynamic conditions of the stirred cultures because both gas ow and stirring speed variations were found to markedly in fluence the spectral signal

Effect of Process Conditions on the Growth of Three-Dimensional Dermal-Equivalent Tissue Obtained by Microtissue Precursor Assembly

Bottom-up approach is an appealing strategy to build complex three-dimensional (3D) viable tissues in vitro starting from microtissue precursors (μTP). In this work we biofabricated a thick dermal-like tissue by sequentially combining two steps: a μTPs production and assembly followed by tissue maturation in a purpose-built bioreactor. The μTPs were produced by first seeding bovine primary fibroblasts on gelatine microparticles and then cultivating them in stirring conditions until a thick layer of ∼80μm of de novo synthesized extracellular matrix uniformly covered the microparticle surface. The μTPs were then loaded into a cylindrical chamber (2mm in depth and 35mm in diameter) and let to maturate and assemble into a 3D viable biohybrid tissue under specific fluid flow conditions. Several combinations of perfusion and/or tangential fluid flow were applied and their effect on the tissue formation and maturation was assessed. Results show that structural composition and mechanical features of the final 3D bioengineered tissue are strongly affected by the hydrodynamic environment and demonstrate that by optimizing culture conditions a 3D viable tissue with properties similar to that of native derma could be produced. © 2011 Mary Ann Liebert, Inc

Enhanced production of L-(+) lactic acid in chemostat by Lactobacillus casei DSM20011 using anion-exchange resins and cross-flow filtration in a fully automated pilot plant controlled via NIR.3

Due to the lack of suitable in-process sensors, on-line monitoring of fermentation processes is restricted almost exclusively to the measurement of physical parameters only indirectly related to key process variables, i.e., substrate, product, and biomass concentration. This obstacle can be overcome by near infrared(NIR) spectroscopy, which allows not only real-time process monitoring, but also automated process control, provided that NIR-generated information is fed to a suitable computerized bioreactor control system. Once the relevant calibrations have been obtained, substrate, biomass and product concentration can be evaluated online and used by the bioreactor control system to manage the fermentation. In this work, an NIR-based controlsystem allowed the full automation of a small-scale pilot plant for lactic acid production and provided an excellent tool for process optimization. The growth-inhibiting effect of lactic acid present in the culture broth is enhanced when the growth-limiting substrate, glucose, is also present at relatively high concentrations. Both combined factors can result in a severe reduction of the performance of the lactate production process. A dedicated software enabling on-line NIR data acquisition and reduction,and automated process management through feed addition, culture removal and/or product recovery by microfiltration was developed in order to allow the implementation of continuous fermentation processes with recycling of culture medium and cell recycling. Both operation modes were tested at different dilution rates and the respective cultivation parameters observed werecompared with those obtained in a conventional continuous fermentation. Steady states were obtained in both modes with high performance on lactate production. The highest lactate volumetric productivity, 138 g L−1 h−1, was obtained in continuous fermentation with cell recycling

The impact of bilayer rigidity on the release from magnetoliposomes vesicles controlled by pemfs

Stimuli-sensitive nanocarriers have recently been developed as a powerful tool in biomedi-cal applications such as drug delivery, detection, and gene transfer techniques. Among the external triggers investigated, low intensity magnetic fields represent a non-invasive way to remotely control the release of compounds from a magneto-sensitive carrier. Magnetoliposomes (MLs), i.e., liposomes entrapping magnetic nanoparticles (MNPs), are studied due to their capacity to transport hydropho-bic and hydrophilic agents, their easy production, and due to the ability of MNPs to respond to a magnetic actuation determining the triggered release of the encapsulated compounds. Here we investigated the design and optimization of the MLs to obtain an efficient on-demand release of the transported compounds, due to the magneto-mechanical actuation induced by applying low-intensity pulsed electromagnetic fields (PEMFs). In particular we studied the effect of the bilayer packing on the ability of MLs, with oleic acid-coated MNPs encapsulated in the bilayer, to respond to PEMFs application. Three kinds of MLs are produced with an increasing rigidity of the bilayer, defined as Liquid Disorder, Liquid Order, and Gel MLs and the delivery of a hydrophilic dye (as a model drug) is investigated. Results demonstrate the efficacy of the magnetic trigger on high-ordered bilayers, which are unable to dampen the perturbation produced by MNPs motion

Membrane-less microbial fuel cell: Monte Carlo simulation and sensitivity analysis for COD removal in dewatered sludge

Dewatered sludge is redundantly found in a municipal wastewater treatment plant, and the amount is increasing every year. However, the dewatered sludge could be used to power the membrane-less microbial fuel cell (ML-MFC), which is operated electrochemically via incorporation of electricity producing micro-organisms. The dewatered sludge normally acts as an electron donating substrate. Results showed that the ML-MFC produced voltage at about 927.7 ± 11.24 mV whereby 178.7 mg/L of chemical oxygen demand (COD) was removed after 240 h of incubation period. Nonetheless, voltage and COD removal values obtained from the dewatered sludge in the ML-MFC might differ every time the study is repeated because the availability of maximum biomass of electrogenic bacteria (EB) will be different due to the heterogeneous properties and EB performance inside the ML-MFC. The parametric uncertainty analysis of COD removal was then assessed using Monte Carlo simulation (stochastic variable) to determine the distribution probability affected by the fluctuation and variation of kinetic model parameters. From the study of 100 000 samples tested (simulation), the results show that the substrate removal (S) value ranged from 172.58 to 185.02 mg/L. The impact of each kinetic parameter on the ML-MFC performance was evaluated via sensitivity analysis. It is found that the ML-MFC performance significantly relied on the growth of EB present

Injectable and in situ gelling dextran derivatives containing hydrolyzable groups for the delivery of large molecules

Recently, we reported the synthesis and characterization of a new dextran derivative obtained by grafting polyethylene glycol methacrylate to a polysaccharide backbone through a carbonate bond. This moiety was introduced because it allows for the fabrication, through a photoinduced crosslinking reaction, of biodegradable hydrogels particularly suitable for the release of high molecular weight molecules. Here, we investigate the influence of the oxyethylene chain length and the molecular weight of the starting dextran on the main properties of the polymeric solutions as well as those of the corresponding hydrogels. All synthesized polymeric derivatives were characterized by FTIR, NMR, and rheological analyses. The photo-crosslinking reaction of the polymers allowed us to obtain biodegradable networks tested for their mechanical properties, swelling, and degradation behavior. The results showed that both the oxyethylene chain length as well as the molecular weight of the starting dextran influenced swelling and degradation of the hydrogel network. As a consequence, the different behaviors in terms of swelling and degradability were able to affect the release of a large model molecule over time, making these matrices suitable candidates for the delivery of high molecular weight drug substances