Butanol production from hexoses and pentoses by fermentation of Clostridium acetobutylicum.

The present paper reports the characterization of ABE (acetone-butanol-ethanol) production by Clostridium acetobutylicum DSM 792 for sugars representative of hydrolysed lignocellulosic biomass (glucose, mannose, arabinose, xylose). The attention was focused on: the selection of an optimal medium for the simultaneous conversion of the investigated sugars; the assessment of interference-synergistic effects during the fermentation of mixtures of the investigated sugars. The synthetic medium was optimised in terms of nutritional factors: the KH2PO4-K2HPO4 concentration was increased up to 5 g/L; the MgSO4 concentration was increased up to 2 g/L; the MnSO4 concentration was increased up to 0.1 g/L; the FeSO4 concentration ranged between 0.002 and 0.01 g/L); the CaCO3 concentration was increased up to 10 g/L. The optimal concentration of the investigated factors was assessed and it varied from one sugar to another. The batch fermentations of a mixture of the four sugars highlighted their synergistic effects. Once set the initial concentration of the sugars (60 g/L), the butanol and solvent concentration increased up to 14.6 and 20.6 g/L, respectively, when the four sugars were present.

Electrooptical monitoring of cell polarizability and cell size in aerobic Escherichia coli batch cultivations.

The time-dependent development of cell polarizability and length in Escherichia coli batch fermentations were observed at-line with electrooptical measurements. While using a measurement system with fully automated sample preparation, the development of these properties can be observed with a comparable high frequency (six measurements per hour). The polarizability as well as the mean cell length both increase soon after inoculation and then decline from the growth phase on until the stationary phase is reached. Based on the dynamic behavior of polarizability, the growth phase can be divided into four distinct stages. Changes in the cultivation temperature or the pre-cultivation conditions lead to alterations in the development of the polarizability and mean cell length. Based on the frequency disperse of polarizability measured at four different frequencies from 210 to 2,100 kHz, a prediction model is established that is based on the relation of the polarizability to the metabolic activity. Applying multi-linear partial least squares methods (N-PLS), the model is able to predict the specific acetate synthesis and uptake with a root mean square error of prediction of 0.19 (6% of the mean). The method represents a tool for characterization of different stages with respect to microbial metabolic activity and the energy balance during batch cultivations.

Interactions between hyphosphere-associated bacteria and the fungus Cladosporium herbarum on aquatic leaf litter.

We investigated microbial interactions of aquatic bacteria associated with hyphae (the hyphosphere) of freshwater fungi on leaf litter. Bacteria were isolated directly from the hyphae of fungi from sedimented leaves of a small stream in the National Park "Lower Oder," Germany. To investigate interactions, bacteria and fungi were pairwise co-cultivated on leaf-extract medium and in microcosms loaded with leaves. The performance of fungi and bacteria was monitored by measuring growth, enzyme production, and respiration of mono- and co-cultures. Growth inhibition of the fungus Cladosporium herbarum by Ralstonia pickettii was detected on leaf extract agar plates. In microcosms, the presence of Chryseobacterium sp. lowered the exocellulase, endocellulase, and cellobiase activity of the fungus. Additionally, the conversion of leaf material into microbial biomass was retarded in co-cultures. The respiration of the fungus was uninfluenced by the presence of the bacterium.

Normal vector method for the RCWA with automated vector field generation.

Early formulations of the RCWA yield, implicated by the erroneous application of factorization rules to discrete Fourier transformations, poor convergence in certain cases. An explanation for this finding and an approach to overcome the problem for crossed gratings was first given by Li [J. Opt. Soc. Am. A 13, 1870 (1996) and 14, 2758 (1997)]. A further improvement was achieved by Schuster et al. [J. Opt. Soc. Am. A 24, 2880 (2007)], using a structure dependent normal vector (NV) field. While it is trivial to create those NV fields for simple geometrical shapes, to our knowledge an appropriate algorithm for arbitrary shapes does not exist, yet. In this work we present such an algorithm.

Emulsion-based synthesis of PLGA-microspheres for the in vitro expansion of porcine chondrocytes.

The in vitro cell expansion of autologous chondrocytes is of high interest in regenerative medicine since these cells can be used to treat joint cartilage defects. In order to preserve chondrocyte phenotype, while optimizing adhesion on microspheres, several processing parameters for the microsphere synthesis were varied. In this study three different polylactide-co-glycolides were used with differing lactide-glycolide ratios (85:15 and 50:50) and differing inherent viscosities. An emulsion route was established, where the polymer was dissolved in chloroform and then injected into a stirred polyvinyl alcohol-water solution at different polymer concentrations and different stirring velocities to produce microspheres with varying diameters. The sphere size distribution and morphology was analyzed using image processing software on SEM pictures. Based on previous experiments with commercial microspheres, three optimum samples were selected for further investigations. The degradation of the microspheres was determined in a long-term experiment in culture medium for 3 months. Adherent cells were characterized after 3 and 5 days by FDA+EB vital staining and in SEM.

Optimization and scale-up of oligonucleotide synthesis in packed bed reactors using computational fluid dynamics modeling.

A computational fluid dynamics (CFD) model for the analysis of oligonucleotide synthesis in packed bed reactors was developed and used to optimize the scale up of the process. The model includes reaction kinetics data obtained under well defined conditions comparable to the situation in the packed bed. The model was validated in terms of flow conditions and reaction kinetics by comparison with experimental data. Experimental validation and the following model parameter studies by simulation were performed on the basis of a column with 0.3 g oligonucleotide capacity. The scale-up studies based on CFD modelling were calculated on a 440 g scale (oligonucleotide capacity).

Production of epoxide hydrolases in batch fermentations of Botryosphaeria rhodina.

The filamentous fungus Botryosphaeria rhodina (ATCC 9055) was investigated related to its ability for epoxide hydrolase (EH) production. Epoxide hydrolase activity is located at two different sites of the cells. The larger part is present in the cytosol (70%), while the smaller part is associated to membranes (30%). In media optimization experiments, an activity of 3.5 U/gDW for aromatic epoxide hydrolysis of para-nitro-styrene oxide (pNSO) could be obtained. Activity increased by 30% when pNSO was added to the culture during exponential growth. An increase of enzyme activity up to 6 U/gDW was achieved during batch-fermentations in a bioreactor with 2.7 l working volume. Evaluation of fermentations with 30 l working volume revealed a relation of oxygen uptake rate to EH expression. Oxygen limitation resulted in a decreased EH activity. Parameter estimation by the linearization method of Hanes yielded Km values of 2.54 and 1.00 mM for the substrates S-pNSO and R-pNSO, respectively. vmax was 3.4 times higher when using R-pNSO. A protein purification strategy leading to a 47-fold increase in specific activity (940 U/mgProtein) was developed as a first step to investigate molecular and structural characteristics of the EH.

Large-scale purification of oligonucleotides by extraction and precipitation with butanole.

Today the synthesis of oligonucleotides is a well-established process. Using automatic synthesizers even kilogram quantities can be produced in a few hours. However, the purification of the final product is still time-consuming and needs a complex apparatus. In this article, a simple and fast purification method for the large-scale syntheses of oligonucleotides is described. According to the method of Sawadago and van Dyke ([1991] Nucleic Acids Res 19:674-675) for small-scale oligonucleotide purification, oligonucleotides in mumol to mmol amounts were purified by liquid-liquid extraction using butanole as the extraction liquid. Choosing appropriate ratios of extraction liquid to oligonucleotide solution, simultaneous purification and precipitation could be achieved. It was found that the yield of the purified oligonucleotide was mainly affected by the temperature. Yield decreased with increasing temperature. The use of this improved extraction procedure allows the purification of gram to kilogram quantities of oligonucleotides in less than a day with simple equipment and high yield.