Automated tangential-flow diafiltration device

Tangential flow filtration (TFF) is a chemical unit operation used to purify and concentrate liquid suspensions of colloids, proteins, or cells. The solution flows tangentially across a membrane, such that a selective part of the fluid permeates the membrane while the filtrated matter is retained, increasing its concentration. TFF is a mild mechanical purification method that does not interact chemically with the filtrate. It is applied in sensitive separation tasks in protein chemistry, microbiology, or immunology. It is a fast alternative for dialysis applications, also applicable in the field of colloid purification. However, the costs of automated lab-scale devices (30,000 €) and the consumable membrane modules (100–600 €) make TFF currently hardly accessible for lab-scale polymer researchers. Therefore, we built a low-cost TFF system (2400 €) partly automated by an Arduino microcontroller and optimized for diafiltration buffer exchange and concentration processes in soft matter colloid research. We use medical hemodialysis membrane modules that only cost a share (20–50 €) of alternative TFF modules, and we demonstrate the functionality of the system for an exemplary colloidal microgel purification process

Carbon dioxide and trace oxygen concentrations impact growth and product formation of the gut bacterium Phocaeicola vulgatus

Abstract Background The promising yet barely investigated anaerobic species Phocaeicola vulgatus (formerly Bacteroides vulgatus) plays a vital role for human gut health and effectively produces organic acids. Among them is succinate, a building block for high-value-added chemicals. Cultivating anaerobic bacteria is challenging, and a detailed understanding of P. vulgatus growth and metabolism is required to improve succinate production. One significant aspect is the influence of different gas concentrations. CO2 is required for the growth of P. vulgatus. However, it is a greenhouse gas that should not be wasted. Another highly interesting aspect is the sensitivity of P. vulgatus towards O2. In this work, the effects of varying concentrations of both gases were studied in the in-house developed Respiratory Activity MOnitoring System (RAMOS), which provides online monitoring of CO2, O2, and pressure under gassed conditions. The RAMOS was combined with a gas mixing system to test CO2 and O2 concentrations in a range of 0.25-15.0 vol% and 0.0-2.5 vol%, respectively. Results Changing the CO2 concentration in the gas supply revealed a CO2 optimum of 3.0 vol% for total organic acid production and 15.0 vol% for succinate production. It was demonstrated that the organic acid composition changed depending on the CO2 concentration. Furthermore, unrestricted growth of P. vulgatus up to an O2 concentration of 0.7 vol% in the gas supply was proven. The viability decreased rapidly at concentrations larger than or equal to 1.3 vol% O2. Conclusions The study showed that P. vulgatus requires little CO2, has a distinct O2 tolerance and is therefore well suited for industrial applications

Regional Investment Under Uncertain Costs of Location

Due to globalization competitive firms face increasing economic opportunities for locating their activities in countries, regions and cities that provide the best business environment for their specific needs. In our study we focus on the impact of economic risk and risk preferences upon regional allocation of investments. The source of risk stems from the difference in stochastic costs of location across regions. A comparative static analysis shows that capital allocation depends upon the firms' risk preferences. As a result regional agglomeration of investments may occur although the objective of the regional policy is aimed at the opposite. Our findings demonstrate the suitability of the two-moment approach as an alternative to the expected utility approach. The impact of changes in distribution parameters, such as the expected costs of location, the variance of costs of location and the correlation between locational costs, can be fully characterized via the elasticity of risk aversion. Elements of risk preferences beyond risk aversion prove to be very important to evaluate regional politics. This insight is of interest for empirical research in regional economics