Treatment of acid lignite mine flooding water by means of microbial sulfate reduction.

During and after mining activities acidic waters containing high amounts of heavy metals and sulfate often occur. In addition to precipitation processes, water purification is also possible with the help of sulfate-reducing bacteria (SRB). A mixed culture of SRB was adapted to methanol as a cheap carbon source. In order to receive high sulfate-reduction rates immobilization on porous materials proved to be advantageous. Continuous laboratory experiments based on immobilized SRB were carried out with original water from a lignite mining site reaching sulfate-reducing rates up to 132 mg SO4(2-)/(1 h). Based on these results a process for the treatment of such waters was designed. Heavy metals are removed by recycling sulfide containing effluent, excess sulfide can be oxidized to elemental sulfur by addition of hydrogen peroxide. The plant with a 3.9 m3 bioreactor with immobilized SRB was constructed at the mine site. This pilot plant was operated successfully for some months. The removal of heavy metals was close to 100%, the pH of the acidic water increased from 3.0 to 6.9. The sulfate-reducing rate again reached 134 mg SO4(2-)/(1 h). The production of sulfur from the excess sulfide is possible.

Influence of relA locus on electrophoretic mobility of a stringent/relaxed Escherichia coli K 12 strain pair.

Stringent (relA+) and relaxed (rel A-) controlled Escherichia coli cells differ in their regulation of many biochemical pathways such as phospholipid and lipopolysaccharide metabolism (LPS) after amino acid limitation. Because such differences could result in various cell envelopes, cells of stringent controlled E. coli strain CP78 (relA+) and relaxed controlled E. coli strain CP79 (relA) were studied regarding their electrophoretic mobility. The graphs of the mobility distributions of both strains were different: cells of strain CP79 caused secondary peaks in addition to the main peaks whereas the mobility distributions of cells of strain CP78 showed only one maximum. In the pH range from 6.0 to 8.0 the location of the main peaks of cells of strain CP79 were changed to less negative values after induction of relaxed response. In contrast to this the stringent response in strain CP78 caused no change of the mobility distributions.

[Dissolution of alloy components from Ni/Cr base alloys by bacterial leaching]. / Die Auslösung von Legierungsbestandteilen aus Ni/Cr-Legierungen durch bakterielle Laugung.

The method of bacterial leaching of non precious dental alloys represents a useful completion of the method arsenal of biological investigations. In contrast to other well known methods it allows to point out small differences in corrosion resistance between alloys of the same type in a biologic system.

[Theoretical determination of the energy efficiency of microbial carbon substrate conversion and comparison with experimental values in phase cultures]. / Theoretische Bestimmung energetischer Wirkungsgrade der mikrobiellen Kohlenstoffsubstratwandlung und Vergleich mit experimentellen Werten an Phasenkulturen.

The phenomenological description of microbial substrate conversion is possible by connecting energy and material balance equations. The change of free enthalpy of microbial substrate conversion was determined on the basis of exact material balance equations. A simultaneous determination of heat production allowed to calculate the energetic efficiency of microbial growth processes. In addition to this the change of free enthalpy by microbial substrate conversion was standardized by the free standard formation enthalpy of biomass. Both quantities were used for comparing microbial combustion of several substrates into biomass. Comparable with the concept of substrate combustion enthalpy standardized by the combustion enthalpy of biomass an optimal strategy of mixing different substrates can be deduced from energy and material balance equations on the basis of theoretic consumption coefficients. Besides the energetic efficiency the binding state of the substrate is important in the search for optimal substrate mixing ratios. This could be shown by experimental work. Thus, the fermentation systems sucrose/yeast, paraffin/yeast, and sucrose/paraffin/yeast were studied using synchronous populations produced by the method of phased cultures. The investigations of real fermentation systems confirm the theoretical predictions on special conditions.

Yield coefficients in dependence on milieu conditions and cell states. II. Influence of perturbations on continuous cultivation of the yeast Lodderomyces elongisporus on hydrocarbons.

The influence of perturbations on continuous yeast cell cultivations on hydrocarbons of crude oil is described. Due to such perturbations the fermentation system leaves its steady state, passes through transitional stages and reaches a new steady state. In the transitional stages a damped oscillation of biomass concentration, percentage of budding cells, oxygen consumption rate, and heat flow is observed. These results can be explained by partial synchronization of yeast cell functions in microorganism populations. In phases of partial synchronization the cell cycle of a single cell is reflected by the behaviour of the microorganism population. The adaptation of the carbon substrate feeding rate to the state of partially synchronized microorganism population makes possible lower specific substrate consumption in biomass production.

[Thermodynamics of microbial processes]. / Thermodynamik mikrobieller Prozesse.

The unique description of the dependences of the specific consumption coefficients on the process state known from the literature is an important prerequisite to the further increase of the intensity and efficiency of the process for the industrial protein synthesis. Suitable measuring quantities for it are entropy production, an important quantity of thermodynamics of irreversible processes, and differential heat flow which can be measured by microcalorimetry. The description of the dependences of consumption coefficients by thermodynamics of irreversible processes allows an ingenious statement of calorimetric measurements of the fermentation process to confirm and to make precise the knowledge deduced from thermodynamics. Thermodynamical considerations and calorimetric measurements are used to describe the dependences of consumption coefficients on substrate concentration, nature of limitation, and periodical perturbations of the process.