Biomedical subjects

Heiko Feitkenhauer

Publications and source records attributed to Heiko Feitkenhauer.

5 recordsLinked to original sources

PubMed2003

Kinetic parameters of continuous cultures of Bacillus thermoleovorans sp. A2 degrading phenol at 65 degrees C.

In this paper, we report on the kinetics of phenol degradation and cell growth in continuous cultures of suspended cells of Bacillus thermoleovorans sp. A2 at 65 degrees C. A high yield coefficient of Y(x/s)=0.84 g cell dry weight g(-1) phenol was measured at a dilution rate of 0.5 h(-1). At the same dilution rate the coefficient for maintenance metabolism (m(s)) was determined to be 0.045 g phenol g(-1) cell dry weight h(-1). The maximal growth rate (wash-out) determined at a phenol inlet concentration of 188 mg l(-1) was 0.9 h(-1). Up to 7 g phenol l(-1) per day were degraded in a continuously operated 2-l stirred tank reactor with suspended cells (feed concentration 660 mg l(-1)). Additionally, yield coefficients for oxygen and ammonium are reported.

Bacillus↗

PubMed2003

New approach to control the methanogenic reactor of a two-phase anaerobic digestion system.

A new control strategy for the methanogenic reactor of a two-phase anaerobic digestion system has been developed and successfully tested on the laboratory scale. The control strategy serves the purpose to detect inhibitory effects and to achieve good conversion. The concept is based on the idea that volatile fatty acids (VFA) can be measured in the influent of the methanogenic reactor by means of titration. Thus, information on the output (methane production) and input of the methanogenic reactor is available, and a (carbon) mass balance can be obtained. The control algorithm comprises a proportional/integral structure with the ratio of (a) the methane production rate measured online and (b) a maximum methane production rate expected (derived from the stoichiometry) as a control variable. The manipulated variable is the volumetric feed rate. Results are shown for an experiment with VFA (feed) concentration ramps and for experiments with sodium chloride as inhibitor.

Algorithms↗

PubMed2003

Degradation of polycyclic aromatic hydrocarbons and long chain alkanes at 60-70 degrees C by Thermus and Bacillus spp [corrected].

Although polycyclic aromatic hydrocarbons (PAH) and alkanes are biodegradable at ambient temperature, in some cases low bioavailabilities are the reason for slow biodegradation. Considerably higher mass transfer rates and PAH solubilities and hence bioavailabilities can be obtained at higher temperatures. Mixed and pure cultures of aerobic, extreme thermophilic microorganisms (Bacillus spp., Thermus sp.) were used to degrade PAH compounds and PAH/alkane mixtures at 65 degrees C. The microorganisms used grew on hydrocarbons as sole carbon and energy source. Optimal growth temperatures were in the range of 60-70 degrees C at pH values of 6-7. The conversion of PAH with 3-5 rings (acenaphthene, fluoranthene, pyrene, benzo[e]pyrene) was demonstrated. Efficient PAH biodegradation required a second, degradable liquid phase. Thermus brockii Hamburg metabolized up to 40 mg (1 h)(-1) pyrene and 1000 mg (1 h)(-1) hexadecane at 70 degrees C. Specific growth rates of 0.43 h(-1) were measured for this strain with hexadecane/pyrene mixtures as the sole carbon and energy source in a 2-liter stirred bioreactor. About 0.7 g cell dry weight were formed from 1 g hydrocarbon. The experiments demonstrate the feasibility and efficiency of extreme thermophilic PAH and alkane biodegradation.

Alkanes↗

PubMed2002

On-line titration of volatile fatty acids for the process control of anaerobic digestion plants.

The on-line titration of volatile fatty acids (VFA) was found to be a reliable method to measure the substrate (metabolite) concentration without the use of expensive analytical devices. A measurement cell was designed that ensures stable long-term operation, high throughputs and copes with both very low and very high VFA concentrations. Using synthetic textile wastewater, a recalibration of the pH probe was necessary only twice a week. A good reproducibility of the VFA concentrations was determined and standard deviations were below +/- 1% of the measured concentration. Changing salt concentrations of the wastewater in the range of 2.5-150 gl(-1) NaCl did not influence the determined VFA concentration significantly. The method was suitable to control the hydraulic retention time in an acidic phase reactor and to determine the acidification rates of wastewater compounds in batch experiments.

Bacteria, Anaerobic↗

PubMedDate not supplied

Microbial desizing using starch as model compound: enzyme properties and desizing efficiency.

A film of sizing agents protects yarn during weaving. Its removal in a subsequent washing process causes 50% of the organic effluent load of textile finishing processes and requires large amounts of auxiliary chemicals (e.g., surfactants). Microbial desizing is a new bioprocess that uses the acidifying culture of a two-phase anaerobic digestion plant for the removal and partial degradation (acidification) of the sizing agent. Soluble starch is used in this study to characterize the enzymatic properties in the supernatant of the desizing culture and to link them to desizing efficiencies. The supernatant of the culture (grown at 37 degrees C, pH 5.5) displayed the highest enzymatic activity between pH 4 and 5 and in a broad temperature range (20-80 degrees C). Highest metabolization rates were determined with the substrate amylose. Short chain dextrins (average of 5 and 10 glucose units) and amylopectin were converted significantly more slowly. At 37 degrees C the half-life time of the enzymatic activity in the supernatant was 45 h. In a desizing test a decisive reduction of the chain length was found already after 1 h (allowing starch solubilization). A microbial desizing experiment with dyed, native maize starch demonstrated the efficiency of the proposed bioprocess.

Bacteria, Anaerobic↗