Im Rahmen der vorliegenden Arbeit wurden die Wechselwirkungen im System Bakterium –Tensid – Schadstoff mittels kalorimetrischer Untersuchungen (ITC, DSC) sowie mit XPS-Analysen und durch Zeta-Potential-Messungen an Bakterienoberflächen charakterisiert. Für die Untersuchungen wurden zwei Gram-positive Rhodococcus-Stämme und ein Gram-negativer Pseudomonas putida-Stamm verwendet. Als Biotenside wurden das Rhamnolipid JBR 425 und der von Rhodococcus erythropolis B7g produzierte Trehalosetetraester (THL-4) ausgewählt. Das synthetische Tensid SDS diente als Referenzsubstanz. Aus den kalorimetrischen Experimenten konnte eine starke Wechselwirkung zwischen den Tensiden und den aktiven Bakterienkulturen abgeleitet werden. THL-4 führte beim Wachstum der Rhodococcen auf n-Hexadecan zur Verkürzung der lag-Phase. SDS wies hingegen eine toxische Wirkung für die Bakterienstämme auf. Thermodynamische Betrachtungen ergaben, dass Wechselwirkungen des SDS mit den Bakterienzellen gegenüber der Mizellbildung bevorzugt werden.

Biodesulfurization (BDS) is an alternative to hydrodesulfurization (HDS) as a method to remove sulfur from crude oil. Dibenzothiophene (DBT) was chosen as a model compound for the forms of thiophenic sulfur found in fossil fuels; up to 70% of the sulfur in petroleum is found as DBT and substituted DBTs; these compounds are however particularly recalcitrant to hydrodesulfurization, the current standard industrial method. My thesis deals with enhancing BDS through novel strains and through nanotechnology. Chapter highlights are: Chapter 2. My first aim was to isolate novel aerobic, mesophilic bacteria that can grow in mineral media at neutral pH value with DBT as the sole sulfur source. Different natural sites in Iran were sampled and I enriched, isolated and purified such bacteria. Twenty four isolates were obtained that could utilize sulfur compounds. Five of them were shown to convert DBT into HBP. After preliminary characterization, the five isolates were sent to the Durmishidze Institute of Biotechnology in Tbilisi for help with strain identification. Two isolates (F2 and F4) were identified as Pseudomonas strains, F1 was a Flavobacterium and F3 belonged to the strain of Rhodococcus. The definite identification of isolate F5 was not successful but with high probability it was a known strain. Since no new strains were apparently discovered, I did not work further in this direction. Chapter 3. In a second approach I studied the desulfurization ability of Shewanella putrefaciens strain NCIMB 8768, because in a previous investigation carried out at Cranfield University, it had been found that it reduced sulfur odour in clay. I compared its biodesulfurization activity profile with that of the widely studied Rhodococcus erythropolis strain IGTS8. However, S. putrefaciens was not as good as R. erythropolis. Chapter 4 and 5. I then turned to nanotechnology, which as a revolutionary new technological platform offers hope to solve many problems. There is currently a trend toward the increasing use of nanotechnology in industry because of its potentially revolutionary paths to innovation. I then asked how nanotechnology can contribute to enhancing the presently poor efficiency of biodesulfurization. Perhaps the most problematic difficulty is how to separate the microorganisms at the end of the desulfurization process. To make BDS more amenable, I explored the use of nanotechnology to magnetize biodesulfurizing bacteria. In other words, to render desulfurizing bacteria magnetic, I made them magnetic by decorating their outer surfaces with magnetic nanoparticles, allowing them to be separated using an external magnet. I used the best known desulfurizing bacterial strain, Rhodococcus erythropolis IGTS8. The decoration and magnetic separation worked very well. Unexpectedly, I found that the decorated cells had a 56% higher desulfurization activity compared to the nondecorated cells. I proposed that this is due to permeabilization of the bacterial membrane, facilitating the entry and exit of reactant and product respectively. Supporting evidence for enhanced permeabilization was obtained by Dr Pavel Grigoriev, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino. In Chapter 6, to optimize attachment of the nanoparticles to the surface of the bacteria I created thin magnetic nanofilms from the nanoparticles and measured the attachment of the bacteria using a uniquely powerful noninvasive optical technique (Optical Waveguide Lightmode Spectroscopy, OWLS) to quantify the attachment and determine how the liquid medium and other factors influence the process.

Ligninolytic fungi are well known for their ability to degrade a wide range of xenobiotics contaminating the environment, including synthetic industrial dyes. In this work Pleurotus ostreatus was used for decolorization of a synthetic textile dye Remazol Brilliant Blue R (RBBR). To set up a model fungal "fixed-bed" bioreactor the fungus was immobilized on a polyurethane foam and artificially contaminated with a model bacterium Rhodococcus erythropolis. The development of bacterial contamination can be expected during a real application of fungal bio filters in wastewater treatment. The main aim of the work was to study interspecies interactions in the model bioreactors during the dye decolorization. Ligninolytic enzyme activities were followed in the bioreactor cultures as markers of fungal biodegradation ability. In contrast to the controls, no bacterial growth was observed in the P. ostreatus bioreactor culture liquid. The results showed that fungal laccase, pH of the culture liquid, and glucose consumption by the fungus had no effect on the bacterial growth. However, 4*105 - 1,3*106 CFU/ml of R. erythropolis was detected to be associated with the fungal solid support. The presence of these bacteria had no effect on the decolorization performance of the bioreactors. Dye decolorization efficiency...