Our research can be divided into subtopics entitled:
- Control of wastewater treatment plants - new methods and process technology
Malte Hermansson, Fred Sörensson, Marina Thörn, Anna Zita, Nabaz Mustafa, Ann Cathrin Olofsson
A consortium with the Rya sewage treatment plant and participants from several departments in Göteborg has been formed with the aim to do research within the project "Control of wastewater treat-ment plants - new methods and process technology", financed by
NUTEK. Two subprojects will be carried out at the department of general and marine microbiology, one dealing with microbial adhesion, aggregation, and floc formation in an activated sludge process (project leader: Malte Hermansson), and one studying the microbial
nitrogen transformations, mainly nitrification and denitrification, involved in the reduction of nitrogen in the effluent from the treatment plant (project leader: Fred Sörensson). The mechanisms regulating the formation of N2O and ammonium from microbial nitrate
reduction have been investigated as well as the formation of a nitrifying biofilm in a trickling filter. The utilization of comp-lex carbon sources (exoenzyme activity) have been studied. Different factors that influence the stability of flocs have been investigated.
- Bacterial gene transfer in the marine environment
Malte Hermansson, Cecilia Dahlberg, Maria Bergström
Biofilms are micro-habitats where gene transfer are expected because of their high cell density. Transfer of genetic information between bacteria is a fundamental biological mechanism and acquisition of al-ready evolved genes from other cells is one of the main
adaptive mechanisms available for bacteria. It is also important for bacterial evolution. Mobile genetic elements such as transposons are often carried from cell to cell via gene transfer. Transposition is a particularly important result of gene transfer that allows genetic
rearrangement within the cell. Dissemination of genetic information is an important com-ponent in biofilm development. This project aims at a better understanding of these mechanisms.
Our research include studies of conjugative gene transfer and transposition in marine bacterial commu-nities and characterisation of mobile genetic elements. We utilise gene reporter systems (GFP), confocal laser scanning microscopy, flow cell biofilm reactors,
conventional molecular biology techniques as well as field studies in our approach.
- Bacterial corrosion
Malte Hermansson, Anders Ulvarsson (CTH), Magdalena Molin (CTH)
When micro-organisms attach and form complex biofilms on metals and alloys they influence the corro-sion of the metal by changing the electrochemical conditions at the metal surface. For instance, at a thickness of only some 10 µm, a reduction of Eh (redoxpotential)
can be seen in the film. Theoretically, these changes may have many effects, ranging from the induction of localised corrosion, to a change in the general corrosion, to corrosion inhibition.
- Adhesion mechanisms of procaryotes at interfaces
Malte Hermansson, Hans Elwing, Anna Zita, Karen Otto
Two main concepts have been useful in describing and even calculate the interaction Gibbs energy of bacterial adhesion. The DLVO-theory can be used to calculate the interaction Gibbs energy between a cell and a surface as a function of the separation distance.
The adhesion which involves contact between cell and surface via short-range interactions can be described by a thermodynamic approach. The sur-face tensions of the bacterium/solid, bacterium/liquid and the solid/liquid interfaces are compared in this latter
We have made use of both approaches in studies of bacterial adhesion in marine waters as well as in bioprocessing of waste water. Recent studies include measurements of adhesive forces influenced by ionic strength, hydrophobic interactions, physico-chemical cell
surface character (charge and cell sur-face hydrophobicity), adhesion of specific bacteria that are genetically tagged (GFP), CLSM of biofilms and aggregates and specific detergent effects.
Conformational changes of proteins at interfaces may be a driving force for bacterial adhesion. We therefore investigate if fimbriae (surface proteins in some bacteria) show such changes and if these may be correlated to bacterial adhesion.
- Growth and control of industrial biofilms
Mariana Björklund, Malte Hermansson, Hans Elwing, Anki Olofsson
Biofouling and bacteria cause severe and costly problems in modern paper mills, like discolouring of the paper, production stops, spore formation, corrosion, destruction of additives, odours and the produc-tion of toxic or explosive gases. Only in Sweden, several
hundreds of tons of biocides are used every year to prevent these problems. Yet, treatments with biocides have not proven to be fully effective, and is often not environmentally friendly. The aim of this project is to develop new non-biocidal inhibitors of biofouling and
strategies to combat problems caused by bacteria in the pulp and paper mill industry. Quantitative and qualitative diagnosis of paper mill biofilms in situ are performed using various staining and microscopic evaluations, polymerase chain reaction, and measurements by
e.g. FTIR of organic and inorganic components of the biofilm. Bimogardâ is a non-biocidal and readily biodegraded commercial product which effectively controls biofilm formation in paper mills. Bimogardâ is developed and manufactured by BIM Kemi AB.
The modes of action of Bimogardâ are studied in order to develop new environmentally friendly pro-ducts combating biofouling. Aggregation, adhesion and synthesis of extra cellular polysaccharides are studied.