Chemistry: molecular biology and microbiology – Apparatus – Including measuring or testing
Reexamination Certificate
1999-11-22
2002-10-08
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Including measuring or testing
C435S287900, C435S297200, C435S817000
Reexamination Certificate
active
06461861
ABSTRACT:
This invention relates to a device for carrying out a procedure, for example an analytical procedure, in which microorganisms or other biological material interacts with components of a fluid.
Microorganisms are employed, because of their wide variety of metabolic pathways, for investigations into the biodegradability of various substances, for analytical purposes, for example for assaying individual substances or classes of substances, and for assessing the extent of pollution of water with biodegradable substances.
Frequently these procedures entail determining the metabolic activity of the microorganisms using suitable sensors. Thus the metabolic activity increases when the sample to be investigated contains substances which are used by the microorganisms as nutrients. Thus, biological oxygen demand (BOD), which is used as indicator for water pollution, is based on determination of oxygen consumption through the metabolic activity of microorganisms which are incubated with the sample to be investigated.
Microorganisms can also be used as toxicity indicators, because the metabolic activity decreases in the presence of toxic substances which lead to a reduction in the activity or even to death of the cells.
Microorganisms can in the above applications be employed as conventional cultures in minireactors or shake cultures in order to follow the metabolic activity of the cells, for example on the basis of the oxygen consumption or the cell growth, over a lengthy period. However, for some years there have also been approaches to shortening the analysis times required by automating sample delivery and shortening the incubation time, especially when it is not necessary to achieve an equilibrium state. In addition, microorganisms can be combined directly with the detectors by enclosing the microbial cells in polymers directly on electrodes or between membranes. Also in some circumstances polymers may be used in which the organisms are embedded for additional protection. These membranes may be fixed adjacent to a detector, for example an electrode with special mounting devices.
Microbial sensors, for example for determining a BOD value, may be fabricated in this way. However, if these sensors are used as detectors in automated analytical systems, special forms of construction need to be provided on the microbial membrane to enable the sample to be passed over the membrane. As a rule, only a small part of the membrane then comes into contact with the sample and for only a short time. The active surface of the membrane, which is restricted by the size of the detector and sample delivery construction, has a limiting effect, as a result of which only a restricted amount of microorganisms can be actively utilized.
Other forms of construction consist of cartridges (known from the use of immobilized enzymes) which are filled, as small columns, with polymers or glass particles on which enzymes or other proteins can be immobilized. Compared with membranes, they have the advantage that the amount of proteins which can be actively utilized is limited only by the size of the cartridge. In addition, because the sample flows through the cartridges of this type, a good contact between proteins and sample is ensured, and thus a good conversion of the analyte is achieved, which leads to relatively large signals. Cartridges of this type are used in flow systems in which the detector is then located downstream.
It is possible in principle to enclose microorganisms in cartridges of this type, because microorganisms can be adsorbed onto porous carriers. However, flow through the reactors is successful only when the internal pressure in the cartridge is not too high. The internal pressure depends, on the one hand, on the particles used to adsorb the cells and, on the other hand, on the mesh width of the gratings used to retain the particles in the cartridge. The fact that the cells are merely adsorbed onto the carrier particles means that they can also be washed off. If the mesh width of the gratings is so small that not only the particles but also washed-off microorganisms are retained in the cartridge, then the internal pressure becomes so high that conventional peristaltic pumps and, even more so, micropumps can no longer ensure transport of the sample through the cartridges. However, without appropriate membranes the microorganisms are discharged from the system, which can lead to falsification of the signals. An additional factor is that in cartridges of this type, reproducible cell loading can be achieved only with difficulty because the number of cells adsorbed on carriers cannot be easily regulated.
The invention is therefore based on the object of developing a novel device for contacting microorganisms or other biological material with fluids, e.g. liquids to be analyzed. The invention particularly relates to microbial membrane reactors for use in a flow system, in which microorganisms can be introduced easily and reproducibly, and discharge of the organisms from the reactor is prevented.
It will be appreciated that where in the following description, microorganisms are referred to, other biological materials may be employed instead of microorganism as such. Thus the term “microorganism” is intended to embrace not only prokaryotic and eukaryotic unicellular organisms but also cells or tissues of human, plant or animal origin.
Thus where the term “microbial membrane reactor” is used, it is intended to refer to a device including a membrane provided with any of the forms of “microorganism” encompassed by the above definition.
According to the present invention there is provided a device for carrying out a process in which microorganisms or other biological materials interact with components of a fluid, comprising a membrane sandwiched between opposed surfaces of first and second structural elements, characterised in that the microorganisms or other biological materials are located between the first structural element and the membrane and the inner surface of the second structural element that abuts the membrane is provided with one or more flow channels for flow of said fluid over the surface of the membrane. The membrane, which is preferably sterile, may be permeable to the fluid and substances dissolved in the fluid, e.g. dissolved gases and substances that may be metabolised by or otherwise interact with the microorganisms.
The present invention paarticularly relates to a microbial membrane reactor for use in flow systems, which has a first element with a planar inner surface to receive the microorganisms and a second element which is likewise provided with a planar inner surface and on which at least one flow pathway is formed, where the first and second element are arranged with their insides in contact, and a sterile membrane is arranged between the elements.
The pore size of the sterile membrane is preferably chosen so that it is impervious to the microorganisms used. The microorganisms are preferably arranged in a microbial membrane located between the inner surface of the first element and the sterile membrane. In other words, the sterile membrane covers the microbial membrane in relation to the flow pathways.
The invention also includes reactors which do not use microbial membrane. This may be by, for example, directly applying the microorganisms to the side of the sterile membrane facing the first element. This might be achieved by filtering the cells through the sterile membrane. It is also possible furthermore for the microorganisms to be applied directly to the planar inside of the first element, for example by applying a solution, a gel or a paste etc., comprising the microorganisms.
The elements of the membrane reactor can preferably be connected together by fixing means, for example by screws which grip through appropriate passages bored in the elements so that the elements are pressed together. However, other connection techniques such as gluing or bonding are possible.
The flow pathways are preferably designed as flow channels, it being possible to alter the contact area betwee
Arnold Tatjana
Binz Dieter
Heim Sabrina
Keeping Sean Crispian
Schillig Henning
ABB Limited
Beisner William H.
Larson & Taylor PLC
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