Chemistry: molecular biology and microbiology – Apparatus – Bioreactor
Reexamination Certificate
2001-06-29
2003-11-04
Redding, David A. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Bioreactor
C435S307100, C435S801000, C252S186100, C252S188100, C252S188250, C252S188280
Reexamination Certificate
active
06642047
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to producing an anaerobic environment. In particular, the present invention relates to a device that utilizes exothermic chemistry to deplete oxygen and generate carbon dioxide to create an environment for the growth of anaerobic microorganisms. The present invention also relates to a method for generating such an anaerobic environment.
DISCUSSION OF THE BACKGROUND
In general, microorganisms are divided into groups based on their need for oxygen. For example, aerobes (aerobic microorganisms) are microorganisms that require oxygen to grow. Another group, facultative anaerobes, are able to grow in either the presence or absence of oxygen. A third group of microorganisms are those that can grow only in the presence of very low levels of oxygen. These microorganisms are termed microaerophiles. A fourth group are microorganisms that cannot tolerate oxygen and are either inhibited or killed by it are called anaerobes (anaerobic microorganisms).
The detection of microorganisms is important in everyday life. For example, microorganisms are the cause of many diseases of man and of other mammals. In order to treat these bacterial diseases, the infecting organism must first be identified so that the correct medication and/or treatment can be prescribed. Additionally, large scale processing of food requires constant monitoring for the presence of microorganisms. Thus, the detection of microorganisms is also essential in the food processing industry.
Detecting anaerobes and microaerophiles is difficult because these microorganisms must be incubated in a controlled gaseous environment that is either oxygen free or extremely oxygen deficient. Often times an oxygen deficient environment is provided by placing a Petri dish containing the microbial culture inside a container that is sealed from the outside atmosphere. For the incubation of Petri dishes, an apparatus such as an anaerobic jar is usually employed. The container (e.g, anaerobic jar) is then depleted of oxygen by any number of means.
The anaerobic jar can mechanically be depleted of oxygen. In U.S. Pat. No. 6,022,730 to Robinson, microbial cultures were placed in an anaerobic jar that was modified to have both a gas inlet and a gas outlet. The gas line into the anaerobic jar was connected to a sterile filter in order to filter out any possible microbial contaminants in the gas reservoir or in the gas line. The anaerobic jar was sealed and periodically flushed with sterile nitrogen gas for several hours until the effluent gas contained 0% oxygen, as measured by an oximeter, to ensure an anaerobic atmosphere.
Alternatively, chemical strategies can be employed to generate an oxygen depleted or oxygen free environment. One such example of oxygen depleting chemistry is used in the BBL GasPak (Becton Dickinson, Cockeysville, Md.). Here, oxygen depletion is accomplished by the reaction of hydrogen, which is generated by the decomposition of sodium borohydride, and atmospheric oxygen in the presence of palladium to form water. Carbon dioxide is generated separately from the oxygen depletion reaction by the reaction between sodium bicarbonate and citric acid in the presence of water.
Another example of oxygen depleting chemistry is the BBL GasPak Pouch, provided by Becton Dickinson, Cockeysville, Md. The BBL GasPak Pouch is a self contained system that produces carbon dioxide and uses up atmospheric oxygen by two independent reactions. In one reaction, carbon dioxide is generated by the reaction of citric acid and inorganic carbonate. In a separate reaction, oxygen is depleted by the formation of rust from the combination of fine iron powder with atmospheric oxygen.
U.S. Pat. No. 5,914,070 to Araki, et al. describes another chemical reaction system for the depletion of oxygen. This system is based on the use of organic acids, such as ascorbic acid, which react with atmospheric oxygen in the presence of a metallic catalyst to adjust the concentration of carbon dioxide. Carbon dioxide absorbers like magnesium or calcium hydroxide are used to maintain the carbon dioxide at an overall concentration of 3-7% and the oxygen concentration to no more than 1%. This chemistry is formulated so that no activation or addition of external reagents is required. The system merely has to be exposed to oxygen to start the chemical reaction.
However, the prior art oxygen depletion methods have several drawbacks such as those listed below.
For example, in mechanical approaches such the forcible gas displacement disclosed in U.S. Pat. No. 6,022,730, it is difficult to establish uniform test conditions, especially if more than one anaerobic jar is used. Additionally, these mechanical approaches are time intensive, often requiring hours until the desired oxygen concentration is obtained. Further, there is a need for equipment maintenance since external equipment is used to pump in the gas to purge the oxygen from the anaerobic jar.
In both the BBL GasPak and the BBL GasPak Pouch, water, an external agent, must be added to initiate the oxygen depletion reaction. Thus, the GasPak reactions require extra reagents and steps for activation. Additionally, in the GasPak chemistries, the rate at which oxygen is removed is not constant. As a result, it is difficult to achieve uniform culture conditions. Further, in the BBL GasPak, a suitable catalyst such as palladium must be added to the atmosphere of the jar. Because hydrogen gas is generated, this chemistry suffers from a potential explosion hazard and therefore can be extremely dangerous.
Although the approach taken by Araki et al. in U.S. Pat. No. 5,914,070 is convenient in the fact that there is no activation required and no need to a separate reagent such as water as in the GasPak chemistries, the reaction utilized is very complicated to formulate to balance the chemistry so that the proper amount of carbon dioxide is generated. Thus, there is a need to maintain the proper concentration of carbon dioxide.
The prior art assays and devices fail to provide a simple, fast, and effective oxygen depletion method that does not require an external reagent for activation, the addition of water or other external reagents, or maintaining the level of carbon dioxide. In view of the aforementioned deficiencies attendant with the prior art methods, it is clear that a need exists for a device and method for making a suitable atmosphere for the culture of the anaerobic bacteria in a simple manner.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention as embodied and broadly described herein, the present invention provides a device that utilizes exothermic chemistry to deplete oxygen and generate carbon dioxide.
It is an object of the present invention to provide an environment suitable for the culture of anaerobic bacteria.
It is another object of the present invention to provide a device that utilizes exothermic chemistry to deplete oxygen and generate carbon dioxide to create an anaerobic environment.
It is yet another object of the present invention to provide a method for creating an anaerobic environment.
It is a further object of the present invention to provide a safe and effective method for generating an anaerobic environment suitable for the culture of anaerobic bacteria.
The above and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the presently preferred embodiments, when considered in conjunction with the drawings, and to the appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various types of exothermic heat dispensing packets known as hand warmers or hot packs are known in the art and are commercially available in sporting good stores. The activation of these packets is accomplished by various means such as exposure to air, mixing with water, kneading, or puncturing of an inner bag to mix the chemicals and start the heat generating reaction. A disposable body warme
Becton Dickinson and Company
Redding David A.
Weintraub Bruce S.
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