Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-03-08
2003-04-15
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C162S161000, C422S028000, C424S778000, C424S725000, C514S690000
Reexamination Certificate
active
06547971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the control of organisms, such as microorganisms, and in particular the inhibition of such organisms by employing hop acids to inhibit the growth of such organisms and/or kill such organisms. By way of illustration only, the invention has particular utility in aqueous systems, such as papermaking systems and process water systems, in particular systems that involve circulating and/or recirculating water systems, such as cooling water systems, etc.
2. Background of the Invention and Related Art
The control of organisms, and microorganisms in particular, has been a continuing and troublesome problem in aqueous systems, such as systems that involve circulating and/or recirculating water systems, such as such as papermaking systems and process water systems, cooling water systems, etc. Such microorganisms cause biofouling, such as deposits of microorganisms or products (such as metabolic products) of microorganisms that cause the formation of deposits such as films, mats and other deposits which can result in plugging of pores, reduced flow, reduced heat exchange rates, clogging, etc.
Slime formation, deposit formation and the formation of filamentous bacteria have been of particular concern, for example.
By way of non-limiting example only, filamentous bacteria (for example,
Sphaerotilus natans
) are often the cause of deposits on paper machines and fouling in cooling systems. Many types of filamentous bacteria grow on submerged surfaces in single chains within structures referred to as “sheaths.” Sheaths are considered to be a protective structure, and as such, the structure promotes the survival of the organism. For example, the sheath structure is thought to protect the organism from biocides, because, for example, getting the biocide into the protective structure poses a problem. Filamentous bacterial growth on submerged surfaces in paper process streams can contribute to the formation of large deposits consisting of cells and inert materials (particulates, fines, fiber, etc.) that become enmeshed in the filaments. Long “stringers” of the filamentous bacteria as well as large clumps of deposits can become dislodged and cause problems such as holes, other defects, and breaks in the paper. This, therefore, can cause significant increases in the cost of producing paper. Filamentous bacteria also cause problems in cooling towers. Submerged surfaces fouled with filamentous and other types of bacteria cause a reduction in the efficiency of heat transfer, in cooling systems for example, as well as other problems resulting from large amounts of biomass becoming dislodged and circulating within an industrial setting.
The control of such microorganisms is even more difficult in view of the fact that many of the microorganisms which are the cause of such problems are resistant to attempts to control them, such as by inhibiting their growth and/or killing them. For example, microorgansims that pose problems in aqueous industrial systems, such as process waters and papermaking systems, are resistant to a broad spectrum of conditions and materials, and thus are able to remain viable in a wide variety of such conditions. Therefore, biocides have been employed in efforts to control such microorganisms. However, conventional biocides are expensive, are not sufficiently environmentally friendly, exhibit an undesirably broad spectrum of activity (i.e., they are not targeted to the specific microorganisms desired to be killed), must be employed in relatively large concentrations, and/or can be harmful and/or dangerous and/or even toxic to humans. Moreover, in aqueous systems or media in which the control of organisms is desired, the compatibility of the compositions and methods employed are also a consideration. Accordingly, a biocide which is effective with regard to the foregoing and which does not exhibit the mentioned disadvantages is desired.
With respect to all of the foregoing, there has been a continuing need for improvement.
It is known in the brewing industry that some hop acids can inhibit the growth of microorganisms that can cause spoilage in beer. For example, U.S. Pat. No. 5,082,975 discloses that the hop acid, hexahydrolupulone, can inhibit the growth of certain Lactobacillus. This patent further discloses that there has been speculation that hops may have helped control brew house bacterial infections due to the presence of hop acids in the wort and beer. However, since the hop beta acids are not found in beer, such control, if it indeed existed, was thought to have been due to the hop alpha acids and iso-alpha acids. Beta acids are known to be highly unstable, being oxidized in the boiling wort to bitter hulupones and by themselves to deteriorate in a matter of days or hours after crystallization. This lack of stability is now shown to be overcome by conversion to hexahydrolupulone (hexahydro beta acids). There is a vast excess of lupulone available as a result of being discarded in the brewing process, making it a potentially inexpensive raw material. U.S. Pat. No. 4,918,240 is a related patent to U.S. Pat. No. 5,082,975. Each of these patents is hereby incorporated by reference as though set forth in full herein.
U.S. Pat. No. 5,455,038 discloses that the hop acids, tetrahydroisohummulone and hexahydrocolupulone (&agr; and &bgr; hops, respectively), a product of the brewing industry, have been identified as compounds that can inhibit food born pathogens from the genera Listeria, Staphylococcus, Bacillus, and Clostridium. In addition, U.S. Pat. No. 5,286,506 discloses that solid food products can be protected from food pathogens, including
Listeria monocytogenes,
by incorporating beta-acids, which are extracted from hops, into such food products. U.S. Pat. No. 5,455,038 discloses the inhibition of Listeria with &agr; and &bgr; hop acids. Each of these patents is hereby incorporated by reference as though set forth in full herein.
Derivatives of the &bgr;-hydrogenated lupulones can inhibit or kill cancer cells (WO 97/31630 and WO 98/11883) as well as antibiotic resistant strains of
Staphylococcus aureus, Mycobacterium tuberculosis
, and
Mycobacterium avian
Complex or enterococcus (“Antimicrobial activity of the Semisynthetic Compound, Hexahydrocolupolone”, Stephan et al.,
Journal of Antimicrobial Chemotherapy
(1998) 41, 519-522). Each of these documents is hereby incorporated by reference as though set forth in full herein. Additionally, &agr; and &bgr; hop acids have been identified as a therapeutic agent for methicillin resistant
Staphylococcus aureus
(Japanese Patent document JP 9067250). This document is hereby incorporated by reference as though set forth in full herein.
U.S. Pat. No. 5,370,863 discloses that oral care compositions containing hop acids or their salts are effective in inhibiting Gram positive bacteria, including
Streptococcus mutans
, which can cause plaque or periodontal disease, which document is hereby incorporated by reference as though set forth in full herein. A representative composition is a toothpaste containing tetrahydroisohumulone.
Hop acids have been considered to be selective to Gram-positive bacteria. See, for example, WO 98/11883, incorporated by reference above.
SUMMARY OF THE INVENTION
The invention provides a method of controlling organisms, such as microorganisms, particularly bacteria, in aqueous systems or media, such as papermaking systems and process water systems, in particular systems that involve circulating and/or recirculating water systems, such as cooling water systems, etc., which method employs materials which are readily available from renewable resources and which are also effective.
The invention provides a method of controlling such organisms in such aqueous systems which method employs materials which are relatively inexpensive.
The invention provides a method of controlling such organisms in such aqueous systems which method is effective against a wide variety of microorganisms but which are also targeted to the microorganisms w
Breen Alexander W.
Cronan, Jr. John M.
Davis Phillip S.
Mayer Michael J.
Singleton Freddie L.
Hercules Incorporated
Hruskoci Peter A.
Rossi Joanne
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