RU2790016C2 - Compositions providing synergetic effect in control of biofilm - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to suppression and removal of biofilm from surfaces in contact with a water system used in the industry. A method for suppression and removal of biofilm from a surface in contact with the water system includes a stage of addition to the water system of a biofilm-destructing agent selected from sodium dodecylbenzolsulfonates and a biocide selected from monochloramines, dichloramines, and a combination thereof, while sodium dodecylbenzolsulfonate is in amount equal to from 1 mg/l to 39 mg/l per a volume of water subjected to processing; and amount of the biocide is from 1 mg/l to 10 mg/l per active chlorine. The ratio of the biocide weight to the weight of the biofilm-destructing agent is from 1:1 to 1:40. A composition for suppression and removal of biofilm from a surface in contact with the water system is also disclosed, containing a biofilm-destructing agent, which is sodium dodecylbenzolsulfonates, and a biocide selected from monochloramines, dichloramines, and a combination thereof, in certain amount.

EFFECT: invention provides a synergetic effect in control of biofilms, which allows for significant reduction in a number of used reagents, while saving the required result in control of biofilm.

3 cl, 2 tbl, 2 ex

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority over Provisional Patent Application No. 62/573871, filed October 18, 2017, which is hereby incorporated by reference in its entirety.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to the control of microorganisms in the aquatic environment.

BACKGROUND OF THE INVENTION

Microbial biofilms that occur in industrial, industrial and urban systems and structures have a significant adverse effect on the operation and operation of these systems and structures, including a decrease in heat transfer, clogging of pipes and pipelines, acting as a reservoir of pathogenic microorganisms, causing mechanical and structural damage, contributing to corrosion, polluting and destroying food, drinking and recreational water, and deteriorating appearance.

In the context of the present invention, biofilms are defined as microbes that settle on surfaces, attach to surfaces and then grow and exist on them. They may be composed of a single species of organism or they may be multispecific and may be composed of bacteria, viruses, fungi, algae and eukaryotic micro- or macro-organisms such as amoeba, diatoms, nematodes and worms. Biofilms can exist in liquid-immersed form, in intermittent wetting zones, in humid environments, and even in dry environments, such as found on the surfaces of sculptures and buildings. Biofilms are structurally composed of microbial cells embedded in a mixed molecular polymer matrix composed of polysaccharides, protein, DNA (deoxynucleic acid), and numerous small molecules. In natural environments, they can also be found in mud, soil, plant material, and other environmental components. This material is often referred to as sludge. The structure of the biofilm is significantly affected by the composition of the environment and the shear force that occurs when the matrix moves over the film.

Unlike microbes floating freely in a high-volume environment, the gene sequences of microbes that live in an immobile environment are extremely broad, with their genomes varying from a few genes to almost 50% of their genomes. These changes have an extremely strong impact on the susceptibility of biofilm cells to chemical biocides, antibiotics, and other environmental stressors. In addition to common physiological changes in biofilm cells, it is in a polymeric matrix, which can interfere with access to cells of biocides or antibiotics, further reducing their susceptibility. More than 1000-fold changes in biocide and antibiotic susceptibility are described in the literature.

The most common technique for combating biofoams has been the use of chemical biocides, including oxidative, reactive, and membrane-active biocides. It has been found that, regardless of the mechanistic class of biocides, biofilms are more resistant to their inhibitory and bactericidal activity for the reasons described in the previous paragraph, this leads to the need to use the biocide at high concentrations to provide the desired effect.

Oxidative biocides are commonly used as biofilm control agents in a wide variety of industrial, industrial and urban environments because they are inexpensive and effective against planktonic microbes. They can be effective in killing microbes, but due to the high concentrations used, the cost of treatment and the corrosive effect of oxidants on building materials, and in some cases regulatory restrictions, their use at concentrations effective for long-term biofilm kill is often difficult.

Although oxidative biocides can destroy significant portions of a biofilm population, they are ineffective in removing biofilms from surfaces. This is unsatisfactory because some of the adverse effects of biofilms are due to their physical presence on the surface. For example, biofilms are excellent insulators and greatly inhibit heat transfer in cooling towers and chillers, and although a treated biofilm may be largely dead, it will still insulate the surface. In addition, a large number of dead cells provides the surviving fragment of the treated population with a ready source of nutrients and biofilms tend to rapidly re-grow to their original density.

To increase the effectiveness of the destruction of microbes and to remove them from the surface, additional treatment with biofilm-destroying materials was carried out in conjunction with treatment with biocides. These biofilm destroying agents are most commonly anionic, cationic, or nonionic surfactants, the proposed mechanism of action of which is interaction with the biofilm structure that allows the biocide to more efficiently penetrate the biofilm and remove the biofilm through their surfactant characteristics. Although these biofilm destroying agents have been commercially available for a long time, they are most often not used in large quantities, probably due to the effectiveness of treatment programs using both oxidative and non-oxidative biocides. However, market conditions, costs, and environmental concerns have led to a demand to reduce the amount of biocides used without compromising the effectiveness of microbial killing programs, and interest in the use of dispersants has begun to increase in various areas of the market, especially those related to industrial cooling water. The relative potency of these biofilm destroying agents can be expected to range from poor to good, and their effectiveness can be influenced by the composition of the bulk matrix. Based on their chemical interactions and effect on biofilm structure, some combinations of oxidative biocides and biofilm disrupting agents would also be expected to be more effective than others.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is essentially illustrative only and is not intended to limit the present invention or the practice and application of the present invention. In addition, one should not be limited by any of the theoretical considerations given in the prior art or the following detailed description of the present invention.

According to the invention, it has surprisingly been found that certain combinations of biocides, preferably oxidizing biocides, and biofilm destroying agents provide a synergistic effect in the fight against biofilms, expressed in both their destruction and removal from the surface. The combined effect of exposure to biocides and biofilm destroyers is substantially greater than simply the combined effect of exposure to the two chemicals, so the amount of one chemical, or the amount of both chemicals, can be substantially reduced and still provide the desired biofilm control effect. This synergistic interaction is not found for all combinations of chemicals, nor for all ratios of the amounts of two chemicals.

The present invention relates to a method for destroying and removing biofilm from surfaces in contact with an industrial water system, comprising the step of adding a biofilm destroying agent in an effective amount and adding a biocide to the water system, which is treated to reduce the number and remove biofilm forming microbes from surface in contact with the water system.

The present invention also relates to a synergistic composition containing a biofilm destroying agent and a biocide.

Oxidizing biocides useful in the present invention include sodium hypochlorite, calcium hypochlorite and other hypochlorites, hypochlorous acid, hypobromic acid, monohaloamine biocides derived from ammonium hydroxide, ammonium chloride, ammonium sulfate, ammonium acetate, ammonium bicarbonate, ammonium bromide, carbonate ammonium, ammonium carbamate, ammonium sulfamate, ammonium nitrate, ammonium oxalate, ammonium persulfate, ammonium phosphate, ammonium sulfide, urea and urea derivatives, and other compounds containing a nitrogen atom, capable of donating an ammonium ion, when reacted with a fragment containing a chlorine or bromine atom, such as a chlorinated or armored oxidizing agent, preferably with hypochlorous acid or hypochlorite, more preferably with hypochlorite; and mixtures of ammonia-derived chloramines such as monochloramine and dichloramine. Such haloamine-based biocides are known in the art, see, for example, US 7285224, US 7052614, US 7837883, US 7820060. Other oxidative biocides include dibromonitrile propionamide, bromochlorodimethylhydantoin and other halogenated hydantoins, and trichloroisocyanuric acid. Non-oxidizing biocides used for biofilm control and for which they are believed to be suitable for use with a dispersant include isothiazolone-based biocides, glutaraldehyde, formaldehyde and formaldehyde-releasing compounds, tetrakishydroxyphosphonium chloride, as well as other non-cationic biocides.

The biofilm destroying agent used in the present invention is an anionic surfactant, preferably an anionic sulfonate surfactant. Anionic surfactant sulfonates for use in the present invention include alkyl sulfonates, linear and branched primary and secondary alkyl sulfonates, and linear or branched alkyl aromatic sulfonates. Particularly preferred are surfactant alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate. Other dodecylbenzenesulfonates can also be used as long as the counterion (in this case being the sodium ion) does not affect the mechanism of action of the destructive agent.

Linear alkylbenzenesulfonates (sometimes also referred to as LABS) are a class of organic compounds represented by the formula C ₆ H ₅ C _n H _2n+1 . Usually, the average value of n is from 10 to 16. Linear alkylbenzenes are usually containing medium length alkyl groups, for example, medium length alkyl groups may be C ₁₂ -C ₁₃ or C ₁₂ -C ₁₃ or C ₁₀ -C ₁₃ .

Sodium dodecylbenzenesulfonates ("DBSN") are alkylbenzenesulfonates. Most sodium dodecylbenzenesulfonates are linear alkylbenzenesulfonates, which means that the dodecyl group (C ₁₂ H ₂₃ ) is unbranched. This dodecyl chain can be attached to the benzenesulfonate group at position 4.

The present invention also relates to a synergistic composition containing a biofilm destroying agent and a biocide, in which the biofilm destroying agent is sodium dodecylbenzenesulfonate and the biocide is a haloamine, preferably selected from the following: monohalogenamine, dihalogenamine, and combinations thereof. The halogenamine may be chloramine. Preferably, the ratio of biofilm destroying agent to oxidizing biocide is from 1 part biocide to more than 1 part biofilm destroying agent. The weight ratio of biocide to biofilm destroying agent may be from 1:1 to 1:20, more preferably from 1:1 to 1:8.

The interaction of two chemicals contained in the composition can occur through three possible mechanisms. In accordance with the first mechanism, the two chemicals interact negatively and with a decrease in the combined effect of exposure to the composition, so that the result provided is less than what would be expected based on the total activities of the substances. Thus, if one substance used alone provides a measurable value of 50 and another substance used alone provides a value of 50, then in a negative interaction the combined reduced value for the two substances is less than 100. According to another mechanism, they can interact additively, with the end result being the simple sum of the two values. Thus, if two substances are combined, each of which can provide a value of 50, then the total combined value is 100. According to the third mechanism, which is most preferred in the case of microbial control, the result of combining two substances, each of which can provide a value equal to 50 is some value greater than 100.

Researchers have developed a formula to determine the nature and degree of interactions of the components contained in the combination. In the art of microbial control, a commonly used equation is that described in Kull et al. (Kull et al., 1961, J. Appl. Microbiology 9:538), which is incorporated herein by reference. Recent patent examples of the use of this equation are those described in US Pat. No. 9,555,018, Synergistic combinations of organic acids useful for controlling microorganisms in industrial process, and US Pat. acid extracts and organic acids. The original Kull equation for potency uses minimum inhibitory concentrations of antimicrobials (MICs) as endpoints. The MIC value is the lowest measured concentration of an antimicrobial agent that results in inhibition of microbial culture growth. Growth inhibition can be determined visually by examining the turbidity of the microbial culture, it can be determined by counting viable cells by culture or microscope techniques, or by some metabolic activity parameter, and other possible techniques. The equation is given below:

Synergy score = (endpoint a/endpoint A) + (endpoint b/endpoint B),

where end point A means the end point for substance A used alone, end point a means the end point for substance A used in combination with substance B, end point B means the end point for substance B used alone, and end point b means the end point point for substance B used in combination with substance A.

In the present invention, the effectiveness of substances used alone and in combination was determined by counting the number of viable cells in the model biofilms remaining after treatment. The Minimum Biofilm Kill Concentration (MBC) is defined as the concentration that results in a 95% reduction in viable cells compared to an untreated control. With relatively non-toxic dispersants, it is not possible to achieve this degree of destruction using physically possible concentrations, so for these substances the MSM Code is considered to be the highest value obtained in the study. Because this value is used as a divisor in the equation for the synergy score, this highest value found in the study is actually an underestimation of the ISM Code and thus the synergy scores are also underestimated.

The present invention is primarily intended for use in industrial process water, especially in cooling towers, evaporators, chillers, condensers, pulp and paper mills, boilers, waste water, reclaimed waste water, mineral slurries, starch slurries, clay slurries, biological treatment waters, sludges, colloidal slurries, irrigation waters, oil and gas production waters, and combinations thereof. However, it can also be used in any industrial process that is compromised by the formation of biofilms in aqueous media. It is expected that the present invention may also be applied to the treatment of geothermal environments, oil and gas recovery, and CIP cleaning procedures.

The concentration of the biofilm destroying agent used, such as SDBS, is in the range of 1 to 100 mg/(L (ppm) of water contained in the aqueous system being treated), or 1 to 50 mg/L, preferably 1 to 15 mg/l, more preferably 2 to 10 mg/l and most preferably 2-6 mg/l.

The biocide is added in an amount calculated as the amount of active Cl ₂ , usually ranging from at least 1.0 ppm, calculated as the amount of Cl ₂ , or at least 1.5 ppm, calculated as the amount of Cl ₂ , or preferably at least 2 ppm calculated as Cl ₂ or more, or at least 2.5 ppm calculated as Cl ₂ or more, and up to 15 ppm million, calculated as the amount of Cl ₂ or more, preferably up to 10 ppm, calculated as the amount of Cl ₂ , based on the addition of 1 mg of biocide in terms of 1 liter of treated water. Preferably, the amount of biocide is between 1.5 and 10 mg per liter of treated water.

Preferably, the ratio of the weight of the biofilm destroying agent to the weight of the biocide, preferably the oxidizing biocide, is from 1 part of the biocide to more than 1 part of the biofilm destroying agent. The weight ratio of biocide to biofilm destroying agent may be from 1:1 to 1:40, preferably from 1:1 to 1:20, more preferably from 1:1 to 1:8. For each component, the values are massive.

One skilled in the art can determine the best addition position, however, a position just before the contamination site is generally preferred. Thus, for example, the present invention can be applied such that the addition position is in the receiver of the cooling tower, or directly in the distribution chamber or headbox of the cooling tower, thus processing the cooling water supply system.

The biofilm destroying agent and the oxidative biocide may be added sequentially or simultaneously, or the components may be mixed together and added as a single composition.

EXAMPLES

Example 1 Synergistic Effects of Monochloramine and SDBS A dose-response study was performed to determine the Minimum Concentration Required to Kill Biofilm (MBA) for monochloramine and SDBS used alone. The MSM is defined as the concentration of agent that results in a 95% reduction in the viable biofilm population compared to the value for the untreated control sample, calculated by viable cell count on a plate. Experiments were then carried out to investigate the effect of combining two agents, an oxidative biocide, monochloramine, and a dispersant, SDBS, on the biofilm population. In the experiments, 3 concentrations of monochloramine and 4 concentrations of SDBS were investigated. The SDBS used in the examples was Bio-Soft™ D-4 (Stepan Company, Northfield, IL).

M9YG medium is a simple minimal salt medium supplemented with 500 mg/l glucose and 0.01% yeast extract. The composition of the salts is designed to reproduce the typical composition of water in a cooling tower. The composition of the medium was prepared according to the following procedure: the salt-containing composition 5XM9 was prepared by mixing 64 g of Na ₂ HPO ₄ ⋅7H ₂ O, 15 g of KH ₂ PO ₄ , 2.5 g of NaCl and 5 g of NH ₄ Cl in 1 l of water. It was divided into 200 ml aliquots and sterilized (autoclaved). Sterile supplemental solutions were added to 750 ml of sterile deionized water with stirring. Addition of CaCl ₂ formed a white precipitate, but it dissolved on stirring. The supplementary solution consisted of 200 ml of composition 5XM9, 2 ml of 1M MgSO ₄ solution, 0.1 ml of 1M CaCl ₂ solution, 20 ml of 20% glucose solution, 1 ml of 10% yeast extract and an amount of water sufficient to obtain 1000 ml of solution. See publication: Molecular Cloning - A Laboratory Manual (Second Edition). 1989. J. Sambrook & T. Maniatis. Cold Spring Harbor Press.

The innoculum used in the examples were overnight cultures of Pseudomonas putida. Pseudomonas are common contaminants of cooling water, and although microbial populations in cooling water are polymicrobial, pseudomonads are often used in such studies as typical representatives of an entire population.

Biofilms were grown on 316 stainless steel samples in a CDC Biolilm reactor using M9YG growth medium with minimal salt for 24 hours. Only SDBS, monochloramine alone, and combinations of oxidizing agent and dispersing agent were added to the wells of a 12-well cell culture plate. A control experiment was performed using the M9YG medium. After biofilm growth, each sample was collected from the unscrewed fragment of the CDC reactor rod and placed in a well of the plate. The plate was then incubated with shaking at 28°C for 2 hours. After incubation, the samples were removed from the wells and placed in 5 ml of phosphate buffered saline (PBS) and sonicated for 6 minutes. The number of viable cells released into the medium was then determined by plate count.

Synergy scores were determined as described in Kull et al. and in Example 1.

From Table 1, it can be seen that using monochloramine alone, a concentration of 20 mg/l is needed to provide a reduction in the viable biofilm population of more than 90%, and SDBS at a concentration of 800 mg/l provides a reduction of 48.62%. However, many ratios of the two agents tested provide higher activity than would be expected by simply summing the activities of the two agents used alone. For example, a combination of 2.5 mg/l MCA (monochloramine) (1/8 of the amount of MCA used alone) and 25 mg/l SDBS (1/32 of the amount of SDBS used alone) can provide the target MCA, which is reduction of viable biofilm cells by 95%. This synergistic effect was obtained with ratios of the amount of MCA to the amount of SDBS ranging from 1:1.25 to 1:31.2.

Example 2 Synergistic Effects of Monochloramine/Dichloramine Mixture and SDBS

A dose-response study was performed to determine the minimum concentration required to kill biofilm (MCBM) for a mixture of monochloramine/dichloramine (MXA/DCA) and SDBS alone. The MSM is defined as the concentration of agent that results in a 95% reduction in the viable biofilm population compared to the value for the untreated control sample, calculated by viable cell count on a plate. Experiments were then performed to investigate the effect of combining two agents, an oxidative biocide, MCA/DCA, and a dispersant, sodium benzenesulfonate, on the biofilm population. In the experiments, 2 concentrations of MCA/DCA and 4 concentrations of sodium benzenesulfonate were investigated.

Briefly, the procedure was as follows: biofilms were grown on 316 stainless steel samples in a CDC Biofilm reactor using M9YG growth medium with minimal salt content for 24 h. Only SDBS, only monochloramine, and combinations of an oxidizing agent and a dispersing agent. A control experiment was performed using the M9YG medium. After biofilm growth, each sample was collected from the unscrewed fragment of the CDC reactor rod and placed in a well of the plate. The plate was then incubated with shaking at 28°C for 2 hours. After incubation, the samples were removed from the wells and placed in 5 ml of phosphate buffered saline (PBS) and sonicated for 6 minutes. The number of viable cells released into the medium was then determined by plate count.

Synergy scores were determined as described in Kull et al. and in Example 1.

It can be seen from Table 2 below that using only a MCA/DCA mixture, a concentration of 10 mg/l is needed to provide a reduction in the viable biofilm population of more than 90%, and SDBS at a concentration of 312 mg/l provides a reduction of 84.58%. many of the ratios of the two agents tested provided higher activity than would be expected from a simple summation of the activities of the two agents used alone. For example, a combination of 2.5 mg/L MCA/DCA (1/8 of the amount of MCA/DCA used alone) and 9.8 mg/L SDBS (1/32 of the amount of SDBS used alone) can provide the final point - MKUB, representing a decrease in viable cells of the biofilm by 99%. This synergistic effect was obtained with ratios of the amount of MCA/DCA to the amount of SDBS ranging from 1:1.6 to 1:31.6.

While at least one exemplary embodiment has been presented in the above detailed description, it should be understood that a large number of modifications exist. It should be understood that the exemplary embodiment or exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the present invention in any way. With the above detailed description, those skilled in the art are rather provided with a suitable embodiment of an exemplary embodiment within the scope of the present invention. It should be understood that various changes can be made to the function and arrangement of the elements described in the exemplary embodiment without departing from the scope of the present invention as set forth in the appended claims and their acceptable equivalents.

Claims (3)

1. A method for suppressing and removing biofilm from a surface in contact with an aqueous system, comprising the step of adding to the aqueous system a biofilm-destroying agent selected from sodium dodecylbenzenesulfonates and a biocide selected from monochloramines, dichloramines, and combinations thereof, while sodium dodecylbenzenesulfonate is in an amount equal to from 1 mg/l to 39 mg/l, in terms of the volume of water being treated; and the amount of biocide is from 1 mg/l to 10 mg/l, in terms of active chlorine; and the ratio of the mass of biocide to the mass of biofilm destroying agent is from 1:1 to 1:40, thereby reducing and removing biofilm from the surface in contact with the water system. 2. The method of claim 1, wherein the water system is selected from the group consisting of: cooling towers, evaporators, chillers, condensers, pulp and paper mills, boilers, wastewater, reclaimed wastewater, mineral slurries, starch slurries, clay slurries, biological treatment waters, sludges, colloidal slurries, irrigation waters, oil and gas production waters, and combinations thereof. 3. A composition for suppressing and removing biofilm from a surface in contact with an aqueous system, containing a biofilm-destroying agent and a biocide, characterized in that the biofilm-destroying agent is sodium dodecylbenzenesulfonates and the biocide is selected from monochloramines, dichloramines, and combinations thereof, while sodium dodecylbenzenesulfonate is in an amount equal to from 1 mg/l to 39 mg/l, in terms of the volume of water being treated; and the amount of biocide is from 1 mg/l to 10 mg/l, in terms of active chlorine; and the ratio of the mass of the biocide to the mass of the biofilm destroying agent is from 1:1 to 1:40.