SYNERGISTIC COMBINATION OF ORTHO-PHENYLPHENOL AND BIS-(3-AMINOPROPYL)DODECYLAMINE

Abstract

A synergistic antimicrobial composition containing ortho-phenylphenol and its salts and bis-(3-aminopropyl)dodecylamine is provided. Also, a method of inhibiting the growth of or controlling the growth of microorganisms in an aqueous medium and an aqueous based product is further provided.

Claims

1. A synergistic antimicrobial composition comprising ortho-phenylphenol or its salts and bis-(3-aminopropyl)dodecylamine.

2. The synergistic antimicrobial composition of claim 1, wherein the weight ratio of the ortho-phenylphenol or it salts to bis-(3-aminopropyl)dodecylamine is from 1:1 to 100:1.

3. An aqueous-based product comprising the synergistic antimicrobial composition of claim 1.

4. An aqueous-based product comprising the synergistic antimicrobial composition of claim 2.

5. A method of inhibiting the growth of or controlling the growth of microorganisms in the aqueous-based product of claim 4.

6. The method of claim 5 wherein the aqueous-based product is used in aqueous systems selected form the group consisting of cooling water, air washer, heat exchangers, boiler water, pulp and paper mill water, ballast water, wastewater, metalworking fluids, oil and gas, latex, paint, coatings, adhesives, inks, tape joint compounds, pigment, water-based slurries, personal care products, detergent, filtration systems, toilet bowel, textiles, leather and leather production system.

Description

EXAMPLES

[0021] The synergism of the biocides combination of the present invention was determined using the Minimum Inhibitory (MIC) test method described by Kull, F. C., et. al in Applied Microbiology 9:538-541 (1961).

[0022] The formula to calculate the synergy index (SI) is

SI=Qa/QA+Qb/QB

Where

[0023] QA=minimum inhibitory concentration in ppm of compound A acting alone
Qa=minimum inhibitory concentration in ppm of compound A in the mixture.
QB=minimum inhibitory concentration in ppm of compound B acting alone.
Qb=minimum inhibitory concentration in ppm of compound B in the mixture.

[0024] Synergism of two biocides is demonstrated when the SI has a value less than 1. The mixtures showed an additive effect if SI is equal to 1 and antagonistic if SI is greater than 1.

[0025] The Minimum Inhibitory Concentration Test (MIC) is designed to evaluate the lowest concentration of a biocide, biocide blend or biocide combination to prevent bacteria growing in a defined broth.

Minimum Inhibitory Concentration (MIC) Testing Protocol:

[0026] The MICs of the single biocides NaOPP and BDA as well as of combinations of these two actives (all in TSB) in 3 different ratios (1:1; 10:1, 100:1) were estimated against each of the 4 microorganisms Staphylococcus aureus (DSMZ#799), Pseudomonas aeruginosa (DSMZ#939) and Candida albicans (DSMZ#1386), Pseudomonas putida, respectively.

[0027] Although the efficacy can vary significantly against different microorganisms the same starting biocide levels were chosen for all strains (3000 ppm for single NaOPP, 200 ppm for single BDA and 200 ppm/200 ppm, 2000 ppm/200 ppm and 3000 ppm/30 ppm for the combinations 1:1, 10:1 and 100:1, respectively).

[0028] The synergy testing was carried out as follows: [0029] 1. The test was executed with a Hamilton MLStarPlus robot using automated turbidity reading with BioTek Synergy H4 plate reader. [0030] 2. Biocide systems were prepared in 2.2 ml deep well plates by transferring and diluting biocides from stock solutions to first rows of the plates. The concentrations of biocides in stock bottles were adjusted to be 20 more concentrated than the highest desired concentration. [0031] 3. Then 15 subsequent serial dilutions with dilution factor 1.3 were performed resulting in 16 different concentrations for each system. [0032] 4. In the next step serially diluted biocide systems were transferred to the media blocks containing 850 l of TSB medium adjusted to pH 5. For each biocide system 100 l was transferred to the media, resulting in 950 l of final volume of media+biocides and 9.5 times dilution of the biocides from the biocide plate. At this point, the concentrations of all biocides in media were 1.053final concentration. [0033] 5. After preparation and mixing of the described systems, 4 aliquots of 190 l were prepared in 96-well microtiter plates. [0034] 6. Preparation of the microbe suspension:

[0035] Bacterial Cultures:

TABLE-US-00001 Pseudomonas aeruginosa DSM # 939 ATCC# 15442 Staphylococcus aureus DSM # 799 ATCC# 6538 Pseudomonas putida n/a n/a [0036] The culture was maintained as a glycerol stock at 80 C. in cryovials. A cryovial was thawed and then 100 l spread on a TSA agar plate. After incubation for 1 day at 30 C. the bacteria were harvested with buffer at pH 7.3. A total viable count on TSA plate was carried out and bacterial suspension was diluted in buffer in order to deliver 210.sup.7 CFU/ml.

[0037] Yeast Culture:

TABLE-US-00002 Candida albicans DSM #1386 ATCC# 10231 [0038] The cultures were maintained as glycerol stocks at 80 C. in cryovials, are thawed and then 100 l spread on MEA (malt extract agar) petri dishes. [0039] The yeast strain plates were incubated at 28 C. for 1-2 days then harvested with buffer pH 5.0. [0040] Based on total viable count results, the inoculum was prepared. [0041] 7. Each test sample (190 l) was inoculated with the 10 l of microbe suspension to provide a level of 110.sup.6 CFU/ml of the bacteria species and 110.sup.5 CFU/ml of the yeast species. [0042] 8. The test samples were mixed and incubated at 30 C. for 2 days (48 hours) when tested against bacteria and 3 days (72 hours), respectively, when tested against yeast. [0043] 9. Growth of the micro-organisms leads to turbidity after incubation, clarity indicates no growth. Reading of the results was carried out by measuring absorbance at 600 nm for each sample at the beginning of the test (t.sub.zero) and after incubation (t.sub.endpoint). t.sub.endpoint was chosen at 48 hours for bacteria and 72 hours for yeast. The difference in absorbance between t.sub.endpoint and t.sub.zero was used to assign a score (1 if >0.2, confirming growth, and 0 if 0.2, confirming no growth) from which the MIC values were derived. The lowest concentration that showed no growth (score of 0) in the broth after incubation is taken as the MIC value.

[0044] The MIC's of single biocide and combinations thereof as well as the synergy indices are presented in Tables 1, 2, and 3.

TABLE-US-00003 TABLE 1 MIC results for single biocides (in ppm): Active ingredients [ppm] NAOPP BDA Staphylococcus aureus DSM# 799 129 91 Pseudomonas aeruginosa DSM# 939 167 200 Candida albicans DSM# 1386 167 260.sup.a Pseudomonas putida 283 200 .sup.aThe MIC couldn't be determined as there was still growth at the highest tested concentration of the active. The MIC indicated is an estimation and represents the next higher concentration (1.3x) than tested. It is likely that the actual MIC is greater than the value indicated.

TABLE-US-00004 TABLE 2 MIC results for combinations of two biocides (in ppm) NAOPP/ NAOPP/ NAOPP/ BDA BDA BDA Active ingredients 1 1 10 1 100 1 Staphylococcus 32 32 66 6.6 99 1.0 aureus DSM# 799 Pseudomonas 25 25 66 6.6 99 1.0 aeruginosa DSM# 939 Candida albicans 41 41 66 6.6 59 0.6 DSM# 1386 Pseudomonas putida 41 41 86 8.6 129 1.3

TABLE-US-00005 TABLE 3 Calculated synergy indices for the combinations in Table 2 Ratio NAOPP:BDA 1:1 10:1 100:1 Staphylococcus aureus DSM# 799 0.6 0.6 0.8 Pseudomonas aeruginosa DSM# 939 0.3 0.4 0.6 Candida albicans DSM# 1386 0.4.sup.b 0.4.sup.b 0.4.sup.b Pseudomonas putida 0.4 0.4 0.5 .sup.bThe Synergy Index is calculated based on a theoretical MIC value of BDA (see .sup.a) or on theoretical MIC values of NaOPP:BDA(10:1); the actual synergy index is less than or equal to the value calculated in the table.