Synergistic combination of bis-(3-aminopropyl)dodecylamine and sorbic acid

Abstract

A synergistic antimicrobial composition containing bis-(3-aminopropyl)dodecylamine and sorbic acid 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 bis-(3-aminopropyl)dodecylamine and sorbic acid.

2. The synergistic antimicrobial composition of claim 1, wherein the weight ratio of the bis-(3-aminopropyl)dodecylamine to sorbic acid is from 1:1 to 1:100.

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 3.

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

Description

EXAMPLES

(1) 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).

(2) The formula to calculate the synergy index (SI) is
SI=Qa/QA+Qb/QB
Where 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.

(3) 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.

(4) 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.

(5) Minimum Inhibitory Concentration (MIC) Testing Protocol:

(6) The MICs of the single biocides BDA and SA as well as of combinations of these two actives (all in TSB) in 3 different ratios (1:1; 1:10, 1:100) were estimated against each of the 2 microorganisms Pseudomonas aeruginosa (DSMZ#939) and Candida albicans (DSMZ#1386).

(7) The synergy testing was carried out as follows: 1. The test was executed with a Hamilton MLStarPlus robot using automated turbidity reading with BioTek Synergy H4 plate reader. 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. 3. Then 15 subsequent serial dilutions with dilution factor 1.3 were performed resulting in 16 different concentrations for each system. 4. In the next step serially diluted biocide systems were transferred to the media blocks containing 850 l of TSB medium which was 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 5. After preparation and mixing of the described systems, 4 aliquots of 190 l were prepared in 96-well microtiter plates. 6. Preparation of the microbe suspension:

(8) Bacterial Culture:

(9) Pseudomonas aeruginosa DSM #939 ATCC#15442

(10) 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.

(11) Yeast Culture:

(12) Candida albicans DSM #1386 ATCC#10231

(13) 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.

(14) The yeast strain plates were incubated at 28 C. for 1-2 days then harvested with buffer pH 5.0.

(15) Based on total viable count results, the inoculum was prepared. 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. 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. 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 determine growth (>0.2) or no growth (0.2). The lowest concentration that showed no growth in the broth after incubation is taken as the MIC value.

(16) The MICs of single biocide and combinations thereof as well as the synergy indices are presented in Tables 1, 2, and 3.

(17) TABLE-US-00001 TABLE 1 MIC results for single biocides (in ppm): Active ingredients [ppm] BDA SA Pseudomonas aeruginosa DSM# 939 200 1226 Candida albicans DSM# 1386 260.sup.a 725 .sup.aThe MIC was above the highest tested concentration of the active.

(18) TABLE-US-00002 TABLE 2 MIC results for combinations of two biocides (in ppm) BDA/SA BDA/SA BDA/SA Active ingredients 1 1 1 10 1 100 Pseudomonas 70 70 24.5 245 7.3 725 aeruginosa DSM# 939 Candida albicans 200 200 31.9 319 3.3 330 DSM# 1386

(19) TABLE-US-00003 TABLE 3 Calculated synergy indices for the combinations in Table 2 Ratio BDA:SA 1:1 10:1 100:1 Pseudomonas aeruginosa DSM# 939 0.4 0.3 0.6 Candida albicans DSM# 1386 1.0.sup.b 0.6.sup.b 0.5.sup.b .sup.bThe Synergy Index is calculated based on the MIC value of BDA being >260 ppm, the highest concentration tested. The actual synergy index is less than or equal to the value calculated in the table.