WO2012062473A1

WO2012062473A1 - Method for inhibition of activity of undesired microorganisms or bacteria by using hop acids in combination with apg

Info

Publication number: WO2012062473A1
Application number: PCT/EP2011/005679
Authority: WO
Inventors: Jason Grech; Matthew Smallman
Original assignee: Betatec Hopfenprodukte GmbH
Current assignee: Betatec Hopfenprodukte GmbH
Priority date: 2010-11-11
Filing date: 2011-11-11
Publication date: 2012-05-18
Anticipated expiration: 2013-05-11

Abstract

The present invention refers to a method to inhibit the activity of undesired microorganisms by using hop acids as anti-microbial active ingredients in combination with an alkyl polyglucoside. A synergistic effect is achieved through the combination of hop acids with an alkyl polyglucoside which significantly increases the anti-microbial efficiency of the hop acids.

Description

D E S C RIPTI O N

The present invention refers to a method for the inhibition of undesired microorganisms or bacteria by using hop acids as anti-microbial or anti-bacterial substances, in combination with alkyl polygluco sides (APG) as an additive to increase the anti-microbial efficiency of the hop acids. The present invention furthermore refers to a substance containing both hop acid and alkyl polyglucoside in combination for the use of the inhibition of undesired microorganisms. Finally the present invention refers to use of alkyl polyglucoside as an additive to hop acids to increase the efficiency of hop acids in the inhibition of the activity of undesired microorganisms.

Outset situation

The use of hop acid as anti-microbial substance for the inhibition of undesired microorganisms has been known for a long time and is widely spread.

A method for combating microorganisms in a sugar-containing, aqueous process medium is known from EP 1 159 458 Bl . In this method, the hop acids are used in an aqueous, alkaline solution and serve the purpose of reducing the formation of lactic acid in the course of the manufacture of sugar from sugar beets. The advantage of using hop acids is that they are naturally derived antibacterial substances and because of their high efficiency can replace more hazardous chemicals, such as formalin, in the course of the manufacture of sugar.

From US 7,361,374 B2, WO 03/097079 as well as from US 2003/0215535 Al, it is known to combine hop acids with propylene glycol for an enhanced stability of the hop acids. From WO 2007/117433 A2, anti-microbial compositions are known referring to alkaline salts of hop acid and their usages. In the course of that, the hop acid can be combined with different carriers, such as alkyl polyethylene oxide, sugar esters, fatty alcohols, alkyl polyglucosides or a combination thereof.

Object of the invention The object of the present invention is to provide a method for inhibiting the activity of undesired microorganisms or bacteria by using hop acids as antimicrobial or anti-bacterial substances and a respective substance to get an increased anti-microbial or anti-bacterial efficiency.

Subject matter of the invention

The afore-mentioned object is solved by the features of claim 1, claim 10 as well as claim 12. Advantageous embodiments of the invention are claimed in the sub- claims.

According to the invention, an alkyl polyglucoside, abbreviated as "APG", is used as a substance for increasing the anti-microbial (i.e. anti-bacterial) efficiency of hop acids. In order to obtain this, a combination product of hop acids and APG is prepared in different ratios. Surprisingly, it has been found that APG per se does not provide any anti-microbial effect, however in combination with hop acids APG contributes a substantial increase of the anti-microbial efficiency of the hop acids. There is a so-called synergetic effect, in other words an effect, which is more than just an additive effect. It has been demonstrated that adding APG can considerably reduce the minimum inhibitory concentration (MIC) of hop acids against various gram-positive microorganisms. By the combination of hop acids and APG, the former stand-alone anti-microbial effect of hop acids will be at a minimum matched or even exceeded. This leads to the effect that where there is a risk of vitiation of taste, a product with a lower concentration of hop acids but with the same or even increased efficiency, can be used in an advantageous manner. "Hop acid" in the sense of this application comprises natural hop acids as well as hop acid derivatives. Said increase of the anti-microbial efficiency results in particular in a higher cell count reduction and/or in a prolonged bacteriostatic activity.

The method according to the present invention is particularly suitable for the fermentation process, in particular for the yeast or fungal fermentation process.

Advantageously, the anti-microbial efficiency of the hop acid will be increased by the addition of APG by a factor of at least 2, preferably at least 3, most preferably at least 4. This also shows the enormous increase in efficiency, which the invention provides.

The increase in anti-microbial efficiency is particularly apparent in the concentration range of 0 ppm - 500 ppm hop acids, preferably 0 ppm - 100 ppm hop acids, preferably of 0 ppm - 50 ppm hop acids, preferably 0 ppm - 20 ppm hop acids, most preferably 0 ppm - 5 ppm.

The scope of the ratio of hop acid: APG to be used ranges from 100: 1 weight percent to 1 : 100 weight percent, preferably 50: 1 weight percent to 1 : 50 weight percent, preferably 25: 1 weight percent to 1 : 25 weight percent, preferably 10 : 1 weight percent to 1 : 10 weight percent, most preferably 1 : 3 weight percent to 3 : 1 weight percent.

In an advantageous way, hop acid and APG can be used as components of an aqueous solution. Hop acid and APG are added for this purpose to an aqueous medium simultaneously or in a timely separated sequence. Preferably, the aqueous medium has a pH-value of 2 - 11.

It is of particular advantage if APG with alkyl chains of a length of C2 - C30 is used.

Hop acids can either be used in their alkaline salt form or in their acid form.

It is of particular advantage if APG with a sugar unit from the group of monosaccharides, oligosaccharides or polysaccharides are used.

In an advantageous way, the hop acid to be used is a member of the group of β- acids, a-acids, hexahydro-P-acids, iso-a-acids, RHO-iso-a-acids, tetrahydro-iso-a- acids, hexahydro-iso-a-acids or a mixture thereof.

In an advantageous manner, the hop acids are present in the formulation in a portion of 1 - 60 weight percent.

In an advantageous manner, APG is present in the formulation in a portion of 1 - 60 weight percent.

Particularly, the pH-value of the aqueous medium, in which the invention is to be used, ranges between pH = 2 and pH = 7. In particular, the invention provides the effect that it can even be used at relatively low pH-values, such as pH -values from 2 to 4.

Additionally, the invention relates to an active ingredient comprising hop acid and APG in combination where APG is added in order to increase the anti-microbial efficiency.

Furthermore the invention relates to a substance for inhibition of the activity of undesired microorganisms or bacteria, which contains a mixture of hop acids and alkyl polyglucoside. This is advantageous since the substance can be provided to industrial users as a ready to use, easy to handle mixture, already containing the desired concentration of hop acids and APG.

In particular, the aforementioned ready to use effect is supported if the mixture described above is liquid or fluid. This has the effect that the substance easily mixes with a liquid or fluid process medium containing undesired microorganisms or bacteria. No further process measures are required. In alternative applications the mixture can for instance easily be sprayed onto surfaces where its use is required for inhibiting microorganisms or bacteria. Examples being meat, furniture, sanitary installations and so on.

Preferably the hop acids are provided as an aqueous solution and the alkyl polyglucoside is mixed in.

The substance can be provided in a transport container. This enables easy shipping and handling before and during usage.

Finally, the present invention relates to the use of APG as an additive to hop acids in order to increase the anti-microbial or anti -bacterial efficiency of hop acids.

Embodiments of the invention Embodiment 1

Two formulations were prepared consisting of a hop acid and APG in a 1 : 1 ratio. The formulations being hop β-acids/APG and hop Iso-a-acids/ APG. These formulations were tested in an aqueous medium at pH 5 in different concentrations (5 ppm, 10 ppm, 50 ppm, 100 ppm, 250 ppm as well as 500 ppm).

For sake of comparison, hop acids without APG were used as controls (beta control and iso control). Subsequently, a starter culture of Lactobacillus plantarum was grown overnight in the appropriate growth medium (pH 5.0) at 30 °C / 200 rpm. 1 x 10⁶ cells from the starter culture were added to the aqueous medium in the presence of 0, 5, 10, 50, 100, 250, 500 ppm (hop acid concentration) of hop acid or the corresponding hop acid /APG formulation. Cultures were incubated aerobically at 30 °C / 200 rpm for 18 hrs . The results of the % inhibition are shown in diagrams la and lb.

As it is evident from diagrams la and lb, a complete inhibition is obtained with beta/ APG and iso/APG in the concentration range of 0 to 5 ppm hop acid. In contrast thereto, the inhibiting effect exerted by the reference substances beta control and iso control is significantly lower, in particular at concentrations below 100 ppm.

From the illustrations, it becomes evident that an enhanced efficacy can be achieved by the addition of APG to hop acids.

Embodiment 2 Embodiment 2 shows the effect of an APG addition on the inhibition of microorganisms by hop acids at pH4. The test conditions correspond to the test conditions in embodiment 1 but at the new pH. Also here, a significant increase of efficiency can be shown by the addition of APG in contrast to hop acid without APG as it is evident from diagrams 2a and 2b.

Embodiment 3

Embodiment 3 shows the effect of an APG addition on the inhibition of microorganisms by hop acids at pH3. The test conditions correspond to the test conditions in embodiment 1 but at the new pH. Here also, a significant increase of efficiency can be shown by the addition of APG in contrast to hop acid without APG as it is evident from diagrams 3a and 3b. Comparative tests

In the comparative tests, APG without hop acid is tested against microorganisms of the strains S. cerevisi e, L. plantarum and E. coli in accordance with embodiment 1

From diagram 4, it is evident that APG per se does not show any inhibiting effect upon microorganisms. The surprising result of the present invention is the finding that a combination of hop acid with APG provides a synergistic effect with respect to the inhibitory effect against undesirable microorganisms, which exceeds the additive effect.

Embodiment 5

Embodiment 5 shows the effect of an APG addition on the inhibition of microorganisms by hop acids under fermentation conditions. A prolonged efficiency of the anti-microbial action of hop acids can be shown by the addition of APG in contrast to hop acids without APG as it is evident from diagrams 5, 6 and 7. The surprising result of the invention is the finding that a combination of hop acid with APG provides a extended effect with respect to the inhibitory effect against undesirable microorganisms or bacteria, which exceeds the additive effect.

The invention makes it possible to combat undesired microorganisms with a highly effective substance in various fields of application, which is comparable with the efficiency of chemicals, such as for example antibiotics, without thereby providing harmful side effects. Therefore, the invention provides a particular contribution to the relevant field of prior art.

Claims

PAT EN T C LAIMS

Method for inhibition of activity of undesired microorganisms by using hop acids as anti-microbial substance, characterized in that an alkyl polyglucoside is used as means for increasing the antimicrobial efficiency of hop acids.

Method according to claim 1 , characterized in that said increase of the anti-microbial efficiency results in a higher cell count reduction and/or in a prolonged bacteriostatic activity.

Method according to claim 1 or 2, characterized in that an alkyl polyglucoside is added such that there is an increase of the anti-microbial efficiency compared to hop acid without addition of alkyl polyglucoside by a factor of at least 2, preferably by a factor of at least 3, most preferably by a factor of at least 4. Method according to at least one of the preceding claims, characterized in that the increase of the anti-microbial efficiency is obtained by addition of alkyl polyglucoside at a concentration of hop acid of 0 ppm - 500 ppm hop acid, preferably of 0 ppm - 100 ppm, preferably of O ppm - 50 ppm, preferably of 0 ppm - 20 ppm, most preferably of 0 ppm - 5 ppm.

Method according to at least one of the preceding claims, characterized in that the composition of hop acid : APG lies within the following ranges: hop acids : APG of 100 : 1 weight percent to 1 : 100, preferably 50 : 1 weight percent to 1 : 50 weight percent, preferably 25 : 1 weight percent to 1 : 25 weight percent, preferably 10 : 1 weight percent to 1 : 10 weight percent, most preferably 3 : 1 weight percent to 1 : 3 weight percent.

Method according to at least one of the preceding claims, characterized in that the hop acid and the alkyl polyglucoside is added to an aqueous medium. Method according to at least one of the preceding claims, characterized in that the alkyl polyglucoside comprises alkyl chains of a length of C2

C30.

Method according to at least one of the preceding claims, characterized in that the alkyl polyglucoside comprises in its formulation at least a sugar unit of the group of monosaccharides, oligosaccharides or polysaccharides.

9. Method according to at least one of the preceding claims, characterized in that the hop acid is present in alkaline salt form or in acid form.

10. Method according to at least one of the preceding claims, characterized in that a hop acid of the subsequent group comprising a-acids, β-acids, RHO- iso-a-acids, iso-a-acids, hexahydro-iso-a-acids, tetrahydro-iso-a-acids and hexahydro-P-acids or a mixture thereof is used as hop acid.

1 1. Active ingredient for the use of inhibition of activity of undesired microorganisms comprising hop acids and alkyl polyglucosides, characterized in that an alkyl polyglucoside is added for increasing the anti-microbial efficiency of the hop acids.

12. Active ingredient according to claim 1 1 , characterized in that the active ingredient is prepared according to at least one of claims 1

10.

13. Substance for use in the inhibition of the activity of undesired microorganism, characterized in that it contains a mixture of hop acid and alkyl polyglucoside.

Substance according to claim 13, characterized in that said mixture is liquid.

Substance according to claim 13 or 14, characterized in that the hop acid is provided as an aqueous solution into which the alkyl polyglucoside is mixed.

Substance according to at least one of the claims 13 to 15, characterized in that the substance is provided in a transport container.

17. Use of alkyl polyglucoside as an additive to hop acids to increase the efficiency of hop acids in the inhibition of the activity of undesired microorganisms.