FI94010C - Mikrobbekämpningsförfarande - Google Patents

Description

94010

Antimicrobial control method This application is cleaved from application 915462.

5

The invention relates to a method for controlling fungi which interfere with the process of the chemical forest industry in a natural manner.

10 Process waters in the chemical forest industry provide favorable conditions for microorganisms, especially bacteria, but also for fungi. Process waters contain organic substances that are favorable for the growth of microorganisms, and otherwise the growth conditions are suitable. An acidity value close to neutral (pH 7-8) favors bacterial growth, while an acidic pH range (pH 5-6) is preferred for fungi. The temperature of the process water in paper and board machines, which is usually in the range of 40-60 ° C, is quite suitable for many microbes, especially bacteria. Fungal growth usually stops at or slightly above about 50 ° C.

In practice, it has been found that high quality paper and board can be produced even if the bacterial concentrations in the circulating water are quite high. Occasionally, microbes that interfere with paper and board production may appear in the normal bacterial population. In terms of production and especially runnability, the greatest disadvantage is caused by filamentous fungi and bacteria, which tend to form disturbing agglomerations. Mushrooms play a key role as determinants of runnability. Somewhat rarer have been found cases where filamentous bacteria have been the backbone of the clumps. Mushroom strings collect e.g. fibers, fibrils, resin, bacteria and fillers, and color particles. Without such stacking frame members, the productivity of paper and 35 board machines would be better than at present.

Special chemicals, antimicrobials, which are broad-spectrum compounds are used to control the microbes that cause agglomerations. This is one of the disadvantages of chemical antimicrobials, as they are effective not only against interfering microbes but also against microbes that are harmless to production. Other disadvantages of chemical antimicrobials are their toxicity to humans and animals, as well as possible residues in paper and board.

The present invention is based on the idea that fast-growing and harmless bacteria could indeed be useful for antimicrobial control by taking up living space from slow-growing fungi and thus inhibiting their growth. So far, there is no chemical known to affect the interfering microbes alone so that other microbes are not affected.

It has now surprisingly been found that harmless, fast-growing bacteria can be used to control the most embarrassing interfering microbes, namely fungi. The ability of bacteria to inhibit the growth of 20 fungi can be based on several mechanisms. One of them is the higher growth rate of bacteria compared to fungi, whereby they displace fungi from the common growth environment in a manner known in microbiology. Another mode of action is metabolic products, i.e. metabolites, which are secreted by the bacteria and are harmful to fungi. These can inhibit fungal growth. A third mode of action is bacterial enzymes, such as lytic enzymes that degrade fungal cell walls, such as chitinases.

The object of the invention is to utilize the bacteria in the process water in the most natural ways possible. In this case, different options are available. One possibility is chemical control by selecting cabbage-35, which is ineffective against inhibitory bacteria but effective against harmful microbes, as the antimicrobial. In this way, the growth of inhibitory bacteria could be favored, which in turn would reduce the growth potential of the disruptive fungi. Unfortunately, most pesticides are broad-spectrum, so finding the right pesticide means a difficult balance between efficacy and side effects.

The object of the invention is to provide an organic, more selective control method. According to the invention, inhibitory bacteria which inhibit the growth of fungi and filamentous bacteria, which can be produced in a fermentor, can be metered into the circulating water at suitable intervals. These bacteria must be shown in advance to be harmless to the production process.

10

Preferred inhibitory bacteria for use in the method of the invention include some strong growing Pseudomonas bacteria which have been found to be quite effective in inhibiting the growth of yeast and mold fungi in the circulating water of the plant and, at best, even destroying them. The barrier bacteria used in the method according to the invention have been isolated from the circulating water of paper and board mills. Inhibitory bacteria should be added to a concentration of at least 102 / ml.

The following examples further illustrate the method of the invention.

Example 1

Inhibitory bacteria were isolated from circulating water from paper and board mills using Difcon culture medium with the following composition: tryptone 2.5 g yeast extract 5.0 g dextrose 1.0 g agar 15.0 g water 1000 ml pH 7.0 ± 0.2 35 Incubation was performed at 37 ° C for 2 days using the filter membrane method.

Fungi (yeasts and molds) were also isolated from the circulating water of paper and cardboard mills using MYGP culture medium: 40 94010 4 malt extract 3.0 g yeast extract 3.0 g peptone 5.0 g glucose 10.0 g 5 agar 20, 0 g water 1000 ml pH 5.5

Incubation was performed at 30 ° C for 3-5 days using 10 filter membrane methods.

Example 2

The studies looked at the ability of circulating bacteria to inhibit the growth of fungi in lean broth. Bacteria and fungi were given similar growth opportunities by inoculating them to grow simultaneously.

A) Bacteria isolated from the circulating water of the board mill were inoculated each into three separate cultures for 20 days in a nutrient broth having the following composition (mg / l): tryptone 330 glucose 240 25 yeast extract 240 peptone 120 malt extract 70 pH 7.0 • t '30 4x105 pcs / ml. At the same time, yeast fungus isolated from the circulating water of the same plant were inoculated into the culture broth of each bacterium. For comparison, pure yeast alone was inoculated.

; Incubation was performed at 30 ° C. Bacterial and yeast levels were reassessed after 1 and 2 days of incubation. The results are shown in Figure 1.

In the comparative experiment, the yeast fungus grew excellently, reaching a concentration of about 108 pcs / ml at 40 l / day. In contrast, the growth of the same fungus was inhibited in the presence of each of the three bacteria and its concentration in all cases was less than 94010 5 than 10 / ml. Two of the blocking bacteria used were unidentified and one was identified as Pseudomonas pseudoalcaligenes.

5 B) The experiment was performed in the same way as in A, but the microbe to be controlled was now a mold from the same board factory instead of a yeast. The blocking bacteria were the same. Bacteria were added to a concentration of 104-5x10 4 pcs / ml and incubated for 5 days in broth. The results are shown in Figure 2.

Bacterium 242 is unidentified, bacterium 243 is P. pseudo-alcalicrenes and bacterium 246 is unidentified.

In the control experiment, the mold grew well to a concentration of about 105 pcs / ml. Bacteria clearly inhibited its growth, especially 15 bacterial strain 243 (P. pseudoalcaligenes). The difference compared to the maximum was more than 3 log units at 3 days, remaining at about 1 log unit at 5 days. In practice, however, a 3-day growth inhibition is completely sufficient. Antimicrobials do not achieve such a long-lasting effect with 20 single doses.

Example 2 shows that strong-growing Pseudomonas bacteria can quite effectively inhibit the growth of yeast and mold fungi in the circulating water of the plant and, at best, even destroy them.

Example 3 In this experiment, in contrast to the methods described in Example 2, a method was used in which the bacteria were first allowed to grow overnight in broth at a bacterial concentration of 107 to 109 pcs / ml. The fungus was then inoculated and grown for 2 days at 30 ° C. Thus, an attempt was made to simulate a situation in which one of the disturbance fungi is trying to conquer an area among a large population of bacteria-35 in circulating waters. At this point, the microbes were given nutrient supplementation (same nutrients as in Example 1). The results are shown in Figure 3. The yeast fungus grew well in comparison, but in the presence of bacterial strain 273 (Pseudomonas cepacia) 94010 6 it did not grow at all, destroying quite completely within 1-2 days. This blocking bacterium was therefore particularly strong. Strains 275 and 276 are unidentified.

5 From the results, it can be concluded that the method involving the pre-culture of the bacterium also works well.

Example 4 In this experiment, a pulp from a paperboard mill was used, the consistency of which was adjusted to 2%. The age of the grind was 1-17 weeks in the experiment.

The groundwood was sterilized and inoculated with inhibitory bacteria isolated from the same plant to grow daily for 15 days. The fungus to be controlled was then inoculated into groundwood.

A) The yeast to be controlled and the inhibitory bacteria were the same as in Example 2A, in which all bacteria were able to control 20 yeasts completely (see Figure 1). The starting concentration of inhibitory bacteria was 2x101 to 5x10 4 pcs / ml. Grown for 3 days at 30 ° C, pH about 5. The same bacteria did not work as well in sterile ground. The best bacterium that inhibited yeast growth was strain 246 (Fig. 4), which had an inhibitory effect of less than 25 for two days. Strain 243 was P. pseudoalcaliuenes.

»B) When the experiment of point A was performed using mold as a fungus to be controlled, it was found that the method works better against mold (Fig. 5) than against yeast (Fig. 4). The starting concentration of bacteria was 6x10 4 pcs / ml. Grown for 5 days at 30 ° C, pH about 5. Against mold, the potency of bacterial strain 244 (Pseudo-1 monas maltophilia) was at best just over 1 log unit.

35 The yeast and mold genera used in the experiments are unidentified.

I.

Claims (2)

94010 1. A method for controlling the growth of harmful fungi in the process water of a plant, characterized in that bacteria isolated from the circulating water of the plant or elsewhere, harmless to the production process, are added to the process water to a concentration of at least 102 / ml, selected from Pseudomonas cepacia. Pseudomonas maltophilia and Pseudomonas pseudoalcaliaenes. Method according to Claim 1, characterized in that the fungus is a mold or yeast. Method according to Claim 1, characterized in that the blocking bacteria are added to the groundwood. 15 1. For use in the manufacture of a process for the manufacture of a process, the conversion of the process to a concentration of up to 102 ex./ml of the fab-20 cepacia. Pseudomonas maltoohilia och Pseudomonas pseudoalcaliaenes. 25 2. For the purposes of patent claim 1, the wording of which is set out in Annex I to this Regulation: Svampen är en mögel- eller jästsvamp. 1 For the purposes of this Regulation, the provisions of this Regulation shall apply to slipmas.