Mic reduction with lithium ions

A process for reducing the minimum inhibitory concentration (MIC) of a biocide against at least one strain of bacteria and/or at least one strain of yeast and/or at least one strain of mould in an aqueous preparation, the process comprising the steps of:

• a) providing an aqueous preparation,
• b) providing at least one biocide selected from the group consisting of phenols, halogenated phenols, halogen-containing compounds, halogen-releasing compounds, isothiazolinones, guanidines, sulfones, thiocyanates, pyrithiones, antibiotics, β-lactam antibiotics, quaternary ammonium salts, peroxides, perchlorates, amides, amines, heavy metals, biocidal enzymes, biocidal polypeptides, azoles, carbamates, glyphosates, sulphonamides, and any mixture thereof,
• c) providing at least one water soluble source of lithium ions,
• d) contacting the aqueous preparation of step a) with the at least one biocide of step b), wherein the at least one biocide is effective against at least one strain of bacteria and/or at least one strain of yeast and/or at least one strain of mould when present in the aqueous preparation,
• e) contacting the aqueous preparation of step a) before and/or during and/or after step d) with the at least one water soluble source of lithium ions of step c),
• wherein the amount of the lithium ions and the amount of the at least one biocide are selected so that the minimum inhibitory concentration (MIC) of the biocide meets meet equation (I):
• MICwithoutLi/MICLi>1.1 (I)
• wherein
• MICwithoutLi is the minimum inhibitory concentration (MIC) of the at least one biocide against the at least one strain of bacteria and/or at least one strain of yeast and/or at least one strain of mould without the at least one water soluble source of lithium ions in ppm, calculated relative to the weight of water in the aqueous preparation of step a),
• MICLi, is the minimum inhibitory concentration (MIC) of the at least one biocide against the at least one strain of bacteria and/or at least one strain of yeast and/or at least one strain of mould with the at least one water soluble source of lithium ions in ppm, calculated relative to the weight of water in the aqueous preparation of step a),
• wherein the total amount of lithium ions is selected from 15.0 to 800.0 mMol/L, calculated relative to the weight of water in the aqueous preparation, and
• wherein the amount of the at least one biocide is selected from 0.4 to 6500.0 ppm, calculated relative to the weight of water in the aqueous preparation;
• and
• wherein the at least one biocide is free of aldehyde-releasing and/or aldehyde-based biocides.