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Microbial contamination causes environmental and costly problems in paper production (gas formation in stored pulp, and biofilm/slime) and waste water systems (biofilm formation causing corrosion of the pipes). Today, chemical-based biocides are used to control these problems. We have developed a biocide substitute consisting of industrial rest products; rye bran or spruce bark. Rye bran is a suitable nutrient for growth of a selected strain of Lactiplantibacillus plantarum. Previous studies have shown that fermented rye bran, as well as spruce bark extracts, contains bioactive metabolites with the power to limit virtually all bacterial growth. These products also contain fibres with potential to be a supplement as raw material in the pulp.

Our intention with this study was to investigate the potential of these rest materials as an antibacterial raw material in paper production. We will specifically determine the antibacterial effect on strains isolated from pulp, process water from the paper mill, and waste water pipes. In addition, likewise analyse the antimicrobial activity of single metabolites discovered in the crude extracts. The results so far, show that the products efficiently inhibit growth of the bacterial strains isolated from waste water and the paper mill. The pure metabolites showed also antibacterial properties, but were less potent as compared to the crude products. The Lactiplantiobacillus strain, used to ferment the rye bran in the present study, was resistant to all the tested products.

In conclusion, fermented rye bran and spruce bark extracts show properties indicating a potential to be used as a bioactive raw material, limiting the need of adding synthetic biocides in paper production and waste water systems.