Microbial contamination causes environmental and costly problems in paper production. Today, chemical-based biocides are used to control these problems. We have developed a biocide substitute that consists of fermented rest products from the cereal industry. Rye bran is a suitable nutrient for growth of a selected strain of Lactiplantibacillus plantarum. Previous studies have shown that fermented rye bran contains bioactive metabolites that powerfully limit virtually all bacterial growth. The cereals also contain fibres with potential to be a supplement in the raw material (pulp) of paper production. Our intention with this study was to investigate the potential of fermented rye bran as an antibacterial raw material in paper production. We will specifically determine the antibacterial effect of fermented rye bran on bacterial strains isolated from pulp and process water at a paper mill. In addition, to analyse the effect of the single metabolites discovered in the fermented rye bran. The results showed that fermented rye bran inhibited growth of the majority of the bacterial strains isolated from the paper mill. The pure metabolites showed also antibacterial properties, but less potent in comparison to the crude fermented rye bran product. The Lactobacillus strain used in the present study was resistant to all the tested metabolites. In conclusion, fermented rye bran shows properties indicating potential to be used as a bioactive raw material, limiting the need to add antimicrobial chemicals in paper production