With the continuously increasing demand for paper and cardboard products, there is growing concern about the bacteria of the papermaking process. Bacterial growth not only affects normal manufacturing, but it also results in paper products with a total number of bacteria that exceeds the acceptable range, and thus poses a risk to the health of consumers. In this study, 99 pure bacterial strains were isolated from old corrugated containers (OCC) slime. The morphological, physiological, and biochemical properties of the bacterial strains were examined. Furthermore, the isolated strains were tested for their ability to form biofilms. The strains that could form biofilms were identified using 16S rDNA sequencing. The results revealed that some bacteria could form both a biofilm that adhered to the smooth tube wall, as well as abundant flocs at the bottom of the test tube. Conversely, the other bacteria could not form a noticeable biofilm. The bacteria with the most powerful biofilm-forming ability were identified as Proteus penneri, Klebsiella variicola, Klebsiella sp., and Proteus mirabilis.