Studies on slime-forming organisms of a paper mill—slime production and its control

Bacteria, yeast and filamentous fungi were isolated from various sites within a paper mill. Bacillus alvei and Aerobacter aerogenes were the most prevalent contaminating bacteria. Maximum slime was produced by A. aerogenes (4.2 mg ml⁻¹) at pH 6.5 and by B. alvei (7.2 mg ml⁻¹) at pH 7.5 in white water. The optimum temperature was 40°C for maximum slime production by both organisms. In the presence of levanase, a 25% reduction in dosages of a biocide (Bioplus^®) was observed. Killing of A. aerogenes, which was achieved in 8 h with 20 ppm Bioplus^®, could be obtained in 6 h with the combined use of levanase and a lower concentration of Bioplus^® (15 ppm). With B. alvei almost the same inhibitory effect (4.22-log decrease) was obtained at 20 ppm Bioplus^®, and in combination with a lower concentration of Bioplus^® (15 ppm) and enzyme. The paper properties did not show any adverse effect after treatment with levanase and Bioplus^®.