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 degrees C for maximum slime production by both organisms. In the presence of levanase, a 25% reduction in dosages of a biocide (Bioplus(R)) was observed. Killing of A. aerogenes, which was achieved in 8 h with 20 ppm Bioplus(R), could be obtained in 6 h with the combined use of levanase and a lower concentration of Bioplus(R) (15 ppm). With B. alvei almost the same inhibitory effect (4.22-log decrease) was obtained at 20 ppm Bioplus(R), and in combination with a lower concentration of Bioplus(R) (15 ppm) and enzyme. The paper properties did not show any adverse effect after treatment with levanase and Bioplus(R).