Production of levanase byRhodotorula sp.

Rhodotorula sp. produced a high yield of levanase (12.5 nkat/mL) in shake flasks in basal medium containing 1% maltose as the sole carbon source. Among the different carbon sources used, maltose was found to be the best for levanase production. The optimum temperature and pH for levanase production were 30°C and 6, respectively. In a batch reactor the enzyme productivity was higher (500 nkat L⁻¹ h⁻¹) than in shaken flasks (347 nkat L⁻¹ h⁻¹).     

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^?. Received 21 March 1995/ Accepted in revised form 15 February 1997