The use of extracellular enzymes from Streptomyces albus ATCC 3005 for thebleaching of eucalyptus kraft pulp

The suitability of culture supernatant from Streptomyces albus ATCC 3005 fo r use in the biobleaching of eucalyptus kraft pulp was investigated. S. alb us was found to grow on a minimal salts medium containing oat spells xylan and yeast extract as the main carbon and nitrogen sources, respectively. Ma ximal extracellular xylanase and peroxidase production was detected after 1 20 h (11.97 U ml(-1)) and 72 h (0.58 U ml(-1)), respectively. Importantly, no cellulase activity could be detected. When the effect of pH on enzyme ac tivity was examined. maximal xylanase and peroxidase activity was obtained at pH 6.5 and pH 9.9, respectively. The optimum hydrogen peroxide (H2O2) co ncentration for peroxidase activity was found to occur at 20 mM, with perox idase remaining active at 100 mM H2O2 after 1 h incubation at 53 degreesC; the half-life of the enzyme at that temperature was estimated to be 33 min. Short-term (1 h) biobleaching of eucalyptus kraft pulp with culture supern atant from S. albus in the presence of H2O2 resulted in a significant reduc tion of kappa number (2.85 units) with no change in viscosity. These result s suggest a potential application of cellulase-free culture supernatants fr om S. albus in biobleaching.