Laccase production by Aspergillus niveus on SSF using wheat bran as alternative carbon source and its synergistic effect on pulp biobleaching using a mix of laccase/xylanase from the same microorganism

Aiming to investigate the production oflaccases by Aspergillus niveus RP05, the performance of this enzyme on cellulose pulp biobleaching wasanalyzed and tests of mixing laccase/xylanases from the same microorganism were also included. A.niveus was cultivated at 30ºC, for 2 weeks on solid state fermentation (SSF) composed by wheat bran and 0.05 M (NH4)2HPO4 (1:2 – w/v) for laccase production. Optima of temperature and pH reaction were 60ºC and 4.5 – 7.0, respectively. The correlation between pH and temperature was investigated using the experimental design and the highest enzyme activity levels were obtained at the central points (55°C, pH 5.0). It was verified that only the temperature had significance in the linear level with the confidence interval of 95%.The enzyme was stable up to 70ºC (more than 80% of residual activity); after 1 hour of incubation laccase lost at least 50% of its initial activity from 75 – 80ºC. Crude extract containing laccase activity itself was used (STRATEGY I) or mixed with xylanase (STRATEGY II) to clarify cellulose pulp. The most interesting result was obtained with a mix of xylanase/laccase, resulting in Kappa efficiency around 56% and an increase in whiteness on the order of 17.2 points.