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Phanerochaete chrysosporium lignin peroxidase (LiP) can degrade synthetic dyes such as heterocyclic, azo, and triphenylmethane on its activation by H2O2. Analysis of the reaction products indicated that N-demethylation reactions are involved in the degradation of crystal violet and methylene blue (MB). We studied LiP oxidation of methylene blue and azure B (AB) in reaction mixtures containing different dye:H2O2 stoichiometric relations aiming at the selective formation of N-demethylated derivatives. High yields, about 70%, of the mono- and didemethylated derivatives, azure B and azure A, were obtained with the use of 1:1 and 1:2 MB:H2O2, respectively. Using azure B as substrate in reaction mixtures containing 1:1 AB:H2O2, a yield of 70% was also observed in azure A. Reaction mixtures containing 1:3 MB:H2O2 and 1:2 AB:H2O2, originated several oxidation products in similar proportions. These results indicated that the process of enzymatic degradation of methylene blue and azure B initiates via N(CH3)2 oxidation. According to the yields that were obtained for azure B and azure A, this enzymatic route can be used for the synthesis of these dyes since these data compare favorably to the chemical route that has a yield of 35%. The use of a dye:H2O2 relation of 1:10 resulted in a decoloration level of about 85%, showing the usefulness of this procedure for wastewater treatment. The reaction products were followed by spectrophotometric analysis within the wavelength of 500-700 nm. The product identifications were performed using a reverse-phase high-performance liquid chromatography (HPLC) C-18 column and thin-layer chromatography.

This work aims to evaluate cell recycle of a recombinant strain of Pichia pastoris GS115 on the Xylanase A (XynA) production of Thermomyces lanuginosus IOC-4145 in submerged fermentation. Fed-batch processes were carried out with methanol feeding at each 12 h and recycling cell at 24, 48, and 72 h. Additionally, the influence of the initial cell concentration was investigated. XynA production was not decreased with the recycling time, during four cell recycles, using an initial cell concentration of 2.5 g/L. The maximum activity was 14,050 U/L obtained in 24 h of expression. However, when the initial cell concentration of 0.25 g/L was investigated, the enzymatic activity was reduced by 30 and 75% after the third and fourth cycles, respectively. Finally, it could be concluded that the initial cell concentration influenced the process performance and the interval of cell recycle affected enzymatic production.