da Silva Madeira Luciana, Ferreira-Leitão Viridiana Santana, da Silva Bon Elba Pinto
Department of Biochemistry, Chemistry Institute, Federal University of Rio de Janeiro - UFRJ, Brazil.
Chemosphere. 2008 Mar;71(1):189-94. doi: 10.1016/j.chemosphere.2007.10.004. Epub 2007 Nov 26.
Its is well known that in the biodesulfurization (BDS) process the low water solubility of sulfur compounds hinders its transference from the oil phase to the cells being the rate-limiting step in the metabolism of dibenzothiophenes (DBT). Thus sulfur compounds derivatives with high water solubility could be more easily transported increasing the BDS efficiency. The present work performed a stepwise evaluation of the enzymatic oxidation of DBT by horseradish peroxidase (HRP). Reactions were carried out in monophasic organic media containing 25% (v/v) acetonitrile. The following parameters were evaluated: DBT:H2O2 molar ratio (1:1-1:20); H2O2 addition mode (single or stepwise); pH (6.0-8.0) and temperature (37-50 degrees C). Best results were observed in a reaction medium at pH 8.0 presenting HRP 0.06IUml(-1), DBT 0.267mM, DBT:H2O2 molar ratio of 1:20 (stepwise hydrogen peroxide addition) and incubated at 45 degrees C for 60min. Under these conditions 60% of DBT was converted into dibenzothiophene sulfoxide (12%) and dibenzothiophene sulfone (46%). The DBT oxidation rate observed in this work, of 5mmolmin(-1)g(-1) of HRP, was 250-fold higher than the BDS rate, 20mumolmin(-1)g(-1) of catalyst. As such a combined enzyme-microbial desulfurization process could be envisaged. Products were determined by HPLC RP C-18.
众所周知，在生物脱硫（BDS）过程中，硫化合物的低水溶性阻碍了其从油相转移到细胞中，这是二苯并噻吩（DBT）代谢的限速步骤。因此，具有高水溶性的硫化合物衍生物可能更容易运输，从而提高BDS效率。本工作对辣根过氧化物酶（HRP）催化DBT的酶促氧化进行了逐步评估。反应在含有25%（v/v）乙腈的单相有机介质中进行。评估了以下参数：DBT:H2O2摩尔比（1:1 - 1:20）；H2O2添加模式（单次或逐步）；pH（6.0 - 8.0）和温度（37 - 50摄氏度）。在pH 8.0的反应介质中观察到最佳结果，其中HRP为0.06IUml(-1)，DBT为0.267mM，DBT:H2O2摩尔比为1:20（逐步添加过氧化氢），并在45摄氏度下孵育60分钟。在这些条件下，60%的DBT转化为二苯并噻吩亚砜（12%）和二苯并噻吩砜（46%）。本工作中观察到的DBT氧化速率为5mmolmin(-1)g(-1) HRP，比BDS速率（20mumolmin(-1)g(-1)催化剂）高250倍。因此，可以设想一种联合酶 - 微生物脱硫工艺。产物通过HPLC RP C - 18测定。
