Aggarwal Shilpi, Karimi I A, Kilbane Ii John J, Lee Dong Yup
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive, Singapore117576.
Mol Biosyst. 2012 Oct;8(10):2724-32. doi: 10.1039/c2mb25127b.
Rhodococcus erythropolis has been widely studied for desulfurization. However, activity levels required for commercial application have not been achieved. A major limitation of the current work in biodesulfurization is inadequate information regarding sulfur metabolism generally, and in particular the metabolism of the sulfur obtained from dibenzothiophene (DBT) metabolism via the 4S pathway. In this work, we have investigated the possible routes taken by the sulfur from DBT to convert into biomass or other metabolites. We propose two alternate hypotheses. In the first, we hypothesize that the cell can convert via sulfite reductase (SR) the sulfite from the metabolism of DBT into sulfide that can be assimilated into biomass. However, in the process, it may convert any excess sulfite into extracellular sulfate via sulfite oxidoreductase (SOR) to avoid the toxic effects of sulfite. In the second, we speculate that the cell cannot assimilate the sulfite directly into biomass via SR. It must first use SOR to produce extracellular sulfate, and then recapture that sulfate into biomass via SR. Thus, either way, we propose that SOR and SR activities, in addition to dsz genes and cofactors, may be critical in increasing desulfurization levels significantly. In particular, we suggest that the simultaneous increase in SOR activity and decrease in SR activity can enable increased desulfurization activity.
红平红球菌已被广泛研究用于脱硫。然而，尚未达到商业应用所需的活性水平。目前生物脱硫工作的一个主要限制是，总体上关于硫代谢的信息不足，特别是关于通过4S途径从二苯并噻吩（DBT）代谢中获得的硫的代谢信息不足。在这项工作中，我们研究了DBT中的硫转化为生物质或其他代谢物的可能途径。我们提出了两个替代假设。第一个假设是，我们假设细胞可以通过亚硫酸盐还原酶（SR）将DBT代谢产生的亚硫酸盐转化为可被同化为生物质的硫化物。然而，在此过程中，它可能会通过亚硫酸盐氧化还原酶（SOR）将任何过量的亚硫酸盐转化为细胞外硫酸盐，以避免亚硫酸盐的毒性作用。第二个假设是，我们推测细胞不能通过SR将亚硫酸盐直接同化为生物质。它必须首先使用SOR产生细胞外硫酸盐，然后通过SR将该硫酸盐重新捕获到生物质中。因此，无论哪种方式，我们都认为除了dsz基因和辅因子外，SOR和SR的活性可能对显著提高脱硫水平至关重要。特别是，我们建议同时提高SOR活性和降低SR活性可以提高脱硫活性。
