Abin-Fuentes Andres, Mohamed Magdy El-Said, Wang Daniel I C, Prather Kristala L J
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Appl Environ Microbiol. 2013 Dec;79(24):7807-17. doi: 10.1128/AEM.02696-13. Epub 2013 Oct 4.
Microbial desulfurization, or biodesulfurization (BDS), of fuels is a promising technology because it can desulfurize compounds that are recalcitrant to the current standard technology in the oil industry. One of the obstacles to the commercialization of BDS is the reduction in biocatalyst activity concomitant with the accumulation of the end product, 2-hydroxybiphenyl (HBP), during the process. BDS experiments were performed by incubating Rhodococcus erythropolis IGTS8 resting-cell suspensions with hexadecane at 0.50 (vol/vol) containing 10 mM dibenzothiophene. The resin Dowex Optipore SD-2 was added to the BDS experiments at resin concentrations of 0, 10, or 50 g resin/liter total volume. The HBP concentration within the cytoplasm was estimated to decrease from 1,100 to 260 μM with increasing resin concentration. Despite this finding, productivity did not increase with the resin concentration. This led us to focus on the susceptibility of the desulfurization enzymes toward HBP. Dose-response experiments were performed to identify major inhibitory interactions in the most common BDS pathway, the 4S pathway. HBP was responsible for three of the four major inhibitory interactions identified. The concentrations of HBP that led to a 50% reduction in the enzymes' activities (IC50s) for DszA, DszB, and DszC were measured to be 60 ± 5 μM, 110 ± 10 μM, and 50 ± 5 μM, respectively. The fact that the IC50s for HBP are all significantly lower than the cytoplasmic HBP concentration suggests that the inhibition of the desulfurization enzymes by HBP is responsible for the observed reduction in biocatalyst activity concomitant with HBP generation.
燃料的微生物脱硫，即生物脱硫（BDS），是一项很有前景的技术，因为它能够对石油工业中当前标准技术难以处理的化合物进行脱硫。BDS商业化的障碍之一是在该过程中生物催化剂活性会随着终产物2-羟基联苯（HBP）的积累而降低。通过将红平红球菌IGTS8静息细胞悬浮液与十六烷在0.50（体积/体积）、含10 mM二苯并噻吩的条件下孵育来进行BDS实验。将树脂Dowex Optipore SD-2以0、10或50 g树脂/升总体积的树脂浓度添加到BDS实验中。随着树脂浓度增加，细胞质内的HBP浓度估计从1100 μM降至260 μM。尽管有这一发现，但生产率并未随树脂浓度增加。这使我们将重点放在脱硫酶对HBP的敏感性上。进行了剂量反应实验，以确定最常见的BDS途径即4S途径中的主要抑制相互作用。HBP是所确定的四种主要抑制相互作用中的三种的原因。导致DszA、DszB和DszC酶活性降低50%的HBP浓度（半数抑制浓度）经测定分别为60±5 μM、110±10 μM和50±5 μM。HBP的半数抑制浓度均显著低于细胞质HBP浓度这一事实表明，HBP对脱硫酶的抑制作用是观察到的生物催化剂活性随HBP生成而降低的原因。
