Simultaneous Removal of Thiophene and Dibenzothiophene by Immobilized Pseudomonas delafieldii R-8 cells

Biodesulfurization （BDS） is a promising technology for deep desulfurization. In this work, Pseudomonas delafieldii R-8 cells are immobilized in calcium alginate beads and used for BDS of transportation fuels. It is found that thiophene and dibenzothiophene （DBT） can be simultaneously metabolized by immobilized R-8 cells. The initial sulfur content in the model oil is 300 mg·kg-1 （thiophene ＂ DI3T= 1 ＂ 1）. After 10 h of treatment, the thiophene concentration is reduced by 40%, while DBT is reduced by 25%. The utilization rate of thiophene is faster than that of DBT. Moreover, the oil/water ratio of alginate immobilized cells is studied to reduce the water volume in desulfurization systems. Long-term recycling of BDS by alginate immobilized cells is carried out with oil/water ratio at 5 ： 1. The immobilized cells are successfully reused over 15 batch cycles. In the last batch, the desulfurization activity remains at least 75% of the first batch.

酿酒酵母产苹果酸的还原TCA路径构建及发酵调控

苹果酸广泛应用于食品、化工行业。文中通过在酿酒酵母内敲除丙酮酸脱羧酶PDC1,并通过构建胞质内还原TCA的路径,即超表达丙酮酸羧化酶和苹果酸脱氢酶,成功地实现了苹果酸的生产。在野生型菌株中基本检测不到苹果酸的生成,而在工程菌株,苹果酸发酵浓度达到了45 mmol/L,同时副产物乙醇的产量也降低了18%。进一步通过发酵调控提高第二信使Ca2+的浓度使苹果酸的产量提高了7%,在此基础上提高丙酮酸羧化酶的辅酶生物素浓度,使苹果酸的产量达到52.5 mmol/L,较原始菌株提高了16%。

药用真菌竹黄主要活性成分的异源生物合成

竹黄是我国一种重要的药用真菌资源,其主要活性成分竹红菌素类化合物已作为天然光敏剂广泛应用于食品、医药、农药等领域,其中竹红菌素软膏已用于临床。然而作为一种珍稀易危的物种,野生竹黄的资源非常有限。而竹红菌素结构复杂化学合成成本高,因此亟待一种有效的方法在保护竹黄野生资源的同时合理利用其药用价值。本文即采用合成生物学技术来获取竹黄中的主要活性成分,以期摆脱对野生资源的依赖。通过对竹黄菌Shiraia sp.cfcc 84681的全基因组进行细致的生物信息学分析,从中挖掘到一条竹红菌素生物合成的候选基因簇hpc;并成功构建了该基因簇的异源表达系统,获得一株产竹红菌素类化合物的重组菌株。该菌株主要产竹红菌甲素和异竹红菌甲素,这与野生竹黄提取物的主要成分基本一致。本研究有望为解决野生竹黄的资源短缺问题提供一种新的有效途径。