School of Biomedical Sciences, Ulster University, Coleraine, BT521SA, Northern Ireland, UK.
Department of Pharmacy, University of Patras, 26504, Patras, Greece.
Microb Cell Fact. 2019 Oct 10;18(1):164. doi: 10.1186/s12934-019-1216-8.
In comparison to synthetically derived surfactants, biosurfactants produced from microbial culture are generally regarded by industry as being more sustainable and possess lower toxicity. One major class of biosurfactants are rhamnolipids primarily produced by Pseudomonas aeruginosa. Due to its pathogenicity rhamnolipid synthesis by this species is viewed as being commercially nonviable, as such there is a significant focus to identify alternative producers of rhamnolipids.
To achieve this, we phenotypically screened marine bacteria for biosurfactant production resulting in the identification of rhamnolipid biosynthesis in a species belonging to the Marinobacter genus. Preliminary screening showed the strain to reduce surface tension of cell-free supernatant to 31.0 mN m. A full-factorial design was carried out to assess the effects of pH and sea salt concentration for optimising biosurfactant production. When cultured in optimised media Marinobacter sp. MCTG107b produced 740 ± 28.3 mg L of biosurfactant after 96 h of growth. Characterisation of this biosurfactant using both HPLC-MS and tandem MS showed it to be a mixture of different rhamnolipids, with di-rhamnolipid, Rha-Rha-C-C being the most predominant congener. The strain exhibited no pathogenicity when tested using the Galleria mellonella infection model.
This study expands the paradigm of rhamnolipid biosynthesis to a new genus of bacterium from the marine environment. Rhamnolipids produced from Marinobacter have prospects for industrial application due to their potential to be synthesised from cheap, renewable feed stocks and significantly reduced pathogenicity compared to P. aeruginosa strains.
与合成表面活性剂相比，微生物培养产生的生物表面活性剂通常被业界认为更具可持续性且毒性更低。生物表面活性剂的一个主要类别是鼠李糖脂，主要由铜绿假单胞菌产生。由于其致病性，该物种的鼠李糖脂合成被认为在商业上不可行，因此，人们非常关注寻找替代的鼠李糖脂生产菌。
为了实现这一目标，我们对海洋细菌进行了表型筛选，以生产生物表面活性剂，从而鉴定出一种属于海洋杆菌属的物种具有鼠李糖脂生物合成能力。初步筛选表明该菌株可将无细胞上清液的表面张力降低至 31.0 mN/m。进行了全因子设计以评估 pH 和海水盐度对优化生物表面活性剂生产的影响。当在优化的培养基中培养时，海洋杆菌 MCTG107b 在 96 小时的生长后产生了 740±28.3mg/L 的生物表面活性剂。使用 HPLC-MS 和串联 MS 对该生物表面活性剂进行的表征表明，它是不同鼠李糖脂的混合物，其中二鼠李糖脂，Rha-Rha-C-C 是最主要的同系物。在用金小蜂感染模型测试时，该菌株没有表现出致病性。
这项研究将鼠李糖脂生物合成的范例扩展到了一种来自海洋环境的新细菌属。与铜绿假单胞菌菌株相比，海洋杆菌产生的鼠李糖脂由于其可以从廉价、可再生的原料中合成，并且具有明显降低的致病性，因此具有工业应用的前景。
