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Rhamnolipid synthesis and production with diverse resources

Qingxin Li

Frontiers of Chemical Science and Engineering 2017, Volume 11, Issue 1, Pages 27-36 doi: 10.1007/s11705-016-1607-x

Abstract: Rhamnolipids are one of the most effective biosurfactants that are of great interest in industrial applications such as enhancing oil recovery, health care, cosmetics, pharmaceutical processes, food processing, detergents for protein folding, and bioremediation due to their unique characteristics such as low toxicity, surface active property to reduce surface/interfacial tensions, and excellent biodegradability. The genes and metabolic pathways for rhamnolipid synthesis have been well elucidated, but its cost-effective production is still challenging. , the most powerful rhamnolipid producer, is an opportunistic pathogen, which limits its large scale production and applications. Rhamnolipid production using engineered strains other than such as and has received much attention. The highest yield of rhamnolipids is achieved when oil-type carbon sources are used, but using cheaper and renewable carbon sources such as lignocellulose would be an attractive strategy to reduce the production cost of rhamnolipids for various industrial applications.

Keywords： biosurfactant rhamnolipid Pseudomonas waste surface tension

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Rhamnolipids Induced by Glycerol Enhance Dibenzothiophene Biodegradation in Burkholderia sp. C3 Article

Camila A. Ortega Ramirez, Abraham Kwan, Qing X. Li

Engineering 2020, Volume 6, Issue 5, Pages 533-540 doi: 10.1016/j.eng.2020.01.006

Abstract:

In highly urbanized areas, pollution from anthropogenic activities has compromised the integrity of the land, decreasing soil availability for agricultural practices. Dibenzothiophene (DBT) is a heterocyclic aromatic hydrocarbon frequently found in urbanized areas, and is often used as a model chemical to study the microbial transformation of pollutants. The potential for human exposure and its health risk makes DBT a chemical of concern; thus, it needs to be environmentally managed. We utilized glycerol to stimulate Burkholderia sp. C3 in order to degrade DBT in respect to ① DBT biodegradation kinetics, ② bacterial growth, ③ rhamnolipid (RL) biosynthesis, and ④ RL secretion. Under an optimum glycerol-to-DBT molar ratio, the DBT biodegradation rate constants increased up to 18-fold and enhanced DBT biodegradation by 25%–30% at day 1 relative to cultivation with DBT alone. This enhancement was correlated with an increase in bacterial growth and RL biosynthesis. Proteomics studies revealed the enzymes involved in the upper and main steps of RL biosynthesis. The RL congeners Rha-C10-C10, Rha-Rha-C10-C10, Rha-Rha-C10-C12, and Rha-Rha-C12-C12 were identified in the medium supplemented with glycerol and DBT, whereas only Rha-C12-C12 was identified in cultures without glycerol or with RL inhibitors. The studies indicated that glycerol enhances DBT biodegradation via increased RL synthesis and bacterial growth. The results warrant further studies of environmental biostimulation with glycerol to advance bioremediation technologies and increase soil availability for agricultural purposes.

Keywords： Biodegradation Bioremediation Biosurfactant Biotransformation Glycerol Microbial metabolism Rhamnolipid