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Rhamnolipids (RMLs) are a widely studied biosurfactant due to its high biodegradability, low toxicity, and environmentally friendly production, which has the bacterium Pseudomonas aeruginosa as producer and renewable source of feedstock. However, the knowledge of the structure-property relationship of several RMLs congeners is imperative for the design of a high efficient application. Aiming to a better understanding of RMLs at a molecular level, we performed a automated search for low energy structures of the most abundant congeners, namely, Rha-C10, Rha-C10-C10, Rha-Rha-C10 and Rha-Rha-C10-C10 and their respective congener with two carbon atoms (C2) at the side chain. Besides that, selected neutral metal complexes were also considered. We thus performed a metadynamics search followed by DFT optimizations of selected geometries. In addition, molecular dynamics simulations were also applied. Our results show a plethora of low energy structures for each congener. Although several of them have internal hydrogen bonds, this interaction alone cannot explain the stability. Moreover, geometries in closed conformation were always more stable than ”open” ones and the effect of chain length on the geometry was found to be more prominent between Rha-Rha-C2-C2 and Rha-Rha-C10-C10 . Finally, the energy differences between open and closed conformations for K+ , Ni2+ , Cu2+ and Zn2+ complexes were found to be 23.5 kcal mol−1, 62.8 kcal mol−1 , 24.3 kcal mol−1 and 41.6 kcal mol−1 , respectively, indicating a huge structural reorganization after the complex formation.

Surfactin, a biosurfactant with great activity on interfaces, have been reported as a great substitute to non-renewable sources, non-biologically synthesized surfactants. It is expected to see more studies at the next years evolving its application, including on marine environments, especially ones impacted with petroleum or other contaminants. In this review we address in details the main aspects of surfactin production, including main microorganisms, cultivation modes, pathways and conditions. We address the main aspects of surfactin production by Bacillus subtilis with the different strategies explored to reach this bioprocess up to large scale, as well as the main challenges encountered. As well, is detailed its recovery and purification methods, that generally combine two or more steps as acid precipitation, solvent extraction, liquid membrane extraction, foam fractionation and membrane-based techniques. We also provide a brief summary of its potential application on marine environments, and our prospects from future application, as a brief outlook on physiochemistry characteristics of the main molecules.

Species of the genusUlvaare common in anthropogenically disturbed areas and have been reported as the cause of green tides in many areas of the world. In addition, they rank among the main marine groups used in a wide range of commercial applications. By displaying few distinctive morphological characters, some taxonomical identifications are difficult and the genus is under a conundrum. Our aims were to provide ecophysiological information about threeUlvaspecies in response to abiotic factors and to evaluate the proposal of ecophysiological information and the chlorophyll-afluorescence technique as auxiliary tool to resolve the long-standing taxonomic confusion. We hypothesize that three cooccurring specimens (U. fasciataDelile,U. lactucaLinnaeus, andU. rigidaC. Agardh) have different ecophysiological responses (as measured by the effective quantum yield of photosystem II by pulse amplitude modulated fluorometers) under manipulated conditions of temperature and nutrient concentration.Ulva lactucaandU. rigidashowed different photosynthetic efficiencies related to temperature, whereas no difference was recorded forU. fasciataindividuals. These results provide a reasonable explanation for the variability in spatial and temporal abundance of these species ofUlvaon rocky shores. We proposed the use of ecophysiological information by chlorophyll-afluorescence as an auxiliary tool to corroborate the taxonomic distinction ofUlvaspecies. We reinforce the statement ofU. fasciataandU. lactucaas distinct valid species.

Rhamnolipids have emerged as a very promising class of biosurfactants in the last decades, exhibiting properties of great interest in several industrial applications, and have represented a suitable alternative to chemically-synthesized surfactants. This class of biosurfactants has been extensively studied in recent years, aiming at their large-scale production based on renewable resources, which still require high financial costs. Development of non-pathogenic, high-producing strains has been the focus of a number of studies involving heterologous microbial hosts as platforms. However, the intricate gene regulation network controlling rhamnolipid biosynthesis represents a challenge to metabolic engineering and remains to be further understood and explored. This article provides an overview of the biosynthetic pathways and the main gene regulatory factors involved in rhamnolipid production within Pseudomonas aeruginosa, the prototypal producing species. In addition, we provide a perspective view into the main strategies applied to metabolic engineering and biotechnological production.

Biosurfactants have potential applications in the remediation of petroleum-contaminated sites. Several strategies can be used to reduce the production costs of these surfactants and make the process more environmentally friendly. In this study, we combined some of these strategies to produce the rhamnolipid-type biosurfactant, including the use of the genetically modified strain Pseudomonas aeruginosa-estA, an industrial coproduct as a carbon source, a simple and low-cost medium, and a simple downstream process. The process resulted in a high yield (17.6 g L−1), even using crude glycerin as the carbon source, with substrate in product conversion factor (YRML/s) of 0.444. The cell-free supernatant (CFS) was not toxic to Artemia salina and selected mammalian cell lineages, suggesting that it can be used directly in the environment without further purification steps. Qualitative analysis showed that CFS has excellent dispersion in the oil-displacement test, emulsifying (IE24 = 65.5 % ), and tensoactive properties. When salinity, temperature and pressure were set to seawater conditions, the values for interfacial tension between crude oil and water were below 1.0 mN m−1. Taken together, these results demonstrate that it is possible to obtain a nontoxic crude rhamnolipid product, with high productivity, to replace petroleum-based surfactants in oil spill cleanups and other environmental applications.

The need to find more stable catalysts has encouraged the study of naturally resilient enzymes, such as those found in extremophile organisms. In the present work, the influence of rare codons on the expression in Escherichia coli of the lipase Pf2001Δ60 from Pyrococcus furiosus was evaluated. Expression was carried out in two E. coli strains, BL21(DE3)pLysS and the rare tRNA supplemented Rosetta(DE3)pLysS. 32 factorial design was used to appraise the influence of temperature and inducer concentration on enzyme expression every hour for the 4-h expression period. Four response surfaces were constructed for each time, and the statistical parameters were evaluated. Lipase production was twice as high for Rosetta(DE3)pLysS than for BL21(DE3)pLysS. The factorial design indicated that optimal expression occurred at 30°C after 4h, with lipase production of 240U/L. The analysis of statistical parameters during the expression time showed that the velocity at which the enzyme was produced affected cell growth and maximum activity, with a higher speed leading to lower expression and cell growth. The presence of rare tRNAs prevented bottlenecks in lipase expression, and the experimental design was shown to be important for maximizing the production strategies and minimizing the metabolic load to which the host is subjected.