A modified Pseudomonas aeruginosa strain capable of overexpressing the estA gene, an encoding gene for a membrane-bound esterase, was constructed and its rhamnolipid (RML) production was studied. Fermentations using wild-type (WT) and modified P. aeruginosa strains were conducted until exhaustion of glycerol in Medium Salt Production, using two different C/N ratios. At a C/N of 83.2, the modified strain produced up to 3.9 times more RMLs than the WT, yielding a maximum concentration of 14.62 g/L RML when measured by HPLC and 22 g/L by the orcinol assay. Cell-free supernatant from the modified strain reduced surface tension to 29.4 mN/m and had a CMC of 240 mg/L and CMD of 56.05. This is the first report on the construction of an estA-based recombinant strain for RML production.

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.

Surfactin, a biosurfactant with great activity on interfaces, has been reported as a great substitute for non-renewable sources and non-biologically synthesized surfactants. It is expected to see more studies in the next years evolving its application, including in marine environments, especially those impacted by petroleum or other contaminants. In this chapter, we address in detail the main aspects of surfactin production, including the 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 a large scale, as well as the main challenges encountered. Also detailed are its recovery and purification methods, which 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 in marine environments and our prospects for future application as a brief outlook on the physiochemical characteristics of the main molecules.