No abstract

Microbial surfactants are amphiphilic molecules with attractive industrial prospects due to their advantages over commonly commercialized chemical surfactants, such as low toxicity, high biocompatibility and biodegradability, and efficiency at extreme conditions. However, the large-scale production of biosurfactants still becomes uncompetitive due to the low yields and onerous costs, being considered the use of renewable substrates as a viable strategy. In this sense, the present study aimed to investigate the sustainable production of biosurfactant by the yeast Issatchenkia orientalis UCP 1603 in 2 L of salt-based medium supplemented with 7.5% cassava wastewater, 5% corn steep liquor and 1% post-frying soybean oil. Fermentation was carried out in 2.8 L-Fernbach flasks for 72 h, at 28°C and 150 rpm, and reduction in surface tension to 30.1 mN/m was verified. The highest yield of the biosurfactant produced (4.02 g/L) was observed after extraction with 70% ethanol (2:1, v/v) and the isolated biosurfactant reduced the surface tension of the medium to 28.7 mN/m, the interfacial tension against n-hexadecane to 16.6 mN/m and has a CMC of 800 mg/L. The biocompound showed anionic and polymeric nature and did not present toxicity against cabbage (Brassica oleracea var. capitata) seeds. The stability in the range of pH 4-10, salinity 5-25% and temperature 5-100°C, evidenced a highly stable biosurfactant, with promising potential of application in several industrial activities or environmental processes in adverse conditions.

The soil has been constantly exposed to a variety of contaminants and their mixtures in various concentrations, organic/inorganic chemical exposure, which mainly includes pesticides and their mixtures of monomers), which contaminate the soil to a greater extent and can also be transported within the soil and transfer the mixed contaminants, integrating into the food chain and passing through different trophic levels, causing health effects of organisms exposed to them. Pesticides are chemical compounds used to eliminate pests. They are chemical or biological agents, which weaken, incapacitate and kill pests. The emerging contaminant glyphosate (N-(phosphonomethyl)glycine) is widely used in agriculture in several countries. It is considered the most widely used herbicide in the world, as well as being one of the most harmful to human health. This compound is used to control harmful or invasive weeds. Glyphosate is the best-selling active ingredient in Brazil, with 195,056 tons sold in 2018. Brazil stands out for the massive agricultural use of glyphosate. An increasing number of countries have begun to restrict/ban the use of glyphosate-based products, such as Germany, Austria, Bulgaria, Colombia, and Costa Rica, among others, based on evidence already available on the direct incidence of glyphosate at various levels of the global ecosystem, as well as favoring the emergence of serious problems in human health. In this sense, the present study emphasizes the importance of knowing the main properties of pesticides and the study in search of efficient technological advances for the recovery of soils impacted by the use of glyphosate.

The literature describes several studies focused on the application of S. maltophilia in different areas of biotechnology. Due to its ease of interaction with numerous environments and living beings, this bacterium has an excellent adaptability, being able to convert different substrates into products of high environmental and technological interest. Stenotrophomonas maltophilia is a gram-negative, aerobic, ubiquitous, rod-shaped bacterium belonging to the class of gammaproteobacteria and can be found in various natural and anthropogenic environments, e.g. soil, water, sediments or in association with plants. Biosurfactants are an alternative, compatible with the environment, for the use of chemically synthesized surfactants, since it is a bioproduct obtained through the metabolism of microorganisms and plants. Like their synthetic counterparts, biosurfactants comprise a wide variety of chemical structures and also excellent surfactant properties. The literature presents a wide range of studies focused on the production of biosurfactant by S. maltophilia using several substrates, temperature conditions, pH, salinade and fermentation times. In addition, there is also a huge variety of application of these biosurfactants produced, which drives the incentive to study this microorganism in the production of biosurfactants.