Biosurfactants production by marine yeasts isolated from zoanthids and characterization of an emulsifier produced by Yarrowia lipolytica LMS 24B.

The present study investigates the potential for biosurfactant production of 19 marine yeast species obtained from zoanthids. Using the emulsification index test to screen the samples produced by the marine yeasts, we verified that five isolates exhibited an emulsification index ≥50%. Additional tests were performed on such isolates, including oil displacement, drop collapse, Parafilm M assay, and surface tension measurement. The tolerance of produced biosurfactants for environmental conditions was also analyzed, especially considering the media's temperature, pH, and salinity. Moreover, the surfactant's ability to emulsify different hydrocarbon sources and to metabolize kerosene as the sole carbon source was evaluated in vitro. Our results demonstrate that yeast biosurfactants can emulsify hydrocarbon sources under different physicochemical conditions and metabolize kerosene as a carbon source. Considering the Yarrowia lipolytica LMS 24B as the yeast model for biosurfactant production from the cell's wall biomass, emulsification indexes of 61.2% were obtained, even at a high temperature of 120 °C. Furthermore, the Fourier-transform middle infrared spectroscopy (FTIR) analysis of the biosurfactant's chemical composition revealed the presence of distinct functional groups assigned to a glycoprotein complex. Considering the status of developing new bioproducts and bioprocesses nowadays, our findings bring a new perspective to biosurfactant production by marine yeasts, especially Y. lipolytica LMS 24B. In particular, the presented results validate the relevance of marine environments as valuable sources of genetic resources, i.e., yeast strains capable of metabolizing and emulsifying petroleum derivatives.

Long-term effects of grazing on the biological, chemical, and physical soil properties of the Caatinga biome.

Soil degradation is a global issue that affects both plant productivity and human life. Intensive grazing practices can accelerate this process, mainly due to rapid removal of biomass from the soil surface. However, the long-term effects of grazing on biological, chemical, and physical properties remain poorly understood, particularly in tropical drylands, such as the Caatinga biome. Our aim was to evaluate the soil properties and combine both culture-dependent and -independent analyses to assess metabolic activity and bacterial community structure. We collected samples (0-20 cm) of three different types of soil in the Caatinga biome: secondary Caatinga forest (NC), grazing exclusion (GE), and degraded areas by overgrazing (OG). We sought to investigate how grazing affects soil properties to determine the effectiveness of grazing exclusion in the restoration of soil fertility/functions. Redundancy analysis demonstrated NC were positively correlated with organic carbon (λ = 0.18, p = 0.0012) and total nitrogen (λ = 0.16, p = 0.0011), while OG was correlated with harmful soil parameters such as Na+ (λ = 0.08, p = 0.0400), electric conductivity (λ = 0.13, p = 0.0060) and exchangeable acidity (λ = 0.11, p = 0.0030). In addition, GE showed lower aluminum content and saturation, reducing these harmful parameters by 48 % and 34 %, respectively. Also, GE showed the highest values for the ß-glucosidase (63.62 mg ρ-nitrophenol kg-1 h-1) and arylsulfatase (5.8 mg ρ-nitrophenol kg-1 h-1) activities. Changes in bacterial community structure were significant (p = 0.0096), with a higher difference comparing GE and OG (p = 0.0135). The GE area showed 20 % more phosphate solubilizers than OG, but there were no differences for siderophores production. All isolates were halotolerant and had at least 60 % nitrogen fixers. Our findings indicate that while soil recovery is slow, with grazing-exclusion areas presenting 18 years of implantation, it seems to improve in subsequent years. Finally, our results provide evidence that microbe-based technologies can mitigate soil degradation in the Caatinga biome.

Purification and characterization of a biosurfactant produced by Bacillus subtilis in cashew apple juice and its application in the remediation of oil-contaminated soil.

The ability of some microorganisms to use clarified cashew apple juice as carbon and energy source for biosurfactant production was assessed under strict controlled conditions. Twelve strains of Bacillus were isolated and evaluated regarding their biosurfactant production capabilities. The biosurfactant obtained with these selected strains showed the capacity of decreasing the surface tension of water from 72.0 to 31.8 mN.m-1 and the interfacial tension of n-hexadecane to 27.2 mN.m-1, with a critical micelle concentration of 12.5 mg.L-1. Not only did the biosurfactant present excellent stability to pH, temperature and salinity, it also showed emulsifying properties in different hydrocarbons. The behavior of the phase diagrams showed the potential of the produced biosurfactant to obtain relatively-stable emulsions for up to 96 h, which allows for its application in several areas. The semi-purified biosurfactant did not show toxicity against Lactuca sativa (lettuce) or Artemia salina (microcrustacean), presenting an LC50 of 612.27 µ mL-1. The surfactant was characterized as being a cyclic lipopeptide with molecular structure similar to that of surfactin. Furthermore, through the employment of the surfactant produced, the remediation effect in oil-contaminated soil could be significantly improved.

Unique crystal structure of a novel surfactant protein from the foam nest of the frog Leptodactylus vastus.

Breeding by releasing eggs into stable biofoams ("foam nests") is a peculiar reproduction mode within anurans, fish, and tunicates; not much is known regarding the biochemistry or molecular mechanisms involved. Lv-ranaspumin (Lv-RSN-1) is the predominant protein from the foam nest of the frog Leptodactylus vastus. This protein shows natural surfactant activity, which is assumed to be crucial for stabilizing foam nests. We elucidated the amino acid sequence of Lv-RSN-1 by de novo sequencing with mass-spectrometry and determined the high-resolution X-ray structure of the protein. It has a unique fold mainly composed of a bundle of 11 α-helices and two small antiparallel ß-strands. Lv-RSN-1 has a surface rich in hydrophilic residues and a lipophilic cavity in the region of the antiparallel ß-sheet. It possesses intrinsic surface-active properties, reducing the surface tension of water from 73 to 61 mN m(-1) (15 µg mL(-1)). Lv-RSN-1 belongs to a new class of surfactants proteins for which little has been reported regarding structure or function.