RESUMO
Environmental pollution associated with the petroleum industry is a major problem worldwide. Microbial degradation is extremely important whether in the extractive process or in bioremediation of contaminants. Assessing the local microbiota and its potential for degradation is crucial for implementing effective bioremediation strategies. Herein, contaminated soil samples of onshore oil fields from a semiarid region in the Northeast of Brazil were investigated using metagenomics and metataxonomics. These soils exhibited hydrocarbon contamination and high salinity indices, while a control sample was collected from an uncontaminated area. The shotgun analysis revealed the predominance of Actinomycetota and Pseudomonadota, while 16S rRNA gene amplicon analysis of the samples showed Actinomycetota, Bacillota, and Pseudomonadota as the most abundant. The Archaea domain phylotypes were assigned to Thermoproteota and Methanobacteriota. Functional analysis and metabolic profile of the soil microbiomes exhibited a broader metabolic repertoire in the uncontaminated soil, while degradation pathways and surfactant biosynthesis presented higher values in the contaminated soils, where degradation pathways of xenobiotic and aromatic compounds were also present. Biosurfactant synthetic pathways were abundant, with predominance of lipopeptides. The present work uncovers several microbial drivers of oil degradation and mechanisms of adaptation to high salinity, which are pivotal traits for sustainable soil recovery strategies.
RESUMO
The production of biosurfactant by Bacillus subtilis ATCC 6633 was investigated using commercial sugar, sugarcane juice and cane molasses, sugarcane juice alcohol stillage, glycerol, mannitol, and soybean oil. Commercial sugar generated the minimum values of surface tension, with the best results (28.7 mN/m, (relative critical micelle concentration [CMC-1] of 78.6) being achieved with 10 g of substrate/L in 48 h. At a pH between 7.0 and 8.0, a higher production of surface-active compounds and a greater emulsifier activity was also observed. Enrichment of the culture medium with trace minerals and EDTA showed maximum yields, whereas supplementation with yeast extract stimulated only cell growth. The kinetic studies revealed that biosurfactant production is a cell growth-associated process; surface tension, CMC, and emulsification index values of 29.6 dyn/cm, 82.3, and 57%, respectively, were achieved, thus indicating that it is feasible to produce biosurfactants from a renewable and low-cost carbon source.