RESUMEN
The waste produced by petrochemical industries has a significant environmental impact. Biotechnological approaches offer promising alternatives for waste treatment in a sustainable and environment-friendly manner. Microbial consortia potentially clean up the wastes through degradation of hydrocarbons using biosurfactants as adjuvants. In this work, microbial consortia were obtained from a production water (PW) sample from a Brazilian oil reservoir using enrichment and selection approaches in the presence of oil as carbon source. A consortium was obtained using Bushnell-Haas (BH) mineral medium with petroleum. In parallel, another consortium was obtained in yeast extract peptone dextrose (YPD)-rich medium and was subsequently compared to the BH mineral medium with petroleum. Metagenomic sequencing of these microbial communities showed that the BH consortium was less diverse and predominantly composed of Brevibacillus genus members, while the YPD consortium was taxonomically more diverse. Functional annotation revealed that the BH consortium was enriched with genes involved in biosurfactant synthesis, while the YPD consortium presented higher abundance of hydrocarbon degradation genes. The comparison of these two consortia against consortia available in public databases confirmed the enrichment of biosurfactant genes in the BH consortium. Functional assays showed that the BH consortium exhibits high cellular hydrophobicity and formation of stable emulsions, suggesting that oil uptake by microorganisms might be favored by biosurfactants. In contrast, the YPD consortium was more efficient than the BH consortium in reducing interfacial tension. Despite the genetic differences between the consortia, analysis by a gas chromatography-flame ionization detector showed few significant differences regarding the hydrocarbon degradation rates. Specifically, the YPD consortium presented higher degradation rates of C12 to C14 alkanes, while the BH consortium showed a significant increase in the degradation of some polycyclic aromatic hydrocarbons (PAHs). These data suggest that the enrichment of biosurfactant genes in the BH consortium could promote efficient hydrocarbon degradation, despite its lower taxonomical diversity compared to the consortium enriched in YPD medium. Together, these results showed that cultivation in a minimal medium supplemented with oil was an efficient strategy in selecting biosurfactant-producing microorganisms and highlighted the biotechnological potential of these bacterial consortia in waste treatment and bioremediation of impacted areas.
RESUMEN
Patients in the neonatal intensive care unit were tested by hearing screening tests including auditory brain stem response (ABR), transient and distortion-product otoacoustic emissions (TEOAEs and DPOAEs), and acoustic stapedius reflex (ASR), and by middle ear function tests including multifrequency tympanometry and pneumatic otoscopy. Pass rates on hearing tests were 75% to 89%. TEOAEs produced the lowest pass rate, and DPOAEs the highest. TEOAE, DPOAE, or ASR testing followed by ABR testing of initial failures produced pass rates of about 90%. The most efficient combination was DPOAEs followed by ABR. Pass rates tended to decrease with age. Of patients who failed 226-Hz and 678-Hz tympanometry, 30% to 67% passed hearing tests, suggesting a high false-positive rate for these immittance tests. The 3 ears that failed the 1000-Hz tympanogram failed all hearing tests. Many ears were abnormal by pneumatic otoscopy but passed hearing tests, suggesting that the usual ear examination criteria may not apply to infants.