Production and characterization of microbial biosurfactants for potential use in oil-spill remediation.

Two biosurfactants, surfactin and fatty acyl-glutamate, were produced from genetically-modified strains of Bacillus subtilis on 2% glucose and mineral salts media in shake-flasks and bioreactors. Biosurfactant synthesis ceased when the main carbohydrate source was completely depleted. Surfactin titers were ∼30-fold higher than fatty acyl-glutamate in the same medium. When bacteria were grown in large aerated bioreactors, biosurfactants mostly partitioned to the foam fraction, which was recovered. Dispersion effectiveness of surfactin and fatty acyl-glutamate was evaluated by measuring the critical micelle concentration (CMC) and dispersant-to-oil ratio (DOR). The CMC values for surfactin and fatty acyl-glutamate in double deionized distilled water were 0.015 and 0.10 g/L, respectively. However, CMC values were higher, 0.02 and 0.4 g/L for surfactin and fatty acyl-glutamate, respectively, in 12 parts per thousand Instant Ocean®[corrected].sea salt, which has been partly attributed to saline-induced conformational changes in the solvated ionic species of the biosurfactants. The DORs for surfactin and fatty acyl-glutamate were 1:96 and 1:12, respectively, in water. In Instant Ocean® solutions containing 12 ppt sea salt, these decreased to 1:30 and 1:4, respectively, suggesting reduction in oil dispersing efficiency of both surfactants in saline. Surfactant toxicities were assessed using the Gulf killifish, Fundulus grandis, which is common in estuarine habitats of the Gulf of Mexico. Surfactin was 10-fold more toxic than fatty acyl-glutamate. A commercial surfactant, sodium laurel sulfate, had intermediate toxicity. Raising the salinity from 5 to 25 ppt increased the toxicity of all three surfactants; however, the increase was the lowest for fatty acyl-glutamate.

Analysis of the peri-implant microbiota in 90 dental implants and its relationship to crevicular fluid volume.

OBJECTIVE: To evaluate the presence within the peri-implant sulcus of Tannerela forsythia (Tf), Porphyromonas gingivales (Pg), Treponema denticola (Td) and Aggregatibacter actinomycetemcomitans (Aa), and relate these bacteria to the peri-implant crevicular fluid volume (PICFV). MATERIAL AND METHOD: A prospective and cross-sectional clinical case series study was made. For the measurement of crevicular fluid, use was made of the Periotron® 8000 (Proflow Incorporated. New York, USA), measuring the volume in Periotron units (PU). For the detection of periodontopathogenic bacteria we used the IAI-PadoTest 4.5 (IAI Inc., IAI Institute, Zuchwil, Switzerland) - a system for the detection of Tf, Pg, Td and Aa based on the use of RNA arrays. RESULTS: We included 34 patients (19 females and 15 males) with a mean age of 56.4 years. Of these subjects, 30.8% were smokers and 69.2% non-smokers. Out of a total series of 213 implants, we analyzed the crevicular fluid and microbiota in 90 implants. A total of 16.5% of the implants presented mucositis, while 83.5% were in healthy peri-implant conditions. The microbiological study revealed the presence of Tf in 17.1% of the implants, Pg in 9.3%, Td in 13.6%, in Aa in none of the implants. The mean Periotron reading was 93.4 PU (range 12-198 PU). A statistically significant (p<0.05) relationship was observed between PICFV and the total percentage bacteria (Tf, Pg and Td) - with a strong association between the Td levels and smoking (p<0.01). In the implants with mucositis, the concentration of Pg and Td was greater. CONCLUSIONS: In the implants studied, the subgingival peri-implant microbiota was characterized by low levels of Pg, Tf, Td, and none of the patients proved positive for Aa. These bacteria showed a positive correlation to crevicular fluid volume, and a statistically significant relationship was observed between Td and smoking.