Nitrogen optimization on rhamnolipid biosurfactant production from Pseudoxanthomonas sp. G3 and its preservation techniques

Biosurfactant is a microbial bioproduct that is used to reduce the surface tension, and can acted as emulsifier, dispersant, and anti-adhesive. Optimization of biosurfactant production needs to be done, not only to increase its production quantity, but also to reduce overall production cost. This study aims to determine the most suitable and optimum concentration of nitrogen source for biosurfactant production and its preservation techniques. The biosurfactant was produced by Pseudoxanthomonas sp. G3 using minimal salt medium with 2% light crude oil as carbon source and different nitrogen sources in the form of urea, sodium nitrate, and ammonium nitrate. The activity of biosurfactants were measured by emulsification index (E24), interfacial tense (IFT), oil drop assay, and dry weight. Potassium sorbate 0.2% (w/v) was used as preservative agent. The results showed that biosurfactant production using sodium nitrate as a nitrogen source provides the highest activity and yield. The E24 value was 76.63% and the clear zone diameter observed was 0.875 cm. The overall decreased in IFT was 35.4% and the biosurfactant dry weight was 0.45 gL-1. Microbial contamination occurred after 3 weeks of storage in the treatment without the addition of preservative. It also showed that the activity of biosurfactants (emulsification and IFT) were gradually decreased during storage. In conclusion, the optimum biosurfactant production by Pseudoxanthomonas sp. G3 was obtained by the addition of sodium nitrate 0.3% (w/v). Meanwhile, the most effective biosurfactant preservation method was by adding potassium sorbate which was stored at 4 ℃

Optimization of enrichment and isolation media of thermophilic hydrocarbonoclastic bacteria isolated from oil reservoir of West Java for microbial enhanced oil recovery (MEOR) application

Microbial enhanced oil recovery (MEOR) is a tertiary oil recovery process which aims to increase the crude oil recovery uptake to 55% from its original oil in place. In its application, indigenous microorganisms are commonly used as the main biological agents, but the isolation processes become more complicated due to environment’s extreme condition. This study aims to determine the optimum formulation for the enrichment and isolation medium, in order to obtain a highly diverse of indigenous hydrocarbonoclastic bacteria. The isolation process was carried out in two stages; the isolation of mild oil fraction degrading bacteria, and isolation of the heavy oil fraction degrading bacteria which confirmed by the SARA (saturated, aromatic, resinic, and asphaltic) fraction chromatography analysis. Four enrichment and five isolation media were formulated based on the distinction in the macro-and micronutrient composition. Overall, a total of 92 isolates were successfully isolated. The highest bacterial diversities were achieved in the enrichment medium B (crude oil used as carbon source which supplemented with sodium lactate) and isolation medium I (nutrient agar with twice agar concentration), each with 37 and 33% of obtained isolates, respectively. The newly formulated medium can be further utilized to isolate various types of indigenous bacteria from the oil well which were able to degrade SARA fraction from crude oil. The result showed that ABG2-7 as the isolate with the highest activity on SARA degradation. The amount of 15% inoculum of ABG2-7 isolate was able to degrade heavy crude oil, thus might serve as potential bacteria for MEOR application

The Potential of Clove Essential Oil Microemulsion as an Alternative Biocide Against Pseudomonas aeruginosa Biofilm

Biocorrosion phenomenon is known to be detrimental in oil and gas industry. Synthetic biocides have been widely used to eliminate microorganisms which promote biocorrosion. However, these biocides are known to be toxic and harmful to the environment. One of the natural agents that potentially serves as an alternative for biocide is clove essential oil which has antimicrobial constituents and also have been shown to inhibit quorum sensing (QS) process of Pseudomonas aeruginosa. In this study, clove essential oil extracted from clove bud and stem were formulated into microemulsion and evaluated for its antibiofilm and anti-QS activity. To observe its antibiofilm activity, minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradicating concentration (MBEC) of clove bud and stem essential oils were determined by microdilution method in microtiter 96 well-plate. Anti-QS activity was observed by analyzing clove bud and stem essential oil effect against P. aeruginosa’s extracellular protease activity and swarming motility. The MIC value of clove bud and stem essential oils microemulsions were 0,33% and 0,5%, while MBIC50% values for clove bud and stem essential oil were 0,33% and 0.5%. However, MBEC value for both clove essential oil could not be determined. In addition, 0.66% clove bud essential oil and 1% clove stem essential oil successfully inhibited extracellular protease activity and swarming motility of P. aeruginosa by 32.06% and 45.56% for clove bud, and 31.43% and 45% for clove stem, respectively

The potency of spores and biosurfactant of Bacillus clausii as a new biobased sol-gel coatings for corrosion protection of carbon steel ST 37 in water cooling systems

The structures of water cooling systems are prone to microbially-influenced corrosion (MIC) due to the favorable conditions for microbial growth. Biofilm formation accelerates corrosion, leading to reduced system efficiency, structural damage, and significant financial losses. Encapsulating viable bacterial spores and biosurfactant within a silica-based sol-gel coating offers an eco-friendly approach to prevent this type of corrosion. Bacillus clausii, known for its antimicrobial biosurfactant production capability, was utilized in this study to investigate the impact of spores and biosurfactant addition to silica-based sol-gel coatings in inhibiting biofilm formation and preventing corrosion in water cooling systems. Microbiological analysis of the biofilm was conducted using the total plate count method, while the corrosion process was analyzed through electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The viability of B. clausii spores within the sol-gel matrix was determined to be 20.8 %. The presence of bacterial spores and biosurfactant significantly increased the hydrophobicity of the sol-gel coating. Incorporating spores within the sol-gel matrix delayed biofilm formation for up to 12 days, while biosurfactant addition showed the smallest biofilm abundance (2.23×105 CFU/mL) at its maturation phase compare to others. After 180 days of incubation, analysis of Bode and Tafel plots demonstrated that the sol-gel coating containing biosurfactant maintained excellent anti-corrosion performance, exhibiting an impedance of 104 Ω cm2, Ecorr of -0.398 V vs SCE, and icorr of 0.51 µA/cm2. SEM-EDS analysis of the surface sample revealed a comparably smooth and uniform surface with a minimal abundance of exposed Fe atoms at 0.12 %. In conclusion, this study demonstrated the high potency of the sol-gel coating supplemented with biosurfactant in inhibiting biofilm formation and corrosion on metals in water cooling systems

The utilization of natural reservoir brine in an enrichment culture medium: An alternative approach for isolation of anaerobic bacteria from an oil reservoir

This study aims to suggest the new approaches of enrichment cultures using natural reservoir brine for enrichment culture medium in order to increase the bacterial population in the enrichment cultures and isolate novel thermophilic anaerobic bacteria from an oil reservoir. The results suggest that the brine-based culture medium should be sterilized by filtration to increase the number of bacterial population and CO2 should be supplied to culture medium to increase the possibility of isolating novel bacteria from oil reservoirs. One of the specific bacteria isolated under the presence of CO2 was a strain AR80 representing a novel bacterium within the genus Petrotoga on the basis of the phylogenetic analysis