Lobna, A. Moussa and Ahmed, Z. Abdel Azeiz( 2013). Identification and characterization of biosurfactants produced by rodococcus equi and bacillus methlyotrophicusJ. Biol. Chem. Environ. Sci., 2013, Vol. 8(2):341-358
Abstract: Biosurfactants are chemical compounds produced by microorganisms and comprise both hydrophilic and hydrophopic moieties in one molecule. It has found many applications in bioremediation, pharmaceutical and food industries. In the present study, 25 and 22 biosurfactant producing isolates were isolated from soil on Minimum Salt Medium (MSM) supplemented with either soy bean oil or petrol as sole sources of carbon, respectively. The biosurfactant was produced by all of the isolated microbial isolates in Mckeen medium and the biosurfactant activity was determined by the emulsification activity method. The bacterial isolates that showed the highest biosurfactant activity from both soy bean oil and petrol were identified by both Bio-log technique and 16S-rRNA gene sequencing methods as Rodococcus equi and Bacillus methylotrophicus, respectively. The biosurfactant production was 7.3 and 1.5 g/l for R. equi and B. methylotrophicus, respectively. The GC/MS analysis for sugars, fatty acids and amino acids in addition to phosphorus determination of both biosurfactants showed that the biosurfactant of R. equi is a phospholipopeptide, while the biosurfactant of B. methylotrophicus was phospholipid. The biosurfactant stability was studied under extreme environmental conditions, such as high temperature and pH. The maximum E24 (56% and 59.09 for soy bean oil and petrol biosurfactants, respectively) were obtained at pH 2. On the other hand, all of the produced biosurfactants showed a good stability in the temperature up to 121 °C. However, the maximum E24 for B. methylotrophicus biosurfactant (54.16%) was obtained at 50°C, while it was 55.55% for R. equi biosurfactant exposed to 100°C. These results suggested that R. equi can be used for biosurfactant production due to its high production, biosurfactant stability and efficiency.
Keywords: (Biosurfactant, Rodococcus equi, Bacillus methylotrophicus, Emulsification activity.)
