a Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Thailand
b Department of Natural Resources and Environment, Faculty of Agriculture, Natural Resources and Environment, Naresuan University, Thailand
Received 3 June 2010, Accepted 20 July 2010
Abstract
The aims of this research were to study biosurfactant producing bacteria isolated from soil and to determine their property and efficiency as biosurfactants in order to inhibit bacterial pathogens. The result showed that there were 8 bacterial isolates out of 136 isolates of the total biosurfactant producing bacteria screened that exhibited the diameter of clear zone more than 1.5 cm. in the oil spreading test. The highest potential of emulsifying activity (%EA24) of 54.4 and the maximum additive concentration, (%MAC) of 24.2 was obtained from the fermentation broth of the G7 isolate which the G7 isolate was later identified as Pseudomonas fluorescens. Escherichia coli, Staphylococcus aureus and Psuedomonas aeruginosa were the tested bacterial pathogens that were most sensitive to the acid precipitated biosurfactant obtained from P. fluorescens G7 with the lowest minimum inhibitory concentration (MIC) of 41.6 mg/ml and minimum bactericidal concentration (MBC) of 41.6 mg/ml compared with the acid precipitated bisurfactants of the other isolates used in the antimicrobial activity test. The type of the separated crude biosurfactant produced by P. fluorescens G7 analyzed later by using the rhamose test, TLC and FT-IR techniques was rhamnolipid.
Keywords: biosurfactant-producing bacteria, antimicrobial activity
* corresponding author : Associate Professor Dr. Siripun Sarin