Evaluation of methods for screening bio-demulsifier producing bacteria and detecting bio-demulsifying efficiency

Six methods for screening and detecting bio-demulsifier producing bacteria, blood agar-plate test, blue agar-plate test, oil agar-plate test, drop-collapse test, oil spreading test, and surface tension test are compared for their ease of use and reliability in relation to the ability of cultures to increase the demulsifying ratio. Twenty-two strains of demulsifying bacteria screened by our lab are used to test these six methods. Results show that the former three methods can rapidly identify the bacterium with potential demulsifying ability. Blood agar-plate test is suitable for screening demulsifying bacteria from oil soil samples and the accuracy is 92.9%; blue agar-plate test can primarily screen demulsifying bacteria from activated sludge samples; and 77.3% demulsifying bacteria can be identified by oil agar-plate test. The latter three can be used to quantitatively evaluate the demulsifying ability. The accuracy of the oil spreading test is 95.5%, surface tension test is 86.4% and the drop-collapse test for demulsifying bacteria only from oil soil samples is 71.4%.