2.4.6. Emulsification indexEmulsifying index
was determined according to Cooper and Goldenberg [21]. Briefly, 2 mL of cell-free supernatant were addedto 2 mL hydrophobic source, and the mixture was vortexed for 2 min. After 24 h, the height of emulsion layer was measured. The emulsification index (EI24) was calculated using the height of theemulsion layer and the height of total solution [21]. The emulsify-ing capacity of the crude biosurfactant in forming stable emulsions was evaluated using motor oil SAE 15W-40 (Texaco) and soybean oil (Bunge).