Comparative studies on the structural composition, surface/interface activity and application potential of rhamnolipids produced by Pseudomonas aeruginosa using hydrophobic or hydrophilic substrates

Pseudomonas aeruginosa SG produced 7.06 g/L and 10.32 g/L of rhamnolipids using glucose or soybean oil. Rhamnolipids produced from glucose contained 8 mono-rhamnolipids homologues and 6 di-rhamnolipids homologues with ratio of 61.46%:38.54%. Rhamnolipids produced from soybean oil contained 9 mono-rhamnolipids and 8 di-rhamnolipids homologues with ratio of 58.68%:41.32%. The main homologues produced from soybean oil possessed longer carbon chain of fatty acid. Rhamnolipids produced from glucose decreased surface tension to 26.3 mN/m with critical micelle concentration (CMC) of 50 mg/L; rhamnolipids produced from soybean oil reduced surface tension to 28.1 mN/m with CMC of 60 mg/L. Two rhamnolipids products were thermo-stable and halo-tolerant. Two rhamnolipids products efficiently cleaned oily sludge. Rhamnolipids produced from glucose possessed better surface activity and antimicrobial activity. Rhamnolipids produced from soybean oil exhibited greater emulsifying activity (EI24=76.1%) to better reduce oil viscosity. Different substrates make P. aeruginosa produce diverse rhamnolipids with distinct application potential.