LAB-SCALE PRODUCTION OF RHAMNOLIPID BY PSEUDOMONAS AERUGINOSA A3 AND STUDY ITS SYNERGISTIC EFFECT WITH CERTAIN ANTIBIOTICS AGAINST SOME PATHOGENIC BACTERIA

• Published in: Iraqi journal of agricultural science Vol. 50; no. 4; pp. 1290 - 1301
• Main Authors: Faqri, A M Alshaikh, Hayder, N H, Hashim, A J
• Format: Journal Article
• Language: English
• Published: Baghdad Jami'at Baghdad 01.01.2019
• Subjects: Ampicillin; Antibacterial activity; Antibiotics; Bacteria; Batch culture; Bioreactors; Cefotaxime; Cell culture; Cellulose acetate; Chromatography; Clinical isolates; Column chromatography; E coli; Embryo fibroblasts; Emulsification; Fourier transforms; Gram-negative bacteria; Laboratories; Minimum inhibitory concentration; Pseudomonas aeruginosa; Rhamnolipids; Silica; Silica gel; Silicon dioxide; Surface tension; Surfactants; Synergistic effect; Toxicity
• ISSN: 0075-0530; 2410-0862

This study was aimed to obtain the considerable amount of the biosurfactant (rhamnolipid) from local isolate of Pseudomonas aeruginosa on industrial-scale. A 7L laboratory bioreactor was appointed to accomplish this task and all conditions of production were set as previously by batch culture experiments. Bioreactor with 3.5 L working volume was conducted for 120 h to obtain 16 g/L at 30°C and 6.5 pH. The supernatant of production medium was used to reduce the surface tension of water from 72 to 27 mN/m, and the emulsification index was reached to 67%. The product was extracted with a mixture of solvents, purified by silica gel using a column of glass chromatography (3.5 x 30cm), and characterized by TLC and FTIR where it turn out that the biosurfactant is composed of both mono- and di-rhamnolipid. Mono-RL was tested for its antibacterial activity against some clinical isolates of Grampositive and Gram-negative bacteria to obtain the MIC, which was about 250µg/ml, also at same concentration, the toxicity against Rat embryonic fibroblast (REF) cell line was reached to 23%. The combination effect of Mono-RL with some antibiotics was studied against pathogenic clinical isolates revealed that there is a synergistic effect with ampicillin against s. aureus and serratia marcescens, with cefotaxime against E. coli and Kelbsiella pneumoniae, same as with tetracycline.