Novel application of Nerium leaf and Image J software in drop collapse assay for rapid screening of biosurfactant producing microorganisms

484-492Biosurfactants are attractive molecules with varied applicationsmainly oil degradation, emulsification, bioremediation, therapeutics and conjugation of nanoparticles. The existing screening methods for biosurfactants are inappropriate and too tedious. Here, we have explored a novel approach with drop collapse assay wherein we replaced the microtiter well plate with the naturally hydrophobic Nerium (Nerium oleander L.) leaf. The stability of beaded drops on the leaf indicates negative phenomenon, and spreading of drop indicates positive phenomenon for surfactant property, as confirmed by the measuring drop diameter using Image J software. Fifty five bacterial cultures isolated from oil contaminated site were screened through this novel approach which revealed that the isolates DNM49 (6.75±0.29 mm), DNM50 (7.45±0.19 mm) and DNM51 (6.14±0.82 mm) were the best in terms of surface tension reduction, although thirty other isolates were also found to be positive. A gradation of activity in terms of surface tension reduction was also established based on drop diameter. The results demonstrated promising application of Nerium leaf with Image J software in drop collapse assay as an eco-friendly and cost-effective and technically authenticated alternative to the existing assays

Novel application of Nerium leaf and Image J software in drop collapse assay for rapid screening of biosurfactant producing microorganisms

Biosurfactants are attractive molecules with varied applicationsmainly oil degradation, emulsification, bioremediation, therapeutics and conjugation of nanoparticles. The existing screening methods for biosurfactants are inappropriate and too tedious. Here, we have explored a novel approach with drop collapse assay wherein we replaced the microtiter well plate with the naturally hydrophobic Nerium (Nerium oleander L.) leaf. The stability of beaded drops on the leaf indicates negative phenomenon, and spreading of drop indicates positive phenomenon for surfactant property, as confirmed by the measuring drop diameter using Image J software. Fifty five bacterial cultures isolated from oil contaminated site were screened through this novel approach which revealed that the isolates DNM49 (6.75±0.29 mm), DNM50 (7.45±0.19 mm) and DNM51 (6.14±0.82 mm) were the best in terms of surface tension reduction, although thirty other isolates were also found to be positive. A gradation of activity in terms of surface tension reduction was also established based on drop diameter. The results demonstrated promising application of Nerium leaf with Image J software in drop collapse assay as an eco-friendly and cost-effective and technically authenticated alternative to the existing assays

Characterization and Cytotoxicity of Pseudomonas Mediated Rhamnolipids Against Breast Cancer MDA-MB-231 Cell Line

A biosurfactant producing bacterium was identified as Pseudomonas aeruginosa DNM50 based on molecular characterization (NCBI accession no. MK351591). Structural characterization using MALDI-TOF revealed the presence of 12 different congeners of rhamnolipid such as Rha-C8-C8:1, Rha-C10-C8:1, Rha-C10-C10, Rha-C10-C12:1, Rha-C16:1, Rha-C16, Rha-C17:1, Rha-Rha-C10:1-C10:1, Rha-Rha-C10-C12, Rha-Rha-C10-C8, Rha-Rha-C10-C8:1, and Rha-Rha-C8-C8. The radical scavenging activity of rhamnolipid (DNM50RL) was determined by 2, 3-diphenyl-1-picrylhydrazyl (DPPH) assay which showed an IC50 value of 101.8 mu g/ ml. The cytotoxic activity was investigated against MDA-MB-231 breast cancer cell line by MTT (4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide) assay which showed a very low IC50 of 0.05 mu g/ ml at 72 h of treatment. Further, its activity was confirmed by resazurin and trypan blue assay with IC50 values of 0.01 mu g/ml and 0.64 mu g/ ml at 72 h of treatment, respectively. Thus, the DNM50RL would play a vital role in the treatment of breast cancer targeting inhibition of p38MAPK