Structural analyses and continual production of an unusual rhamnolipid from a marine Pseudomonas guguanensis

Abstract

Microbial molecules which exhibit a high surface and emulsifying activity are classified as bioemulsifiers biosurfactants Interest in microbial emulsifier has been steadily increasing in recent years due to their diversity environmentally friendly nature In the present work six different marine water samples were collected from three locations Tuticorin Gulf of Mannar and Chennai harbor southeast coast of Tamilnadu India Totally 849 pure cultures were obtained Out of 849 isolates 90 showed positive for oil spread method Of the 90 only 2 isolates showed emulsification activity Highest emulsification activity was observed for isolates A Isolate no 621 hexadecane 46 plus or minus 2 point 12 per cent diesel 40 plus or minus 1point 41 per cent and kerosene 22 plus or minus 1 point 409 per cent and B Isolate no 798 hexadecane 56 plus or minus 1 point 42 per cent diesel 46 plus or minus 2 point 82 per cent and kerosene 48 plus or minus 1 point 40 per cent Isolate A had 100 per cent identity with Pseudomonas aeruginosa and B had 100 per cent identity with Pseudomonas guguanensis The bioemulsifier was extracted from a bacterium Pseudomonas guguanensis previously not reported to have biological activities leave alone emulsification abilities Whilst the crude bioemulsifier of ethyl acetate partitions has an EI of 65 plus or minus 1 point 43 per cent its purified bioemulsifier showed 78 plus or minus 1 point 75 per cent both at 12 point 5 mg ml concentration The complete chemical nature of the compound was elucidated using FT minus IR I and 2D NMRs H and C and GC minus MS fragmentation patterns The isolated bioemulsifier was an unusual type of high molecular weight monorhamnolipid which is attached to esters of palmitic stearic hexa and octadecanoic acids newline