Biosurfactant production and concomitant hydrocarbon degradation potentials of bacteria isolated from extreme and hydrocarbon contaminated environments

Abstract

Amongst the total forty-seven bacterial isolates, eleven potent biosurfactant producing and concomitant hydrocarbon degraders were obtained after primary screening involving drop collapse method (DCM) and Oil-spreading method (OSM) followed by secondary screening comprising of Haemolytic assay (HA), Cetyl trimethyl ammonium bromide (CTAB) assay, Surface tension (ST), Emulsification index (E24) and Emulsification activity (EA). 16S-rRNA sequencing and phylogenetic analysis revealed the presence of Achromobacter, Bacillus, Citrobacter, Lysinibacillus, Ochrobactrum and Pseudomonas. Two genera, Achromobacter (PS1) (observed for the first time) and Bacillus (SLDB1) were found to be glycolipid producers as evident by TLC, FT-IR and GC–MS chromatograms. The surface tension values were 30.43mN/m and 31.10mN/m with (E24) of 69.90% and 65.23% respectively. Similarly the TLC, FT-IR and GC–MS results of the other two genera Ochrobactrum (GREW1) and Bacillus (SB2) confirmed them as lipopeptide biosurfactant producers with surface tension values of 31.14mN/m and 28.16mN/m and (E24) of 59.51% and 61.35% respectively. Qualitative 2,6-Dichlorophenol Indophenol (2,6-DCPIP) and quantitative methods for hydrocarbon degradation revealed that Achromobacter sp. (PS1) showed a maximum degradation (46.32%) of 2% (w/v) crude oil with 70.77% and 77.17% reduction in peak area of aliphatic and aromatic fractions respectively with simultaneous lowering of surface tension from 59.27mN/m (control) to 32.43mN/m in 7days. In case of Achromobacter sp. (PS1) and Bacillus sp. (SB2 and SLDB1), glucose supported biosurfactant production, whereas in Ochrobactrum sp. (GREW1) glucose along with 1% diesel enhanced biosurfactant production. This signifies the role of substrate in the nature of biosurfactants produced.