Isolation and characterization of a novel hydrocarbonoclastic and biosurfactant producing bacterial strain: Fictibacillus phosphorivorans RP3

Abstract

In this study, an indigenous novel hydrocarbonoclastic (kerosene and diesel degrading) and biosurfactant producing strain Fictibacillus phosphorivorans RP3 was identified. The characteristics of bacterial strain were ascertained through its unique morphological and biochemical attributes, 16S rRNA sequencing, and phylogenetic analysis. The degradation of hydrocarbons by F. phosphorivorans RP3 was observed at Day 7, Day 10 and Day 14 of the experimental duration. GC-FID chromatograms demonstrated a significant increase in hydrocarbon degradation (%) with progressing days (from 7 to 14). The bacterium exhibited capability to utilize and degrade n-hexadecane (used for primary screening) and petroleum hydrocarbons (kerosene and diesel; by ≥ 90%). With increase in the number of experimentation days, the optical density of the culture medium increased, whereas pH declined (became acidic) for both Kerosene and Diesel. Absence of resistance to routinely used antibiotics makes it an ideal candidate for future field application. The study is, thus, significant in view of toxicological implications of hydrocarbons and their degradation using environmentally safe techniques so as to maintain ecological and human health.

Keywords: Biodegradation; Bioremediation; Biosurfactant; Degradation rate; Petroleum hydrocarbons.

Fig. 1

Preliminary screening for biosurfactant production by bacterium Fictibacillus phosphorivorans RP3. a Positive result for hemolytic assay; b Negative result on CTAB test; c Control of Oil spreading technique; d Oil displacement shown by the isolate; e Beaded drop of control in drop collapse method; f Collapsed drop showing positive result for biosurfactant production; g The stable emulsion after 24 h showing positive result for biosurfactant production

Fig. 2

Evolutionary relationships of isolated bacteria Fictibacillus phosphorivorans RP3 with reference closest NCBI strains based on 16S rRNA gene sequence. The evolutionary history was inferred using the Neighbor-Joining method. The optimal tree with the sum of branch length = 0.10697072 is shown. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) is shown next to the branches. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site. The analysis involved 16 nucleotide sequences. All ambiguous positions were removed for each sequence pair. There were a total of 1572 positions in the final dataset. Evolutionary analyses were conducted in MEGA X. Bootstrap values more than 50 are given. The collection centre of all the type strains is NCBI

Fig. 3

GC-FID chromatogram of residual hydrocarbons extracted after 7 and 14 days from flasks supplemented with 1% diesel (a–c) and 1% kerosene (d–f) with respect to control, when incubated with bacterium Fictibacillus phosphorivorans RP3

Fig. 4

Variations in optical density (OD) and pH with number of days for diesel (a, b) and kerosene (c, d) incubated with bacterium Fictibacillus phosphorivorans RP3, analysed by non-linear regression (third-order polynomial)

Fig. 5

The susceptibility profile of isolated bacteria Fictibacillus phosphorivorans RP3 to various antibiotics determined using disk-diffusion method. The values in parenthesis along each antibiotic indicates the concentration in µg disc^‒1