Directional culture of petroleum hydrocarbon degrading bacteria for enhancing crude oil recovery.

•Effect of nitrogen and phosphorus nutrients on bacteria growth was examined.•Nutrients stimulated growth and metabolism of hydrocarbon degrading bacteria.•Multi-stage transmission culture with nutrients led to Bacillus as the final genus.•Biodegradation of crude oil resulted in its effective emulsification.•Biosurfactant formation and surface tension reduction help enhancing oil recovery.