Isolation and molecular characterization of potential paraffin wax- degrading thermophilic bacterial strains

Three thermophilic bacterial strains that could degrade paraffin wax were isolated from 
paraffin wax-contaminated soil using enrichment culture and minimal salts medium (MSM) 
containing n-hexadecane, as reprehensive of paraffin wax, and incubation at 55 °C. When the three 
isolates, TUSB-B001, TUSB-B002 and TUSB-B003 were tested for their capability for growth and 
n-hexadecane degradation, they revealed a varying growth patterns and biodegradation efficiency 
with the isolate TUSB-B001 being the superior. It exhibited a specific growth rate in n-hexadecane
supplemented MSM of 0.11 h-1 and growth yield of 1.12 gcells / g-hexadecane compared to 0.065, 0.883 
and 0.055 h-1, 0.74 gcells / g-hexadecane for TUSB-BOO2 and TUSB-BOO3 isolates,  respectively. In 
addition, an efficient paraffin wax degradation of up to 94% was also recorded for the bacterial 
isolate TUSB-BOO1 compared to 63.8 and 55.2 % for the other ones, respectively. 
Characterization of bacterial isolates was performed at protein level using polyacrylamide gel 
electrophoresis (PAGE) and at the molecular level using random amplified polymorphic DNA 
(RAPD) analysis. Based on the morphological, physiological, biochemical characteristics, and API 
profile; the isolates were identified as Bacillus spp. Moreover, 16S-rDNA gene sequencing 
confirmed the identification of the strain TUSB-BOO1 at the molecular level as Bacillus 
thuringiensis. The coding gene of the key hydrocarbon degrading enzyme, catechol 2, 3 
dioxygenase was detected in the genome of the strain TUSB-BOO1 using PCR amplification and 
sequencing.