Abstract
The aim of this work was to investigate the criteria that allow a marine bacterium to degrade
hydrocarbons. 13 strains were selected in this study from a collection of 119 strains isolated and
identified in a previous work (DJAHNIT et al., 2019).
The biochemical characterization of the strains showed that 73% of the bacteria used are gramand only 27% of them are gram+ bacteria, all the strains tested are catalase positive and oxidase
positive with the exception of Halomonas venusta and Gordonia hongkongensis strains which are
oxidase negative bacteria.
The majority of the isolates showed significant biosurfactant production with important
emulsification activities useful in biodegradation and biofilm formation. The highest
emulsification activity was detected in Brevibacterium celere which belongs to the phylum
Actinobacteria with 35% emulsification, it exceeds that of bacteria belonging to the phylum
Proteobacteria, Pseudomonas Taiwanensis and Alcanivorax borkumensis which present 27%
activity.
Bacterial growth is low in media supplemented with 10 g/L NaCl across all bacteria, and as the
concentration of NaCl increases in the media, bacterial growth increases until the bacteria reach
their tolerance threshold (20 to 30g/ NaCl) with the exception of Gordonia hongkongensis which
can grow at 40 g/L NaCl. Moreover, the strains used show a specific growth towards the type of
hydrocarbon used. For example, Erythrobacter citreus and Alcanivorax dieselolei show increased
growth in the presence of hexadecane. Alcanivorax borkumensis, Alcanivorax xenomutans, show
better growth in the presence of octadecane. On the other hand, Brevibacterium celere and
Gordonia hongkongensis showed an increased growth in media containing toluene. Regarding
biodegradation, 73% of the bacteria showed difficulty in degrading aromatic hydrocarbons
compared to aliphatic ones with Brevibacterium celere showing the lowest rate with only 13%
aromatic degradation compared to 45% aliphatic degradation. The genus Alcanivorax performed
best in terms of PAH degradation with rates ranging from 33% up to 67% with the exception of
one of the strains Alcanivorax borkumensis which showed a 19% degradation result.
Keywords: Crude oil - Marine bacteria - Hydrocarbonoclast - Biosurfactants - Biofilms -
Bioremediation – Alcanivorax
The aim of this work was to investigate the criteria that allow a marine bacterium to degrade
hydrocarbons. 13 strains were selected in this study from a collection of 119 strains isolated and
identified in a previous work (DJAHNIT et al., 2019).
The biochemical characterization of the strains showed that 73% of the bacteria used are gramand only 27% of them are gram+ bacteria, all the strains tested are catalase positive and oxidase
positive with the exception of Halomonas venusta and Gordonia hongkongensis strains which are
oxidase negative bacteria.
The majority of the isolates showed significant biosurfactant production with important
emulsification activities useful in biodegradation and biofilm formation. The highest
emulsification activity was detected in Brevibacterium celere which belongs to the phylum
Actinobacteria with 35% emulsification, it exceeds that of bacteria belonging to the phylum
Proteobacteria, Pseudomonas Taiwanensis and Alcanivorax borkumensis which present 27%
activity.
Bacterial growth is low in media supplemented with 10 g/L NaCl across all bacteria, and as the
concentration of NaCl increases in the media, bacterial growth increases until the bacteria reach
their tolerance threshold (20 to 30g/ NaCl) with the exception of Gordonia hongkongensis which
can grow at 40 g/L NaCl. Moreover, the strains used show a specific growth towards the type of
hydrocarbon used. For example, Erythrobacter citreus and Alcanivorax dieselolei show increased
growth in the presence of hexadecane. Alcanivorax borkumensis, Alcanivorax xenomutans, show
better growth in the presence of octadecane. On the other hand, Brevibacterium celere and
Gordonia hongkongensis showed an increased growth in media containing toluene. Regarding
biodegradation, 73% of the bacteria showed difficulty in degrading aromatic hydrocarbons
compared to aliphatic ones with Brevibacterium celere showing the lowest rate with only 13%
aromatic degradation compared to 45% aliphatic degradation. The genus Alcanivorax performed
best in terms of PAH degradation with rates ranging from 33% up to 67% with the exception of
one of the strains Alcanivorax borkumensis which showed a 19% degradation result.
Keywords: Crude oil - Marine bacteria - Hydrocarbonoclast - Biosurfactants - Biofilms -
Bioremediation – Alcanivorax