AUTHOR=Hentati Dorra , Abed Raeid M. M. , Abotalib Nasser , El Nayal Ashraf M. , Ashraf Ijaz , Ismail Wael 

TITLE=Biotreatment of oily sludge by a bacterial consortium: Effect of bioprocess conditions on biodegradation efficiency and bacterial community structure

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.998076

DOI=10.3389/fmicb.2022.998076

ISSN=1664-302X

ABSTRACT=<p>We studied the biodegradation of oily sludge generated by a petroleum plant in Bahrain by a bacterial consortium (termed as AK6) under different bioprocess conditions. Biodegradation of petroleum hydrocarbons in oily sludge (C<sub>11</sub>-C<sub>29</sub>) increased from 24% after two days to 99% after 9 days of incubation in cultures containing 5% (w/v) of oily sludge at 40°C. When the nitrogen source was excluded from the batch cultures, hydrocarbon biodegradation dropped to 45% within 7 days. The hydrocarbon biodegradation decreased also by increasing the salinity to 3% and the temperature above 40°C. AK6 tolerated up to 50% (w/v) oily sludge and degraded 60% of the dichloromethane-extractable oil fraction. Illumina-MiSeq analyses revealed that the AK6 consortium was mainly composed of <italic>Gammaproteobacteria</italic> (ca. 98% of total sequences), with most sequences belonging to <italic>Klebsiella</italic> (77.6% of total sequences), <italic>Enterobacter</italic> (16.7%) and <italic>Salmonella</italic> (5%). Prominent shifts in the bacterial composition of the consortium were observed when the temperature and initial sludge concentration increased, and the nitrogen source was excluded, favoring sequences belonging to <italic>Pseudomonas</italic> and <italic>Stenotrophomonas</italic>. The AK6 consortium is endowed with a strong oily sludge tolerance and biodegradation capability under different bioprocess conditions, where <italic>Pseudomonas</italic> spp. appear to be crucial for hydrocarbon biodegradation.</p>