BIODIVERSITAS ISSN: 1412-033X Volume 23, Number 8, August 2022 E-ISSN: 2085-4722 Pages: 4138-4143 DOI: 10.13057/biodiv/d230835 Short Communication: Determination of crude oil degradation efficiency of biofilm producing bacteria isolated from oil contaminated site DE-HWA KHOO, POOJA SHIVANAND  , HUSSEIN TAHA Environmental and Life Sciences Programme, Faculty of Science, Universiti Brunei Darussalam. Jl. Tungku Link BE1410, Brunei Darussalam. Tel: +673-2460922, Fax: +673-2461502,  email: pooja.shivanand@ubd.edu.bn Manuscript received: 2 June 2022. Revision accepted: 27 July 2022. Abstract. Khoo DH, Shivanand P, Taha H. 2022. Short Communication: Determination of crude oil degradation efficiency of biofilm producing bacteria isolated from oil contaminated site. Biodiversitas 23: 4138-4143. Microbes have gained much attention for their application in the bioremediation of petroleum contaminated areas, and biofilm producing bacteria are considered potential candidates for this purpose. The aim of this study was to screen six oil degrading bacterial strains for their ability to form biofilm, and to measure the crude oil degradation efficiency of selected strains. It was found that only two strains, Micrococcus sp. UBDBH15 and Pseudomonas sp. UBDBH26 were categorized as strong biofilm producers, with the latter showing the highest amount of biofilm formed. Under the conditions tested, Pseudomonas sp. UBDBH26 was also found to have the highest degradation rate (0.0047 g/day) with a significant degradation of 7.07 ± 3.02 and 11.38 ± 2.93 % of crude oil after 7 and 14 days respectively. Micrococcus sp. UBDBH15 had a lower rate of degradation (0.0033 g/day), resulting in a non-significant degradation. However, in comparison with a non-biofilm producer, Enterobacter sp. UBDBH06, this study suggested that biofilm might enhance the degradation of oil, but further studies are needed to confirm this assumption. Keywords: Bacteria, biodegradation, biofilm, bioremediation, petroleum INTRODUCTION Polycyclic aromatic hydrocarbons (PAHs) are a group of petroleum chemicals comprising approximately 10,000 toxic and ubiquitous environmental pollutants (Ukiwe et al. 2013). These chemicals can be exposed through direct contact, vapors, or secondary contamination of water supplies (Thapa et al. 2012). PAHs are very dangerous for all living things, one of them for humans (Mohanty and Das 2018). Cellular functions can be affected by the cytotoxicity, carcinogenicity and mutagenicity of the chemicals, leading to various human diseases (Das et al. 2014; Hamoudi-Belarbi et al. 2018). Thus, great attention has been given to microbial bioremediation of crude oil from contaminated areas (Meliani and Bensoltane 2014). Bacteria are known to be the primary and most active hydrocarbon degraders (Lima et al. 2019). Many bacteria can utilize hydrocarbons as a carbon source by utilizing enzymes such as oxygenases and peroxidases to degrade the chemical compounds (Bisht 2015). The harmful hydrocarbons can be transformed into harmless products such as carbon dioxide and water (Das and Chandran 2011). Most bacteria exist as sessile communities in the form of biofilm instead of in planktonic form (Davies et al. 1998). The biofilm can consist of mono- or multi-species community (Edwards and Kjellerup 2013), resulting in a variety of complex relationships involving inter- and/or intra-species interaction (Simões et al. 2009). The bacteria are typically found enclosed in self-secreted slimy and glue-like substances called extracellular polymeric substances which aid the anchorage of the microbial cells on surfaces (Costerton et al. 1999; Wimpenny et al. 2000; Singh et al. 2006). Biofilm can form on various surfaces, including living tissues, medical devices, water systems and aquatic ecosystems (Prakash et al. 2003). Biofilm is known to have many properties which enable the microbes to adapt better to the environment when compared to their planktonic forms (Simões et al. 2009; Sharma et al. 2019). This is through interaction and communication within the community, gene transfer, nutrient availability, and protection from environmental stressors such as temperature, UV radiation, desiccation and toxic contaminants (Costerton et al. 1999; Edwards and Kjellerup 2013). Thus, biofilm producing bacteria are suitable candidates to be used as a tool in the bioremediation of PAHs. In this study, six petroleum degrading bacterial strains that were previously isolated from oil-contaminated sites (Taha et al. 2020) were screened for their ability to form biofilm. The strong biofilm producers were then selected for the determination of their crude oil degradation efficiency. MATERIALS AND METHODS Petroleum degrading bacteria Six strains of culturable petroleum degrading bacteria were used in this study. These strains were previously isolated and identified through DNA barcoding by our