Abstract
Biosurfactants play an important role in bioremediation of organic pollutants such as petroleum hydrocarbon. The unique properties of biosurfactants make them possible to be used in the remediation of hydrocarbon contaminated sites. Therefore, the existence of indigenous microorganisms that have the ability to consume petroleum hydrocarbon as carbon source and simultaneously produce biosurfactants in order to facilitate the hydrocarbon metabolism can be manipulated for bioremediation purposes. In this study, isolation and screening of potential biosurfactant-producing bacteria from two sampling points in Kuantan Port seawater were successfully done. Amongst the isolates, 4 out of 7 isolates from Point A were Gram negative bacteria and 2 out 5 isolates from Point B were Gram negative bacteria. The positive oxidase test resulted for all isolates from Point A and only B5 from Point B produced negative result. Catalase test conducted produced positive results on isolates from Point A (A3, A5, A6& A7) and Point B (B1, B2, B4 & B5).The highest percentage emulsification index measured belonged to isolate B4 and B5 which are 67%, thus make these isolates to be the most promising biosurfactant producers. Further identification by 16S rRNA gene found that isolates were closely related to Rhodococcus erythropolis (A1), Psedomonas stutzeri (A2), Pseudoalteromonas lipolytica (A3, A6 and B4), Vibrio brasiliensis (A4 and B2), Vibrio tubiashii (B1), Marinobacter salsuginis (A5), Labrenzia aggregate (A7), Marinococcus halophilus (B3) and Thalassospira xianmenensis(B5). Hence, through biosurfactant activities exhibited by isolates, B4 and B5 were the most potential isolates to produce biosurfactant. Therefore, these isolates can potentially be exploited to aid in bioremediation of petroleum hydrocarbon contaminated sites and would also be useful to enhance oil recovery in petroleum industry.
Highlights
Hydrocarbons are widespread environmental pollutants; the higher molecular weight compounds polycyclic aromatic hydrocarbons (PAHs) which are potent carcinogens and recognized as priority pollutants by both the EU and the US EPA [1,2]
Seawater samples were collected from two sampling points which are Point A (3°58ʹ13.9ʺN 103°25ʹ41.4ʺE) that was located near the ships area and Point B (3°58ʹ49.0ʺN 103°24ʹ46.4ʺE) that was located a little bit far from ships area at Kuantan Port, Kuantan, Pahang
A total of 12 bacteria was successfully isolated from seawater samples of Kuantan Port using Bushnell Haas supplemented with 1% (v/v) petroleum crude as sole carbon source
Summary
Hydrocarbons are widespread environmental pollutants; the higher molecular weight compounds polycyclic aromatic hydrocarbons (PAHs) which are potent carcinogens and recognized as priority pollutants by both the EU and the US EPA [1,2]. Biosurfactant-producing microorganisms can be isolated from sites contaminated by petroleum or other substances containing hydrocarbons; where they are indigenous population of those sites [6] They can thrive in these polluted environments and at the same time degrade and metabolize the hydrocarbons which they use as their carbon source. In order to facilitate the metabolism of these insoluble hydrocarbons, microorganisms can produce a variety of substances These substances are amphiphilic surface-active compounds produced as part of the microorganisms’ cell membrane or excreted extracellularly. The hydrophilic group consists of mono-, oligo-, or polysaccharides, peptides or proteins while the hydrophobic moiety usually contains saturated, unsaturated and hydroxylated fatty acids or fatty alcohols [7] These compounds can be generally divided into two main classes; low-molecular-weight compounds called biosurfactants and high-molecular-weight polymers called bioemulsifiers [8]
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