**1. Introduction**

Heterocyclic hydrocarbon has been known to manifest various cytotoxic effect such as severe toxicity, cytotoxicity, mutagenicity, carcinogenicity and photoinduced toxicity [1–3]. Gas, petroleum and coal are the three main natural resource of hydrocarbons. One of the examples of hydrocarbon causing toxic affect to the environment is the accidental crude oil spill in seawater [4]. It was reported that a black bag containing 15 to 20 liters of oil was dumped in the seawater of Redang island in Terengganu [5]. The marine life along the shore was affected, especially turtles landing on the island to lay eggs. Moreover, the toxic chemicals found in the crude oil could also affect human health especially kidney system, liver and sensory system. Some of the hydrocarbons that have their degradation product detected in

industrial waste water, contaminated sites are carbazole, biphenyl, dibenzofuran, dibenzothiophene and fluorine.

Carbazole is one of the heterocyclic hydrocarbons that is highly mutagenic and toxic especially to aquatic organism as documented in a recent study [1, 2, 6]. However, this compound has also been widely used in the raw industry for various purpose such as dye productions, medicines and plastics. Carbazole compound is a derivation of shale oil, crude oil and creosote and it has been proven as non-human carcinogen although however its derivatives such as N-methylcarbazole, which are detected in automobile emission and cigarette smokes are highly genotoxic and are now classified as IARC Group 2B carcinogens [1, 7].

Biodegradation has been known to be a technology that provides various benefits for organic pollutants. As it has been understood for so long, microorganism was able to degrade pollutant, bioremediation sets a goal to transform organic pollutant to various type of nontoxic or environmental friendly metabolites or mineralize it into water and carbon dioxide [8]. Many researches have been done using carbazole as sole carbon source where various bacteria with degradable properties has been isolated from different type of environment by enrichment culture method. Most carbazole degrading bacteria are gram negative and aerobic such as *Microbacterium esteraromaticum* strain SL6 [9].
