Benzo(a)pyrene degradation and microbial community responses in composted soil

Benzo(a)pyrene degradation was compared in soil that was either composted, incubated at a constant temperature of 22 °C, or incubated under a temperature regime typical of a composting process. After 84 days, significantly more (61%) benzo(a)pyrene was removed from composted soil compared to soils incubated at a constant temperature (29%) or at composting temperatures (46%). Molecular fingerprinting approaches indicated that in composted soils, bacterial community changes were driven by both temperature and organic amendment, while fungal community changes were primarily driven by temperature. Next-generation sequencing data revealed that the bacterial community in composted soil was dominated by Actinobacteria (order Actinomycetales), Firmicutes (class Bacilli), and Proteobacteria (classes Gammaproteobacteria and Alphaproteobacteria), regardless of whether benzo(a)pyrene was present or not. The relative abundance of unclassified Actinomycetales (Actinobacteria) was significantly higher in composted soil when degradation was occurring, indicating a potential role for these organisms in benzo(a)pyrene metabolism. This study provides baseline data for employing straw-based composting strategies for the removal of high molecular weight PAHs from soil and contributes to the knowledge of how microbial communities respond to incubation conditions and pollutant degradation

Production of biosurfactants and bioemulsifiers by indigenous bacteria isolated from petroleum sludge and their association with total petroleum hydrocarbon degradation

Microbial biosurfactants and bioemulsifiers are amphiphilic, surface-active compounds produced during biodegradation, increasing the bioavailability of organic pollutants such as hydrocarbons. Both are known to be produced by bacteria to facilitate the process of hydrocarbon degradation and at the same time enhancing oil recovery in petroleum industry. Therefore, the existence of indigenous microorganisms that have the ability to consume petroleum hydrocarbon as carbon source and simultaneously produce biosurfactants and bioemulsifiers in order to facilitate hydrocarbon metabolism can be manipulated for bioremediation purposes. This study aimed to determine the association between the ability of indigenous bacteria isolated from petroleum sludge to produce biosurfactants and bioemulsifiers with their ability to degrade total petroleum hydrocarbons (TPH). Preliminary screenings of biosurfactant (i.e surface tension measurement) and bioemulsifier activity (i.e emulsification assay) from the total number of 26 isolates revealed some potential biosurfactant-producing bacteria (BSP) while some were potentially bioemulsifier-producing bacteria (BEP). Highest emulsification index (E24) exhibited by potential BEP (≈ 72.81 %) while for the rest of the isolates were between 64 to 68 %. Surface tension measurement revealed the biosurfactant activity of the isolates, which were as low as ≈ 18.92 mN/m for a potential BSP; while the rest were between the range of 45 to 28 mN/m. Two of these bacterial isolates (one potential BSP and one potential BEP) were further investigated for TPH biodegradation study using GC-MS. Assuming growth-linked biodegradation; growth curves of these bacterial isolates showed acclimation period for up to more than 72 hours of incubation; whereby no evident disappearance of TPH had been detected. However, after six days, rate of TPH loss became rapid; whereby biodegradation percentage of TPH was about (≈ 73 %). By the twelfth day of biodegradation study, the percentage of TPH loss was up to (≈ 85 %). In conclusion, both potential BSP and BEP were potent hydrocarbon biodegraders and that both biosurfactants and bioemulsifiers were unique microbial products showing advantageous features in hydrocarbon biodegradation. Both bioemulsifiers and biosurfactants could be extracted and purified from bacteria as both molecules have great potential for application in green technology

ISOLATION AND SCREENING OF BIOSURFACTANT-PRODUCING MARINE BACTERIA FROM KUANTAN PORT, PAHANG, MALAYSIA

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

Opportunistic bacteria dominate the soil microbiome response to phenanthrene in a microcosm-based study

Bioremediation offers a sustainable approach for removal of polycyclic aromatic hydrocarbons (PAHs) from the environment; however, information regarding the microbial communities involved remains limited. In this study, microbial community dynamics and the abundance of the key gene (PAH-RHDα) encoding a ring hydroxylating dioxygenase involved in PAH degradation were examined during degradation of phenanthrene in a podzolic soil from the site of a former timber treatment facility. The 10,000-fold greater abundance of this gene associated with Gram-positive bacteria found in phenanthrene-amended soil compared to unamended soil indicated the likely role of Gram-positive bacteria in PAH degradation. In contrast, the abundance of the Gram-negative PAHs-RHDα gene was very low throughout the experiment. While phenanthrene induced increases in the abundance of a small number of OTUs from the Actinomycetales and Sphingomonadale, most of the remainder of the community remained stable. A single unclassified OTU from the Micrococcaceae family increased ∼20-fold in relative abundance, reaching 32% of the total sequences in amended microcosms on day 7 of the experiment. The relative abundance of this same OTU increased 4.5-fold in unamended soils, and a similar pattern was observed for the second most abundant PAH-responsive OTU, classified into the Sphingomonas genus. Furthermore, the relative abundance of both of these OTUs decreased substantially between days 7 and 17 in the phenanthrene-amended and control microcosms. This suggests that their opportunistic phenotype, in addition to likely PAH-degrading ability, was determinant in the vigorous growth of dominant PAH-responsive OTUs following phenanthrene amendment. This study provides new information on the temporal response of soil microbial communities to the presence and degradation of a significant environmental pollutant, and as such has the potential to inform the design of PAH bioremediation protocols

Isolation and Characterization of Hydrocarbon Tolerant Microorganisms from Marine Environment

Industrial activities have contributed to the releases of toxic organic compound into environment and have become a major public concern. This particularly of those industries that are located along coastal areas, which are the gateways for water transport. A study of the isolation and characterization of hydrocarbon tolerant microorganisms from marine samples collected at the jetty site of Tanjung Lumpur, Kuantan, Pahang, was conducted. There were very few studies have been done related to marine hydrocarbon tolerant microorganisms in Kuantan. Hence, this research was done to investigate the presence of microbial community that can thrive in the environment with oil-spillage. Enrichment culture technique by using MSM broth supplemented with 1% engine oil was utilized to isolate the desired microorganisms. Biochemical and molecular approaches were applied to identify and characterize the isolates. Six isolates wereidentified as genera Vibrio, Halomonas, Pseudoaltromonas, Idiomarina, Staphylococcus and Halophilic bacterium. In addition, phylogenetic study helps further in understand the relationship among the isolated bacteria

Antibiotic resistance microbes in tropical mangrove sediments, East Coast Peninsular, Malaysia

The study has been conducted at Tanjung Lumpur, mangrove swamp on January 2009 to isolate and identify the bacterial community in mangrove soil and their resistance against antibiotics. Identified bacteria were Aeromonas hydrophila group 1 and 2, Escherichia coli 1, Chryseomonas luteola, Chromobacterium violaceum, Pseudomonas aeruginosa, Serratia rubudaea, Klebsiella pnuemoniae and Enterobacter cloacae. The identified bacteria were introduced to fourteen different antibiotics to determine the bacterial susceptibility. All the isolates showed 100% resistant towards β-lactam antibiotics (ampicillin, amoxicillin and penicillin), vancomycin, sulphafurazole, gentamicin, erythromycin, tetracycline, novobiocin, clindamycin and bacitracin indicates the presence of bacterial amidases and β-lactamases in the bacteria which inhibit the action of β- lactam antibiotics. Bacteria isolated from mangrove soil showed 66.7 and 77.8% resistance against chloramphenicol and streptomycin, respectively, suggesting that the lipid composition might play a key role in preventing the entrance or binding of antibiotic to the cell. All the isolates were susceptible to ciprofloxacin since it inhibits the enzyme topoisomerase II that cause the negative super coil in DNA and thus permits transcription or replication. All bacterial isolates showed Multi Antibiotic Resistance (MAR) index higher than 0.2 and proved high-risk sources of contamination of the environment. This study proved the presence of antibiotic resistant bacterial strains in mangrove soil that could be used for further studies

Opportunistic Bacteria Dominate the Soil Microbiome Response to Phenanthrene in a Microcosm-Based Study

Bioremediation offers a sustainable approach for removal of polycyclic aromatic hydrocarbons (PAHs) from the environment; however, information regarding the microbial communities involved remains limited. In this study, microbial community dynamics and the abundance of the key gene (PAH-RHDα) encoding a ring hydroxylating dioxygenase involved in PAH degradation were examined during degradation of phenanthrene in a podzolic soil from the site of a former timber treatment facility. The 10,000-fold greater abundance of this gene associated with Gram-positive bacteria found in phenanthrene-amended soil compared to unamended soil indicated the likely role of Gram-positive bacteria in PAH degradation. In contrast, the abundance of the Gram-negative PAHs-RHDα gene was very low throughout the experiment. While phenanthrene induced increases in the abundance of a small number of OTUs from the Actinomycetales and Sphingomonadale, most of the remainder of the community remained stable. A single unclassified OTU from the Micrococcaceae family increased ~20-fold in relative abundance, reaching 32% of the total sequences in amended microcosms on day 7 of the experiment. The relative abundance of this same OTU increased 4.5-fold in unamended soils, and a similar pattern was observed for the second most abundant PAH-responsive OTU, classified into the Sphingomonas genus. Furthermore, the relative abundance of both of these OTUs decreased substantially between days 7 and 17 in the phenanthrene-amended and control microcosms. This suggests that their opportunistic phenotype, in addition to likely PAH-degrading ability, was determinant in the vigorous growth of dominant PAH-responsive OTUs following phenanthrene amendment. This study provides new information on the temporal response of soil microbial communities to the presence and degradation of a significant environmental pollutant, and as such has the potential to inform the design of PAH bioremediation protocols

Polycyclic aromatic hydrocarbons: characteristics and its degradation by biocatalysis remediation

An excessive released of polycyclic aromatic hydrocarbons (PAHs) to surroundings is one of the major factors that cause environmental pollution to increase globally. This issue had gained scientist’s attention to study PAHs biodegradation pathways and their toxicity towards humans and the environment. They found that the major mechanism responsible for the ecological recovery of PAH-contaminated sites happened to be from the microbial degradation process. However, there are a few limitations faced by the PAHs degrading bacteria where the bacteria die due to extremely polluted areas. This leads the researchers to utilize genetic engineering to produce enzymes that can withstand and survive in extreme environments. Recent information and technology such as path sources, properties and biochemical pathways by means to produce the simplest and less harmful components in polluted ecosystems are discussed in this review. In-depth studies in regards to bacteria biocatalysis involving bacterialproduced-enzymes to degrade PAHs help develop new methods to enhance the bioremediation effectiveness in the future