Characterization and Evaluation of the Potential of a Diesel-Degrading Bacterial Consortium Isolated from Fresh Mangrove Sediment

Hydrocarbons are ubiquitous and persistent organic pollutants in the environment. In wetlands and marine environments, particularly in mangrove ecosystems, their increase and significant accumulation result from human activities such as oil and gas exploration and exploitation operations. Remediation of these ecosystems requires the development of adequate and effective strategies. Natural attenuation, biostimulation, and bioaugmentation are all biological soil treatment techniques that can be adapted to mangroves. Our experiments were performed on samples of fresh mangrove sediments from the Cameroon estuary and mainly from the Wouri River in Cameroon. This study aims to assess the degradation potential of a bacterial consortium isolated from mangrove sediment. The principle of our bioremediation experiments is based on a series of tests designed to evaluate the potential of an active indigenous microflora and three exogenous pure strains, to degrade diesel with/without adding nutrients. The experiments were conducted in laboratory flasks and a greenhouse in microcosms. In one case, as in the other, the endogenous microflora showed that it was able to degrade diesel. Under stress of the pollutant, the endogenous microflora fits well enough in the middle to enable metabolism of the pollutant. However, the Rhodococcus strain was more effective over time. The degradation rate was 77 and 90%in the vials containing the sterile sediments and non-sterile sediments, respectively. The results are comparable with those obtained in the microcosms in a greenhouse where only the endogenous microflora were used. The results of this study show that mangrove sediment contains an active microflora that can metabolize diesel. Indigenous and active microflora show an interesting potential for diesel degradation

Biodegradation of Polycyclic Aromatic Hydrocarbons in Mangrove Sediments Under Different Strategies: Natural Attenuation, Biostimulation, and Bioaugmentation with Rhodococcus erythropolis T902.1

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that occur in mangrove sediments. Their removal by bacteria often depends on specific characteristics as the number of benzene rings they possess and their solubility. Their removal also depends on environmental factors, such as pH, temperature, oxygen, and the ability of the endogenous or exogenous microflora to metabolize hydrocarbons.With the aim of treating mangrove sediments polluted by hydrocarbons in a biological way, a biodegradation experiment was conducted using mangrove sediments artificially contaminated with a mixture of four PAHs. The study used Rhodococcus erythropolis as an exogenous bacterial strain in order to assess the biodegradation of the PAH mixture by natural attenuation, biostimulation, bioaugmentation, and a combination of biostimulation and bioaugmentation. The results showed that the last three treatments were more efficient than natural attenuation. The biostimulation/bioaugmentation combination proved to be the most effective PAH degradation treatment

The Effect of Nutrients on the Degradation of Hydrocarbons in Mangrove Ecosystems by Microorganisms

peer reviewedMangrove ecosystems are areas prone to various types of pollution, especially hydrocarbons. These hydrocarbons mostly stem from human activities such as spills coming from offshore oil operations, runoff from surrounding urban areas or atmospheric deposition. This pollution causes the decline of mangroves, which results in an imbalance in the functioning of this particular ecosystem with damages to the microbiota. Biodegradation allows to restore these ecosystems. This biodegradation can only be effective in specific environmental conditions. The presence of nutrients, which stimulate bacterial growth and promote biodegradation, is a key parameter to be considered. During this experiment, we achieved biodegradation tests to assess the effect of nitrogen and phosphorus on the process. The results showed that the biodegradation rates were strongly bound to the presence of nutrients. The degradation rates depended on the medium. The treatment that reached the best rate of degradation of diesel after 10 days was the one using 20% of a nutrient solution (MSM) containing nitrogen and phosphorus. This treatment led to a maximal degradation of 84.7% ± 4.7% obtained in the flasks containing 20% of a nutrient solution (MSM) containing nitrogen and phosphorus

Overview of current knowledge management of pollution by oil mangroves

peer reviewedOverview of current knowledge on management of hydrocarbon pollution in mangroves. Mangrove forests are vital in terms of biomass production and maintenance of the natural balance in coastal areas in the tropics. However, mangroves are subject to pollution from human activities. Oil pollution is one of the causes leading to the decline of mangroves, which represent only 1% of the area of all the world’s tropical forests. Several techniques are available for the remediation of oil contaminated areas. Biodegradation appears to be the best suited to mangrove ecosystems. However this technique remains confined to the laboratory. Field tests in situ need to be conducted in order to evaluate the results obtained in the laboratory

Salt-Tolerant Rhizobia for Enhancing Common Bean (Phaseolus vulgaris L.) Productivity under Salt Stress

Salinity is one of the most important abiotic factors which are responsible for lower yields. To reduce its impact, conventional methods have been unable to solve the problem at all. In this context, developing sustainable methods which increase the productivity of saline soils without harming the environment is necessary. Some microorganisms such as rhizobia are tolerant to salt stress and can then grow in saline areas. Therefore, salt tolerant (ST) rhizobia are believed to reduce the impact of salinity on plant productivity. The aim of this study is to select the major salt-tolerant isolate of rhizobia that can alleviate salt stress in the common bean. Five salt-tolerant rhizobia were used for bean inoculation in greenhouse under salt stress (0 mM, 25 mM and 50 mM). A month after sowing, plants are harvested and analyzed for nodulation, growth and biochemical stress markers production. Collected data are analyzed statistically using SPSS 12.0. Results show that plant inoculation with ISRA352, PvNk8, PvMb1, PvNk7 reduces the effects of stress through the increase of growth, total pigments and osmolytes (proline and glycine betaine) contents compared to positive and negative controls. Plant inoculation with PvMb1 and ISRA352 led to low stress at 50 mM of NaCl. PvMb1, PvNk8 and PvNj5 are good inoculants for bean cultivation even in salt-affected soils. This research study contributes to allow the cultivation of bean in salty areas. On the other hand, the study comes up with a solution for remediation of saline soils yet to be enhanced.</jats:p