Approaching chlorpyrifos bioelimination at bench scale bioreactor.

Chlorpyrifos (CP) is one of the most commonly applied insecticides for control of pests and insects. The inappropriate use of this kind of chemicals has caused heavy contamination of many terrestrial and aquatic ecosystems thus representing a great environmental and health risk. The main purpose of this work is to investigate novel microbial agents (Pseudomonas stutzeri and the previously obtained consortium LB2) with the ability to degrade CP from polluted effluents. This goal was achieved by operating at different lab scales (flask and bioreactor) and operation modes (batch and fed-batch). Very low degradation and biomass levels were detected in cultures performed with the consortium LB2. In contrast, near complete CP degradation was reached by P. stutzeri at the optimal conditions in less than 1 month, showing a depletion rate of 0.054 h(-1). The scale-up at bench scale stirred tank bioreactor allowed improving the specific degradation rate in ten folds and total CP degradation was obtained after 2 days. Moreover, biomass and biodegradation profiles were modelled to reach a better characterization of the bioremediation process.

Efficient PAHs biodegradation by a bacterial consortium at flask and bioreactor scale.

In this work, the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) such as Phenanthrene (PHE), Pyrene (PYR) and Benzo[a]anthracene (BaA) has been investigated. A bacterial consortium consisting of two strains was used for the first time based on preliminary promising biodegradation data. They were tentatively identified as Staphylococcus warneri and Bacillus pumilus. Degradation values higher than 85% were obtained for each single PAH when operating at flask scale, whereas minimum levels of 90% of PAHs removal were obtained after just 3 days of cultivation at bioreactor scale. The operation in cometabolic conditions led to maximum levels about 75% and 100% at flask and bioreactor scale, respectively. All the experimental data were analyzed in the light of logistic and Luedeking and Piret type models, with the purpose to better characterize the biodegradation process by S. warneri and B. pumilus. Finally, the metabolic pathway followed to degrade each PAH was ascertained.