Biodegradation of carbazole in oil/water biphasic system by a newly isolated bacterium Klebsiella sp. LSSE-H2

Modeling growth kinetics and carbazole degradation kinetics of a Pseudomonas aeruginosa strain isolated from refinery sludge and uptake considerations during growth on carbazole

Although bacterial degradation of polynuclear aromatic hydrocarbons (PAH) have been studied using various pure cultures, only a few studies have explored the degradation kinetics and uptake mechanism of nitrogen heterocyclic PAHs (PANH) with three or more rings. This work explored growth kinetics of a PAH degrading bacterial strain, Pseudomonas aeruginosa RS1 on carbazole (CBZ) and concomitant degradation kinetics of CBZ over the concentration range 25 to 500 mg/L. For CBZ acclimatized strain, the specific growth rate (μ) and specific CBZ uptake rate (q) varied from 0.96 ± 0.05 to 2 ± 0.15 day^-1 and from 0.002 ± 0.001 to 0.02 ± 0.01 mg CBZ mg VSS^-1 day^-1, respectively. The Moser and Monod model provided best fits to the μ vs CBZ concentration and q vs CBZ concentration profiles, respectively. Biosurfactant activity did not play a role in CBZ uptake. However, elevation in cell surface hydrophobicity as revealed through the water contact angle values on bacterial cell mat indicated the possible role of direct interfacial uptake in facilitating CBZ uptake over and above uptake after dissolution. Elevated catechol 1,2-dioxygenase enzyme activity was observed during CBZ degradation. Interestingly, the specific activity of this enzyme was higher in the culture supernatant than in the cell extract. However, during CBZ degradation, accumulation of some toxic metabolites in the aqueous phase was revealed through increase in TOC of the aqueous phase and Kirby-Bauer disc diffusion study performed using a E. coli strain. Both aqueous phase TOC and toxicity decreased beyond the log growth phase indicating further utilization of the degradation intermediates.

Preparation of a bioflocculant by using acetonitrile as sole nitrogen source and its application in heavy metals removal

A novel bioflocculant, A-GS408, produced by Klebsiella oxytoca GS-4-08 cultured in acetonitrile (ACN) as sole nitrogen source was investigated in this study. A complete degradation of 1 g l^-1 of ACN was achieved in 350 h, and 4.6 g of crude A-GS408 can be obtained in one litter of synthetic medium. The as-prepared bioflocculant exhibits good flocculation efficiency (over 90%) toward Kaolin solution with the aid of Fe³⁺. Chemical analysis showed that the bioflocculant was mainly composed of polysaccharides (46.3%) and proteins (20.6%). FTIR and XPS results indicated the abundant carboxyl, amine and hydroxyl groups in A-GS408 s, which play an important role on Pd²⁺ and Cu²⁺ adsorption. The adsorption of heavy metals can be well stimulated by Freundlich isotherm equation, and the K_f was up to 439.2 mg^1-1/n l^1/n g^-1 and 112.2 mg^1-1/n l^1/n g^-1 for Pb²⁺ and Cu²⁺, respectively. The kinetic fitting results proved that the adsorption of heavy metals by A-GS408 was chemisorption. This study may provide a new method for preparation of bioflocculant, which can not only degrade toxic compound i.e., acetonitrile, but also can reuse considerable nitrogen source from nitrile-containing wastewater.

Biodegradation of carbazole by newly isolated Acinetobacter spp

In this study, two bacterial isolates designated Alp6 and Alp7 were isolated from soil collected from dye industries and screened for their ability to degrade carbazole. Growing cells of the isolates Alp6 and Alp7 could degrade 99.9% and 98.5% of carbazole, respectively in 216 h. The specific activity for degradation by the resting cells of Alp6 was found to be 7.96 μmol/min/g dry cell weight, while for Alp7 it was 5.82 μmol/min/g dry cell weight. Phylogenetic analysis based on 16S rDNA gene sequences showed that isolates Alp6 and Alp7 belonged to the genus Acinetobacter. To the best of our knowledge, this is the first report on the Acinetobacter spp. showing utilization of carbazole as carbon and nitrogen source.

Experimental investigation of bio-removal of toxic organic pollutants from highly saline solutions in a triphasic system

A combined solvent extraction and biphasic biodegradation process was proposed to remove organic pollutants from highly saline solutions, where the organic solvent is biocompatible and the organic-aqueous interface remains quasi-quiescent during the process. Phenol and Pseudomonas putida BCRC 14365 were selected as the model organic compound and biomass, respectively. The effects of added NaCl concentration (50-200 g/L) and pH (1.0-9.0) in synthetic solutions on phenol removal and cell growth were studied at 30 degrees C. The initial cell concentration was fixed at 0.025 g/L. Within the examined range, the adjustment of solution pH to 3.0 resulted in the best removal performance of 1100 mg/L phenol from such saline solutions (an apparent removal rate of about 20 mg/(Lh)) when using kerosene as the organic solvent. The overall process appeared to be favored when the salt concentration in saline solution was in the range of 100-150 g/L. The application potentials of such a triphasic process for the removal of toxic organics (phenol) from highly saline and acidic wastewaters were finally demonstrated in fed-batch mode.