A carbazole-utilizing bacterium was isolated by enrichment from petroleum-contaminated soil. The isolate,designated Sphingomonas sp. strain XLDN2-5, could utilize carbazole (CA) as the sole source of carbon,nitrogen, and energy. Washed cells of strain XLDN2-5 were shown to be capable of degrading dibenzofuran(DBF) and dibenzothiophene (DBT). Examination of metabolites suggested that XLDN2-5 degraded DBF to2-hydroxy-6-(2-hydroxyphenyl)-6-oxo-2,4-hexadienic acid and subsequently to salicylic acid through the angulardioxygenation pathway. In contrast to DBF, strain XLDN2-5 could transform DBT through the ringcleavage and sulfoxidation pathways. Sphingomonas sp. strain XLDN2-5 could cometabolically degrade DBFand DBT in the growing system using CA as a substrate. After 40 h of incubation, 90% of DBT was transformed,and CA and DBF were completely removed. These results suggested that strain XLDN2-5 might be useful inthe bioremediation of environments contaminated by these compounds.

A new technology for 6-hydroxy-3-succinoyl-pyridine(HSP) production from (S)-nicotine in tobacco waste bywhole cells of a Pseudomonas sp. has been developed.Whendeionized water was used in the transformation reactionas a medium and the initial pH value of reaction mixturewas adjusted to 7.0, 1.45 g/L HSP was produced from 3 g/Lof nicotine in 5 h with 3.4 g/L of cells in a 5-L flask at 30°C. HSP could be easily purified from the reaction withoutperplexing separation steps. A quantity of 1.3 g of HSPwas recovered without impurity, and the overall yield of HSPwas 43.8% (w/w), based on an initial concentration of3.0 g/L of nicotine in reaction. This biotransformation madeit possible to convert nicotine in tobacco wastes withhigh nicotine content into valuable compounds.

On an industrial scale, the production of pyruvate at a high concentration from the cheaper lactate substrate is a valuable process. To produce pyruvate from lactate by whole cells, various lactate-utilizing microorganisms were isolated from soil samples. Among them, strain WLIS, identified as Acinetobacter sp., was screened as a pyruvate producer. For the pyruvate preparation from lactate, the preparative conditions were optimized with whole cells of the strain. The cells cultivated in the medium containing 100mM of L-lactate showed the highest biotransformation efficiency from lactate to pyruvate. The optimized dry-cell concentration, pH, and temperature of reaction were 6g/L, pH 7.0-7.5, and 30℃, respectively. The influences of ethylenediaminetetraacetic acid (EDTA) and aeration on a biotransformation reaction were carried out under the test conditions. Under the optimized reaction conditions, L-lactate at concentrations of 200 and 500mM were almost totally stoichiometrically converted into pyruvate in 8 and 12h, respectively. About 60% of 800mM of L-lactate was transformed into pyruvate in 24h. This reduced conversion rate is probably due to the high substrate inhibition in biotransformation.

Polycyclic aromatic heterocycles, such as carbazole, are environmental contaminants suspected of posinghuman health risks. In this study, we investigated the degradation of carbazole by immobilized Sphingomonassp. strain XLDN2-5 cells. Four kinds of polymers were evaluated as immobilization supports for Sphingomonassp. strain XLDN2-5. After comparison with agar, alginate, and carrageenan, gellan gum was selected as theoptimal immobilization support. Furthermore, Fe3O4 nanoparticles were prepared by a coprecipitation method, andthe average particle size was about 20 nm with 49.65-electromagnetic-unit (emu) g-1 saturation magnetization.When the mixture of gellan gel and the Fe3O4 nanoparticles served as an immobilization support, the magneticallyimmobilized cells were prepared by an ionotropic method. The biodegradation experiments were carriedout by employing free cells, nonmagnetically immobilized cells, and magnetically immobilized cells in aqueousphase. The results showed that the magnetically immobilized cells presented higher carbazole biodegradationactivity than nonmagnetically immobilized cells and free cells. The highest biodegradation activity was obtainedwhen the concentration of Fe3O4 nanoparticles was 9 mg·ml-1 and the saturation magnetization ofmagnetically immobilized cells was 11.08 emu g-1. Additionally, the recycling experiments demonstrated thatthe degradation activity of magnetically immobilized cells increased gradually during the eight recycles. Theseresults support developing efficient biocatalysts using magnetically immobilized cells and provide a promisingtechnique for improving biocatalysts used in the biodegradation of not only carbazole, but also other hazardousorganic compounds.

A kinetic model of continuous treatment of waste water by Rhodopseudomonas palustris Y6 immobilized on soft fibre in a columnar bioreaction system was established. Good agreement was found between the model prediction and the experimental data from continuous operation [initial chemical oxygen demand (COD) concentration" 29.700g/l] of the system. The optimum operational conditions for the maximum COD reduction capacity were investigated from the model prediction and the experimental data. The waste water treatment process may significantly increase the waste reduction capacity because a large amount of active biomass for COD reduction is immobilized in the system, resulting in operation stability. The results presented here provide a useful basis for further scaling up and e