The dibenzothiophene (DBT) desulfurization pathway of a facultative thermophilic bacterium Mycobacterium sp. X7B was investigated. Metabolites were identified by gas chromatography-mass spectrometry, and the results showed that 2-hydroxybiphenyl, the end product of the previously reported sulfur-specific pathway (also called 4S pathway), was further converted to 2-methoxybiphenyl. This is the first strain to possess this ability and therefore, an extended 4S pathway was determined. In addition, the DBT-desulfurizing bacterium Mycobacterium sp. X7B was able to grow on DBT derivatives such as 4-methylDBT and 4,6-dimethylDBT. Resting cells could desulfurize diesel oil (total sulfur, 535 ppm) after hydrodesulfurization. GCflame ionization detection and GCatomic emission detection analyses were used to qualitatively evaluate the effect of Mycobacterium sp. X7B treatment on the content of the diesel oil. The total sulfur content of the diesel oil was reduced 86% using resting cell biocatalysts for 24h at 45℃.

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.

Biodegradation of carbazole was enhanced by the presence of a non-aqueous phase liquid (logKo/w≥3.1) at phase ratio of 1:1 (organic/aqueous). In a cyclohexane/aqueous phase system, the maximum specific degradation rate (3.34mg carbazole min−1g dry cell−1) was at an organic/aqueous ratio of 1:1. Pseudomonas sp. XLDN4-9 degraded 47% (w/w) of 1g carbazole l−1 in cyclohexane phase directly within 1h.

In this study, the glycerol metabolism by Klebsiella pneumoniae is stoichiometrically analyzed according to energy (ATP), reducing equivalent and product balances. The theoretical analysis reveals that a microaerobic condition is more perfect for the production of 1,3-propanediol (1,3-PD) from glycerol by K. pneumoniae than anaerobic and aerobic conditions. The yields of 1,3-PD, biomass and ATP to glycerol under microaerobic conditions depend not only on the molar fraction of reducing equivalent oxidized completely by molecular oxygen in tricarboxylic acid (TCA) cycle (δ), but also on the molar fraction of TCA cycle in acetyl-CoA metabolism. The maximum theoretical yield of 1,3-PD to glycerol could reach to 0.85mol/mol rather than 0.72mol/mol if all acetyl-CoA entered into TCA cycle instead of acetic acid pathway under anaerobic conditions. The yield of 1,3-PD is still higher than 0.72mol/mol in a range of δ between 0.11 and 0.48, which corresponds to respiratory quotient (RQ) between 11.34 and 2.66. In the same range of δ or RQ, the biomass under a microaerobic condition is more than that of an anaerobic culture. The experimental results of batch cultures demonstrate that microaerobic cultivations are favorable for cell growth, reduction of culture time and ethanol formation, and enhancement of volumetric productivity of 1,3-PD. In addition, no aeration could improve the yield of 1,3-PD to glycerol in comparison with that of an anaerobic or aerobic culture.

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