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

The microbial production of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae under micro-aerobic conditions was investigated in this study. The experimental results of batch fermentation showed that the final concentration and yield of 1,3-PD on glycerol under micro-aerobic conditions approached values achieved under anaerobic conditions. However, less ethanol was produced under microaerobic than anaerobic conditions at the end of fermentation. The batch micro-aerobic fermentation time was markedly shorter than that of anaerobic fermentation. This led to an increment of productivity of 1,3-PD. For instance, the concentration, molar yield, and productivity of 1,3-PD of batch microaerobic fermentation by K. pneumoniae DSM 2026 were 17.65g/l, 56.13%, and 2.94g l-1 h-1, respectively, with a fermentation time of 6 h and an initial glycerol concentration of 40g/l. Compared with DSM 2026, the microbial growth of K. pneumoniae AS 1.1736 was slow and the concentration of 1,3-PD was low under the same conditions. Furthermore, the microbial growth in fed-batch fermentation by K. pneumoniae DSM 2026 was faster under micro-aerobic than anaerobic conditions. The concentration, molar yield, and productivity of 1,3-PD in fed-batch fermentation under micro-aerobic conditions were 59.50g/l, 51.75%, and 1.57g l-1 h-1, respectively. The volumetric productivity of 1,3-PD under microaerobic conditions was almost twice that of anaerobic fedbatch fermentation, at 1.57 and 0.80g l-1 h-1, respectively.

A lactate oxidase was purified about 36-fold from a newly screened strain KY6 of gram negative bacterium from soil to yield a homogeneous protein. The native enzyme had a molecular mass of 204 kDa easured by Sephadex G-200 and that of subunit on the SDS-PAGE was found to be 45 kDa. The enzyme was optimally active at pH 7.7 and showed stability at pH range of 5.7 to 9.5 for 24 h at 4℃. The optimum temperature was 70℃ and the enzyme activity was stable for 10min up to 45℃. The half-life of the enzyme activity was about 10 min at 55℃. The best substrate of the enzyme was D-lactate and Km value for D-lactate was 0.14raM. The Km value for DL-lactate was 0.20mM. Substrate inhibition of the enzyme was observed at higher concentrations than 20mM of DL-lactate and 10mM of D-lactate.