Dibenzothiophene (DBT) is the most excessive and refractory sulfur compound in fossil fuels. The methods for removing DBT, using bacteria, were twofold: the first one involved the destruction of the carbon skeleton; the second, the use of a sulfur-specific process of biodesulfurization, without cleaving the carbon ring. Because the second method does not degrade the value of the fuel, it is considered by most researchers to be the method of choice. Bacteria used for this study, were obtained from the soil collected from a field that contained waste water from a refinery. Using GC/MS, it was confirmed that the metabolic pathway used by this bacterium, involved a sulfur-specific process of biodesulfurization, named the '4S pathway'. This strain appears to have the ability to remove the organic sulfur from thiophenic compounds over a wide temperature range from 25 to 45℃. And the half time of the whole cells desulfurization activity was 32 days, three times more than Rhodococcus erythropolis IGTS8. With the excellent stability, it may have industrial application for biodesulfurization.

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.

Ethanol concentration and fermentation productivity using Saccharomyces cerevisiae were substantially increased in shake flask cultures with a normal inoculum by combining 3 methods: (a) by making nutrient additions to the standard medium for ethanol production, (b) by immobilizing the cells in alginate beads and (c) by using a glucose step-feeding batch process. Ethanol concentration by free yeast was improved from 5.9% (w/w) to 9.6% (w/w) when a further 0.8% yeast extract and 1% animal peptone were added to the standard 30% (w/v) glucose nutrient medium. This was further increased to 12.8% (w/w) by using alginate immobilized yeast. The ethanol concentration was increased again, to 15.0% (w/w) by using the glucose step-feeding batch process.

Previous research suggested that Pseudomonas spp. may attack the pyrrolidine ring of nicotine in a waysimilar to mammalian metabolism, resulting in the formation of pseudooxynicotine, the direct precursor of apotent tobacco-specific lung carcinogen. In addition, the subsequent intermediates, 6-hydroxy-3-succinoylpyridine(HSP) and 2,5-dihydroxypyridine (DHP) in the Pseudomonas nicotine degradation pathway are twoimportant precursors for drug syntheses. However, there is little information on the molecular mechanism fornicotine degradation via the pyrrolidine pathway until now. In this study we cloned and sequenced a 4,879-bpgene cluster involved in nicotine degradation. Intermediates N-methylmyosmine, pseudooxynicotine, 3-succinoylpyridine,HSP, and DHP were identified from resting cell reactions of the transformant containing the genecluster and shown to be identical to those of the pyrrolidine pathway reported in wild-type strain Pseudomonasputida S16. The gene for 6-hydroxy-3-succinoylpyridine hydroxylase (HSP hydroxylase) catalyzing HSP directlyto DHP was cloned, sequenced, and expressed in Escherichia coli, and the purified HSP hydroxylase (38 kDa)is NADH dependent. DNA sequence analysis of this 936-bp fragment reveals that the deduced amino acidshows no similarity with any protein of known function.

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.