Aerobic conditions tests

Endosulfan in aqueous solutions is also expected to undergo biodegradation. In laboratory tests at pH 7 and 20 , Pseudomonas bacteria degraded endosulfan (isomers not specified) under aerobic conditions with a half-life of about 1 week (Greve and Wit 1971). Biotic and abiotic transformations of endosulfan in seawater/sediment microcosms have been reported (Gotham and Bidleman 1989). In biotic tests, half-lives for the a- and P-isomers in seawater-only microcosms (pH 8) were about 5 and 2 days, respectively. In seawater-only microcosms under sterile conditions at a pH of 8 or higher, the half-life for the a-isomer was 2-3 days, whereas the half-life for the p-isomer was 1-2 days. Half-lives were longer in seawater/sediment microcosms, possibly because of the lower pHs (7.3-7.7) in these test systems half-lives were 22 and 8.3 days for the a- and P-isomers, respectively. Endosulfan diol was the main metabolite identified. 

In a very recent work, the Pd-catalysed cross-coupling reactions with arenediazonium salts under aerobic conditions in the presence of a chiral monothiourea ligand were reported (Scheme 25) [106]. Even if this Hgand bears four chiral centres, no test in asymmetric Heck-type reaction has been described so far. 

Ready biodegradability refers to the situation in which the test compound is totally degraded (under aerobic conditions to COj, HjO, etc.) within the time span of a standardized test usually lasting 5, 7, or 28 d. 

Tests were carried out at 25°C and at initial pH 6.9. Cultures in the liquid medium were incubated in 50 mL Falcon tubes, continuously shaked at 220 rpm. Each culture contained a fresh Pseudomonas sp. 0X1 colony in 10 mL of medium. The airlift with 10 g of pumice was sterilized at 121°C for 30 min and then housed in a sterile room. One-day culture was transferred to the reactor and, after a batch phase, liquid medium with phenol as the only carbon source was continuously fed. The reactor volume V was fixed at 0.13 L. Aerobic conditions were established sparging technical air. Under these conditions microorganism started to grow immobilized on the solid s support. When immobilized biomass approached steady state, cyclic operation of the airlift was started by alternating aerobic/anaerobic conditions. 

High cell densities are not only a prerequisite for high productivity additionally an effective on-line control and modeling of the bioprocesses is necessary. For industrial applications, optical measurement methods are more attractive because they are non-invasive and more robust. The potential of the BioView sensor for on-line bioprocess monitoring and control was tested. For high-cell-density cultivation of Escherichia coli, maintaining aerobic conditions and removal of inhibitory by-products are essential. Acetic acid is known to be one of the critical metabolites. Information about changes in the cell metabolism and the time of important process operations is accessible on-line for optimization... 

Production. Xanthan gum is produced by the microorganism X. campestris, originally isolated from the mtabaga plant. The gum is produced commercially by culturing X. campestris purely under aerobic conditions in a medium containing commercial glucose, a suitable nitrogen source, dipotassium phosphate, and appropriate essential elements. When the fermentation is complete, the gum is recovered from the fermentation broth by precipitation with isopropyl alcohol, and dried, milled, tested, and packed. 

Thus, the rates of biodegradation are likely to vary considerably, depending on the environment to which a chemical is released, as tests from various media have demonstrated (Boethling et al., 1995 Federle et al., 1997). Also, the rates under different conditions may vary depending upon the type of chemical structure. For example, nitro aromatic compounds are usually fairly resistant to biodegradation under aerobic conditions but are reduced rapidly to amines under anaerobic conditions. 

Marcomini, A., and M. Zanette. 1996. Biodegradation mechanisms of aliphatic alcohol polyethoxy-lates (AE) under standardized aerobic conditions (modified OECD screening test 301E). Riv. Ital. Sost. Grasse 73, 213-218. 

It is visualized that the proposed coal slurry pipelines could be used as biological plug flow reactors under aerobic conditions. The laboratory corrosion studies under dynamic test conditions show that use of a corrosion inhibitor will limit the pipeline corrosion rate to acceptable levels. 

Sediment estimated first-order t,/2 = 23-69.3 d from biodegradation rate constant k = 0.01-0.03 d 1 at 9-21°C by river die-away test in slurry sediment of aquatic systems (Lee Ryan 1979 quoted, Scow 1982) t,/2 = 27 d for sediment-water microcosm under aerobic conditions (quoted, Muir 1991). 

Biodegradation aqueous aerobic t,2 = 168-672 h, based on unacclimated aqueous aerobic screening test data (Gummer 1979 Kanazawa 1987 quoted, Howard et al. 1991) aqueous anaerobic t,/2 = 672-2688 h, based on estimated unacclimated aqueous aerobic biodegradation half-life (Howard et al. 1991) t, 2 = 44 d under aerobic conditions and t,/2 = 59 d under anaerobic conditions in water used a combination of activated sludge, silt loam soil and sediment as an inoculum t,/2 = 78 d under aerobic conditions and t, 2 = 125 d under anaerobic conditions at pH 6.9 (Howard 1991). 

---