Sulfur-deprived

In the approach followed in this invention [29], a biocatalytic agent converts the sulfur heterocycles into different molecules that do not exhibit the hydrophobic interactions. This is achieved by selectively cleaving carbon-sulfur bonds. The selectivity of the biocatalytic agent employed is limited to the carbon-sulfur bonds and no attack to the carbon-carbon skeleton was reported. Thus, it is expected that the proposed biocatalytic reduction of viscosity would not diminish the fuel value of the treated petroleum liquids. The biocatalyst employed consisted of the strain ATCC No. 53968 (see Section 20 and references therein), in an aqueous culture conventionally prepared by fermentation under aerobic conditions. The fermenting bioreactor is fed with a suitable nutrient medium, which comprises a conventional carbon source (dextrose and glycerol are recommended carbon sources. To confer maximal biocatalytic activity for the desired cleavage of organic C—S bonds, the bacteria was kept in a state of sulfur deprivation. 

Tsygankov, A.A., Kosourov, S.N., Tolstygina, I.V., Ghirardi, M.L., Seibert, M. 2006. Hydrogen production by sulfur-deprived Chlamydomonas reinhardtii under photoautrophic conditions. Int J Hydrogen Energy 31 1574-1585. 

Antal TK, Krendeleva TE, Laurinavichene TV, Makarova VV, Ghirardi ML, Ruhin AB, Tsygankov AA, Seihert M (2003) The dependence of algal H2 production on photosystem 11 and O2 consumption activities in sulfur-deprived Chlamydomonas reinhardtii cells. Biochim Biophys Acta 1607 153-160... 

Methionine and Cystine Replacement. Under conditions of sulfur deprivation (0.06 mAf sulfate), addition of 3 mM Na2SeOs to the growth medium of E. coli results in the formation of alkaline phosphatase with a specific activity that is 30% that of the normal enzyme. The selenium... 

Figure 8.9 Accumulation of PolyPs in Aerobacter aerogenes (Harold, 1966) (a) sulfur deprivation, cells placed at 0 h in a Pi- free medium (b) phosphate overplus, cells placed at 0 h in a Pi-free medium, with P was added after 4 h (1) PolyP (2) polyphosphate kinase activity (3) exopolyphosphatase activity.

Although hydrogenase linked H2 production does not require ATP utilization, normal aerobic fixation of atmospheric CO2 does. As will be discussed below, when CO2 fixation does not occur (as is the case under anaerobic, sulfur-deprived condi tions), the accumulation of ATP molecules in the stroma inhibits ATPase function. This results in the non dissipation of the proton gradient and causes the build-up of the proton motive force. It has been shown that, under these conditions, photosynthetic electron transport is down regulated917 and consequently reductant is not available for efficiently producing H2.140... 

In order to address the low cell density issue associated with sulfur-deprived cell suspensions, cell immobilization strategies have been investigated. This resulted in an 18 times increase in the H2-production rates on a per-cell culture volume basis and a 6 times longer period of H2 production by algal cultures immobilized on glass fibers.138 Additionally, the immobilized cultures have increased productivity (2.5 times) on a per illuminated area basis, compared to cell suspensions. 

Ghirardi, M.L. and Amos, W. 2004. Hydrogen photoproduction by sulfur-deprived green algae - status of the research and potential of the system. Biocycle, 45, 59. 

Kosourov, S, M Seibert and ML Ghirardi. 2003. Effects of extracellular pH on the metabolic pathways in sulfur-deprived, H2-producing Chlamydomonas reinhardtii cultures. Plant Cell Physiol. 44,146-155. 

Laurinavichene, T., Tolstyginina, I. and Tsygankov, A. 2004. The effect of light intensity on hydrogen production by sulfur-deprived Chlamydomonas reinhardtii. J. Biotechnol. 114, 143-151. 

Tsygankov, A., Kosourov, S., Seibert, M. and Ghirardi, M.L. 2002. Hydrogen photoproduction under continuous illumination by sulfur-deprived, synchronous Chlamydomonas rein-hardtii cultures. J. Intern. Hydrogen Energy 27, 1239-1244. 

Zhang, L., Happe, T. and Melis, A. 2002. Biochemical and morphological characterization of sulfur deprived and H2-producing Chlamydomonas reinhardtii (green algae). Planta 214, 552 561. 

An early system designed for the sulfur-deprived process required several days to poise the cells for Hj production. This transition period represented lost production compared to continuous operation. Daily start-up of the photobioreactor at sunrise may also decrease production if it extends into the daylight hours. Some other operations, for example, H2 liquefaction processes, would not be a logical choice for a diurnal cycle because of the losses and inefficiencies of starting up and shutting... 

For a stand-alone photobiological (sulfur-deprived, algal) H2-production facility producing 300 kg/day of H2, the total capital investment was estimated to be 5 million with a H2 selling price of approximately 14/kg of hydrogen and a 15% return on investment. This system assumed moderate improvements in the H2-production rate and included PSA purification with high-pressure compressed H2 storage. The total photobioreactor area was 110,000 m with a 10-cm pond depth, 0.2 g/1 cell concentration, and 10/m reactor cost. ... 

Laurinavichene, T.V. et al.. Demonstration of sustained hydrogen photoproduction by immobilized, sulfur-deprived Chlamydomonas reinhardtii cells, Int. J. Hydrogen Energy, 31, 659, 2006. 

Fouchard, S. et al.. Autotrophic and mixotrophic hydrogen photoproduction in sulfur-deprived Chlamydomonas cells, Appl. Environ. Microbiol., 71, 6199, 2005. 

Davies JP, Yildiz F and Grossman AR. (1994). Mutants of Chlamydomonas with aberrant responses to sulfur deprivation. The Plant Cell 6,53-63. 

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