Stabilized chlorine dioxide for contamination control in zymomonas fermentation
AssigneeE. I. Du Pont de Nemours and Company
InventorsMaria C. Leana, Brian G. Lefebvre
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Abstract
Though chlorine dioxide is generally used to control bacterial contamination, a method was developed which allows the use of stabilized chlorine dioxide (SCD) for controlling contamination during fermentation that uses the bacteria Zymomonas as the biocatalyst, even though Zymomonas is sensitive to chlorine dioxide. Parameters were identified for inoculating a composition for fermentation with Zymomonas cells after a time period has elapsed following SCD addition.
Claims26
A fermentation method for controlling bacterial contamination in a fermentation process comprising a Zymomonas biocatalyst comprising:
- a) providing a growth medium having the potential for being contaminated by a bacterial species;
- b) adding an effective amount of stabilized chlorine dioxide to the growth medium of (a) forming a stabilized chlorine dioxide mixture wherein the temperature of the stabilized chlorine dioxide mixture is greater than about 33° C.;
- c) inoculating the mixture of b) with Zymomonas cells at a temperature suitable for Zymomonas cells to produce an inoculated broth;
- and
- d) fermenting the inoculated broth under conditions suitable for growth of the Zymomonas cells;
- wherein bacterial contamination is controlled during fermentation.
A fermentation method for controlling bacterial contamination in a fermentation process comprising a Zymomonas biocatalyst comprising:
- a) providing a seed medium lacking cellulosic biomass hydrolysate selected from the group consisting of:
- i) defined medium, ii) medium containing a non-cellulosic biomaterial sugar source, and iii) clarified cellulosic biomass hydrolysate;
- b) inoculating the seed medium of a) with Zymomonas ethanologen cells to form a seed culture;
- c) growing the Zymomonas cells in the seed culture of b);
- d) Inoculating a fermentation medium with the seed culture of c) to produce an inoculated fermentation medium;
- e) providing a saccharification reaction slurry;
- f) mixing the inoculated fermentation medium with the saccharification reaction slurry to form a fermentation beer;
- and
- g) growing the Zymomonas ethanologen cells in the fermentation beer under conditions whereby ethanol is produced;
- wherein;
- anyone of the fermentation beer and the saccharification reaction slurry contains cellulosic biomass hydrolysate;
- and
- wherein:
- stabilized chlorine dioxide is added to at least one of i) the seed medium of step a);
- ii) the saccharification reaction slurry of step e) or iii) the fermentation medium of step d):
- and
- wherein:
- if the stabilized chlorine dioxide is added to the seed medium of step a) the seed medium is maintained at a temperature of at least about 33° C. for at least about 6 hours prior to inoculation with the Zymomonas ethanologen;
- and
- wherein:
- if the stabilized chlorine dioxide is added to the saccharification reaction slurry of step e) the saccharification reaction slurry is maintained at a temperature of at least about 33° C. for at least about 8 hours prior to mixing with the inoculated fermentation medium;
- and
- wherein:
- if the stabilized chlorine dioxide is added to the fermentation medium of step d) the fermentation medium is maintained at a temperature of at least about 33° C. for at least about 8 hours prior to the mixing with the saccharification reaction slurry;
- and
- wherein:
- any one of the seed culture, the inoculated inoculated fermentation medium or the fermentation beer comprising Zymomonas cells contains less than about 5 g/L of lactic acid during the period of the growth of the Zymomonas cells.
A fermentation medium composition comprising:
- a) fermentation medium comprising cellulosic biomass hydrolysate;
- and
- b) stabilized chlorine dioxide.
A saccharification reaction slurry composition comprising:
- a) cellulosic biomass;
- b) at least one cellulase enzyme;
- and
- c) stabilized chlorine dioxide.
Dependencies are inferred from the claim text.