Method of fermentation

Abstract

The invention provides a process for the production of biomass by culturing a microorganism in an aqueous liquid culture medium circulating in a loop reactor having an effluent gas removal zone where from carbon dioxide-containing effluent gas is removed from the reactor and upstream thereof a degassing zone in which a driving gas is introduced to drive carbon dioxide in the liquid phase into a separable effluent gas phase and having upstream of said degassing zone a nutrient gas introduction zone in which oxygen is introduced into the reactor and mixed with the liquid culture medium therein, characterized in that oxygen introduction in said nutrient gas introduction zone is effected at a plurality of locations along the flow path through said loop reactor at a rate such that the average dissolved oxygen content of said liquid culture medium measured using a polarographic oxygen electrode does not exceed 25 ppm.

1 . A process for generating biomass comprising:
 culturing a microorganism in a liquid reaction medium which circulates in a loop reactor, wherein said reactor has an effluent gas removal zone, and, upstream of said effluent gas removal zone, an effluent gas-liquid reaction medium separating zone, and wherein oxygen and/or methane is fed into the liquid reaction medium in said effluent gas-liquid reaction medium separating zone; and
 harvesting biomass from said reactor. 
   
   
   
       2 . The process as claimed in  claim 1  wherein said liquid reaction medium contains a methanotrophic bacterium and wherein oxygen and methane are introduced into said reactor and are mixed with said liquid reaction medium. 
   
   
       3 . The process as claimed in  claim 1  further comprising separating biomass from a liquid. 
   
   
       4 . A process for the production of a chemical compound comprising:
 culturing a microorganism in a liquid reaction medium which circulates in a loop reactor, wherein said reactor has an effluent gas removal zone, and, upstream of said effluent gas removal zone, further has an effluent gas-liquid reaction medium separating zone, and wherein oxygen and/or methane is fed into the liquid reaction medium in said separating zone;
 harvesting biomass from said reactor; and 
   separating therefrom a chemical compound produced by said microorganism.   
   
   
       5 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate at a plurality of locations along a loop-reactor flow path through said loop reactor so as to achieve an average dissolved oxygen content of said liquid reaction medium measured using a polarographic oxygen electrode of not greater than 25 parts per million (ppm) by weight. 
   
   
       6 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate at a plurality of locations along a loop-reactor flow path through said loop reactor so as to achieve an average dissolved oxygen content of said liquid reaction medium measured using a polarographic oxygen electrode of not greater than 15 parts per million (ppm) by weight. 
   
   
       7 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate at a plurality of locations along a loop-reactor flow path through said loop reactor so as to achieve a dissolved oxygen content of said liquid reaction medium at each said location of at least 0.5 parts per million (ppm) by weight. 
   
   
       8 . The process as claimed in  claim 1  wherein a driving gas is introduced at a driving gas inlet and wherein oxygen is introduced at a controlled rate so as to achieve a dissolved oxygen content of the liquid reaction medium over at least 30% of the path length of the loop reactor of at least 10 parts per million (ppm) by weight, a dissolved oxygen content of the liquid reaction medium immediately prior to the driving gas inlet of at least  3  parts per million (ppm) by weight, and an oxygen content of said effluent gas of at least 1 mole %. 
   
   
       9 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate into said liquid reaction medium in a nutrient gas introduction zone so as to achieve between the nutrient gas introduction zone and the effluent gas-liquid reaction medium separating zone a dissolved oxygen content of the liquid reaction medium of not less than 3 parts per million (ppm) by weight. 
   
   
       10 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate into said liquid reaction medium so as to achieve a dissolved oxygen content of said liquid reaction medium of not less than 3 parts per million (ppm) by weight over a path length of the loop reactor corresponding to more than 30 seconds. 
   
   
       11 . The process as claimed in  claim 1  wherein said fluid culture medium is circulated through said loop reactor under the action of a propeller having overlapping or multiple, radially curved blades. 
   
   
       12 . The process as claimed in  claim 1  wherein nutrient gas and liquid reaction medium are mixed in said loop reactor by passage through a static mixer comprising a stack of parallel corrugated flexible plates arranged with the stacking direction perpendicular to the direction of flow of said fluid medium and with the corrugation ridges thereof angled to said direction of flow and with their angle to the direction of flow being substantially equal and opposite for adjacent plates. 
   
   
       13 . The process as claimed in  claim 1  wherein oxygen is introduced at a controlled rate into said liquid reaction medium in a nutrient gas introduction zone so as to achieve between said nutrient gas introduction zone and the effluent gas-liquid reaction medium separating zone a dissolved oxygen content of the liquid culture medium of not less than X parts per million (ppm) by weight, where X is defined by
     X= 1.35 Y·B      
     where B is the biomass content of the culture medium in g/L and Y is from 0.75 to 1.25, and B is from 5 to 30. 
   
   
       14 . The process as claimed in  claim 1  wherein said loop reactor has a flow path of at least 40 m. 
   
   
       15 . A fermentation reactor comprising an effluent gas-liquid reaction medium separating zone upstream of an effluent gas removal zone, wherein said separating zone comprises an inlet for feeding oxygen and/or methane into liquid reaction medium contained in said effluent gas-liquid reaction medium separating zone. 
   
   
       16 . A fermentor apparatus comprising a loop reactor comprising an effluent gas-liquid reaction medium separating zone upstream of an effluent gas removal zone, wherein said separating zone has an inlet for feeding oxygen and/or methane into liquid reaction medium therein.