Oxygen-assisted fermentation process

Abstract

A fermentation process uses substantially pure oxygen. The oxygen is the only reactive gas which is injected into a fermentation vessel. The oxygen is moved through the vessel solely by its own pressure. The process can be used with both mechanically-agitated and air-lifted fermenters. The mechanically-agitated fermenter includes an analyzer for measuring oxygen concentration in the exhaust line, and adjusting the flow of fresh oxygen into the vessel accordingly. In the air-lifted fermenter, an analyzer measures the oxygen concentration in the head space of the vessel, and operates valves which either recycle the gas from the head space, or vent that gas to the outside, according to the measured concentration. A stream of nitrogen is periodically injected into the vessel to drive out carbon dioxide and other gases, to control the pH of the fermentation medium. The present invention substantially improves the efficiency of a commercial fermentation process.

1 . In a fermentation process, the process including the steps of placing a fermentation medium in a vessel, maintaining the fermentation medium in the vessel for a sufficient time to enable a fermentation process to occur in the vessel, and withdrawing a product from the vessel,
 the improvement wherein a stream of substantially pure oxygen is injected into the vessel while the fermentation process is occurring, and wherein the stream of substantially pure oxygen comprises the sole reactive gas, from any source external to the vessel, that is injected into the vessel.   
     
     
         2 . The improvement of  claim 1 , wherein the stream of substantially pure oxygen is moved through the vessel solely due to pressure in an oxygen supply. 
     
     
         3 . The improvement of  claim 1 , wherein the process further comprises mechanically agitating the fermentation medium, measuring a concentration of oxygen in an exhaust line extending from the vessel, and adjusting a flow of oxygen into the vessel in response to a measured concentration of oxygen. 
     
     
         4 . The improvement of  claim 3 , wherein the measuring and adjusting steps are performed substantially continuously. 
     
     
         5 . A fermentation process comprising directing substantially pure oxygen into a vessel containing a fermentation medium, so as to promote fermentation in said medium, wherein said substantially pure oxygen is the only reactive gas, external to the vessel, that is injected into the vessel. 
     
     
         6 . The process of  claim 5 , wherein oxygen is moved through the vessel solely due to pressure of oxygen. 
     
     
         7 . The process of  claim 5 , wherein the process further comprises mechanically agitating the fermentation medium, measuring a concentration of oxygen in an exhaust line extending from the vessel, and adjusting a flow of oxygen into the vessel in response to a measured concentration of oxygen. 
     
     
         8 . The improvement of  claim 7 , wherein the measuring and adjusting steps are performed substantially continuously.