In most bioprocesses glucose is the carbon and energy source for the organism (or cell). Therefore glucose is a very important biochemical parameter in bioprocess monitoring and control.
Online monitoring instrumentation provides for real time control of fermentation and cell culture processes. Instantaneous glucose measurement in the process allows for optimization of the glucose feed rate, which increases production yields.
A fed-batch culture in essence is a batch culture which is supplied with either fresh nutrients (e.g. growth-limiting substrates) or additives (e.g. precursors to products).
First, a high concentration of cells is built up in the growth process of fermentation. This is followed by the formation of the desired biochemical induced by the switching of the cellÕs metabolism from the growth phase to secondary metabolism. This induction of secondary metabolism may be affected by the depletion of required nutrient for growth. If growth was merely stopped by eliminating the supply of the energy source, the cells would immediately start to die at a high rate.
The energy source of glucose and oxygen is fed at a rate sufficient to maintain the energy needs of the cells and for synthesis of the biochemical.
If too much glucose is fed, the cells will grow and this may result in the cell switching from production to growth metabolism. It would also mean that the oxygen transfer capabilities of the process would be exceeded. This would result in glucose being completely converted to carbon dioxide, resulting in the accumulation of organic acids.
A powerful control technique for a fed-batch fermentation is feedback control, which involves online monitoring of the concentration of a nutrient, such as glucose, and adjusting the feed rate to optimize the glucose concentration.
Hardware needed for a fed-batch with feedback control: bioreactor, online glucose analyzer with control output, feedpump (with variable speed and remote control input) and a controller such as BioXpert.
A truly online glucose analysis for your bioprocess is now available! Based on a patented third-generation, long-life biosensor, high stability glucose measurements are realized. The AppliSens biosensor features direct electron contact through a conduction polymer between the enzyme and the anode. Thus an amperometric measurement is possible without the formation of any peroxides that would deteriorate the biosensor. The system is fully integrated with an aseptic (0.2-µm pore size) sampling filter.
The glucose analyzer can be placed on the bench top for use with an autoclavable bioreactor or be mounted directly onto the 25-mm port of an in situ steam sterilizable bioreactor.
Sensors are available in various measuring ranges (0-1 g, 0-5 g glucose/L). The accuracy of the measurement is 2% of full scale, while detection limits as low as 0.05 mM glucose can be reached.
Measuring intervals can range from two minutes up to 24 hours.