Indirect Methods for Monitoring Cell Concentration
These methods use parameters that are indirectly related to cell concentration and measure concentration of viable cells. The parameters Include rates of oxygen uptake, carbon-dioxide evolution and ATP production. Oxygen uptake rate (OUR) and ATP production rate (APR) if known can give cell concentration, each using a constant specific oxygen uptake rate (SOUR) or specific ATP production rate (SAPR) respectively, which are experimentally determined, but fluctuate with physiological state of the cells.

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