The present invention relates to the use of online biomass capacitance monitoring in cultures as a way to control the growth of cells through the use of a temperature control loop. In certain embodiments, a biomass capacitance probe is used to measure the cell density, and a predetermined growth curve is used to adjust the temperature in the culture.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62/650,430, filed Mar. 30, 2018, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Understanding cell growth is critical for developing efficient and robust bioreactor processes. Due to exponential growth characteristics, small perturbations in process conditions such as inoculation density, media composition, and pH can have large impacts on cell density and process performance. In addition standard offline measurement techniques fail to capture important data such as the exact cell peak time and density. This can make cell density based process decisions such as temperature shifting difficult to time.

[0003] There is a need in the art for mechanisms to dynamically adjust cell growth to precisely control the timing of cell growth from inoculation to peak.

SUMMARY OF THE INVENTION

[0004] In some embodiments, the invention is directed to a method of controlling the growth of cells in a bioreactor comprising: a) measuring the viable cell density of the cells growing in culture using a biomass capacitance probe; and b) utilizing a temperature control loop to adjust the growth rate of the cells.

[0005] In certain embodiments, the invention is directed to a method of modulating reactor temperature to control the growth of cells in a bioreactor comprising: a) measuring the viable cell density of the cells growing in culture using a biomass capacitance probe; and b) utilizing a temperature control loop to modulate the reactor temperature and adjust the growth rate of the cells.

[0006] In embodiments, the invention is directed to a method of minimizing the growth fluctuation of cells in a bioreactor comprising: a) measuring the viable cell density of cells growing in culture using a biomass capacitance probe; and b) utilizing a temperature control loop to adjust the growth rate of the cells.

[0007] In some embodiments, a pre-determined growth curve is utilized to adjust the temperature in the culture.

[0008] In embodiments, a bolus feed is added to the bioreactor daily. In certain embodiments, the daily bolus feed is begun starting on about day 1, about day 1.5, about day 2, about day 2.5, about day 3, about day 3.5, about day 4, about day 5, about day 6, about day 7, about day 8, about day 9 or about day 10 after the culture is inoculated. In particular embodiments, the daily bolus feed volume is about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 15% or more of the initial working volume. In some embodiments, the daily bolus feed volume is about 3%, about 3.1%, about 3.2%, about 3.3%, about 3.4%, about 3.5%, about 3.6%, about 3.7%, about 3.8, about 3.9% or about 4% of the initial working volume. In one embodiment, the daily bolus feed volume is about 3.6% of the initial working volume.

[0009] In embodiments, a bolus feed is added to the bioreactor hourly. In certain embodiments, the hourly bolus feed is begun starting on about day 1, about day 1.5, about day 2, about day 2.5, about day 3, about day 3.5, about day 4, about day 5, about day 6, about day 7, about day 8, about day 9 or about day 10 after the culture is inoculated. In an embodiment, the hourly bolus feed is about 1/24 of the calculated volume for a daily bolus feed. In one embodiment, the hourly bolus feed is about 0.1%, about 0.11%, about 0.12%, about 0.13%, about 0.14%, about 0.15%, about 0.16%, about 0.17%, about 0.18%, about 0.19%, about 0.2%, about 0.25%, about 0.3%, about 0.4% or about 0.5% of the initial working volume. In particular embodiments, the hourly bolus feed volume is about 0.15% of the initial working volume.

[0010] In some embodiments, the viable cell density is plotted to a temperature range of about 30-40° C. In certain embodiments, the viable cell density is plotted to a temperature range of about 31-37° C. In embodiments, daily temperature oscillations in the reactor have a peak to peak amplitude of about 10° C., about 9° C., about 8° C., about 7° C., about 6° C., about 5° C., about 4° C., about 3° C., about 2° C., about 1° C. or less.

[0011] In embodiments, the cells produce a polypeptide of interest. In certain embodiments, the polypeptide of interest is an antibody. In some embodiments, the cells are mammalian cells. In particular embodiments, the cells are CHO cells.

[0012] In embodiments, the biomass capacitance probe is an INCYTE probe.

[0013] In some embodiments, the pH of the culture is about 6.5 to about 8.0, about 7.0 to about 8.0, or about 7.0 to about 7.5. In particular embodiments, the pH of the culture is about 7.1 to about 7.4.

[0014] In embodiments, the culture is inoculated with cells at a density of about 1×10.sup.5, about 2×10.sup.5, about 3×10.sup.5, about 4×10.sup.5, about 5×10.sup.5, about 6×10.sup.5, about 7×10.sup.5, about 8×10.sup.5, about 9×10.sup.5, or about 10×10.sup.5 cells/ml. In particular embodiments, the culture is inoculated with cells at a density of about 6×10.sup.5 cells/ml.