Studies On The Application And Development Of Biomass Monitor In Bioprocess Optimization

The amount of viable biomass is an important physiological parameter, which is correlated with the cell growth, metabolism and productivity. Conventional off-line biomass mesurements, such as dry cell weight, optical density and packed mycelial volume, commonly have some disadvantages containing complex operation, long lag time and the result is the sum of live cells and dead cells. In recent years, many measurements have been developed for the direct on-line determination of cell concentration based on a couple of principles: in-situ near-infrared measurements, impedance spectroscopy measurements and capacitance measurements. Biomass Monitor is becoming an established tool for monitoring the capacitance to evaluate viable biomass in the cell suspension. In this paper, Biomass Monitor was employed to study and direct the application in fermentation processes of bacteria, actinomycetes, yeast, mold, animal cells and plant cells.The results showed that Biomass Monitor was able to detect the on-line viable cell concentration by selecting the appropriate detection modes. The capacitance measurement had good linear relationships with the conventional off-line indicators of biomass concentration and physiological parameters, like OUR, CER, specific growth rate, consumption rate of sugar, viscosity and product. Conductivity had a good linear relationship with the main nutrient concentration.It could be found that, the process conditions, like temperature, agitation, aeration, and the change of the culture medium would affect the capacitance and conductivity measurements. They could be corrected using equations to avoid a wrong understanding and judgment.During the polyhydroxyalkanoates (PHAs) fermentation with Ralstonia eutropha, the capacitance values measured at680kHz could reflect variations of microbial morphology and viability. Furthermore, oxygen uptake rate, specific oxygen uptake rate and specific growth rate were measured in real-time and compared with the capacitance value. In addition, a fed-batch control strategy based on the on-line capacitance measurement was proposed to improve the PHAs production by22%.In the fermentation process of rifamycin SV, Biomass Monitor was able to obtain the real-time viable biomass concentration excluding the interference of solid materials. The capacitance values were correlated well with OUR and CER. At the same time, there was a close connection between the capacitance measurement and mycelial morphology. Furthermore, using defatted soybean meal to replace the original expensive peptone in the culture medium, the lag phase caused by nitrogen source conversion was eliminated, which could ensure the high specific growth rate.The domestic biomass sensor was designed with Zhejiang Puchuang instrument co., LTD. It was found that the offline and online tests had excellent performance which were nearly equal to Biomass Monitor (Aber). The electrode could sterilize in situ and was hardly affected by particle or scaling. This technology meets Process Analytical Technology (PAT) requirements, and it is certified to be a useful tool for the development, optimization, monitoring and control in cell culture processes.