CONCLUSION
Based on CFD technology, a model was established to evaluate two
important parameters, oxygen supply level and mixing efficiency of
microtiter plates. The reliability of the model was verified by
comparing it with the experimental literature data. In order to achieve
high-throughput culturing and screening of DHA producing strains, the
existing microplates were evaluated and modified. The superiority of
microplates with hexagonal cross sections was determined. In the
follow-up research, a high-precision RSM model based on the numerical
calculation results of CFD was established. Baffles were introduced and
reaction parameters (liquid filling volume and rotation speed) were
optimized to improve oxygen transport and mixing efficiency in the new
bioreactor. Finally, a hexagonal bioreactor with 6 baffles was
developed. It has a liquid filling capacity of 15% and a rotation speed
of 800 rpm. A KLa of 0.61 s-1 can be
achieved, which is sufficient to meet the oxygen supply requirements of
DHA producing strains, and provides the perfect mixing effect. This
result was also verified in subsequent experiments and the liquid
splashing problem was solved. The robustness of the strains was better
than that under ordinary culture conditions. Furthermore, using the new
microplate, a high-quality DHA producing strain was screened and the
culture conditions were optimized. The new microtiter plate model
designed in this paper provides not only a good model for the culture
screening of DHA-producing strains but also a good new idea for the
high-throughput culture screening of many high oxygen-consuming
microorganisms in the future.