Microbial polymer synthesis in simulated microgravity: An investigation of the diffusion of nutrients in a modified bioreactor

As shown previously, microgravity has an enhancing effect on bacterial growth with respect to experiments performed conventionally under the influence of gravity. The focus of this research project was to investigate the nutrient concentration within the cell clusters as well as outside these clusters in an effort to contribute to the understanding of bacterial growth in simulated microgravity using a modified bioreactor. Azotobacter vinelandii UWD and Alacaligenus latus were used in this study. A commercial NASA bioreactor, HARV vessel, was redesigned and modified to facilitate samples withdrawal from clusters for analysis to investigate nutrients diffusion gradients within the reactor. The nutrient assay results supported quantitatively the effects observed in fermentation experiments and showed that the bioreactor does minimize convection while creating diffusional limitations that further support simulated microgravity. The glucose concentration differences between the culture and surrounding liquid observed, suggests that the modified bioreactor suppresses the growth phase convection as well as establishing a diffusion field.