(70b) Developing Bacterial Pelletized Culture to Enhance Yield and Simplify Harvest for Lignin Bioconversion

Pelletized culture has been long sought after for filamentous fungi fermentation due to its several advantages such as easier separation, decreased viscosity. However, pelletized culture was achieved little in bacteria, which prevents the further increase of bioproduct yield and the utilization of lower cost filtration harvest. We have developed a novel pelletized culture system for Gram positive bacteria Rhodococcus opacus PD630 and applied the new system to lignin bioconversion. Moreover, we have identified several factors impacting the pelletization performance and thus optimized the system to increase lignin to lipid conversion. We found that inoculum size, centrifugation speed, soluble solid content (SSC), glucose content, and nitrogen content each had an impact on the pellet formation. The results showed that pellet percentage increased with the increase of SSC to 41.91%, when 50g/L SSC was added into medium. And the pellet percentage varied from 29.31% to 50.63%, when glucose was added with a concentration increase from 0g/L to 8g/L. The highest percentage of pelletization was achieved at 2g/L glucose. Further analysis indicated that the lipid content within pellets remains stable even SSC increased up to 50g/L, whereas the lipid content of the cells in solution phase varies depending on the SSC. Overall, this is the first report of bacterial pelletized culture without addition of flocculant. When further optimized, the innovative platform provides a new solution for improving bioproduct yield and reducing harvest cost in bacterial cultures. In addition, as applied to lignin bioconversion, the technology has potential to transform bioproduction from lignin by simplifying harvest and increasing yield.