Like stars falling down from the sky: resins effectively assist in and facilitate centrifugal separation and recycling of tiny microbial cells†

Microbial cell separation and recycling have become the major major high-cost procedures in commercial fermentation biotechnology, especially for the difficult-to-cultivate strains. In this regard, high-speed centrifugation is a significant industrial operation for bacterial separation but at the cost of high-end equipment and energy consumption. Therefore, the present study proposes a novel resin particle assisted method to facilitate the centrifugal separation and recycling of microbial cells from fermentation broths, which significantly reduces the centrifuge force of three representative microbial cells, yeast, Gram-positive bacteria and Gram-negative bacteria, by 26% to 36%. In particular, the resin assisted centrifugation successfully achieves an efficient separation at 563g for the small size bacteria of Gluconobacter oxydans. By comparison with glass or steel particles, the mechanism of resin-assisting cell sedimentation was analyzed from the aspects of resin granularity, porosity, charged groups and the isoelectric point of bacterial cells. The interaction model was therefore hypothesized for the resin particle with microbial cells. In addition, efficient separation was easily realized for cell reuse and resin recovery by a simple operation of fresh fermentation medium injection. The resin assisting strategy provides a simple and green technological approach for the separation and recycling of small bacterial cells in the fermentation and biotechnological industry.