Immobilization of Clostridium acetobutylicum DSM 792 as macroporous aggregates through cryogelation for butanol production

• New method for microbial cell immobilization.
• Highly macroporous structure consisting of crosslinked aggregated bacterial cells.
• High production of butanol in batch using immobilized Clostridium acetobutylicum.

In this study, a new cell immobilization technique is presented. Cells of Clostridium acetobutylicum DSM 792 form a macroporous aggregate through cryogelation with concomitant crosslinking together with activated polyethyleneimine (PEI) and poly(vinyl alcohol) (PVA). The cell based cryogel presents a highly porous, elastic structure with walls consisting of densely packed crosslinked cells. The immobilization process maintained the viability of cells as new bacterial cells were observed when gel-plugs were incubated in liquid medium, glucose was consumed and solvent production was observed. Solvent production was improved 2.7-fold in immobilized cells in comparison to free cells. It was possible to reuse the gel-plugs 3–5 times in partial or completely fresh medium, reaching a maximum butanol concentration in the broth of 18.2 g/l and yield of 0.41 (g/g) in one of the cycles. The use of cells based cryogels can be a good alternative for improvement of acetone-butanol-ethanol (ABE) process as cells are immobilized in a macroporous structure with low limitations for mass transfer with potential for high yield production.