Crosslinked, cryostructured Lactobacillus reuteri monoliths for production of 3-hydroxypropionaldehyde, 3-hydroxypropionic acid and 1,3-propanediol from glycerol

- Lactobacillus reuteri immobilization by crosslinking during cryostructuration.
- PEI/PVA gave stable monolith with maintained viability and biocatalytic activity.
- Determining metabolic fluxes from glycerol to 3HPA, 3HP and 1,3PDO in Pdu pathway.
- L. reuteri cryogel monolith operated in continuous and fed-batch modes of operation.
- Monolith embedded in plastic carriers showed high mechanical stability as plug flow.

Crosslinked, cryostructured monoliths prepared from Lactobacillus reuteri cells were evaluated as potential immobilized whole-cell biocatalyst for conversion of glycerol, to potentially important chemicals for the biobased industry, i.e. 3-hydroxypropionaldehyde (3HPA), 3-hydroxypropionic acid (3HP) and 1,3-propanediol (1,3PDO). Glutaraldehyde, oxidized dextran and activated polyethyleneimine/modified polyvinyl alcohol (PEI/PVA) were evaluated as crosslinkers; the latter gave highly stable preparations with maintained viability and biocatalytic activity. Scanning electron microscopy of the PEI/PVA monoliths showed high density of crosslinked cells with wide channels allowing liquid flow through. Flux analysis of the propanediol-utilization pathway, incorporating glycerol/diol dehydratase, propionaldehyde dehydrogenase, 1,3PDO oxidoreductase, phosphotransacylase, and propionate kinase, for conversion of glycerol to the three chemicals showed that the maximum specific reaction rates were −562.6, 281.4, 62.4 and 50.5 mg/gCDW h for glycerol consumption, and 3HPA (extracellular), 3HP and 1,3PDO production, respectively. Under optimal conditions using monolith operated as continuous plug flow reactor, 19.7 g/L 3HPA was produced as complex with carbohydrazide at a rate of 9.1 g/Lh and a yield of 77 mol%. Using fed-batch operation, 1,3PDO and 3HP were co-produced in equimolar amounts with a yield of 91 mol%. The monoliths embedded in plastic carriers showed high mechanical stability under different modes in a miniaturized plug flow reactor.