Utilizing crude waste glycerol in the bio refinery: glycerol gels for in situ substrate delivery to whole cell biocatalysts.

Sol-gel methods were used to facilitate the in-situ controlled delivery of glycerol as a substrate for whole cell biocatalysis. The entrapment of the polyol within a silica gel matrix enabled the utilization of crude and moderately toxic bio-derived substrates that could not be used in fed-batch mode. Different grades of glycerol were incorporated in gels and fed to C. butyricum for 1,3-propanediol production and E.coli for recombinant protein production. Of particular note was the successful use of crude glycerol gels with E.coli. By virtue of gel immobilisation, previously toxic crude glycerol samples were rendered active; and the use of gel technologies was therefore shown to expand the range of biomass that can be utilised in whole cell biocatalytic processes. Specific matching of the acid used in the gel synthesis with the fermentation medium further supported cell growth.