EtAc: Process development for the production of ethyl acetate from whey by microbial ester-synthesis and innovative process-integrated product-removal

During the production of milk products in Germany 12,7 mio. tons (2012) of whey remain and an increase of the residues is foretold to be 1 - 2 % annually.

Further contents, like proteins or lactose can be extracted from whey, leaving over a mother liquor that is hard to treat due to its salinity.

Nevertheless, this mother liquor is an interesting raw material for biotechnological processes and is the main topic of this research. The production of ethanol and β-galactosidase is on an industrial scale possible, although the ethanol-process has disadvantages: (a) high number of process-steps; (b) long process-time due to inhibitory effects; (c) biomass activity under anaerobic conditions; and (d) high energy expenditure for the product recovery.

Alternatively, the mother liquor’s lactose can be converted aerobically into ethyl acetate by yeast. Ethyl acetate is an organic solvent that is used in i.e. chemical reactions or as extraction agent. Around 1.7 mio. tons of ethyl acetate were produced exclusively from natural gas or petroleum by petrochemical processes in the year 2013.

The chair for bioprocess technology examined in detail the microbial synthesis of ethyl acetate by yeast in the last years. Especially studied was the yeast Kluyveromyces marxianus that is one of the fastest-growing eukaryotes and is known to synthesize huge amounts of ethyl acetate. Compared to ethanol, ethyl acetate is highly volatile and thus removed from the aerates system which offers the chance for a process-integrated product recovery.

A process for production and recovery of ethyl acetate in a laboratory scale is to be developed in cooperation with the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS). The chair for bioprocess technology shall design the production process and optimise it, while the IKTS develops ceramic membranes that are to detach specifically ethyl acetate out of the process air.