A Novel Cell Factory for Efficient Production of Ethanol from Dairy Waste

Microbial production of fuels has gained a lot of attention lately. Various industries, especially the food sector, often have waste streams rich in carbohydrates which could serve as alternative feedstock for such bioprocesses. The dairy industry is a good example, where large amounts of cheese whey or various processed forms thereof, are generated.

Jianming Liu of the Technical University of Denmark generated a Lactococcus lactis strain which produces ethanol as its sole product from the lactose contained in residual whey permeate (RWP), by introducing lactose catabolism into a L. lactis strain CS4435, where the carbon flow has been directed towards ethanol instead of lactate.

To achieve growth and ethanol production on RWP, the team added corn steep liquor hydrolysate (CSLH) as the nitrogen source. The outcome was an efficient ethanol production. The combination of a low-cost medium from industrial waste streams and an efficient cell factory, would make the developed process industrially interesting.

The results demonstrate that it is possible to achieve sustainable bioconversion of waste products from the dairy industry (RWP) and corn milling industry (CSLH) to ethanol. The process shows great potential for commercial use.