EBI Personnel Directory Ryan, Kathleen

Biofuels Production

Kathleen Ryan

krr@berkeley.edu

 

 

Project(s)

Controlling Fermentation Hygiene via Chlorate Addition and Expression of Chlorate Dismutase in Process Organisms

Our objective is to demonstrate proof-of-concept for a novel bioprocess hygiene strategy. Industrial fermentation facilities are vulnerable to contamination with unwanted eukaryotes, bacteria, and bacteriophage. Growth of contaminating organisms can reduce product yields or lead to bioreactor collapse, entailing financial losses. In Saccharomyces cerevisiae-based fuel ethanol fermentations, lactic acid bacteria and wild yeasts are common contaminants (5, 41). Some facilities use antibiotics to treat or prevent bacterial infections in fuel bioreactors, but antibiotics are not universally effective against bacteria, and they do not prevent contamination by wild yeasts. In the case of bacterial fermentations, antibiotics could be used to selectively inhibit or spare certain species, but they do not protect process organisms from bacteriophage infection. We propose a strategy in which process organisms are engineered to produce the enzyme chlorite dismutase (Cld), which detoxifies the disinfectant compound chlorite by converting it to chloride and molecular oxygen (43). Chlorite added to the fermentation system would then selectively damage non-Cld-expressing contaminants, including eukaryotes, bacteria, and bacteriophage. We will demonstrate that Cld expressed in S. cerevisiae will protect this organism from concentrations of chlorite that kill or inhibit the growth of known contaminants of fuel ethanol fermentations. These studies pave the way for the development of a widely applicable technique to address fermentation hygiene concerns in a variety of industrial fermentations.