- 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 preventcontamination 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.
- In this study, we will accomplish two steps toward this goal. First, we will demonstrate that a Cld-expressing bacterium is protected from phage-mediated lysis by the addition of chlorite. Second, 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 will pave the way for the development of a widely applicable technique to address fermentation hygiene concerns in a variety of industrial fermentations.
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