Metabolic engineering of microbial competitive advantage for industrial fermentation processes

Xenobiotics to the rescue Contaminating microorganisms can be highly detrimental to the large-scale fermentation of complex low-cost feedstocks, such as sugarcane or dry-milled corn for biofuels or other industrial purposes. The challenge is that foreign organisms have to be inhibited without using antibiotics because of concerns about spreading antibiotic resistance. Shaw et al. engineered bacteria and yeast to use rare compounds as sources of nutrients (see the Perspective by Lennen). Engineering the common biocatalyst Escherichia coli , for example, to consume melamine as a nitrogen source allowed it to outcompete contaminating organisms. Similarly, engineering yeast to use cyanamide for nitrogen or phosphite for phosphorus also improved competitive fitness. Science , this issue p. 583 ; see also p. 542