The combined liquefaction stream and yeast propagation tank
were consistently contaminated and are likely sources of persistent
contamination in this biofuel facility. The most abundant contaminants
identified were Lactobacillus sp., particularly L. plantarum,
L. casei, L. mucosae, and L. fermentum. Biofilm-forming strains were
present throughout the survey and may be involved in the persistence
of contamination. However, there was no apparent correlation
between the ability of isolates to form biofilms and the
capacity to inhibit ethanol production. Ethanol inhibition appeared
to be related to acetic acid production, particularly by obligately
heterofermentative species such as L. fermentum and L. mucosae