Microbial contamination of commercial corn-based fuel ethanol fermentations

Authors: Rich, Joseph; Anderson, Amber; LEATHERS, TIMOTHY - Former ARS Employee; BISCHOFF, KENNETH - Former ARS Employee; Liu, Siqing; Skory, Christopher - Chris

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2020
Publication Date: 4/18/2020
Citation: Rich, J.O., Anderson, A.M., Leathers, T.D, Bischoff, K.M., Liu, S., and Skory, C.D. 2020. Microbial contamination of commercial corn-based fuel ethanol fermentations. Bioresource Technology. 11:100433. https://doi.org/10.1016/j.biteb.2020.100433.
DOI: https://doi.org/10.1016/j.biteb.2020.100433

Interpretive Summary: Microbial contamination in commercial corn-based fuel ethanol facilities reduces efficiency and profitability, so understanding what organisms are present throughout the production plants is important for preventing future contamination. Most studies to date have relied on isolating microbial contaminants at these facilities, but this does not always give an accurate portrayal of all the strains that are present. In this research, we utilized culture-independent DNA sequencing methods to identify different types of microbial isolates found at likely points of contamination at numerous ethanol facilities. Several common areas in these facilities were determined to be potential sources of contamination. These results will be important to researchers developing improved methods to control microbial contamination in fuel ethanol production.

Technical Abstract: Microbial contamination in commercial corn-based fuel ethanol facilities reduces efficiency and profitability. In this study, bacterial and fungal contamination in five wet mill and five dry grind plants was quantitated using culture-independent DNA sequencing methods. Fermentors primarily showed contamination by Lactobacillus with little contamination by fungi. In wet mill facilities, Lactobacillus predominated in steep water and was widespread at many process points, offering multiple opportunities for persistence and reinfection. In dry grind facilities, yeast propagation tanks, backset water, and combine liquefaction streams were likely sources of contamination. Time-course studies were performed at two dry grind facilities immediately before and after shutdowns for cleaning. The relative abundance on contaminants changed during the fermentations, and cleaning seemed to have little effect on the reoccurrence of contaminants. One dry grind facility was intermittently sampled over a 67-month period. Major contaminants showed persistence and stability, but gradually changed in relative abundance over time.