Contaminant occurrence, identification and control in a pilot-scale corn fiber to ethanol conversion process

Area of Science:

• Biotechnology
• Industrial Microbiology
• Bioenergy

Background:

• Increasing interest in bioethanol production from lignocellulosic feedstocks.
• Limited pilot-plant data and operating experience available for this emerging industry.

Purpose of the Study:

• To evaluate pilot-plant scale fermentation of corn fiber-derived sugars to ethanol.
• To identify and address challenges encountered during fermentation, particularly microbial contamination.

Main Methods:

• Conducted batch and continuous fermentation runs up to six weeks in a pilot-plant.
• Utilized glucose-fermenting and recombinant glucose/xylose-fermenting yeasts.
• Investigated contamination by Lactobacillus bacteria and their metabolic byproducts.

Main Results:

• Lactobacillus contamination was common, consuming arabinose and producing detrimental acids.
• Acetic and lactic acid production by contaminants significantly impaired fermentation performance.
• Virginiamycin effectively controlled infections, but is cost-prohibitive for routine use.

Conclusions:

• Contamination issues in lignocellulosic bioethanol production are significant, likely exacerbated by feedstock purity.
• Future facilities will likely adopt strategies from the corn-based ethanol industry for infection control.
• Employing fermentative microorganisms capable of consuming all biomass-derived sugars presents a promising avenue for effective contamination management.