Contamination issues in a continuous ethanol production corn wet milling facility

Area of Science:

• Biotechnology
• Industrial Microbiology
• Biofuel Production

Background:

• Low ethanol yields and poor yeast viability are critical issues in continuous corn wet milling ethanol facilities.
• These problems can significantly impact the economic viability and efficiency of biofuel production.

Purpose of the Study:

• To investigate the causes of low ethanol yields and poor yeast viability in a commercial ethanol production facility.
• To compare the fermentation performance of laboratory-prepared hydrolysates with plant-derived hydrolysates.
• To identify potential microbial contaminants affecting the ethanol fermentation process.

Main Methods:

• Laboratory-scale preparation of starch hydrolysates mimicking commercial processes.
• Comparative fermentation trials using laboratory and plant hydrolysates.
• Analysis of final ethanol concentrations and total yeast counts.
• Fermentation controls using uninoculated hydrolysates.
• Microbial analysis including cycloheximide and virginiamycin plating, DNA sequencing, and fingerprinting.

Main Results:

• Laboratory-prepared hydrolysates yielded higher ethanol concentrations (15.8% v/v) compared to plant hydrolysates (13.4% v/v).
• Uninoculated controls produced significant ethanol, indicating microbial contamination in both hydrolysate types.
• Microbial analysis confirmed the presence of a contaminant and revealed dissimilar microbial communities across different facility points.

Conclusions:

• A contaminating microorganism was identified as a primary cause of reduced ethanol yields and yeast viability.
• The contamination likely originates from various stages within the corn wet milling and ethanol production process.
• Implementing effective control strategies against microbial contamination is essential for improving ethanol production efficiency.