Protease increases fermentation rate and ethanol yield in dry-grind ethanol production

Area of Science:

• Biotechnology
• Biochemical Engineering
• Fermentation Technology

Background:

• Yeast fermentation is crucial for ethanol production.
• Optimizing fermentation conditions, including nitrogen sources, is key to maximizing yield.
• The role of proteases in altering yeast nitrogen requirements during fermentation requires further investigation.

Purpose of the Study:

• To evaluate the impact of acid protease and urea on yeast fermentation for ethanol production.
• To determine if protease addition affects yeast nitrogen requirements.
• To assess the economic viability of using protease in industrial ethanol fermentation.

Main Methods:

• Fermentation trials were conducted with and without acid protease and varying urea concentrations.
• Ethanol production rates and final yields were measured.
• Process engineering and economic models were employed to analyze cost-effectiveness.

Main Results:

• Acid protease addition significantly enhanced both fermentation rate and ethanol yield compared to controls.
• Protease addition, with or without urea, led to higher final ethanol yields.
• Supplemental nitrogen levels exceeding 1200 ppm inhibited ethanol production.
• Protease addition reduced overall processing costs by up to $0.01/L of denatured ethanol.

Conclusions:

• Acid protease is an effective additive for improving ethanol fermentation efficiency and yield.
• Optimized urea supplementation can complement protease action, but excess nitrogen is detrimental.
• Protease addition presents a cost-effective strategy for industrial ethanol production.