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Homo- and heterofermentative lactobacilli differently affect sugarcane-based fuel ethanol fermentation
Thiago Olitta Basso1, Fernanda Sgarbosa Gomes, Mario Lucio Lopes
1Novozymes Latin America Ltda., Rua Professor Francisco Ribeiro 683, Araucária, 83707-660, Brazil, to.basso@gmail.com.
Antonie Van Leeuwenhoek
|November 8, 2013
Summary
Bacterial contamination impacts fuel ethanol production. Heterofermentative bacteria are more detrimental than homofermentative types under industrial conditions, reducing ethanol yield and yeast viability.
Area of Science:
- Industrial microbiology
- Biotechnology
- Biochemical engineering
Background:
- Bacterial contamination poses significant economic challenges in industrial yeast fermentation for fuel ethanol.
- Lactic acid bacteria (LAB), both homo- and heterofermentative, are common contaminants affecting yeast performance and ethanol yield.
- Understanding the differential impact of LAB strains is crucial for optimizing fuel ethanol production processes.
Purpose of the Study:
- To investigate the distinct effects of homofermentative and heterofermentative lactic acid bacteria on yeast fermentative performance in sugarcane-based fuel ethanol production.
- To compare the detrimental impacts of Lactobacillus plantarum (homofermentative) and Lactobacillus fermentum (heterofermentative) on Saccharomyces cerevisiae CAT-1.
- To elucidate the influence of bacterial contamination under varying inoculation conditions mimicking industrial settings.
Main Methods:
- Comparative analysis of yeast fermentation performance when co-inoculated with homofermentative (Lactobacillus plantarum) and heterofermentative (Lactobacillus fermentum) bacteria.
- Evaluation of yeast viability, ethanol formation, and glycerol production under different bacterial contamination scenarios.
- Simulation of industrial fuel ethanol production conditions, including high yeast cell densities and short fermentation times, with specific attention to cell recycle.
Main Results:
- Homofermentative Lactobacillus plantarum reduced yeast viability and ethanol formation more significantly than heterofermentative Lactobacillus fermentum at equal cell numbers, likely due to higher lactic acid production.
- Under simulated industrial conditions (high yeast density, short fermentation, cell recycle), the heterofermentative strain proved more deleterious, lowering ethanol yield and outcompeting yeast.
- Yeast overproduction of glycerol was observed exclusively in the presence of the heterofermentative bacterium.
Conclusions:
- Heterofermentative lactic acid bacteria present a greater threat to industrial fuel ethanol fermentation than homofermentative strains under typical Brazilian conditions.
- The findings highlight the need for strain-specific antimicrobial strategies to combat bacterial contamination effectively.
- Further research into targeted antimicrobial agents could significantly improve the efficiency and economics of fuel ethanol production.
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