Challenges faced by Fermentation Industry in Ethanol production due to Bacterial contamination – The Catalysts Group

Challenges faced by Fermentation Industry in Ethanol production due to Bacterial contamination

Ethanol production holds a potential global market in Fermentation Industry. Due to its scale and unit processes, several enzymes have been used for the hydrolysis of starch substrates to maintain the fermentation process under aseptic conditions. Sterilization of this treated starch substrate is not feasible at the large-scale production. Most of the ethanol production are carried out in the presence of measurable amount of bacterial contamination. This leads to the reduction in the production of ethanol yield and generally inhibit yeast growth and its activity. Several studies reported that the presence of 106-107 bacterial count leads to the loss of 1-3% of ethanol production while 107-108 bacterial count can lead to the loss of 3-5%. Other study reported the loss of 17% in ethanol yield in presence of 4.5 X 108 bacterial contaminants per ml in the batch fermentation for 30 hrs.

This problem can be reduced by using continuous processes instead of batch process to increase the productivity but still the bacterial contamination is becoming serious issue day by day. Since ancient times, bacterial contamination is one of the major drawbacks possess by the ethanol fermentation industry in terms of reduction in the ethanol yield and the annual output. Incapability to tackle and control the bacterial contamination, several fermentation plants went under complete closure overseas.

Due to the recently developed microbial and molecular techniques, this has become possible to isolate, biochemically characterize and identify these bacterial microorganisms in the lab scale. Molecular identification provides a high throughput pipeline to identify and characterize the bacterial contamination with complete bacterial gene sequence. With this information, we can develop and suggest specific

products to address microbial challenges with precise dosages required to run the fermentation. This workflow will be helpful in maintaining the best possible high yield of commercial ethanol.



Sr. No.


Biochemical Characterization



L.fermentum L.casei B. subtilis P. aeruginosa E. coli C. perfringens
1. Esculin Hydrolysis Negative Positive Positive variable variable variable
2. H2S Production Negative Negative Negative Negative Negative Positive
3. Indole production Negative Negative Negative Negative Positive Negative
4. Nitrate Reduction Positive Negative Positive Positive Positive variable
5. Glucose Negative Negative Positive Positive Positive Positive
7. Starch Hydrolysis Negative Negative Positive Positive Negative Variable
8. Gram staining Positive Positive Positive Negative Negative Positive







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