Improving Fermentation process in Ethanol Production

Deriving ethanol (Alcohol) from fermenting sugars is an age-old technique known to human beings. In historical times, the alcohol thus produced was used primarily for human consumption and medical use. During the last century, another important use for ethanol was discovered. This was to blend ethanol with gasoline to use as biofuel.

This changed the dynamics of ethanol production worldwide as the volumes required for blending with gasoline were much larger than previously required. This became the importance for lot of scientific research to produce ethanol from various feedstock and in a very efficient manner.

Author - Pradeep Dhotey, VP – Praj Bioproducts Division Author has over 30 years’ experience in Ethanol & Sugar Industry.

In earlier times, fermentation process was considered to be an art with emphasis on taste and organoleptic characteristics of the alcohol produced. Presently, many countries such as USA, Brazil, Thailand and India have adopted a systematic approach to production of biofuels. In Thailand the daily production of ethanol is to the tune of 2.5 – 3 Million liters. This makes is very important to analyse the efficiencies involved in production of ethanol as they will directly affect the profitability of the ethanol production.

One of the most important factor which contributes to convert the sugars into ethanol is a tiny microorganism i.e. ‘Yeast’. As the research progressed the primary focus was on the following factors of yeast performance;

• Selection of best suitable yeast strain
• How much maximum Alcohol concentration it can tolerate
• Factor affecting Yeast growth kinetics

As all the above are important for yeast to perform, it was necessary to understand them and develop a yeast strain which could give best results in fermentation while converting simple sugars like glucose & fructose into ethanol. Though there are many yeast strains developed, Saccharomyces Cerevisiae is a proven to be best suitable for sugary feedstock.

Another important factor is the characteristics/quality of feedstock such as molasses / sugarcane juice, Cassava, Corn, Rice etc. which are used for production of ethanol. For the sake of this study, let’s consider sugar-based feedstock which are the most widely used in South East Asia.

Sugarcane molasses based alcohol fermentation process faces following typical challenges:

• Molasses is generally pre loaded with organic acids ie Volatile acids comprising mainly lactic bacteria and Mesophilic bacteria, which not only complete with Yeast but also inhibit yeast performance.
• Color of molasses is called Caramel. If this is higher than 0.35 O.D. Yeast Productivity decreases sharply.
• Some of the molasses comes with very less nutrients’, so those needs to be supplemented asper requirement of the healthy yeast growth.
• Sludge in molasses like calcium, silica, other solids causes problems like scaling.
• Other than fermentable sugar, molasses lso contains non-fermentable sugars , other solids and organic matters like proteins, lipids, carbohydrates, gums, waxes, inorganic minerals etc.

Yeast Cells Photo

Thus, to have an efficient fermentation process, it is necessary to have in-depth knowledge and analysis of the feedstock and then apply this knowledge to development of most suitable yeast strain to convert the sugars into ethanol by fermentation. However, only sugar is not sufficient for yeast to convert the sugar efficiently to ethanol,

• There is requirement of micronutrients and macronutrients for better performance of yeast metabolism.
• High Volatile acids or higher Osmotic pressure will inhibit the Yeast metabolism and thus affects the Fermentation process resulting in low yield.
• Hygienic environment, suitable temperature and pH play a critical role during the process.
• Contaminants or Bacteria in the feedstock also plays the major role in fermentation as Bacteria significantly consumes sugars along with Yeast. So there is loss of fermentable sugars which is supposed to be converted to ethanol by yeast.

To overcome these limitations for healthy fermentation, there should be systematic approach. Thus, in order to have an efficient fermentation operation, following key factors should be considered;

• Advanced fermentation operation philosophy with correct material of construction and hygienic piping. This should have adequate provisions for cleaning during operations
• Feedstock mapping with its seasonal variations of feedstock in terms of quality change
• Deploying correct type of yeast for the process
• Correct application of additives in form of performance enhancers to reduce contamination

Praj Industries is a 35-year-old world leading technology company and has built more than 750 projects in 75 countries around the world. In South East Asia, Praj has executed more than 50 projects and more than 3 million liters of ethanol is produced everyday from Praj Plants in South East Asia.

Praj has a dedicated Research and Development centre i.e. ‘Praj Matrix’ which continuously carrying out various studies for improvement of processes and has developed its own yeast strain suitable for all types of feedstocks. These are given as part of Praj’s technology license to its customers and the yeast culture is free for the life of the plant. Thus, there is no additional expense on account of yeast for ethanol production.
PRAJ’s Bioproducts Division, due to its extensive analysis data base of feed stock characterization and in plant experience, has developed the series of products for Enhancing the performance of Fermentation as well as for Sugar factory operations.

Product series named Effytone is especially the Performance Enhancer’s (PE’s) for the fermentation process to maintain the efficiencies and yield. These products are customized based on the feedstock whether it is Cane/Beet Molasses, Cane/Beet Juice or Syrup, Cassava tuber or Cassava dried chips, grains like maize, rice, wheat and starch powder fermentation. Each product is specific for every feedstock considering their fermentation process parameters.

These Performance Enhancers supports yeast growth under harsh conditions of fermentation like high solids, high alcohol concentration, and competition by contaminants. It not only increases alcohol yield but also arrests the production of volatile acids and contamination during fermentation.

Praj’s Additives is a specific tool for the distilleries to achieve high performance at plant level. Following are the key advantages;

• When dosed during fermentation, it arrests growth of bacteria and generation of additional volatile acidity during Fermentation. For Ex.: It can reduce levels of acetic acid propionic acid.
• It controls infection developed by Lactic acid and butyric acid bacteria, clostridia & spore formers in fermentation processes.
• Polymer Degrading Enzymes present in PE’s helps Conversion of unfermentable polymers of glucose and sucrose into fermentable sugars.
• FAN liberating Enzymes present in PE’s helps in conversion of proteins into assimilable form of nitrogen.
• Provides vital trace of nutrition to yeast during fermentation.

In conclusion, we can safely say that even though Fermentation is a complex process, it can be efficiently controlled and made highly efficient by adopting best practices of operations. Performance enhancers and in plant support by Praj team can help ethanol producers to increase productivity and profitability of their plants. We can undertake plant level process analysis and recommend right course of performance improvement to all the industry as required.

Sugar Process Enhancers for Sugar Mills:

Praj, after successfully establishing the PE’s for the distillery plants globally has successfully introduced its unique range of sugar process enhancers to overcome the Sugar Process Challenges like;

1) Microbial Spoilage in the mill due to various Bacteria, Yeasts & Fungi pose rapid growth of microbes, mud flora contamination.

2) Non-sugar Polysaccharides also pose major hurdles in the sugar process due to presence of Dextran & Starch.

To overcome this issues Praj has developed following SUGAR PE’s.

JUICEZYME is a single product with blend of thermo stable enzymes dextranase & amylase suitable for the enzymatic degradation of Dextran & Starch in Sugar Production Streams.

Juicezyme significantly reduces viscosity of Juice, Syrup & Masscuite, & helps to Improve the clarification & Evaporation which leads improvement of filter performance, improvement in crystallization resulting in better sugar quality, improvement in sugar color & structure(ICUMSA).

JUICESAFE is a specifically developed biocide for improved Sanitation / Hygiene of Sugar Mills & Sugarcane Juice Processing dosed at fiberizing & in mixed juice.