Ethanol production

RAW MATERIALS, PRODUCTION AND APPLICATIONS OF ETHANOL

1. Ethanol Production M.AMRUTHTHA ASSISTANT PROFESSOR IN BIOCHEMISTRY SACWC, CUMBUM

2. INTRODUCTION Ethanol is a clear, colourless liquid with a characteristic, agreeable odour. Ethanol has been made since ancient times by the fermentation of sugars. Internationally, sugarcane, sweet sorghum and sugar beet are used for the production of ethanol as sugar containing feedstock. Maize, wheat and other cereals contain starch that can relatively easily be converted to sugar. In India, ethanol is primarily produced using sugarcane molasses. B iofuels that uses biomass containing large amounts of sugar or materials that can be converted to sugar such as starch, for the generation of ethanol. Enzyme from yeast, changes the simple sugars into ethanol and carbon dioxide. Starches from potatoes, corn, wheat, and other plants can also be used in the production of ethanol by fermentation. 

3. Chemical structure Ethanol is a 2-carbon alcohol. Its  molecular formula  is CH 3 CH 2 OH. An alternative notation is CH 3 −CH 2 −OH, which indicates that the carbon of a  methyl group (CH 3 −) is attached to the carbon of a  methylene group (−CH 2 –), which is attached to the oxygen of a  hydroxyl group (−OH). It is a constitutional  isomer of  dimethyl ether. Ethanol is sometimes abbreviated as  EtOH , using the common organic chemistry notation of representing the ethyl group (C 2 H 5 −) with Et.

4. Raw materials Sugarcane molasses Cane juice Sugar beets Cassava Yams Grains Hemp Potato Corn

5. Microorganism used in ethanol production Clostridium thermocellum Clostridium thermohydosulphuricum Clostridium thermosaccharolyticum Klebsiella pneumoniae Candida brassica Zymomonas mobilis Thermoanaerobacter ethanolicus Mongolia Fusarium

6. Physical requirements The ideal pH is around 4.0-4.5. The initial temperature is kept between 21-26 ºC. Ethanol gets evaporated at 27 ºC. Aeration is initially required for the growth of microbes. Later, anaerobic condition are created by withdrawing oxygen coupled with the production of carbon dioxide.

7. Chemical requirements Nitrogen source: Urea is the most suitable source. Gaseous ammonium increases the pH of the medium. Ammonium sulfate can lead to incrustation. Phosphorus source: Diammonium phosphate used as a source. Hydrolytic enzymes: They can also be added to convert biopolymers and non-fermentable substances in the molasses to monosaccharides or amino acids.

8. Ethanol fermentation by yeast Alcoholic fermentation is carried out mainly by Saccharomyces cerevisiae yeast, which is the common yeast in bread or beer, which converts 90% of the sugar into equimolar amounts of alcohol and CO2. Raw materials are Sucroid substances such as cane sugar, beets, and fruit juices. The main raw material is molasses. The glycolysis pathway is also known as the EMP ( Embden -Meyerhof Parnas ) pathway. It degrades into a three-carbon compound through a series of steps. An anaerobic glycolysis carried out by organisms to produce ethanol and carbon dioxide from sugar or polysaccharides.

9. Ethanol fermentation by Bacteria Zymomonas mobilis  is a  Gram negative, facultative anerobic   , non- sporulating , polarly -flagellated, rod-shaped bacterium. It is the only species found in the genus  Zymomonas Zymomonas mobilis  degrades sugars to pyruvate   using the Enter- Doudoroff pathway. The pyruvate is then  fermented  to produce  ethanol  and  carbondioxide  as the only products (analogous to yeast). The advantages of  Z. mobilis  over  S. cerevisiae  with respect to producing  bioethanol higher sugar uptake and ethanol yield up to 2.5 times higher and lower biomass production H igher Ethanol tolerance up to 16% (v/v ) Does not require controlled addition of oxygen during the fermentation

10. However, in spite of these attractive advantages, several factors prevent the commercial usage of  Z. mobilis   in cellulosic ethanol   production. The foremost hurdle is that its substrate range is limited to  glucose, fructose and sucrose. Wild-type  Z. mobilis  cannot ferment C5 sugars like xylose and arabinose which are important components of lignocellulosic hydrolysates . Unlike  E. coli  and yeast,  Z. mobilis  cannot tolerate toxic inhibitors present in lignocellulosic hydrolysates such as acetic acid and various phenolic compounds.  Concentration of acetic acid in lignocellulosic hydrolysates can be as high as 1.5% (w/v), which is well above the tolerance threshold of  Z. mobilis .

11. pathway

12. Pretreatment Dilution: Molasses must be diluted to below to 25 ° Bx (Brix) as yeast start to ferment quickly at this concentration. Sedimentation: To prevent any incrustation in the pipelines or distillation towers due to ash content in molasses greater than 10%. The special chelating agent can also be used to remove the incrustation. Addition of org & inorganic compounds: Done to offset the negative effect of salt which in turn increases the osmotic pressure. Yeast strains resistant to salts are also developed. Microfiltration: To remove the impurities that stick to the surface of the biocatalyst when immobilize cells are used.

13. Steps involved in Industrial production of ethanol DESIGN OF FERMENTOR CULTURE OF MICROBES FORMULATION OF MEDIUM RECOVERY OF ETHANOL

14. Formulation of medium The most commonly used raw materials are molasses, whey , grains,potatoes and wood wastes The sugar concentration of the cane molasses favours the growth of the microorganisms The pH of the medium is adjusted to 4-5 by adding sulfuric acid or lactic acid The starchy media like corn ,rye and barley are hydrolysed with dilute acids before they are pumped into the fermentor The hydrolysis of starch yields simple sugars which are directly converted into ethanol Amylase converts starch into 80% maltose and 20% dextrin that can be easily converted into glucose

15. Designing of fermentation system Molasses tank is loaded with a large volume of molasses It is named as storage tank The stored molasses enter another tank where the molasses diluted properly with water Then it enters into sterilisation tank for sterilisation This sterilised medium is used for fermentation Microbes are cultured in the seed tanks to carry out fermentation

16. Designing of fermentation system

17. A fermentor is a large vessel to carry our ethanol production It has three inlets at its top to receive sterilised medium for the sterilisation tank Inoculum from the seed tank and chemicals It has an outlet at the base to harvest the broth The fermentor is cooled by a water jacket It is connected with wash chamber by a pipeline Harvested broth is transferred to the wash chamber for distillation

18. Culture of microbes The microbial inoculum is pumped into the fermentor to carry out ethanol fermentation Temperature inside the fermentor is regulated by circulating cold water through the water jacket 330 k is suitable for fermentation Fermentation is complete in about 3 days The enzyme invertase of Z ymomonas converts sucrose in the molasses into glucose Zymase converts glucose into ethanol

19. RECOVERY of ethanol The fermented broth in the fermentor is called wash The distillation set up consists of two tall fractionating columns provided with perforated plates One column is called analyser The other is called rectifier Steam is passed through the base of the analyser to carry the alcohol vapour to the base of the rectifier The spent liquor is collected from the outlet of the analyser Alcohol vapour in the rectifier is collected through a pipe jacketed with cool water to get 95% ethanol

20. Production of ethanol from sugarcane

21. Production of ethanol from corn

22. Applications of ethanol Used in manufacture of synthetic rubber Acetaldehyde Perfumed Synthetic fibres like rayon, polyester

23. Act as an active solvent of dyes, lubricants, adhesives pesticides paints , explosives and resins Used in extraction of certain pharmaceutical products Useful as an organic solvent for the extraction of some organic compounds

24. Used as a transport fuel to replace gasoline Used as a fuel for fuel cells by thermo chemical reactions Used as a fuel for fuel for power generation by thermal combustion Used as fuel in cogeneration systems