Understanding Carbohydrates: From Starch to Sugars in Biofuels, Study notes of Engineering

Download Understanding Carbohydrates: From Starch to Sugars in Biofuels and more Study notes Engineering in PDF only on Docsity! Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Conversion of Starch into Sugars Vijay Singh Associate Professor Department of Agricultural & Biological Engineering University of Illinois at Urbana-Champaign, Urbana, IL 1st Brazil-U.S. Biofuels Short Course São Paulo, Brazil July 27 - August 7, 2009 • Carbohydrates, or “hydrates of carbon,” are an important group of naturally occurring organic compounds. Carbohydrates and Fermentable Sugars • Commonly these are formed by green plants through photosynthesis • Carbohydrates are any of the various compounds comprised of carbon, hydrogen and oxygen, general formula Cx(H20)y • Carbohydrates are used to store energy until required by the organism – Sugars, starches, cellulose, glycogen and related substances • Saccharides, the simplest form of carbohydrates, consist of single sugar units with five or six carbon atoms in ring form – They are commonly called “sugars” or “sweeteners” Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign • Starch and cellulosic compounds are polymeric molecules – Made up of basic unit called monomers Carbohydrates and Fermentable Sugars – These monomers are joined together by a chemical bond called a glycosidic link • Carbohydrates can be divided into four basic classes – Monosaccharides – Diasaccharides – Oligosaccharides – Polysaccharides • Each of these comprises of successively more of the same basic unit or units • Monosaccharides – Glucose and Fructose Carbohydrates and Fermentable Sugars • Can be fermented to ethanol by yeast, only under anaerobic conditions Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Starch Structure • Crystallinity – Packing of amylose and amylopectin within starch granule is not random but is very organized – Prevents enzymes to breakdown starch granule – Can be disrupted by gelatinization of starch H H H H H Hydrogen Bonding Gelatinization of Starch 67°C 75°C 85°C Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Solubilization of Starch Granules • Even at 95°C not all of the starch gets solublized (pasted or gelatinized) N d b k d f 5 i• ee s to e coo e or m nutes at 110°C to completely solubilize starch • Pasting or gelatinization temperature starts at 60°C, but is not complete until > 105°C Uncooked 75°C 85°C 90°C 95°C Dextrose Equivalent • Glucose is a reducing sugar – Free aldehyde group on carbon-1 Reducing End Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign • In starch molecule Dextrose Equivalent Reducing End OH Non Reducing End • With each hydrolytic cleavage of an alpha 1,4 or alpha 1,6 bonds, one reducing group on a glucose molecule is freed Dextrose Equivalent • Dextrose equivalent is measure of the percentages of glucosidic bonds that are hydrolyzed • DE is determined by measuring the amount of reducing sugars in a sample relative to the amount of dextrose • As starch is hydrolyzed, more and more dextrose is d d d th t f d i d DE ipro uce , an e amoun o re uc ng sugars an ncrease Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Enzymes • Comparison of enzymatic and nonenzymatic reaction kinetics Liquefaction • Liquefaction is the process of turning starches, into smaller molecules called dextrins – Alpha amylase (AA) enzyme is need for Liquefaction – Granular structure of starch needs to be broken before AA can bring about hydrolysis of starch to dextrins – AA breaks randomly breaks alpha 1,4 glucosidic linkages but not alpha 1,6 linkages Swollen Starch Molecule Dextrins Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Typical Alpha Amylase D.E. Development in Liquefaction D.E. Rate in Secondary Liquefaction 4 6 8 10 12 D.E. • The rate of D.E. is dependent on conditions mentioned above • By increasing the dose 50%, the rate increases by 50% • Mash iodine color should be purple to amber to be “starch negative—blue color means raw starch is still present. 0 2 30 60 90 120 minutes Saccharification • New dry grind ethanol plants do Simultaneous Saccharification and Fermentation (SSF) • Some plants still have separate saccharification process Singh – Starch into SugarsIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil University of Illinois at Urbana-Champaign Saccharification versus SSF alpha-amylaseGlucoamylase Different Enzyme Actions pullulanase Reducing End fungal amylase or beta-amylase