Enzymatic bioconversions
- 1. Enzymatic Bioconversions Eg. Starch and sugar conversion processes Submitted by : S. Akshaya Gayathri Class : II MSc., Biotechnology College : Bon Secours College for Women
- 2. Carbohydrates and Fermentable Sugars Carbohydrates, or “hydrates of carbon,” are an important group of naturally occurring organic compounds. 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’’
- 3. Starch and cellulosic compounds are polymeric molecules: • Made up of basic unit called monomers • 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
- 5. Monosaccharides: Glucose and Fructose Can be fermented to ethanol by yeast, only under anaerobic Conditions. Diasaccharides: Sucrose and Maltose Sucrose is fructose and glucose molecule linked together Sucrose is obtained from sugar cane and sugar beets Commonly known as table sugar Maltose comprises of two molecules of glucose linked together Both maltose and sucrose are fermentable to ethanol by yeast
- 6. Oligosaccharides Are saccharides with more than three but less than eight units. Oligosaccharides can not be fermented by yeast to produce ethanol. Polysaccharides Polymeric carbohydrates of many thousand of monomeric sugar units linked together through glycosidic linkages. Starch, glycogen or cellulose. Neither starch or cellulose can be directly fermented by yeast to produce ethanol. Must be hydrolyzed to fermentable sugars.
- 8. Enzymes that convert starch to sugar • Starch conversion enzymes convert the starch in grist to flavor components and fermentable sugars. Starch is glucose molecules linked together in a linear polymer (amylose) or a branched polymer (amylopectin). Several key enzyme groups, primarily amylases, take part in the conversion of grain starches. • Alpha- amylases: they rapidly but randomly break starch molecules starch molecules to produce water-soluble fragments of starch called dextrins – unfermentable carbohydrates that contribute to beer flavor, body, and mouthfeel • Beta- amylases: these act only at the ends of starch molecules and fragments to produce maltose. • Glucoamylases: break off single molecules of glucose from starch molecules, dextrins and maltose. • The bonds that form branches in amylopectin polymer starch are resistant to the action of amylase enzymes. • Pullulanase: it is a starch-debranching enzyme, can break these bonds and give amylase enzymes faster access to starch molecules • Cellulase and Lipase: break down cell walls and lipid inclusion complexes to release starch for conversion.
- 10. 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.
- 11. GELATINIZATION • Starch gelatinization is a process of breaking down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen sites (the hydroxyl hydrogen and oxygen) to engage more water. • This irreversibly dissolves the starch granule in water.
- 12. Blue Iodine Colour: When Iodine complexes with starch, it forms a color complex which is different for amylose and amylopectin The goal of the system and enzyme are to solubilize and lower all the starch in the grain—indicated by an amber to yellow iodine test color.
- 13. SOLUBLIZATION OF STARCH Even at 95°C not all of the starch gets solubilized (pasted or gelatinized). Needs to be cooked for 5 minutes at 110°C to completely solubilize starch. Pasting or gelatinization temperature starts at 60°C, but is not complete until > 105°C.
- 14. Iodine Color – Facts: • Different chain lengths = different colors • All color changes occur between Dp12 & Dp45 • Six glucose units are required per iodine • Retrogradation occurs with Dp150 - Dp200 oligosaccharides.