tailieunhanh - Handbook of plant based biofuels - Chapter 7

7 Bioethanol from Starchy Biomass Part I Production of Starch Saccharifying Enzymes Subhash U Nair, Sumitra Ramachandran, and Ashok Pandey contents Abstract 87 Introduction . 88 Enzymes Hydrolyzing α-1,4-Glucosidic Linkages. 88 Endo-amylases (EC ) 88 Exo-amylases (β-amylases EC ). 88 Enzymes Hydrolyzing α-1,6-Glucosidic Linkages. 88 Pullulanases (EC ) 90 Isoamylases (EC ) .90 . | 7 Bioethanol from Starchy Biomass Part I Production of Starch Saccharifying Enzymes Subhash U Nair Sumitra Ramachandran and Ashok Pandey CONTENTS Enzymes Hydrolyzing a-1 4-Glucosidic Endo-amylases EC .88 Exo-amylases P-amylases EC .88 Enzymes Hydrolyzing a-1 6-Glucosidic Pullulanases EC .90 Isoamylases EC .90 Transglycosylation to Form a-1 4 and or a-1 6-Glucosidic Cyclodextrin Glucotransferase EC CGTases .90 Hydrolysis of Both a-1 4- and a-1 6-Glucosidic Glucoamylases EC. .90 Sources . 91 a- and Pullulanase . 96 References. 102 ABSTRACT There has been a substantial shift in global perception of the production of ethanol from plant-based biomass. These could be of starchy or cellulosic or lignocellulosic 87 2009 by Taylor Francis Group LLC 88 Handbook of Plant-Based Biofuels nature which requires a step of hydrolysis to produce fermentable sugars which then can be fermented to ethanol. The hydrolysis of the starchy raw materials can be done by acids or enzymes but due to several advantages enzymatic hydrolysis offers it is the preferred choice for industrial applications. The enzymes involved in hydrolysis include a-amylase p-amylase glucoamylase and pullulanase. These enzymes can be obtained from plant and microbial sources but industrial demand is met through the latter. This chapter presents a brief description of the sources applications and production of these enzymes. INTRODUCTION The amylases a term that refers to a-amylase and p-amylase here can be generally defined as the enzymes that hydrolyze the ơ-glycosyl linkage of starch. a-Amylases are one of the most popular and important forms of the industrial amylases and have different reaction and product specificities which include exo-