Cellulases, Hemicellulases, and Pectinases: Applications in the Food and Beverage Industry

Pectin is structurally and functionally the most complex polysaccharide in plant cell walls. Pectin has functions in plant growth, morphology, development, and plant defense and also serves as a gelling and stabilizing polymer in diverse food and specialty products and has positive effects on human health and multiple biomedical uses. Pectin is a family of galacturonic acid-rich polysaccharides including homogalacturonan, rhamnogalacturonan I, and the substituted galacturonans rhamnogalacturonan II (RG-II) and xylogalacturonan (XGA). Pectin biosynthesis is estimated to require at least 67 transferases including glycosyl-, methyl-, and acetyltransferases. New developments in understanding pectin structure, function, and biosynthesis indicate that these polysaccharides have roles in both primary and secondary cell walls. Manipulation of pectin synthesis is expected to impact diverse plant agronomical properties including plant biomass characteristics important for biofuel production.

Hemicelluloses currently represent the largest polysaccharide fraction wasted in most cellulosic ethanol pilot and demonstration plants around the world. The reasons are based on the hemicelluloses heterogeneous polymeric nature and their low fermentability by the most common industrial microbial strains. This paper will review, in a "from field to fuel" approach the various hemicelluloses structures present in lignocellulose, the range of pre-treatment and hydrolysis options including the enzymatic ones, and the role of different microbial strains on process integration aiming to reach a meaningful consolidated bioprocessing. The recent trends, technical barriers and perspectives of future development are highlighted. Copyright 2010 Elsevier Ltd. All rights reserved.