Food Sci. Biotechnol. 22(6): 1683-1690 (2013) DOI 10.1007/s10068-013-0267-6 Pomelo Citrus grandis (L.) Osbeck Peel as an Economical Alternative Substrate for Fungal Pectinase Production I. Darah, M. M. J. Taufiq, and S. H. Lim Received: 16 January 2013 / Revised: 16 April 2013 / Accepted: 21 April 2013 / Published Online: 31 December 2013 © KoSFoST and Springer 2013 Abstract Polygalacturonase production by Aspergillus niger LFP-1 was studied in solid state fermentation (SSF) using pomelo (Citrus grandis) peel as a substrate. This local agricultural waste product is rich in lignocellulolytic material, including pectin, which can act as an inducer of pectinase production. Using the parameters of 5 g of 0.75 mm (particle size) pomelo peel as a substrate, moisture content ratio of 1:1 (w/v), inoculum size of 1×10 7 spores/ mL, cultivation temperature of 30ºC, and no mixing, static fermentation conditions with addition of 1.2% ammonium nitrate produced the highest polygalacturonase production rate of 8.90 U/g of substrate and a fungal growth rate of 2.07 mg of glucosamine/g of substrate on day 5 of cultivation. A large increase (1,434.5%) in enzyme production occurred after improvement of the growth parameters. Under optimum bioprocess conditions, pomelo peel can be used as solid substrate for production of pectinase. Keywords: pomelo peel, pectinase, solid state fermentation, optimization, Aspergillus niger Introduction Pectinases, also known as pectinolytic enzymes, are a group that catalyzes degradation of pectic substances into polygalacturonic acids and, finally, into galacturonic acid (1) Pectinases can be divided into pectin lyase (EC 4.2.2.10), pectin esterase (EC 3.1.1.11), pectate lyase (EC 4.2.2.2), and polygalacturonase (EC 3.2.1.15) based on the mode of action of hydrolyzing glycosidic linkages in the pectic polymer (2). However, polygalacturonase is the most studied and widely used pectinase. It exists in the two forms of endo-polygalacturonase and exo-polygalacturonase, both of which act only on pectin with a degree of esterification of less than 50-60%. Endo-polygalacturonase acts randomly at the 1, 4-polygalacturonase acid backbone and results in a pronounced decrease in viscosity. Exo- polygalaturonase acts at the non-reducing ends of the chain releasing small fragments from the chain and does not significantly reduce the viscosity (3). Pectinases have extensive applications in the fruit juice industry for improvement of fruit juice yield and clarity (4). The use of liquefying enzymes for mash treatment results in improvement of juice flow, leading to a shorter press time without the necessity for pressing aids. At the same time, pectin is broken down to such an extent that the viscosity of the mash is reduced (5). Other areas of application include the pulp and paper industry (6), retting flax and other vegetable fibers (7,8), haze removal from wines (9), coffee and tea fermentation (10), bioscouring of cotton fibers (11), degumming of plant bast fibers (12-14) and waste management (1). Solid-state fermentation (SSF) is generally defined as cultivation of microorganisms on solid materials in the absence or near-absence of free water (15) and, thus, approximates the natural environment to which microorganisms are adapted. Synthesis of pectinase is induced or stimulated by the presence of pectin, and for economic reasons this is normally supplied by adding lignocellulosic materials that are rich in cellulose and hemicelluloses that can, in addition, be used as carbon and energy sources. Several agro-industrial wastes, such as orange bagasse (16,17), soy bran (18), lemon peel (19), sunflower head (19), sugarcane bagasse (20), wheat bran (21), and cashew apple pomace (22) have been found to be effective substrates for pectinase production using SSF.In Malaysia, pomelo peel is abundant and is usually dumped I. Darah , M. M. J. Taufiq, S. H. Lim () Industrial Biotechnology Research Laboratory (IBRL), School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia Tel: +6012-4629487; Fax: +604-6565125 Email: limshehhong77@gmail.com RESEARCH ARTICLE