Chestnut shell and barley bran as potential substrates for laccase production by Coriolopsis rigida under solid-state conditions Jose ´ Go ´ mez, Marta Pazos, Susana Rodrı ´guez Couto, M a A ´ ngeles Sanroma ´n * Department of Chemical Engineering, University of Vigo, Lagoas Marcosende, 36200 Vigo, Spain Received 4 April 2004; accepted 12 June 2004 Abstract The potential of two lignocellulosic wastes chestnut shell and barley bran for laccase production by the white-rot fungus Corio- lopsis rigida under solid-state conditions was assessed. These materials were selected due to their availability and low cost, since they are by-products of the food processing industries abundant in most countries. Barley bran gave the highest laccase activities, show- ing a maximum value of 3 Æ 10 5 nkat/L, which was around 25-fold higher than the value attained in the chestnut shell cultures. In addition, the ability to degrade three structurally different dyes (Indigo Carmine, Methyl Orange and Methyl Green) by the extra- cellular liquid from the barley bran copper-supplemented cultures (1 mM) was analysed. Nearly complete decolourization was obtained for the dyes Indigo Carmine and Methyl Green, whereas Methyl Orange showed more resistance to decolourization. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Barley bran; Chestnut shell; Coriolopsis rigida; Food processing industry; Laccase; Solid-state fermentation 1. Introduction The main limitation for the extensive industrial appli- cation of microbial enzymes is their high cost. There- fore, a good strategy to increase the productivity of the fermentation processes would be the optimisation of the culture conditions. Since the nutritive substances employed in the culture medium suppose a high percent- age of the total production costs, the reduction in the substrate expenses would increase the productivity of the process. Solid state cultivation is generally defined as the growth of microorganisms on solid materials in the ab- sence or near absence of free water (Pandey, 1992). Comparative studies between submerged and solid state cultures claim higher yields, simpler techniques, reduced energy requirements, low wastewater output and im- proved product recovery (Moo-Young, Moreira, & Tengerdy, 1983; Pandey, Selvakumar, Soccol, & Nigam, 1999). However, there are several major problems in the development of SSF on an industrial scale, including the mass- and heat-transfer limitations and difficult solids handling inherent in the process as run in existing reac- tors and the lack of kinetic and design data on various fermentation processes (Lonsane, Ghildyal, Budiatman, & Ramakrishna, 1985). On the other hand, solid state cultivation offers the possibility of using by-products and wastes from food and agricultural industries. The food processing industry generates a great amount of wastes annually worldwide, which causes a serious disposal problem. The composi- tion of such wastes is usually rich in sugars, which due to their organic nature are easily assimilated for microor- ganisms. This makes them very suitable as raw materials for the production of secondary metabolites of industrial significance by microorganisms. Various agricultural 0260-8774/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2004.06.005 * Corresponding author. Fax: +34 986 812382. E-mail address: sanroman@uvigo.es (M a .A ´ ngeles Sanroma ´n). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 68 (2005) 315–319