Process Biochemistry 36 (2000) 255 – 261 Hydrolytic enzyme production in solid-state fermentation by Aspergillus niger 3T5B8 Sonia Couri a, *, Selma da Costa Terzi a , Gustavo A. Saavedra Pinto a , Suely Pereira Freitas a , Antonio Carlos Augusto da Costa b a Embrapa Food Technology, A. das Ame ´ricas 29501, 23020 -470 Guaratiba Rio de Janeiro, Brazil b Uniersidade do Estado do Rio de Janeiro, Instituto de Quı ´mica, Departamento de Tecnologia de Processos Bioquı ´micos, 23020 -470 Guaratiba Rio de Janeiro, Brazil Received 21 December 1999; received in revised form 30 May 2000; accepted 17 June 2000 Abstract A mixture containing polygalacturonase, cellulase, xylanase and protease enzymes was produced using Aspergillus niger 3T5B8 on different agroindustrial residues by solid-state fermentation and tested for vegetable oil extraction. The enzymic activities were evaluated using second-order empirical models from experimental data as a function of fermentation time and cellobiose concentration in the fermentation medium. The use of wheat bran as substrate without cellobiose addition and 42 h of fermentation were the most favourable conditions for producing the mixture of hydrolytic enzymes (polygalacturonase 30.75 U/ml, xylanase 30.62 U/ml, protease 5.27 U/ml). Another favourable condition was obtained when mango peel was used as substrate in the presence of 0.2% cellobiose and 24 h of fermentation (FPCAse 3.5 U/ml, xylanase 20.33 U/ml). Enzymic formulations with suitable polygalacturonase and FPCAse activities were favourable to extract oil from the pulp of tropical fruits and oleaginous seeds. © 2000 Published by Elsevier Science Ltd. All rights reserved. Keywords: Hydrolytic enzymes; Solid-state fermentation; Cellobiose; Aspergillus niger ; Agroindustrial residues; Oil extraction www.elsevier.com/locate/procbio 1. Introduction Plant cell degrading enzymes are used industrially for enhancing the quality of products and improving the efficiency of the clarification of fruit juices and wines as well as the extraction of oils. Enzyme preparations usually contain the main hydrolytic enzymes important for these processes, such as polygalacturonase, cellulase and hemicellulase. Some ongoing research conducted at Embrapa Food Technology Center, showed that enzymes produced by the mutant fungus Aspergillus niger 3T5B8 are suitable for the extraction of oils from the pulp of oleaginous fruits [1,2]. Additional studies are being conducted with the purpose of improving the activities of these en- zymes, and, consequently, oil seed extraction. The present paper aims to study the influence of medium composition on solid-state fermentation by A. niger 3T5B8, especially the kinetics of hydrolytic en- zyme production, and to develop empirical models for quantitative interpretation of the interrelationships among the variables. In the current work being con- ducted, different agroindustrial residues were used as substrates in order to minimize problems associated with their disposal. Cellobiose, an essential product from the enzymic hydrolysis of cellulose, was added as a cellulase inducer [3]. The preparations were tested in the extraction of palm oil. 2. Materials and methods 2.1. Microorganism The microorganism used in this study was the mor- phological mutant A. niger 3T5B8 from the Embrapa * Corresponding author. E-mail address: scoury@ctaa.embrapa.br (S. Couri). 0032-9592/00/$ - see front matter © 2000 Published by Elsevier Science Ltd. All rights reserved. PII:S0032-9592(00)00209-0