© by PSP Volume 31 – No 3. 2009 Advances in Food Sciences 158 SCREENING STUDIES ON THE FORMATION OF ß- GLUCOSIDASE FROM SOME FILAMENTOUS FUNGI Ali Mohamed Elshafei 1* , Mohamed Mohamed Hassan 1 , Nagwa Mohamed Moursi 2 and Dina Helmy Elghonemy 1 1 Department of Microbial Chemistry, National Research Centre, Dokki, Cairo, Egypt. 2 Department of Botany, Faculty of Science, Cairo University, Giza , Egypt ABSTRACT Twenty-five strains of different filamentous fungi were screened for their abilities to produce intracellular β-gluco- sidase using modified D-cellobiose Czapek Doxś liquid medium. The results revealed that nearly all fungi under study (23 out of 25) produced β-glucosidase in different proportions. Aspergillus terreus NRRL 265, A. phoenicis NRRL 365, Penicillium martensii NRC 345, P. purpures- cens NRC 846 and P. cyclopium NRC 881, producing con- siderable amounts of enzyme as compared to the other cul- tures, were selected for β-glucosidase quantitative assay. Among them, Aspergillus terreus NRRL 265 was found to produce high levels of an intracellular β-glucosidase be- sides the other two components of cellulase system, namely exo-(1,4)-β-D-glucanase ( FPase, EC 3.2.1.91 ) and endo- (1,4)-β-D-glucanase (carboxymethyl cellulase (CMCase), EC 3.2.1.4). KEYWORDS: β-glucosidase; screening; filamentous fungi; As- pergillus terreus. INTRODUCTION Filamentous fungi have been widely exploited for ho- mologous and heterologous protein production, because of the high capacity of their protein secretion machinery [1, 2]. In filamentous fungi, a wide variety of enzymatic activities is found, either intracellular or extracellular. An increasing number of these activities, produced by some strains of the genera Aspergillus and Trichoderma, are com- mercially exploited after partial or complete purification of the desired activity from the fermentation medium, or by using the entire organism as a biocatalyst for the indus- trial production of traditional foods, such as miso and cheese, or beverages, such as shochu and sake, [2-4]. Fungi have the property to degrade naturally occurring polymers as lignocellulosic materials to low molecular weight sub- stances, which could be then transferred to the cell through the cell membrane and used as nutrient [5-7]. In general, fungal enzymes have attractive properties, such as low optimum pH, broad optimum temperature and high prote- ase resistance. The filamentous fungi are unique in the di- versity of their metabolic activities and many of these ac- tivities are of direct biotechnological interest. The annual world market for fungal enzymes used in food and bever- age industries including β-glucosidase is considered to be more than a billion American dollars. Cellulase produced by fungi usually contains three components: (i) endo-1,4- beta-glucanase (EC 3.2.1.4), (ii) exo-cellobiohydrolase or exo-1,4-beta-glucanase (EC 3.2.1.91) and (iii) β-D- gluco- sidases (β-D-glucoside glucohydrolase, EC 3.2.1.21) [8]. The hydrolysis of natural cellulose to glucose depends on the synergism of these three enzymes [9]. Until recently, two types of synergism were observed, that among endo- glucanase and exo-cellobiohydrolase upon cellulose to pro- duce cellobiose and synergism upon the addition of cello- biase which cleaved cellobiose to glucose. Both endoglu- canase and cellobiohydrolase activities are often inhibited by cellobiose [8, 10]. In some filamentous fungi (e.g. Trichoderma reesei), the produced cellulase is poor in cellobiase, thus restrict- ing the conversion of cellobiose to glucose. The accumu- lation of cellobiose will cause feedback inhibition to the cellulase degradation reaction. Therefore, improving the activity of cellobiase in cellulase system is the key to raise the saccharification [11]. Thus, cellobiase is generally re- sponsible for the regulation of the whole cellulolytic proc- ess, and cellobiase activity is a rate-limiting factor during enzymatic hydrolysis of cellulose [12]. The objective of the present study is to search for a new producer of β-D-glucosidase that recently gained sig- nificant economic values in many fields. MATERIALS AND METHODS Microorganisms Twenty-five fungal strains obtained from different sources were screened for their abilities to produce intracel- lular β-glucosidase. The sources of cultures were as follows: DSM: Deutsche Sammlung von Mikroorganismen. Göt- tingen, Federal Republic of Germany.