Abstract

The aim of this study was to select the wild microorganism with the capacity to produce cellulases. Microbial sources were rotten grass, leaves and straws. Natural lignocellulose as the sole carbohydrate was used to enrich microorganisms. After isolation, the strains were inoculated into liquid media. Filter paper activity (FPA) was used as an index for selection. Sequencing of 26S rDNA D1/D2 region was used to identify the microorganism. Lactose, lactobionic acid, Tween 80 and yeast extract were added into cultivation system to improve FPA. Optimum temperature and pH of cellulase were investigated. After enrichment, isolation and selection according to FPA, one strain was selected. Trichoderma sp. A6 was named according to the sequencing results. When lactose (10 g/L) was added into the cultivation system, the FPA was improved from 0.16 to 0.56 IU. Lactose addition could improve FPA significantly. After addition, the FPA at two days amounted to the highest value. However, the addition of lactobionic acid did not increase FPA. Tween 80 addition only improved the FPA at four days to small extent. The 15 g/L yeast extract could increase the FPA at 2 days from 0.60 to 0.92 IU. The combination of Tween 80 and yeast extract did not improve the FPA compared with the treatment of Tween 80 addition. The optimum range of temperature and pH were 37-60 and 4.5-5.5°C, respectively.

Key words: Cellulase, Trichoderma, selection, cultivation condition, optimization.