ISOLATION AND CHARACTERIZATION OF CELLULOSE-DEGRADING BACTERIA FROM THE SPENT MUSHROOM COMPOST

Abstract

The edible and medicinal mushroom industry in Vietnam is undergoing significant development. Mushrooms are not only a source of clean food but also contain pharmaceutical substances for disease prevention and treatment. Statistics have revealed that the production of 1 kg of mushrooms generates 5 - 6 kg of post-harvest substrates. These substrates contain various polysaccharides, including hemicellulose, cellulose, and residual mycelia. If left untreated, they could contribute to environmental pollution. However, with appropriate treatment, these post-harvest substrates can be transformed into bioproducts, enhancing soil quality and providing nutrients for crops. This study aims to isolate and characterize bacterial strains capable of synthesizing cellulase, an enzyme that breaks down cellulose, from post-harvest substrate compost. The mushroom samples were collected from the mushroom farms in Ha Noi city and Thai Binh province and a total of 44 bacteria strains were isolated. By the agar well diffusion method, 27 strains of bacteria exhibiting cellulase activity were obtained. Notably, the strains FG16 and FG18 had the highest cellulase activity (0.253 U/ml and 1.137 U/ml), respectively. Therefore, these two strains were selected for further experiments. The optimal conditions for cellulase synthesis by strains FG16 and FG18 were found to be as follows: 1.0% and 0.5% CMC added to the culture medium, pH: 5.0 and 7.0, temperatures: 40°C and 45°C, with the raw enzyme collected after 24 hours. Both strains FG16 and FG18 are bacilli, gram positive, positive for MR (Methyl Red), VP (Voges Proskauer) reactions and capable of biosynthesizing some extracellular enzymes such as amylase, chitinase and protease. Based on compairing nucleotide 16S rRNA, strain FG18 closed to strain Bacillus subtilis NR112629.1, thus it was called Bacillus subtilis FG18.