Studies On Cellulase-producing Actinomycete And Its Enzyme Properties And Microbial Communities In Freshwater Lakes

1. Studies on cellulase-producing actinomycete and its enzyme properties In order to study cellulase-producing actinomycete and its enzyme properties, five strains of actinomyces which can degrade cellulose were isolated from compost, and one strain of them, named NO5, which grew better on Congo Red agar medium, was selected for further research. Morphological, physiological and biochemical characters of NO5 were studied. It is a gram positive aerobic actinomycete. The substrate mycelium is composed of extensively branched nonfragmenting hyphae, and the aerial mucelium is straight, not too long. Motile spores are oval and their surface is smooth. According to BLAST results in GenBank, molecular phylogenetic tree (Paup 4.0), and the morphological, physiological and biochemical characters, the strain was preliminarily identified as a Streptomyces. sp. and it was close to S. thermodiastaticus in relationship. The conditions for production of carboxymethyl cellulose (CMCase) and β-glucosidase (EG) were examined. The optimal incubating time for both CMCase and EG is 120 hours and the optimal temperature and pH are 50℃and 8.5-9.5, repectively. The optimal carbon source of Solid State Culture for enzyme production is alkali-pretreated Whatman cellulose and alkali-pretreated corn cobs, respectively for CMCase and EG. Thermostability study showed that 60% enzyme activity of CMCase remained after 2h incubating at 60℃, while 30% remained at 70℃for the same incubating period. 2. Microbial communities in freshwater lakes In order to investigate the role of microbial community of lake sediment in aquatic ecology and nutrient transformation in the development of eutrophication in large shallow freshwater lakes along Yangtze River, the microbial community in the depth-related sediment in Lake Chaohu and Lake Longganhu was compared. Lake Chaohu is one of the three most polluted lakes in China. However, the neighboring Lake Longganhu is relatively pristine. The total phosphorous (TP) and total nitrogen (TN) concentration in water were detected as 0.193 mg/l and 3.035 mg/l for Lake Chaohu,...