| Sugarcane bagasse is one of the most abundant byproducts of agroindustry insouth China as well as the world. Bagasse as a kind of biomass resources, is mainly composed of lignocellulosic material, including cellulose, hemicellulose, and lignin. It is attracting more and more attentions that a way for the effective utilization of the biomass. Deep sea microorganism is abundant and distinctive in heredity, physiology and ecological functions. Utilization of marine bacteria to degrade bagasse will be a new way for the efficient use of bagasse.Bagasse-degrading bacteria in the sea water of the deep sea and offshore environments were enriched in situ, and their diversities were then studied by construction and sequencing of 16 S r RNA gene clone library and sequencing. The bacterial groups and their abundance were different between these two samples. Most species in the enriched samples from the deep sea belonged to γ-Proteobacteria, while most of the species in the enriched samples from offshore environment belonged to Bacteroidetes, Proteobacteria, Chlorobi and Fibrobacteres. Bagasse-degrading bacteria species were isolated from those two samples by conventional culture methods. There were a total of 29 bagasse-degrading bacteria species isolated from the two samples. These bagasse-degrading bacteria belonged to Proteobacteria and Firmicutes.Bacillus aryabhattai GZ03 and Bacillus amyloliquefaciens GZ04 were isolated from deep sea water of the South China Sea, which can produce glucose and fructose by degrading bagasse at 28℃. The enzymolysis conditions of Bacillus aryabhattai GZ03 degrading bagasse were established. Firstly, the enzymolysis time, enzymolysis temperature, agitation speed, concentration of bagasse, particle size of bagasse, nutrient source, salts concentrations were evaluated in the single-factor test. The results showed that the optimum single-factor conditions for the highest oligosaccharide yield were as followed: enzymolysis time 60 h, enzymolysis temperature 35℃, inoculum 4%, concentration of bagasse in the medium 5%, the particle size of bagasse was 60 mesh, and Na Cl 3%. In order to investigate the biomass degradation capability of B. amyloliquefaciens GZ04, we monitored the degradation rates of the relevant components during the bio-pretreatment and saccharification process of bagasse. It was found that, the hemicellulose degradation percentage was 20% in 5 days at 28℃.A levansucrase gene(GH5) from B. aryabhattai GZ03 was isolated from a genomic library and the nucleotide sequence of the GH5 structural gene was analyzed. GH5 is of 1455 bp length and encodes 484 amino acid residues with a calculated molecular mass of 53.7 k Da. In this study, we cloned, expressed the recombinant GH5 protein in E. Coli BL21, and characterized the enzymatic properties of purified recombinant GH5 protein. Optimum p H for D-glucose production and levan formation was determined to be 6.0 and 7.8, respectively. Besides, optimum temperature and optimum sucrose concentration were 30℃ and 400 m M, respectively. At the end of fermentation, the levan was biosynthesized under the optimum conditions. It was found that the levan appeared to be synthesized at a faster rate after 36 h. It was found that B. amyloliquefaciens GZ04 could produce xylanase. The xylanase was most active at 40 and p H ℃5.0, and exhibited good thermostability at 40 ℃and stability over a broad range of p H values(between 4.0 and 10.0).This study presents an efficient way for the direct degradation of bagasse, which does not required any nutrient source and thus simplify the technological process. Most importantly, the resulting glucose and fructose from bagasse degradation had a good application prospect. In conclusion, this study may provide a solid foundation for scientific research and industrial application of bagasses degradation in the future. |
PDF Full Text Request