Abstract
The composting ecosystem provides a potential resource for finding new microorganisms with the capability for cellulose degradation. In the present study, Congo red method was used for the isolating of thermostable lignocellulose-degrading bacteria from chicken manure compost. A thermophilic strain named as Geobacillus thermodenitrificans Y7 with acid-resident property was successfully isolated and employed to degrade raw switchgrass at 60°C for 5 days, which resulted in the final degradation rates of cellulose, xylan, and acid-insoluble lignin as 18.64, 12.96, and 17.21%, respectively. In addition, GC-MS analysis about aromatic degradation affirm the degradation of lignin by G. thermodenitrificans Y7. Moreover, an endocellulase gene belong to M42 family was successfully cloned from G. thermodenitrificans Y7 and expressed in Escherichia coli BL21. Recombinant enzyme Cel-9 was purified by Ni-NTA column based the His-tag, and the molecular weight determined as 40.4 kDa by SDA–PAGE. The characterization of the enzyme Cel-9 indicated that the maximum enzyme activity was realized at 50°C and pH 8.6 and, Mn2+ could greatly improve the CMCase enzyme activity of Cel-9 at 10 mM, which was followed by Fe2+ and Co2+. Besides, it also found that the β-1,3-1,4, β-1,3, β-1,4, and β-1,6 glucan linkages all could be hydrolyzed by enzyme Cel-9. Finally, during the application of enzyme Cel-9 to switchgrass, the saccharification rates achieved to 1.81 ± 0.04% and 2.65 ± 0.03% for 50 and 100% crude enzyme, respectively. All these results indicated that both the strain G. thermodenitrificans Y7 and the recombinant endocellulase Cel-9 have the potential to be applied to the biomass industry.
Highlights
Energy-related issues and degradation of lignocellulose have attracted widespread attention of researchers, for the sugar and other by-products obtained from lignocellulose degradation possess great economic value and be important to the development of the green energy industry
Chemical, and biological methods are generally used for pretreatment at lab- or industrial-base (Yi et al, 2009), the biological method is a good approach for the pretreatment, which mainly rely on microorganisms to promote saccharification of the lignocellulose biomass, such as fungi and bacteria
Chicken manure compost was collected from the Jiangsu Tianmiaoli Fertilizer Co., Ltd., Long straw-like switchgrass was air dried before transferred into lab, washed with water and dried at 60◦C in oven, which crushed using a high-speed pulverizer to 40 mesh and oven-dried for further experiments
Summary
Energy-related issues and degradation of lignocellulose have attracted widespread attention of researchers, for the sugar and other by-products obtained from lignocellulose degradation possess great economic value and be important to the development of the green energy industry. Chemical, and biological methods are generally used for pretreatment at lab- or industrial-base (Yi et al, 2009), the biological method is a good approach for the pretreatment, which mainly rely on microorganisms to promote saccharification of the lignocellulose biomass, such as fungi and bacteria. These microbes secret unique cellulase enzymes that allow the utilization of different forms of cellulose (Saddler, 1982; Gilkes et al, 1991). Cellulosic microbes and cellulases have a broad research value and the potential to be applied to the industry
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