The Character of Normal Temperature Straw-Rotting Microbial Community

Bioconversion of un-pretreated lignocellulosic materials by a microbial consortium XDC-2

The present study investigated the degradation of un-pretreated wheat straw, corn stalk, and rice straw by a lignocellulose-degrading microbial consortium XDC-2. Following six days of cultivation, exocellular xylanase activities were 414.9, 491.9, and 335 U/mL, respectively. After 12 days, the rice straw had lost 39.71% of its weight, hemicellulose and cellulose losses of 78.27% and 14.08%, respectively. The total amount of volatile products reached a maximum on day six for rice straw degradation. The four major types of volatile products were acetic acid, propionic acid, butanoic acid, and glycerin, all of which would be suitable substrates for conversion to methanol by anaerobic digestion. According to PCR-DGGE analysis, XDC-2 remained stable during the degradation process of untreated lignocellulosic biomass. These results demonstrate the potential for further development and application of XDC-2; it is capable of degrading un-pretreated lignocellulosic materials, and has a low cost of operation.

Characterization of a microbial consortium capable of degrading lignocellulose

A microbial consortium, designated WCS-6, was established by successive subcultivation in the presence of rice straw under static conditions. The degradation efficiencies of WSC-6 for 0.5 g filter paper, cotton and rice straw after 3 days of cultivation were 99.0±0.7%, 76.9±1.5% and 81.3±0.8%, respectively as determined by gravimetrical methods. Nine bacterial isolates were obtained from WCS-6 plated under aerobic conditions, and sequencing of their 16S rDNA indicated that these bacteria were related to Bacillus thermoamylovorans BTa, Paenibacillus barengoltzii SAFN-016, Proteobacterium S072, Pseudoxanthomonas taiwanensis CB-226, Rhizobiaceae str. M100, Bacillus sp. E53-10, Beta proteobacterium HMD444, Petrobacter succinimandens 4BON, and Tepidiphilus margaritifer N2-214. DGGE (denaturing gradient gel electrophoresis) and sequencing of 16S rDNA sequences amplified from total consortium DNA revealed the presence of sequences related to those of Ureibacillus thermosphaericus, uncultured bacterium clone GC3, uncultured Clostridium sp. clone A1-3, Clostridium thermobutyricum, and Clostridium thermosuccinogenes in addition to the sequences identified from the cultured bacteria. The microbial community identified herein is a potential candidate consortium for the degradation of waste lignocellulosic biomass.