Fibrobacter succinogenes S85 was incubated in medium containing rice straw as the sole carbon source for 48 h and centrifuged (2300 g, 4 °C, 10 min), and the supernatant was filtered through a sterile filter (0.22 μm; Millipore, Billerica, MA) in the anaerobic chamber

(Coy, Grass Lake, MI) maintained at the atmosphere of 95% CO2 and 5% H2. A cell suspension of strain R-25 with OD660 nm = 0.2 was inoculated to the obtained culture supernatant of F. succinogenes S85 and grown to mid-log phase. The control (rice straw medium without inoculation of APO866 nmr F. succinogenes S85) was processed as above. In addition, cultures of strain R-25 incubated in basal medium containing 0.5% (w/v) cellooligosaccharides (SEIKAGAKU BIOBUSINESS, Tokyo, Japan) or xylooligosaccharides (Wako, Osaka, Japan) as the sole carbon source was used for comparative study. Extracellular and intracellular enzyme assays were performed following the protocol described above. Rice straw particles in the monoculture and coculture were sampled at 48 h. The samples were washed three times with 50 mM potassium phosphate buffer (pH 6.8) and fixed with 3% glutaraldehyde in the same buffer for 1 h at room temperature. After fixation, the samples were washed four times with 50 mM potassium phosphate buffer and postfixed

for 30 min in 1% osmic acid (OsO4) in the same buffer. After washing four times, the samples were dehydrated by graded ethanol solution series [50, 70, 90, 99.5% (v/v), 10 min at each concentration] AZD0530 nmr and exposed to isoamyl acetate for 20 min twice. Isoamyl acetate was removed with a critical point dryer using liquid CO2 (HCP-2; Hitachi, Tokyo, Japan) in eight 15-min treatments. The samples were coated with gold in an ion sputter (E101; Hitachi) and

observed in a JSM-6301 low vacuum scanning electron microscope (JEOL, Tokyo, Japan) at an accelerating voltage of 5 kV. The means of DM digestion, metabolites, 16S rRNA gene copy number, and enzyme activity for each CYTH4 treatment were analyzed by one-way analysis of variance of spss ver. 16.0 J (IBM, Tokyo, Japan). P < 0.05 was regarded as significant. DM digestion of rice straw by F. succinogenes S85 was 32.8%, while strain R-25 did not digest rice straw (Table 1). DM digestion with coculture of strains R-25 and F. succinogenes S85 was 1.13-fold higher (P < 0.05) than that of monoculture of F. succinogenes S85 (36.9% and 32.8%, respectively). The extracellular CMCase and xylanase activities in monoculture of strain R-25 or F. succinogenes S85 and their coculture are shown in Table 1. For both CMCase and xylanase, the activities in coculture were higher than those of the F. succinogenes S85 monoculture (P < 0.05). Changes in 16S rRNA gene copy number for strains R-25 and F. succinogenes S85 in monoculture and in their coculture are presented in Table 2. At the beginning of incubation, the copy numbers of 16S rRNA gene for strain R-25 and F. succinogenes S85 were 8.1 × 106 mL−1 and 9.0 × 106 mL−1, respectively.