• Asian-Australasian Journal of Animal Sciences
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• v.31 no.5
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• pp.738-747
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• 2018

Objective: In a previous study, analysis of Illumina sequenced metagenomic DNA data of bacteria in Vietnamese goats' rumen showed a high diversity of putative lignocellulolytic genes. In this study, taxonomy speculation of microbial community and lignocellulolytic bacteria population in the rumen was conducted to elucidate a role of bacterial structure for effective degradation of plant materials. Methods: The metagenomic data had been subjected into Basic Local Alignment Search Tool (BLASTX) algorithm and the National Center for Biotechnology Information non-redundant sequence database. Here the BLASTX hits were further processed by the Metagenome Analyzer program to statistically analyze the abundance of taxa. Results: Microbial community in the rumen is defined by dominance of Bacteroidetes compared to Firmicutes. The ratio of Firmicutes versus Bacteroidetes was 0.36:1. An abundance of Synergistetes was uniquely identified in the goat microbiome may be formed by host genotype. With regard to bacterial lignocellulose degraders, the ratio of lignocellulolytic genes affiliated with Firmicutes compared to the genes linked to Bacteroidetes was 0.11:1, in which the genes encoding putative hemicellulases, carbohydrate esterases, polysaccharide lyases originated from Bacteroidetes were 14 to 20 times higher than from Firmicutes. Firmicutes seem to possess more cellulose hydrolysis capacity showing a Firmicutes/Bacteroidetes ratio of 0.35:1. Analysis of lignocellulolytic potential degraders shows that four species belonged to Bacteroidetes phylum, while two species belonged to Firmicutes phylum harbouring at least 12 different catalytic domains for all lignocellulose pretreatment, cellulose, as well as hemicellulose saccharification. Conclusion: Based on these findings, we speculate that increasing the members of Bacteroidetes to keep a low ratio of Firmicutes versus Bacteroidetes in goat rumen has resulted most likely in an increased lignocellulose digestion.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.254-264
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• 2010

To obtain an efficient natural lignocellulolytic complex enzyme, we screened an efficient lignocellulose-degrading composite microbial system (XDC-2) from composted agricultural and animal wastes amended soil following a long-term directed acclimation. Not only could the XDC-2 degrade natural lignocelluloses, but it could also secrete extracellular xylanase efficiently in liquid culture under static conditions at room temperature. The XDC-2 degraded rice straw by 60.3% after fermentation for 15 days. Hemicelluloses were decomposed effectively, whereas the extracellular xylanase activity was dominant with an activity of 8.357 U/ml on day 6 of the fermentation period. The extracellular crude enzyme noticeably hydrolyzed natural lignocelluloses. The optimum temperature and pH for the xylanase activity were $40^{\circ}C$ and 6.0. However, the xylanase was activated in a wide pH range of 3.0-10.0, and retained more than 80% of its activity at $25-35^{\circ}C$ and pH 5.0-8.0 after three days of incubation in liquid culture under static conditions. PCR-DGGE analysis of successive subcultures indicated that the XDC-2 was structurally stable over long-term restricted and directed cultivation. Analysis of the 168 rRNA gene clone library showed that the XDC-2 was mainly composed of mesophilic bacteria related to the genera Clostridium, Bacteroides, Alcaligenes, Pseudomonas, etc. Our results offer a new approach to exploring efficient lignocellulolytic enzymes by constructing a high-performance composite microbial system with synergistic complex enzymes.

• Journal of Microbiology and Biotechnology
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• v.22 no.4
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• pp.462-469
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• 2012

A metagenomic fosmid library was constructed from genomic DNA isolated from the microbial community residing in hindguts of a wood-feeding higher termite (Microcerotermes sp.) collected in Thailand. The library was screened for clones expressing lignocellulolytic activities. Fourteen independent active clones (2 cellulases and 12 xylanases) were obtained by functional screening at pH 10.0. Analysis of shotgun-cloning and pyrosequencing data revealed six ORFs, which shared less than 59% identity and 73% similarity of their amino acid sequences with known cellulases and xylanases. Conserved domain analysis of these ORFs revealed a cellulase belonging to the glycoside hydrolase family 5, whereas the other five xylanases showed significant identity to diverse families including families 8, 10, and 11. Interestingly, one fosmid clone was isolated carrying three contiguous xylanase genes that may comprise a xylanosome operon. The enzymes with the highest activities at alkaline pH from the initial activity screening were characterized biochemically. These enzymes showed a broad range of enzyme activities from pH 5.0 to 10.0, with pH optimal of 8.0 retaining more than 70% of their respective activities at pH 9.0. The optimal temperatures of these enzymes ranged from $50^{\circ}C$ to $55^{\circ}C$. This study provides evidence for the diversity and function of lignocellulose-degrading enzymes in the termite gut microbial community, which could be of potential use for industrial processes such as pulp biobleaching and denim biostoning.