Culture-independent phylogenetic analysis of the microbial community in industrial sugarcane bagasse feedstock piles.

Sugarcane bagasse is an important lignocellulosic by-product with potential for conversion to biofuels and chemicals in biorefinery. As a step towards an understanding of microbial diversity and the processes existing in bagasse collection sites, the microbial community in industrial bagasse feedstock piles was investigated. Molecular biodiversity analysis of 16S rDNA sequences revealed the presence of a complex bacterial community. A diverse group of mainly aerobic and facultative anaerobic bacteria was identified reflecting the aerobic and high temperature microenvironmental conditions under the pile surface. The major bacterial taxa present were identified as Firmicutes, Alpha- and Gammaproteobacteria, Acidobacteria, Bacteroidetes, and Actinobacteria. Analysis of the eukaryotic microbial assemblage based on an internal transcribed spacer revealed the predominance of diverse cellulolytic and hemicellulolytic ascomycota. A microbial interaction model is proposed, focusing on lignocellulose degradation and methane metabolism. The insights into the microbial community in this study provide a basis for efficient utilization of bagasse in lignocellulosic biomass-based industries.

Insights into the phylogeny and metabolic potential of a primary tropical peat swamp forest microbial community by metagenomic analysis.

A primary tropical peat swamp forest is a unique ecosystem characterized by long-term accumulation of plant biomass under high humidity and acidic water-logged conditions, and is regarded as an important terrestrial carbon sink in the biosphere. In this study, the microbial community in the surface peat layer in Pru Toh Daeng, a primary tropical peat swamp forest, was studied for its phylogenetic diversity and metabolic potential using direct shotgun pyrosequencing of environmental DNA, together with analysis of 16S rRNA gene library and key metabolic genes. The community was dominated by aerobic microbes together with a significant number of facultative and anaerobic microbial taxa. Acidobacteria and diverse Proteobacteria (mainly Alphaproteobacteria) constituted the major phylogenetic groups, with minor representation of archaea and eukaryotic microbes. Based on comparative pyrosequencing dataset analysis, the microbial community showed high metabolic versatility of plant polysaccharide decomposition. A variety of glycosyl hydrolases targeting lignocellulosic and starch-based polysaccharides from diverse bacterial phyla were annotated, originating mostly from Proteobacteria, and Acidobacteria together with Firmicutes, Bacteroidetes, Chlamydiae/Verrucomicrobia, and Actinobacteria, suggesting the key role of these microbes in plant biomass degradation. Pyrosequencing dataset annotation and direct mcrA gene analysis indicated the presence of methanogenic archaea clustering in the order Methanomicrobiales, suggesting the potential on partial carbon flux from biomass degradation through methanogenesis. The insights on the peat swamp microbial assemblage thus provide a valuable approach for further study on biogeochemical processes in this unique ecosystem.

Simultaneous non-thermal saccharification of cassava pulp by multi-enzyme activity and ethanol fermentation by Candida tropicalis.

Cassava pulp, a solid by-product from starch processing, is a promising and underused biomass that can be converted to biofuels and other value-added bio-products. In this study, an alternative cassava pulp saccharification process, which utilizes the multi-activity enzyme from Aspergillus niger BCC17849 and obviates the need for a pre-gelatinization step, was developed. The crude multi-enzyme composed of non-starch polysaccharide hydrolyzing enzyme activities, including cellulase, pectinase and hemicellulase act cooperatively to release the trapped starch granules from the fibrous cell wall structure for subsequent saccharification by raw starch degrading activity. A high yield of fermentable sugars, equivalent to 716 mg glucose and 67 mg xylose/g of cassava pulp, was obtained after 48 h incubation at 40 degrees C and pH 5 using the multi-enzyme, which was greater than the yield obtained from the optimized combinations of the corresponding commercial enzymes. The multi-enzyme saccharification reaction can be performed simultaneously with the ethanol fermentation process using a thermotolerant yeast Candida tropicalis BCC7755. The combined process produced 14.3 g/l ethanol from 4% (w/v) cassava pulp after 30 h of fermentation. The productivity rate of 0.48 g/l/h is equivalent to 93.7% of the theoretical yield based on total starch and cellulose, or 85.4% based on total fermentable sugars. The non-thermal enzymatic saccharification process described is more energy efficient and yields more fermentable sugar than the conventional enzymatic process. Furthermore, the process is applicable for production of various bio-products of economic importance.