Abstract
BackgroundUnderstanding the dynamics of the microbial communities that, along with their secreted enzymes, are involved in the natural process of biomass composting may hold the key to breaking the major bottleneck in biomass-to-biofuels conversion technology, which is the still-costly deconstruction of polymeric biomass carbohydrates to fermentable sugars.However, the complexity of both the structure of plant biomass and its counterpart microbial degradation communities makes it difficult to investigate the composting process.ResultsIn this study, a composter was set up with a mix of yellow poplar (Liriodendron tulipifera) wood-chips and mown lawn grass clippings (85:15 in dry-weight) and used as a model system. The microbial rDNA abundance data obtained from analyzing weekly-withdrawn composted samples suggested population-shifts from bacteria-dominated to fungus-dominated communities. Further analyses by an array of optical microscopic, transcriptional and enzyme-activity techniques yielded correlated results, suggesting that such population shifts occurred along with early removal of hemicellulose followed by attack on the consequently uncovered cellulose as the composting progressed.ConclusionThe observed shifts in dominance by representative microbial groups, along with the observed different patterns in the gene expression and enzymatic activities between cellulases, hemicellulases, and ligninases during the composting process, provide new perspectives for biomass-derived biotechnology such as consolidated bioprocessing (CBP) and solid-state fermentation for the production of cellulolytic enzymes and biofuels.
Highlights
Understanding the dynamics of the microbial communities that, along with their secreted enzymes, are involved in the natural process of biomass composting may hold the key to breaking the major bottleneck in biomass-to-biofuels conversion technology, which is the still-costly deconstruction of polymeric biomass carbohydrates to fermentable sugars
We examined the expression patterns of a total of six P. chrysosporium genes at seven sampling time points; we glean from the expression profiling data that the two Manganese peroxidase (MnP) genes are likely to be regulated differently, between themselves and from the Lignin peroxidase (LiP) examined (Figure 5)
The following observations and implications highlight the value of using biomass compost for demystifying the enigma of “natural biomass conversion” in terms of lignocellulolytic gene expressions, enzymatic activities and their effects on deconstruction of plant biomass materials
Summary
Understanding the dynamics of the microbial communities that, along with their secreted enzymes, are involved in the natural process of biomass composting may hold the key to breaking the major bottleneck in biomass-to-biofuels conversion technology, which is the still-costly deconstruction of polymeric biomass carbohydrates to fermentable sugars. The intertwining matrix of biopolymers (celluloses, hemicelluloses, and lignins, as prominent examples) of which plant cell walls are composed poses a major obstacle to the deconstruction of these walls to simple sugars and chemicals that can serve as raw materials for the fermentative production of alternative liquid fuels and other bioproducts. This major bottleneck in Traditionally, composting is defined as a process that heaps together organic materials (notably food waste, manure, plant leaves and stems, grass trimmings, crop residues, paper, and wood, etc.), and allows them to decay enough to be ready either for use as soil enhancers or for disposal. These advantages make composting studies a rich area to be mined for activities useful in both biological pretreatment of biomass feedstocks and in the ultimate saccharification step
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