Tracking dynamics of plant biomass composting by changes in substrate structure, microbial community, and enzyme activity

Wei Hui, Tucker, Baker, Harris Michelle, Luo Yonghua, Xu Qi, Himmel, Ding, Ding Shi-You

Description

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. However, the complexity of both the structure of plant biomass and its counterpart microbial degradation communities makes it difficult to investigate the composting process. Results In 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 The microbial rDNA abundance data obtained from analyzing weekly-withdrawn composted samples suggested population-shifts from bacteria-dominated to fungus-dominated communities.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. Conclusion The 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.

Sujets

• Compost
• Liriodendron tulipifera
• Microbial population biology
• Gene expression
• Enzyme catalysis
• Cellulase
• Hémicellulose
• Ligninase
• Biofuel

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Wei et al . Biotechnology for Biofuels 2012, 5 :20 http://www.biotechnologyforbiofuels.com/content/5/1/20

R E S E A R C H Open Access Tracking dynamics of plant biomass composting by changes in substrate structure, microbial community, and enzyme activity Hui Wei 1* , Melvin P Tucker 2 , John O Baker 1 , Michelle Harris 1 , Yonghua Luo 1 , Qi Xu 1 , Michael E Himmel 1 and Shi-You Ding 1*

Abstract Background: 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. However, the complexity of both the structure of plant biomass and its counterpart microbial degradation communities makes it difficult to investigate the composting process. Results: In 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. Conclusion: The 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. Keywords: Compost, Plant biomass, Yellow poplar, Microbial community, Microbial rDNA abundance, Gene expres- sion, Enzymatic activity, Cellulase, Hemicellulose, Ligninase, Consolidated bioprocessing (CBP), Solid-state fermenta- tion, Biofuels

Background biomass conversion technology can be mitigated by 1) The intertwining matrix of b iopolymers (celluloses,  reducing plant biomass recalcitrance through genetic hemicelluloses, and lignins, as prominent examples) of engineering of energy crops , thereby 2) minimizing the which plant cell walls are composed poses a major requirement for thermo-che mical feedstock pretreat- obstacle to the deconstruction of these walls to simple ment, 3) improving performance of the enzymes used sugars and chemicals that can serve as raw materials for for saccharification, and 4) introducing the one step the fermentative production of alternative liquid fuels conversion concept, or consolidated bioprocessing and other bioproducts. This major bottleneck in  (CBP), in which enzyme production, enzymatic hydroly- sis, and fermentation are combined for microbial pro- * 1 B C io o s r c r i e e s n p c o e n s d C e e nc nt e: er, Hu N i. at W io ei n @ al nr R e e l. n g e o w v; a S bl h e i.y E o n u e . r D g i y ng La @ b n o r r e a l. t g o o ry v ,Golden,CO du T c r ti a o d n iti o o f n b a i ll o y f , ue c l o s m us p i o n s g ti b n i g o i m s a d ss efi a n s e s d ub a s s tr a at p e r s o [ c 1 e ] s . sthat 80401, USA heaps together organic materials (notably food waste, Full list of author information is available at the end of the article © 2012 Wei et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.