Multifaceted characterization of cell wall decomposition products formed during ammonia fiber expansion (AFEX) and dilute acid based pretreatments

Chundawat, Shishir P. S.; Vismeh, Ramin; Sharma, Lekh N.; Humpula, James F.; Sousa, Leonardo da Costa; Chambliss, C. Kevin; Jones, A. Daniel; Balan, Venkatesh; Dale, Bruce E.

doi:10.1016/j.biortech.2010.06.027

Cited by 230 publications

(252 citation statements)

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“…Pretreatment reorients the physical structure of the plant cell wall and reduces the recalcitrance of the polysaccharides, cellulose, and hemicellulose (10). Depending on the pretreatment, some plant polymers, primarily hemicellulose and lignin, are depolymerized, and the resulting substrate is enriched in cellulose (11).…”

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Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Eichorst

Joshua

Sathitsuksanoh

et al. 2014

Appl Environ Microbiol

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e Microbial communities that deconstruct plant biomass have broad relevance in biofuel production and global carbon cycling. Biomass pretreatments reduce plant biomass recalcitrance for increased efficiency of enzymatic hydrolysis. We exploited these chemical pretreatments to study how thermophilic bacterial consortia adapt to deconstruct switchgrass (SG) biomass of various compositions. Microbial communities were adapted to untreated, ammonium fiber expansion (AFEX)-pretreated, and ionicliquid (IL)-pretreated SG under aerobic, thermophilic conditions using green waste compost as the inoculum to study biomass deconstruction by microbial consortia. After microbial cultivation, gravimetric analysis of the residual biomass demonstrated that both AFEX and IL pretreatment enhanced the deconstruction of the SG biomass approximately 2-fold. Two-dimensional nuclear magnetic resonance (2D-NMR) experiments and acetyl bromide-reactive-lignin analysis indicated that polysaccharide hydrolysis was the dominant process occurring during microbial biomass deconstruction, and lignin remaining in the residual biomass was largely unmodified. Small-subunit (SSU) rRNA gene amplicon libraries revealed that although the dominant taxa across these chemical pretreatments were consistently represented by members of the Firmicutes, the Bacteroidetes, and Deinococcus-Thermus, the abundance of selected operational taxonomic units (OTUs) varied, suggesting adaptations to the different substrates. Combining the observations of differences in the community structure and the chemical and physical structure of the biomass, we hypothesize specific roles for individual community members in biomass deconstruction.

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Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Eichorst

Joshua

Sathitsuksanoh

et al. 2014

Appl Environ Microbiol

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“…Production of lignocellulosic hydrolysates typically requires pretreatment with either an acid or a base, which release different lignin derivatives into hydrolysates (31, 49, 50). We chose to investigate E. coli physiology during ethanologenesis in hydrolysates derived by alkaline pretreatment, specifically, ammonia fiber expansion (AFEX), because it yields a feedstock containing both C 5 and C 6 sugars and generates fewer lignin-derived inhibitors of microbial growth (19,81,82). Furthermore, hydrolysates prepared from AFEX-pretreated biomass, such as AFEXpretreated corn stover hydrolysate (ACSH), are replete in nutrients and permissive to growth to the extent that engineered strains of E. coli can consistently produce significant amounts of ethanol from glucose (49,50,60,66).…”

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confidence: 99%

Complex Physiology and Compound Stress Responses during Fermentation of Alkali-Pretreated Corn Stover Hydrolysate by an Escherichia coli Ethanologen

Schwalbach

Keating

Tremaine

et al. 2012

Appl Environ Microbiol

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ABSTRACTThe physiology of ethanologenicEscherichia coligrown anaerobically in alkali-pretreated plant hydrolysates is complex and not well studied. To gain insight into howE. coliresponds to such hydrolysates, we studied anE. coliK-12 ethanologen fermenting a hydrolysate prepared from corn stover pretreated by ammonia fiber expansion. Despite the high sugar content (∼6% glucose, 3% xylose) and relatively low toxicity of this hydrolysate,E. coliceased growth long before glucose was depleted. Nevertheless, the cells remained metabolically active and continued conversion of glucose to ethanol until all glucose was consumed. Gene expression profiling revealed complex and changing patterns of metabolic physiology and cellular stress responses during an exponential growth phase, a transition phase, and the glycolytically active stationary phase. During the exponential and transition phases, high cell maintenance and stress response costs were mitigated, in part, by free amino acids available in the hydrolysate. However, after the majority of amino acids were depleted, the cells entered stationary phase, and ATP derived from glucose fermentation was consumed entirely by the demands of cell maintenance in the hydrolysate. Comparative gene expression profiling and metabolic modeling of the ethanologen suggested that the high energetic cost of mitigating osmotic, lignotoxin, and ethanol stress collectively limits growth, sugar utilization rates, and ethanol yields in alkali-pretreated lignocellulosic hydrolysates.

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“…RE 2, which is abundant in β-glucosidases but deficient in exo-cellulases, gave close to 5-10% glucan conversion suggesting that several gluco-oligomers released from the cell wall after AFEX pretreatment are relatively easily digested to glucose by β-glucosidases. Recent analysis of oligomers released from the cell wall after AFEX pretreatment have revealed the presence of a range of low-to high-molecular weight oligosaccharides with degree of polymerization ranging from 2 to 20 (Chundawat et al, 2010;Vismeh et al, 2013).…”

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confidence: 99%

Shotgun Approach to Increasing Enzymatic Saccharification Yields of Ammonia Fiber Expansion Pretreated Cellulosic Biomass

et al. 2017

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Multifaceted characterization of cell wall decomposition products formed during ammonia fiber expansion (AFEX) and dilute acid based pretreatments

Cited by 230 publications

References 29 publications

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Complex Physiology and Compound Stress Responses during Fermentation of Alkali-Pretreated Corn Stover Hydrolysate by an Escherichia coli Ethanologen

Shotgun Approach to Increasing Enzymatic Saccharification Yields of Ammonia Fiber Expansion Pretreated Cellulosic Biomass

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