Effects of phenolic monomers on growth of <i>Acidothermus cellulolyticus</i>

Joh, Lawrence D.; Rezaei, Farzaneh; Barabote, Ravi D.; Parales, Juanito V.; Parales, Rebecca E.; Berry, Alison M.; VanderGheynst, Jean S.

doi:10.1002/btpr.525

Cited by 6 publications

(2 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additional literature discusses inhibition by products formed during biomass pretreatment [4,5,40-43]. Many of the non-carbohydrate compounds are believed to be inhibitory in nature [42,44-47]. …”

Section: Resultsmentioning

confidence: 99%

Industrial Robustness: Understanding the Mechanism of Tolerance for the Populus Hydrolysate-Tolerant Mutant Strain of Clostridium thermocellum

et al. 2013

View full text Add to dashboard Cite

BackgroundAn industrially robust microorganism that can efficiently degrade and convert lignocellulosic biomass into ethanol and next-generation fuels is required to economically produce future sustainable liquid transportation fuels. The anaerobic, thermophilic, cellulolytic bacterium Clostridium thermocellum is a candidate microorganism for such conversions but it, like many bacteria, is sensitive to potential toxic inhibitors developed in the liquid hydrolysate produced during biomass processing. Microbial processes leading to tolerance of these inhibitory compounds found in the pretreated biomass hydrolysate are likely complex and involve multiple genes.Methodology/Principal FindingsIn this study, we developed a 17.5% v/v Populus hydrolysate tolerant mutant strain of C. thermocellum by directed evolution. The genome of the wild type strain, six intermediate population samples and seven single colony isolates were sequenced to elucidate the mechanism of tolerance. Analysis of the 224 putative mutations revealed 73 high confidence mutations. A longitudinal analysis of the intermediate population samples, a pan-genomic analysis of the isolates, and a hotspot analysis revealed 24 core genes common to all seven isolates and 8 hotspots. Genetic mutations were matched with the observed phenotype through comparison of RNA expression levels during fermentation by the wild type strain and mutant isolate 6 in various concentrations of Populus hydrolysate (0%, 10%, and 17.5% v/v).Conclusion/SignificanceThe findings suggest that there are multiple mutations responsible for the Populus hydrolysate tolerant phenotype resulting in several simultaneous mechanisms of action, including increases in cellular repair, and altered energy metabolism. To date, this study provides the most comprehensive elucidation of the mechanism of tolerance to a pretreated biomass hydrolysate by C. thermocellum. These findings make important contributions to the development of industrially robust strains of consolidated bioprocessing microorganisms.

show abstract

Section: Resultsmentioning

confidence: 99%

Industrial Robustness: Understanding the Mechanism of Tolerance for the Populus Hydrolysate-Tolerant Mutant Strain of Clostridium thermocellum

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Possible inhibitory compounds include phenolic compounds, which are a byproduct of lignin degradation (Almeida et al, 2007; Palmqvist and Hahn‐Hagerdal, 2000). Lignin has been shown to decrease growth and enzyme activity in Trichoderma reesei (Vohra et al, 1980) and lignin‐derived compounds have been shown to inhibit cellulases and xylanases produced by thermophilic bacteria (Joh et al, 2011; Ximenes et al, 2010). To prevent inhibition in future adaptation studies, enriched samples could be leached prior to inoculating subsequent batches of feedstock.…”

Section: Discussionmentioning

confidence: 99%

Bioenergy feedstock‐specific enrichment of microbial populations during high‐solids thermophilic deconstruction

Reddy

Allgaier

Singer

et al. 2011

Biotech & Bioengineering

Self Cite

View full text Add to dashboard Cite

Thermophilic microbial communities that are active in a high-solids environment offer great potential for the discovery of industrially relevant enzymes that efficiently deconstruct bioenergy feedstocks. In this study, finished green waste compost was used as an inoculum source to enrich microbial communities and associated enzymes that hydrolyze cellulose and hemicellulose during thermophilic high-solids fermentation of the bioenergy feedstocks switchgrass and corn stover. Methods involving the disruption of enzyme and plant cell wall polysaccharide interactions were developed to recover xylanase and endoglucanase activity from deconstructed solids. Xylanase and endoglucanase activity increased by more than a factor of 5, upon four successive enrichments on switchgrass. Overall, the changes for switchgrass were more pronounced than for corn stover; solids reduction between the first and second enrichments increased by a factor of four for switchgrass while solids reduction remained relatively constant for corn stover. Amplicon pyrosequencing analysis of small-subunit ribosomal RNA genes recovered from enriched samples indicated rapid changes in the microbial communities between the first and second enrichment with the simplified communities achieved by the third enrichment. The results demonstrate a successful approach for enrichment of unique microbial communities and enzymes active in a thermophilic high-solids environment.

show abstract