Simultaneous Saccharification and Cofermentation of Dilute-Acid Pretreated Yellow Poplar Hardwood to Ethanol Using Xylose-Fermenting Zymomonas mobilis

McMillan, James D.; Newman, Mildred M.; Templeton, David W.; Mohagheghi, Ali

doi:10.1385/abab:79:1-3:649

Cited by 82 publications

(27 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Given the proven adeptness of Z. mobilis in industrial-scale fermentation, the ability to express high levels of active cellulases shown in this study and the capacity to secrete these enzymes, the foundation has been laid for further investigations in the establishment of Z. mobilis as a CBP organism. While CBP might be considered the ultimate goal, any significant production of cellulolytic enzymes by Z. mobilis could be considered a success, as this would reduce the required loading levels of exogenously produced cellulases during simultaneous saccharification and fermentation or cofermentation, processes in which Z. mobilis has already been tried and tested (14,24,36).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, Z. mobilis has the ability to ferment sugars at low pH and has a naturally high tolerance to many of the inhibitory compounds found in hydrolysates derived from lignocellulosic biomass (45, 46) Furthermore, the use of the Entner-Doudoroff pathway (37) allows Z. mobilis to achieve the near-theoretical maximum ethanol yields during fermentation while achieving relatively low biomass formation. Accordingly, Z. mobilis has been used successfully in SSF and SSCF processes (14,24,36). Additionally, Z. mobilis has been successfully engineered to ferment the pentose (C 5 ) sugars, xylose (45) and arabinose (10).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Heterologous Expression and Extracellular Secretion of Cellulolytic Enzymes byZymomonas mobilis

Linger

Adney

Darzins

2010

Appl Environ Microbiol

View full text Add to dashboard Cite

Development of the strategy known as consolidated bioprocessing (CBP) involves the use of a single microorganism to convert pretreated lignocellulosic biomass to ethanol through the simultaneous production of saccharolytic enzymes and fermentation of the liberated monomeric sugars. In this report, the initial steps toward achieving this goal in the fermentation host Zymomonas mobilis were investigated by expressing heterologous cellulases and subsequently examining the potential to secrete these cellulases extracellularly. Numerous strains of Z. mobilis were found to possess endogenous extracellular activities against carboxymethyl cellulose, suggesting that this microorganism may harbor a favorable environment for the production of additional cellulolytic enzymes. The heterologous expression of two cellulolytic enzymes, E1 and GH12 from Acidothermus cellulolyticus, was examined. Both proteins were successfully expressed as soluble, active enzymes in Z. mobilis although to different levels. While the E1 enzyme was less abundantly expressed, the GH12 enzyme comprised as much as 4.6% of the total cell protein. Additionally, fusing predicted secretion signals native to Z. mobilis to the N termini of E1 and GH12 was found to direct the extracellular secretion of significant levels of active E1 and GH12 enzymes. The subcellular localization of the intracellular pools of cellulases revealed that a significant portion of both the E1 and GH12 secretion constructs resided in the periplasmic space. Our results strongly suggest that Z. mobilis is capable of supporting the expression and secretion of high levels of cellulases relevant to biofuel production, thereby serving as a foundation for developing Z. mobilis into a CBP platform organism.The biological conversion of lignocellulosic biomass to ethanol represents a potential major source of future domestic transportation fuels, but the current cost of converting biomass to fermentable sugars still needs to be reduced further (12). Most current strategies for ethanol production via biochemical conversion of lignocellulosic feedstocks utilize simultaneous saccharification and fermentation (SSF) or simultaneous saccharification and cofermentation (SSCF) processes (8,21,22). The process configuration known as consolidated bioprocessing (CBP) (20) would alleviate the financial strain of producing saccharolytic enzyme cocktails by combining the necessary steps for ethanol production as the action of one microorganism.A particularly attractive microbial candidate for the development of a CBP microorganism is the Gram-negative fermentative bacterium Zymomonas mobilis. Z. mobilis has been studied for its exceptionally high ethanol production rate, yield, and tolerance to the toxicity of the final product (15-17, 20, 31-33, 35, 43). In addition, Z. mobilis has the ability to ferment sugars at low pH and has a naturally high tolerance to many of the inhibitory compounds found in hydrolysates derived from lignocellulosic biomass (45, 46) Furthermore, the use of the Entner-Doudoroff...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Heterologous Expression and Extracellular Secretion of Cellulolytic Enzymes byZymomonas mobilis

Linger

Adney

Darzins

2010

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…The carbohydrate content of SSO was determined via quantitative saccharification (QS) method based on 2 hours incubation in 72wt% H 2 SO 4 at 30 o C (Ruiz and Ehrman, 1996;McMillan et al, 1999;Moxley and Zhang, 2007). The cell mass was determined by counting colony forming units on agar plates as described in (Zhang et al, 2009).…”

Section: Methodsmentioning

confidence: 99%

“…This model accounts for cellulose and hemicellulose enzymatic hydrolysis and competitive uptake of glucose and xylose. There are only a few published studies on the conversion of cellulose and hemicellulose via SSCF (McMillan et al, 1999;Teixeira et al, 2000;Kim and Lee, 2005) and only few kinetic models have been proposed in the literature (Shao, 2007, Zhang, 2008. A kinetic model development used in this work was based on a semi-mechanic rate equation for cellulose hydrolysis as initially proposed by (South et al, 1995) and further modified by (Shao, 2007) and (Zhang, 2008) to accommodate cellulose and hemicellulose hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

KINETIC MODEL DEVELOPMENT ON SOURCE-SEPARATED ORGANIC WASTE FOR ETHANOL PRODUCTION BY S. cerevisiae STRAIN

Bekmuradov

Luk

Crupi³

et al. 2017

International Conference on Bioscience and Biotechnology

View full text Add to dashboard Cite

Ethanol production from organic fraction of municipal solid waste with inclusion of construction/demolition waste can be an effective waste management strategy to overcome the growing problems with landfill space and dependency on conventional fuels. The main challenge in ethanol conversion is the high cost of processing in which pre-treatment, enzymatic hydrolysis and fermentation are the major steps. This study investigates impact of several key parameters, namely: pH, temperature, adsorption capacity, cellulose hydrolysis rate, cell mass, enzyme and substrate loading doses on ethanol yield. The pre-treatment incorporates pre-processing and enzymatic hydrolysis steps through the use of a thermal screw press (TSP) and cellulose-organic-solvent based lignocellulosic fractionation (COSLIF) on the source-separated organic (SSO) waste to liberate fermentable sugars. Enzymatic hydrolysis experiments were featured with the addition of a commercially available enzyme complex, Accellerase 1500, to mediate the process and increase sugar yields. A kinetic model that uses a semi-mechanistic rate equation for cellulose hydrolysis was adapted and modified to accommodate batch simultaneous saccharification and co-fermentation (SSCF) process on pre-treated SSO waste by yeast, Saccharomyces cerevisiae DA2416. New experimentally defined SSO parameters have been fitted into a kinetic model to evaluate the sugar and ethanol yields. It was found that the model was capable of predicting ethanol productions with diminutive variance from experiments with substrate concentrations between 10 g/L and 50 g/L. Model predictions from experimental data deviated significantly with substrate loading rate from 60 g/L and higher. Fermentation results demonstrated that S. cerevisiae DA2416 produced ethanol in the range of 35 -50 g/L, with ethanol yield of 0.48 -0.50 g of ethanol/g sugar, in 5 days with 96% cellulose conversion. This study provides important insights for investigation on the use of SSO waste for ethanol production by S. cerevisiae DA2416. Furthermore, the model was proven to be a useful tool to facilitate future process optimization for up-scale bioreactors.

show abstract

“…A process based on the use of Zymomonas mobilis using lignocellulose obtained from hard woods (McMillan et al, 1999) consists of in situ cellulase production to enable simultaneous sacarifi cation and fermentation. The cost estimated for ethanol obtained by this process is 0.36 USD per liter.…”

Section: Some Commercial Processes For Ethanol Production From Lignocmentioning

confidence: 99%

Ethanol from lignocellulosic biomass

Abril

Abril²

2009

Cienc. Inv. Agr.

View full text Add to dashboard Cite

Ethanol is the liquid combustible that has become the most promising alternative substitute for gasoline because of the experience gained in its production, the possibility of mixing it with gasoline in different proportions, the possibility of using the existing gasoline distribution infrastructure, and the fact that major changes in engines are not required for its use. Lignocelluloses offer great potential as a biomass source for ethanol production, although their use still requires in-depth analysis with an objective and holistic focus that includes present and future technologic implications. The present article reviews current knowledge about the characteristics and sources of vegetable biomass, as well as the development and possibilities for obtaining ethanol from lignocellulosic sources.

show abstract

Simultaneous Saccharification and Cofermentation of Dilute-Acid Pretreated Yellow Poplar Hardwood to Ethanol Using Xylose-Fermenting Zymomonas mobilis

Cited by 82 publications

References 19 publications

Heterologous Expression and Extracellular Secretion of Cellulolytic Enzymes byZymomonas mobilis

Heterologous Expression and Extracellular Secretion of Cellulolytic Enzymes byZymomonas mobilis

KINETIC MODEL DEVELOPMENT ON SOURCE-SEPARATED ORGANIC WASTE FOR ETHANOL PRODUCTION BY S. cerevisiae STRAIN

Ethanol from lignocellulosic biomass

Contact Info

Product

Resources

About