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Birgitte K. Ahring
Bioproducts, Sciences and Engineering Laboratory, Washington State University, Tri-cities, Richland, USA

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Article
Published: 10 September 2020 in BioEnergy Research
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Anaerobic digestion (AD) of animal manure converts only half of the organic material into biogas due to the presence of a significant amount of lignocellulosic materials in manure. In this study, alkaline thermal pretreatment was used for improving anaerobic digestion of residual manure fibers after AD. Anaerobic digestion of pretreated manure fibers was done in batch culture under mesophilic and thermophilic conditions. The results of the study showed that degradation of manure fibers was improved ca. 43.6% as a result of alkaline thermal pretreatment with 3% w/w NaOH added. Methane yield improved by 143.5 and 180.2% under mesophilic and thermophilic conditions, respectively. Compositional analysis of the effluent after AD showed the percentile conversion of 50.8% of cellulose, 59.5% of hemicellulose, 39.9% of acid-soluble and 21.7% of acid-insoluble lignin to methane under mesophilic conditions. Under thermophilic conditions, 57.3% of cellulose, 70.1% of hemicellulose, 39.4% of acid-soluble and 19.4% of acid-insoluble lignin were converted to methane. The result showed that alkaline thermal pretreatment of manure fibers can enhance the performance of AD while shortening the time needed to recover the maximum amount of biogas from AD.

ACS Style

Muhammad Usman Khan; Birgitte K. Ahring. Anaerobic Digestion of Digested Manure Fibers: Influence of Thermal and Alkaline Thermal Pretreatment on the Biogas Yield. BioEnergy Research 2020, 1 -10.

AMA Style

Muhammad Usman Khan, Birgitte K. Ahring. Anaerobic Digestion of Digested Manure Fibers: Influence of Thermal and Alkaline Thermal Pretreatment on the Biogas Yield. BioEnergy Research. 2020; ():1-10.

Chicago/Turabian Style

Muhammad Usman Khan; Birgitte K. Ahring. 2020. "Anaerobic Digestion of Digested Manure Fibers: Influence of Thermal and Alkaline Thermal Pretreatment on the Biogas Yield." BioEnergy Research , no. : 1-10.

Journal article
Published: 27 July 2020 in Molecules
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Wet explosion pretreatment of hybrid poplar sawdust (PSD) for the production of fermentable sugar was carried out in the pilot-scale. The effects of pretreatment conditions, such as temperature (170–190 °C), oxygen dosage (0.5–7.5% of dry matter (DM), w/w), residence time (10–30 min), on cellulose and hemicellulose digestibility after enzymatic hydrolysis were ascertained with a central composite design of the experiment. Further, enzymatic hydrolysis was optimized in terms of temperature, pH, and a mixture of CTec2 and HTec2 enzymes (Novozymes). Predictive modeling showed that cellulose and hemicellulose digestibility of 75.1% and 83.1%, respectively, could be achieved with a pretreatment at 177 °C with 7.5% O2 and a retention time of 30 min. An increased cellulose digestibility of 87.1% ± 0.1 could be achieved by pretreating at 190 °C; however, the hemicellulose yield would be significantly reduced. It was evident that more severe conditions were required for maximal cellulose digestibility than that of hemicellulose digestibility and that an optimal sugar yield demanded a set of conditions, which overall resulted in the maximum sugar yield.

ACS Style

Rajib Biswas; Philip J. Teller; Muhammad U. Khan; Birgitte K. Ahring. Sugar Production from Hybrid Poplar Sawdust: Optimization of Enzymatic Hydrolysis and Wet Explosion Pretreatment. Molecules 2020, 25, 3396 .

AMA Style

Rajib Biswas, Philip J. Teller, Muhammad U. Khan, Birgitte K. Ahring. Sugar Production from Hybrid Poplar Sawdust: Optimization of Enzymatic Hydrolysis and Wet Explosion Pretreatment. Molecules. 2020; 25 (15):3396.

Chicago/Turabian Style

Rajib Biswas; Philip J. Teller; Muhammad U. Khan; Birgitte K. Ahring. 2020. "Sugar Production from Hybrid Poplar Sawdust: Optimization of Enzymatic Hydrolysis and Wet Explosion Pretreatment." Molecules 25, no. 15: 3396.

Journal article
Published: 02 December 2019 in Bioresource Technology
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This study examine ways to make biorefinery lignin accessible for anaerobic digestion. The raw material was the residue after removing carbohydrates by Wet Explosion pretreatment at 190 °C and 7.5% O2 followed by enzymatic hydrolysis. The residual solid was mainly composed of lignin and was the raw material for a second WEx pretreatment operated at 220 °C with 4% oxygen and variable concentrations of NaOH (0–2%). Lignin B was the residue after pretreated without NaOH, Lignin C was pretreated at 1% NaOH, and Lignin E at 2% NaOH. Anaerobic digestion was carried out on all lignin fractions (Lignin A, B, C and E) at thermophilic conditions (52 °C) by mixing 70% of each lignin fractions with 30% clarified manure. The results showed that the lignin samples were demethoxylated as part of the biodegradation and that the highest severity pretreatment (with oxygen and 2% NaOH) resulted in the highest methane yield.

ACS Style

Muhammad Usman Khan; Birgitte Kiaer Ahring. Anaerobic digestion of biorefinery lignin: Effect of different wet explosion pretreatment conditions. Bioresource Technology 2019, 298, 122537 .

AMA Style

Muhammad Usman Khan, Birgitte Kiaer Ahring. Anaerobic digestion of biorefinery lignin: Effect of different wet explosion pretreatment conditions. Bioresource Technology. 2019; 298 ():122537.

Chicago/Turabian Style

Muhammad Usman Khan; Birgitte Kiaer Ahring. 2019. "Anaerobic digestion of biorefinery lignin: Effect of different wet explosion pretreatment conditions." Bioresource Technology 298, no. : 122537.

Journal article
Published: 22 July 2019 in Molecules
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Lignin, while economically and environmentally beneficial, has had limited success in use in reinforcing carbon fibers due to harmful chemicals used in biomass pretreatment along with the limited physical interactions between lignin and polyacrylonitrile (PAN) during the spinning process. The focus of this study is to use lignin obtained from chemical-free oxidative biomass pretreatment (WEx) for blending with PAN at melt spinning conditions to produce carbon fiber precursors. In this study, the dynamic rheology of blending PAN with biorefinery lignin obtained from the WEx process is investigated with the addition of 1-butyl-3-methylimidazolium chloride as a plasticizer to address the current barriers of developing PAN/lignin carbon fiber precursors in the melt-spinning process. Lignin was esterified using butyric anhydride to reduce its hydrophilicity and to enhance its interactions with PAN. The studies indicate that butyration of the lignin (BL) increased non-Newtonian behavior and decreased thermo-reversibility of blends. The slope of the Han plot was found to be around 1.47 for PAN at 150 °C and decreased with increasing lignin concentrations as well as temperature. However, these blends were found to have higher elasticity and solution yield stress (47.6 Pa at 20%wt BL and 190 °C) when compared to pure PAN (5.8 Pa at 190 °C). The results from this study are significant for understanding lignin-PAN interactions during melt spinning for lower-cost carbon fibers.

ACS Style

Jinxue Jiang; Keerthi Srinivas; Alper Kiziltas; Andrew Geda; Birgitte K. Ahring. Rheology of Polyacrylonitrile/Lignin Blends in Ionic Liquids under Melt Spinning Conditions. Molecules 2019, 24, 2650 .

AMA Style

Jinxue Jiang, Keerthi Srinivas, Alper Kiziltas, Andrew Geda, Birgitte K. Ahring. Rheology of Polyacrylonitrile/Lignin Blends in Ionic Liquids under Melt Spinning Conditions. Molecules. 2019; 24 (14):2650.

Chicago/Turabian Style

Jinxue Jiang; Keerthi Srinivas; Alper Kiziltas; Andrew Geda; Birgitte K. Ahring. 2019. "Rheology of Polyacrylonitrile/Lignin Blends in Ionic Liquids under Melt Spinning Conditions." Molecules 24, no. 14: 2650.

Journal article
Published: 02 February 2019 in Fermentation
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Extensive research has been done on examining the autotrophic growth of Acetobacterium woodii with gaseous substrates (hydrogen and carbon dioxide) to produce acetic acid. However, only limited work has been performed on the heterotrophic growth of A. woodii using pure sugars or lignocellulosic feedstocks-derived sugars as substrates. In this study, we examine the growth kinetics and acetic acid production of A. woodii on glucose and xylose. While good growth was observed with glucose as substrate, no significant growth was obtained on xylose. Kinetic studies were performed in batch culture using different concentrations of glucose, ranging from 5 g/L to 40 g/L. The highest acetate production of 6.919 g/L with a product yield of 0.76 g acetic acid/g glucose was observed with 10 g/L glucose as initial substrate concentration. When testing A. woodii on corn stover hydrolysate (CSH) and wheat straw hydrolysate (WSH) formed after pretreatment and enzymatic hydrolysis, we found that A. woodii showed acetic acid production of 7.64 g/L and a product yield of 0.70 g acetic acid/g of glucose on WSH, while the acetic acid production was 7.83 g/L with a product yield of 0.65 g acetic acid/g of glucose on CSH. These results clearly demonstrate that A. woodii performed similarly on pure substrates and hydrolysates, and that the processes were not inhibited by the heterogenous components present in the lignocellulosic feedstock hydrolysates.

ACS Style

Supriya C. Karekar; Keerthi Srinivas; Birgitte K. Ahring. Kinetic Study on Heterotrophic Growth of Acetobacterium woodii on Lignocellulosic Substrates for Acetic Acid Production. Fermentation 2019, 5, 17 .

AMA Style

Supriya C. Karekar, Keerthi Srinivas, Birgitte K. Ahring. Kinetic Study on Heterotrophic Growth of Acetobacterium woodii on Lignocellulosic Substrates for Acetic Acid Production. Fermentation. 2019; 5 (1):17.

Chicago/Turabian Style

Supriya C. Karekar; Keerthi Srinivas; Birgitte K. Ahring. 2019. "Kinetic Study on Heterotrophic Growth of Acetobacterium woodii on Lignocellulosic Substrates for Acetic Acid Production." Fermentation 5, no. 1: 17.

Review
Published: 19 May 2017 in Fermentation
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Carboxylic acids are traditionally produced from fossil fuels and have significant applications in the chemical, pharmaceutical, food, and fuel industries. Significant progress has been made in replacing such fossil fuel sources used for production of carboxylic acids with sustainable and renewable biomass resources. However, the merits and demerits of each carboxylic acid processing platform are dependent on the application of the final product in the industry. There are a number of studies that indicate that separation processes account for over 30% of the total processing costs in such processes. This review focuses on the sustainable processing of biomass resources to produce carboxylic acids. The primary focus of the review will be on a discussion of and comparison between existing biochemical processes for producing lower-chain fatty acids such as acetic-, propionic-, butyric-, and lactic acids. The significance of these acids stems from the recent progress in catalytic upgrading to produce biofuels apart from the current applications of the carboxylic acids in the food, pharmaceutical, and plastics sectors. A significant part of the review will discuss current state-of-art of techniques for separation and purification of these acids from fermentation broths for further downstream processing to produce high-value products.

ACS Style

Nanditha Murali; Keerthi Srinivas; Birgitte K. Ahring. Biochemical Production and Separation of Carboxylic Acids for Biorefinery Applications. Fermentation 2017, 3, 22 .

AMA Style

Nanditha Murali, Keerthi Srinivas, Birgitte K. Ahring. Biochemical Production and Separation of Carboxylic Acids for Biorefinery Applications. Fermentation. 2017; 3 (2):22.

Chicago/Turabian Style

Nanditha Murali; Keerthi Srinivas; Birgitte K. Ahring. 2017. "Biochemical Production and Separation of Carboxylic Acids for Biorefinery Applications." Fermentation 3, no. 2: 22.

Journal article
Published: 01 March 2017 in Bioresource Technology
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Volatile fatty acids (VFA) have been used as platform molecules for production of biofuels and bioproducts. In the current study, we examine the VFA production from wet-exploded corn stover through anaerobic fermentation using rumen bacteria. The total VFA yield (acetic acid equivalents) was found to increase from 22.8g/L at 2.5% total solids (TS) to 40.8g/L at 5% TS. It was found that the acetic acid concentration increased from 10g/L to 22g/L at 2.5% and 5% TS, respectively. An increased propionic acid production was seen between day 10 and 20 at 5% TS. Valeric acid (4g/L) was produced at 5% TS and not at 2.5% TS. Composition analysis showed that 50% of the carbohydrates were converted to VFA at 5% TS and 33% at 2.5% TS. Our results show that rumen fermentation of lignocellulosic biomass after wet explosion can produce high concentrations of VFA without addition of external enzymes of importance for the process economics of lignocellulosic biorefineries.

ACS Style

Nanditha Murali; Sebastian Fernandez; Birgitte Kiaer Ahring. Fermentation of wet-exploded corn stover for the production of volatile fatty acids. Bioresource Technology 2017, 227, 197 -204.

AMA Style

Nanditha Murali, Sebastian Fernandez, Birgitte Kiaer Ahring. Fermentation of wet-exploded corn stover for the production of volatile fatty acids. Bioresource Technology. 2017; 227 ():197-204.

Chicago/Turabian Style

Nanditha Murali; Sebastian Fernandez; Birgitte Kiaer Ahring. 2017. "Fermentation of wet-exploded corn stover for the production of volatile fatty acids." Bioresource Technology 227, no. : 197-204.

Journal article
Published: 05 January 2017 in AMB Express
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In this study we describe the heterologous expression of the recently identified cyanobacterial pathway for long chain alkane biosynthesis, involving the reduction of fatty acyl-ACP to fatty aldehyde and the subsequent conversion of this into alkanes, in the filamentous fungus Aspergillus carbonarius ITEM 5010. Genes originating from Synechococcus elongatus strain PCC7942, encoding acyl-ACP/CoA reductase and aldehyde deformylating oxygenase enzymes, were successfully expressed in A. carbonarius, which lead to the production of pentadecane and heptadecane, alkanes that have not been previously produced by this fungus. Titers of 0.2, 0.5 and 2.7 mg/l pentadecane and 0.8, 1.6 and 10.2 mg/l heptadecane were achieved using glucose, Yeast malt and oatmeal media, respectively. Besides producing alkanes, we found elevated levels of internal free fatty acids and triglycerides in the alkane producing transformant. These findings can indicate that a yet unidentified, native fatty aldehyde dehydrogenase channels back the fatty aldehydes into the fatty acid metabolism, thus competing for substrate with the heterologously expressed fatty aldehyde deformylating oxygenase. These findings will potentially facilitate the future application of robust, fungal cell factories for the production of advanced biofuels from various substrates.

ACS Style

Malavika Sinha; István Weyda; Annette Sørensen; Kenneth S. Bruno; Birgitte K. Ahring. Alkane biosynthesis by Aspergillus carbonarius ITEM 5010 through heterologous expression of Synechococcus elongatus acyl-ACP/CoA reductase and aldehyde deformylating oxygenase genes. AMB Express 2017, 7, 1 -9.

AMA Style

Malavika Sinha, István Weyda, Annette Sørensen, Kenneth S. Bruno, Birgitte K. Ahring. Alkane biosynthesis by Aspergillus carbonarius ITEM 5010 through heterologous expression of Synechococcus elongatus acyl-ACP/CoA reductase and aldehyde deformylating oxygenase genes. AMB Express. 2017; 7 (1):1-9.

Chicago/Turabian Style

Malavika Sinha; István Weyda; Annette Sørensen; Kenneth S. Bruno; Birgitte K. Ahring. 2017. "Alkane biosynthesis by Aspergillus carbonarius ITEM 5010 through heterologous expression of Synechococcus elongatus acyl-ACP/CoA reductase and aldehyde deformylating oxygenase genes." AMB Express 7, no. 1: 1-9.

Journal article
Published: 01 September 2015 in Bioresource Technology
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The logging and lumbering industry in the Pacific Northwest region generates huge amount of forest residues, offering an inexpensive raw material for biorefineries. Wet explosion (WEx) pretreatment was applied to the recalcitrant biomass to optimize process conditions including temperature (170-190 °C), time (10-30 min), and oxygen loading (0.5-7.5% of DM) through an experimental design. Optimal pH for enzymatic hydrolysis of the optimized samples and a complete mass balance have been evaluated. Results indicated that cellulose digestibility improved in all conditions tested with maximum digestibility achieved at 190 °C, time 30 min, and oxygen loading of 7.5%. Glucose yield at optimal pH of 5.5 was 63.3% with an excellent recovery of cellulose and lignin of 99.9% and 96.3%, respectively. Hemicellulose sugars recovery for xylose and mannose was found to be 69.2% and 76.0%, respectively, indicating that WEx is capable of producing relative high sugar yield even from the recalcitrant forest residues.

ACS Style

Rajib Biswas; Philip J. Teller; Birgitte K. Ahring. Pretreatment of forest residues of Douglas fir by wet explosion for enhanced enzymatic saccharification. Bioresource Technology 2015, 192, 46 -53.

AMA Style

Rajib Biswas, Philip J. Teller, Birgitte K. Ahring. Pretreatment of forest residues of Douglas fir by wet explosion for enhanced enzymatic saccharification. Bioresource Technology. 2015; 192 ():46-53.

Chicago/Turabian Style

Rajib Biswas; Philip J. Teller; Birgitte K. Ahring. 2015. "Pretreatment of forest residues of Douglas fir by wet explosion for enhanced enzymatic saccharification." Bioresource Technology 192, no. : 46-53.

Journal article
Published: 01 April 2015 in Fungal Biology
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The filamentous fungus, Asperigillus carbonarius, is able to produce a series of hydrocarbons in liquid culture using lignocellulosic biomasses, such as corn stover and switch grass as carbon source. The hydrocarbons produced by the fungus show similarity to jet fuel composition and might have industrial application. The production of hydrocarbons was found to be dependent on type of media used. Therefore, ten different carbon sources (oat meal, wheat bran, glucose, carboxymethyl cellulose, avicel, xylan, corn stover, switch grass, pretreated corn stover, and pretreated switch grass) were tested to identify the maximum number and quantity of hydrocarbons produced. Several hydrocarbons were produced include undecane, dodecane, tetradecane, hexadecane 2,4-dimethylhexane, 4-methylheptane, 3-methyl-1-butanol, ethyl benzene, o-xylene. Oatmeal was found to be the carbon source resulting in the largest amounts of hydrocarbon products. The production of fungal hydrocarbons, especially from lignocellulosic biomasses, holds a great potential for future biofuel production whenever our knowledge on regulators and pathways increases.

ACS Style

Malavika Sinha; Annette Sørensen; Aftab Ahamed; Birgitte Kiær Ahring. Production of hydrocarbons by Aspergillus carbonarius ITEM 5010. Fungal Biology 2015, 119, 274 -282.

AMA Style

Malavika Sinha, Annette Sørensen, Aftab Ahamed, Birgitte Kiær Ahring. Production of hydrocarbons by Aspergillus carbonarius ITEM 5010. Fungal Biology. 2015; 119 (4):274-282.

Chicago/Turabian Style

Malavika Sinha; Annette Sørensen; Aftab Ahamed; Birgitte Kiær Ahring. 2015. "Production of hydrocarbons by Aspergillus carbonarius ITEM 5010." Fungal Biology 119, no. 4: 274-282.

Journal article
Published: 17 February 2015 in BioEnergy Research
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Lignocellulosic biomass resources especially agricultural and forests residues, perennial crops, farm wastes, and the organic fraction of municipal solid waste hold significant potential for the widespread production of sustainable fuels, chemicals, and bioproducts worldwide. For biochemical conversion processes, deconstruction of lignocellulosic biomass into its components (cellulose, hemicellulose, and lignin) for further microbial conversion has been a major challenge due to the recalcitrant nature of lignocellulose. Thus pretreatment is prerequisite for efficient hydrolysis of lignocellulose and cost for such treatment is currently about one third of the overall processing costs in a cellulosic biorefinery. Thus, the development of a more efficient and cost-effective pretreatment method is crucial for the commercialization of lignocellulosic biorefineries. Wet explosion (WEx), a thermochemical pretreatment method with additional features of oxygen addition and explosive decompression, can be adjusted to different biomass feedstock and to subsequent bio-catalytic and microbial processes. The WEx pretreatment method has been successfully applied in combination with both microbial fermentation and anaerobic digestion processes using both agricultural and forest residues as well as manure fibers. Steam explosion, represents a related process to WEx pretreatment where high pressure is used but no oxygen is added. This process has been tested in demonstration scale while WEx is on its way to commercialization. Presented here is a summary of the basic concepts and parameters involved in WEx pretreatment.

ACS Style

Rajib Biswas; Hinrich Uellendahl; Birgitte K. Ahring. Wet Explosion: a Universal and Efficient Pretreatment Process for Lignocellulosic Biorefineries. BioEnergy Research 2015, 8, 1101 -1116.

AMA Style

Rajib Biswas, Hinrich Uellendahl, Birgitte K. Ahring. Wet Explosion: a Universal and Efficient Pretreatment Process for Lignocellulosic Biorefineries. BioEnergy Research. 2015; 8 (3):1101-1116.

Chicago/Turabian Style

Rajib Biswas; Hinrich Uellendahl; Birgitte K. Ahring. 2015. "Wet Explosion: a Universal and Efficient Pretreatment Process for Lignocellulosic Biorefineries." BioEnergy Research 8, no. 3: 1101-1116.

Journal article
Published: 01 October 2014 in Bioresource Technology
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Co-cultivation of fungi may be an excellent system for on-site production of cellulolytic enzymes in a single bioreactor. Enzyme supernatants from mixed cultures of Trichoderma reesei RutC30, with either the novel Aspergillus saccharolyticus AP, Aspergillus carbonarius ITEM 5010 or Aspergillus niger CBS 554.65 cultivated in solid-state fermentation were tested for avicelase, FPase, endoglucanase and beta-glucosidase activity as well as in hydrolysis of pretreated wheat straw. Around 30% more avicelase activity was produced in co-cultivation of T. reesei and A. saccharolyticus than in T. reesei monoculture, suggesting synergistic interaction between those fungi. Fermentation broths of mixed cultures of T. reesei with different Aspergillus strains resulted in approx. 80% efficiency of hydrolysis which was comparable to results obtained using blended supernatants from parallel monocultures. This indicates that co-cultivation of T. reesei with A. saccharolyticus or A. carbonarius could be a competitive alternative for monoculture enzyme production and a cheaper alternative to commercial enzymes.

ACS Style

Marta Kolasa; Birgitte Kiær Ahring; Peter Stephensen Lübeck; Mette Lübeck. Co-cultivation of Trichoderma reesei RutC30 with three black Aspergillus strains facilitates efficient hydrolysis of pretreated wheat straw and shows promises for on-site enzyme production. Bioresource Technology 2014, 169, 143 -148.

AMA Style

Marta Kolasa, Birgitte Kiær Ahring, Peter Stephensen Lübeck, Mette Lübeck. Co-cultivation of Trichoderma reesei RutC30 with three black Aspergillus strains facilitates efficient hydrolysis of pretreated wheat straw and shows promises for on-site enzyme production. Bioresource Technology. 2014; 169 ():143-148.

Chicago/Turabian Style

Marta Kolasa; Birgitte Kiær Ahring; Peter Stephensen Lübeck; Mette Lübeck. 2014. "Co-cultivation of Trichoderma reesei RutC30 with three black Aspergillus strains facilitates efficient hydrolysis of pretreated wheat straw and shows promises for on-site enzyme production." Bioresource Technology 169, no. : 143-148.

Journal article
Published: 05 July 2014 in Analytical and Bioanalytical Chemistry
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Compared to traditional IR methods, Raman spectroscopy has the advantage of only minimal interference from water when measuring aqueous samples, which makes this method potentially useful for in situ monitoring of important industrial bioprocesses. This study demonstrates real-time monitoring of a Saccharomyces cerevisiae fermentation process using a Raman spectroscopy instrument equipped with a robust sapphire ball probe. A method was developed to correct the Raman signal for the attenuation caused by light scattering cell particulate, hence enabling quantification of reaction components and possibly measurement of yeast cell concentrations. Extinction of Raman intensities to more than 50 % during fermentation was normalized with approximated extinction expressions using Raman signal of water around 1,627 cm−1 as internal standard to correct for the effect of scattering. Complicated standard multi-variant chemometric techniques, such as PLS, were avoided in the quantification model, as an attempt to keep the monitoring method as simple as possible and still get satisfactory estimations. Instead, estimations were made with a two-step approach, where initial scattering correction of attenuated signals was followed by linear regression. In situ quantification measurements of the fermentation resulted in root mean square errors of prediction (RMSEP) of 2.357, 1.611, and 0.633 g/L for glucose, ethanol, and yeast concentrations, respectively.

ACS Style

Jens Asmus Iversen; Rolf W. Berg; Birgitte Kiær Ahring. Quantitative monitoring of yeast fermentation using Raman spectroscopy. Analytical and Bioanalytical Chemistry 2014, 406, 4911 -4919.

AMA Style

Jens Asmus Iversen, Rolf W. Berg, Birgitte Kiær Ahring. Quantitative monitoring of yeast fermentation using Raman spectroscopy. Analytical and Bioanalytical Chemistry. 2014; 406 (20):4911-4919.

Chicago/Turabian Style

Jens Asmus Iversen; Rolf W. Berg; Birgitte Kiær Ahring. 2014. "Quantitative monitoring of yeast fermentation using Raman spectroscopy." Analytical and Bioanalytical Chemistry 406, no. 20: 4911-4919.

Journal article
Published: 20 June 2014 in Applied Microbiology and Biotechnology
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An in situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution NMR (HR-NMR) spectroscopy. In situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at 500 MHz, and aliquots of the bioreactor contents were taken for 600-MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol, and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in situ NMR bioreactor facilitated monitoring of the fermentation process, enabling identification of intermediate and endpoint metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts.

ACS Style

Junfeng Xue; Nancy G. Isern; R. James Ewing; Andrei V. Liyu; Jesse A. Sears; Harlan Knapp; Jens Iversen; Daniel R. Sisk; Birgitte K. Ahring; Paul D. Majors. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles. Applied Microbiology and Biotechnology 2014, 98, 8367 -8375.

AMA Style

Junfeng Xue, Nancy G. Isern, R. James Ewing, Andrei V. Liyu, Jesse A. Sears, Harlan Knapp, Jens Iversen, Daniel R. Sisk, Birgitte K. Ahring, Paul D. Majors. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles. Applied Microbiology and Biotechnology. 2014; 98 (19):8367-8375.

Chicago/Turabian Style

Junfeng Xue; Nancy G. Isern; R. James Ewing; Andrei V. Liyu; Jesse A. Sears; Harlan Knapp; Jens Iversen; Daniel R. Sisk; Birgitte K. Ahring; Paul D. Majors. 2014. "New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles." Applied Microbiology and Biotechnology 98, no. 19: 8367-8375.

Journal article
Published: 01 January 2014 in SpringerPlus
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The aim of the present study was to compare bioethanol production from wet exploded corn stover (WECS) and loblolly pine (WELP) hydrolyzed with in-house and commercial enzymes and fermented separately (SHF) and simultaneously (SSF). In-house enzymes produced from Trichoderma reesei, RUT-C30 and a novel fungal strain, Aspergillus saccharolyticus were loaded as 5 and 15 FPU/g glucan and supplemented with 10 and 30 CBU/g glucan, respectively. For hydrolysis and fermentation, slurries of WECS and WELP at 5 and 10% (w/w) solids loading (SL) were utilized. Saccharomyces cerevisae was used for ethanol fermentation at 33°C. Maximally, 15.6 g/L and 13.4 g/L (corresponding to theoretical ethanol yield of 76% and 67%, respectively) were achieved in SSF process from WECS and WELP, respectively at 5% SL and 15 FPU/g glucan loading of in-house enzymes. Ethanol concentrations in all cases were higher for SSF compared to SHF under same conditions. A cross comparison of SSF with commercial enzymes (Celluclast 1.5 L + Novozym 188) showed highest ethanol concentration of 17.3 g/L and 15.4 g/L (corresponding to theoretical ethanol yield of 84% and 77%, respectively) from WECS and WELP, respectively at 5% SL and 15 FPU/g glucan. These findings demonstrated that in-house enzymes were comparable to commercial enzymes as these fungi produced other lignocellulolytic enzymes beyond cellulase and hence enhanced the overall enzyme activity.

ACS Style

Vandana Rana; Anahita D Eckard; Birgitte K Ahring. Comparison of SHF and SSF of wet exploded corn stover and loblolly pine using in-house enzymes produced from T. reesei RUT C30 and A. saccharolyticus. SpringerPlus 2014, 3, 516 .

AMA Style

Vandana Rana, Anahita D Eckard, Birgitte K Ahring. Comparison of SHF and SSF of wet exploded corn stover and loblolly pine using in-house enzymes produced from T. reesei RUT C30 and A. saccharolyticus. SpringerPlus. 2014; 3 (1):516.

Chicago/Turabian Style

Vandana Rana; Anahita D Eckard; Birgitte K Ahring. 2014. "Comparison of SHF and SSF of wet exploded corn stover and loblolly pine using in-house enzymes produced from T. reesei RUT C30 and A. saccharolyticus." SpringerPlus 3, no. 1: 516.

Journal article
Published: 01 January 2013 in AMB Express
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Sugarcane bagasse is a potential feedstock for cellulosic ethanol production, rich in both glucan and xylan. This stresses the importance of utilizing both C6 and C5 sugars for conversion into ethanol in order to improve the process economics. During processing of the hydrolysate degradation products such as acetate, 5-hydroxymethylfurfural (HMF) and furfural are formed, which are known to inhibit microbial growth at higher concentrations. In the current study, conversion of both glucose and xylose sugars into ethanol in wet exploded bagasse hydrolysates was investigated without detoxification using Scheffersomyces (Pichia) stipitis CBS6054, a native xylose utilizing yeast strain. The sugar utilization ratio and ethanol yield (Yp/s) ranged from 88-100% and 0.33-0.41 ± 0.02 g/g, respectively, in all the hydrolysates tested. Hydrolysate after wet explosion at 185°C and 6 bar O2, composed of mixed sugars (glucose and xylose) and inhibitors such as acetate, HMF and furfural at concentrations of 3.2 ± 0.1, 0.4 and 0.5 g/l, respectively, exhibited highest cell growth rate of 0.079 g/l/h and an ethanol yield of 0.39 ± 0.02 g/g sugar converted. Scheffersomyces stipitis exhibited prolonged fermentation time on bagasse hydrolysate after wet explosion at 200°C and 6 bar O2 where the inhibitors concentration was further increased. Nonetheless, ethanol was produced up to 18.7 ± 1.1 g/l resulting in a yield of 0.38 ± 0.02 g/g after 82 h of fermentation.

ACS Style

Rajib Biswas; Hinrich Uellendahl; Birgitte K Ahring. Conversion of C6 and C5 sugars in undetoxified wet exploded bagasse hydrolysates using Scheffersomyces (Pichia) stipitis CBS6054. AMB Express 2013, 3, 42 -42.

AMA Style

Rajib Biswas, Hinrich Uellendahl, Birgitte K Ahring. Conversion of C6 and C5 sugars in undetoxified wet exploded bagasse hydrolysates using Scheffersomyces (Pichia) stipitis CBS6054. AMB Express. 2013; 3 (1):42-42.

Chicago/Turabian Style

Rajib Biswas; Hinrich Uellendahl; Birgitte K Ahring. 2013. "Conversion of C6 and C5 sugars in undetoxified wet exploded bagasse hydrolysates using Scheffersomyces (Pichia) stipitis CBS6054." AMB Express 3, no. 1: 42-42.

Journal article
Published: 01 January 2013 in Biotechnology for Biofuels
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Caldicellulosiruptor saccharolyticus is a thermophilic, Gram-positive, non-spore forming, strictly anaerobic bacterium of interest in potential industrial applications, including the production of biofuels such as hydrogen or ethanol from lignocellulosic biomass through fermentation. High-resolution, solution-state nuclear magnetic resonance (NMR) spectroscopy is a useful method for the identification and quantification of metabolites that result from growth on different substrates. NMR allows facile resolution of isomeric (identical mass) constituents and does not destroy the sample.

ACS Style

Nancy G Isern; Junfeng Xue; Jaya V Rao; John R Cort; Birgitte K Ahring. Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy. Biotechnology for Biofuels 2013, 6, 47 -47.

AMA Style

Nancy G Isern, Junfeng Xue, Jaya V Rao, John R Cort, Birgitte K Ahring. Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy. Biotechnology for Biofuels. 2013; 6 (1):47-47.

Chicago/Turabian Style

Nancy G Isern; Junfeng Xue; Jaya V Rao; John R Cort; Birgitte K Ahring. 2013. "Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy." Biotechnology for Biofuels 6, no. 1: 47-47.

Journal article
Published: 30 June 2012 in Bioresource Technology
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We present quantitative analysis of pretreatment for obtaining high conversion and release of sugars from loblolly pine. We use wet explosion (WEx): wet oxidation followed by steam explosion and enzymatic hydrolysis (EH) at high dry matter to solubilize sugars. WEx was conducted at 25% (w/w) solids in presence of oxygen at pressures 6.5–7.2 bar, temperatures 170–175 °C and residence time from 20 to 22.5 min. EH of pretreated samples was performed by Cellic® Ctec2 (60 mg protein/g cellulose) and Cellic® Htec2 enzymes (10% of Ctec2) at 50 °C for 72 h. At the optimal WEx condition 96% cellulose and nearly 100% hemicellulose yield were obtained. The final concentrations of monomeric sugars were 152 g/L of glucose, 67 g/L of xylose, and 67 g/L of minor sugars (galactose, arabinose and mannose). Compared to previous work WEx seems to be superior for releasing high concentrations of monomeric sugars.

ACS Style

Diwakar Rana; Vandana Rana; Birgitte K. Ahring. Producing high sugar concentrations from loblolly pine using wet explosion pretreatment. Bioresource Technology 2012, 121, 61 -67.

AMA Style

Diwakar Rana, Vandana Rana, Birgitte K. Ahring. Producing high sugar concentrations from loblolly pine using wet explosion pretreatment. Bioresource Technology. 2012; 121 ():61-67.

Chicago/Turabian Style

Diwakar Rana; Vandana Rana; Birgitte K. Ahring. 2012. "Producing high sugar concentrations from loblolly pine using wet explosion pretreatment." Bioresource Technology 121, no. : 61-67.