Scale‐up and integration of alkaline hydrogen peroxide pretreatment, enzymatic hydrolysis, and ethanolic fermentation

Banerjee, Goutami; Car, Suzana; Liu, Tongjun; Williams, Daniel L.; Meza, Sarynna López; Walton, Jonathan D.; Hodge, David B.

doi:10.1002/bit.24385

Cited by 114 publications

(74 citation statements)

References 47 publications

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“…Upon analyzing the results from a one-way ANOVA test (available in the Additional file 1), it became apparent that neither response was significantly impacted by the solids loading during deacetylation, while the reaction time was a minor factor-the responses were largely driven by reaction temperature and the sodium hydroxide loading. We also found that in experiments conducted at sodium hydroxide loadings of less than 1.5 g/g acetate, the pH of the post-extraction liquor was consistently in a neutral range (6)(7)(8). This indicates that the sodium hydroxide is actually consumed in the reaction, rather than simply acting as a catalyst.…”

Section: Resultsmentioning

confidence: 63%

“…Other processes have been explored that use neutral, ionic liquids or alkaline chemistry, including hydrothermal pretreatment [5], ionic liquid pretreatment using imidazole [6], peroxide pretreatment, oxidative lime pretreatment, and pulping-like sodium hydroxide pretreatments [7][8][9][10][11][12][13][14][15]. However, these processes are typically intended to function as a stand-alone pretreatment, and the severity of the process is increased to enable effective enzymatic hydrolysis with no further processing.…”

Section: Introductionmentioning

confidence: 99%

“…However, these processes are typically intended to function as a stand-alone pretreatment, and the severity of the process is increased to enable effective enzymatic hydrolysis with no further processing. The increased severity, while effective in achieving high cellulose conversion yields through lignin extraction, also results in the solubilization and degradation of a significant fraction of hemicellulosic sugars; in many cases, greater than 20 % is found in the alkaline liquor stream [8,11]. Due to the low concentrations of sugars and comparatively high concentrations of undesirable components, including salts and acetic acid, this stream is typically treated as waste.…”

Section: Introductionmentioning

confidence: 99%

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Development and characterization of a high-solids deacetylation process

Shekiro

Chen

Smith

et al. 2016

Sustain Chem Process

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Background: Dilute-acid pretreatment has proven to be a robust means of converting herbaceous feedstock to fermentable sugars. However, it also releases acetic acid, a known fermentation inhibitor, from acetyl groups present in the biomass. A mild, dilute alkaline extraction stage was implemented prior to acid pretreatment to separate acetic acid from the hydrolysate sugar stream. This step, termed deacetylation, improved the glucose and xylose yields from enzymatic hydrolysis and ethanol yields from fermentation of the sugars relative to the control experiments using dilute-acid pretreatment of native corn stover without deacetylation. While promising, deacetylation as it was historically practiced is conducted at low solids loadings, and at fixed conditions. Thus, many questions have been left unanswered, including the relationship between sodium hydroxide and solids loading, and acetate and xylan solubilization, as well as the impact of temperature and residence time on the process efficacy.Results: A central composite experiment was designed to evaluate the impact of solids loading, sodium hydroxide loading, reaction time and temperature during deacetylation on the acetate and xylan solubilization of corn stover. Using the ANOVA test, it became apparent that neither of the responses was significantly impacted by the solids loading, while the reaction time was a minor factor-the responses were largely driven by reaction temperature and the sodium hydroxide loading. Based on the results, we successfully demonstrated the ability to transition the low-solids (10 % w/w) deacetylation process to a higher-solids process (30 % w/w) with minimal impact on the ability to extract acetate from biomass. Conditions were selected to minimize xylose loss during deacetylation, while also removing 70 % of acetyl groups. The impact of selected conditions on the enzymatic hydrolysis and fermentation was further investigated. Conclusions:Evaluation of the whole-process impact demonstrated that despite the upfront reduction in carbohydrate loss during deacetylation, the overall process sugar yields were depressed by the high-solids, low alkali process relative to the historical control. Consequently, ethanol titers were reduced, though strong fermentation performance was still observed, indicating that 70 % acetate removal is sufficient to depress acetic acid concentrations to a level that does not substantially inhibit ethanol fermentation by rZymomonas.

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Section: Resultsmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development and characterization of a high-solids deacetylation process

Shekiro

Chen

Smith

et al. 2016

Sustain Chem Process

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“…Alkaline hydrogen peroxide (AHP) pretreatment is one such approach that has been studied since the 1980s [6][7][8]. AHP results in significant improvement in the enzymatic digestibility of commelinid monocots including corn stover and wheat straw [9,10] and can generate hydrolysates with more than 100 g/L of monomeric sugars that are fermentable without detoxification (manuscript in preparation). The mechanisms by which AHP pretreatment reduces recalcitrance include the fragmentation and solubilization of ester-linked xylan and lignin [11,12], as well as the oxidation, solubilization, and at high H 2 O 2 loadings, mineralization of lignin [7].…”

Section: Introductionmentioning

confidence: 99%

Rapid and Effective Oxidative Pretreatment of Woody Biomass at Mild Reaction Conditions and Low Oxidant Loadings

Li¹,

Chen²,

Hegg³

et al. 2015

New Microbial Technologies for Advanced Biofuels

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Background: One route for producing cellulosic biofuels is by the fermentation of lignocellulose-derived sugars generated from a pretreatment that can be effectively coupled with an enzymatic hydrolysis of the plant cell wall. While woody biomass exhibits a number of positive agronomic and logistical attributes, these feedstocks are significantly more recalcitrant to chemical pretreatments than herbaceous feedstocks, requiring higher chemical and energy inputs to achieve high sugar yields from enzymatic hydrolysis. We previously discovered that alkaline hydrogen peroxide (AHP) pretreatment catalyzed by copper(II) 2,2΄-bipyridine complexes significantly improves subsequent enzymatic glucose and xylose release from hybrid poplar heartwood and sapwood relative to uncatalyzed AHP pretreatment at modest reaction conditions (room temperature and atmospheric pressure). In the present work, the reaction conditions for this catalyzed AHP pretreatment were investigated in more detail with the aim of better characterizing the relationship between pretreatment conditions and subsequent enzymatic sugar release. Results: We found that for a wide range of pretreatment conditions, the catalyzed pretreatment resulted in significantly higher glucose and xylose enzymatic hydrolysis yields (as high as 80% for both glucose and xylose) relative to uncatalyzed pretreatment (up to 40% for glucose and 50% for xylose). We identified that the extent of improvement in glucan and xylan yield using this catalyzed pretreatment approach was a function of pretreatment conditions that included H 2 O 2 loading on biomass, catalyst concentration, solids concentration, and pretreatment duration. Based on these results, several important improvements in pretreatment and hydrolysis conditions were identified that may have a positive economic impact for a process employing a catalyzed oxidative pretreatment. These improvements include identifying that: (1) substantially lower H 2 O 2 loadings can be used that may result in up to a 50-65% decrease in H 2 O 2 application (from 100 mg H 2 O 2 /g biomass to 35-50 mg/g) with only minor losses in glucose and xylose yield, (2) a 60% decrease in the catalyst concentration from 5.0 mM to 2.0 mM (corresponding to a catalyst loading of 25 μmol/g biomass to 10 μmol/g biomass) can be achieved without a subsequent loss in glucose yield, (3) an order of magnitude improvement in the time required for pretreatment (minutes versus hours or days) can be realized using the catalyzed pretreatment approach, and (4) enzyme dosage can be reduced to less than 30 mg protein/g glucan and potentially further with only minor losses in glucose and xylose yields. In addition, we established that the reaction rate is improved in both catalyzed and uncatalyzed AHP pretreatment by increased solids concentrations.

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“…Esse pré-tratamento adicional tem como objetivo principal promover a deslignificação da biomassa [16].…”

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Otimização de parâmetros operacionais do pré-tratamento da palha de cana-de-açúcar

et al. 2017

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O compromisso de atender as necessidades do presente sem comprometer a possibilidade de suprir as necessidades das gerações futuras, torna a diversificação da matriz energética brasileira e mundial fator cada vez mais compulsório. Diante disso, o uso de biomassas lignocelulósicas para obtenção de combustíveis mais limpos do ponto de vista ambiental é amplamente discutido na atualidade. O etanol combustível pode ser obtido a partir de fontes alternativas de energia, como as biomassas lignocelulósicas. Esse tipo de matéria-prima possui elevado teor de açúcares fermentescíveis em sua composição. Porém, esses não se encontram diretamente disponíveis, sendo necessárias etapas adicionais para sua obtenção. Este trabalho teve como objetivo a otimização da etapa de pré-tratamento da palha de cana-de-açúcar, por meio de um delineamento experimental 2 2 com três repetições no ponto central. As variáveis de estudo foram: a razão palha/água (m/v) na etapa de pré-tratamento hidrotérmico e a temperatura reacional do pré-tratamento alcalino sequencial ao hidrotérmico. O estudo mostrou que a deslignificação não promoveu melhora significativa na conversão da celulose em glicose na hidrólise enzimática, o que não justifica a realização dessa etapa adicional, nas condições avaliadas. Já o pré-tratamento hidrotérmico apresentou bons resultados, alcançando na etapa de hidrólise conversões superiores a 85%, em especial para as razões palha/água 1:6,7 e 1:20 (m/v).Palavras-chave: palha de cana-de-açúcar, otimização, pré-tratamento sequencial, pré-tratamento hidrotérmico, bioetanolThe commitment to meeting the needs of the present without compromising the ability to meet the needs of future generations makes the diversification of the Brazilian and the global energy matrix a compulsory factor. Thus, the use of lignocellulosic biomass to obtain cleaner fuels from an environmental point of view is widely discussed today. Fuel ethanol has been obtained from alternative energy sources, as lignocellulosic biomass. This type of biomass has high content of fermentable sugars. However, these sugars were not directly available, which need to include additional steps in the process to achieve this goal. This study aims to carry out an operational parameters optimization in the sugarcane straw pretreatment through a 2 2 experimental design with three replications at the central point. The study variables were: straw-water ratio (m/v) in the hydrothermal pretreatment and the temperature reaction in the alkaline pretreatment, sequential to hydrothermal. The study reveals that the delignification did not promote significant improvements in glucose conversion during the enzymatic hydrolysis. Thus, this addition step was not justified, under the evaluated conditions. Furthermore, the hydrothermal pretreatment showed good results reaching conversions higher than 85% in the hydrolysis step, in particular for the straw-water ratios 1:6.7 and 1:20 (m/v).

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Scale‐up and integration of alkaline hydrogen peroxide pretreatment, enzymatic hydrolysis, and ethanolic fermentation

Cited by 114 publications

References 47 publications

Development and characterization of a high-solids deacetylation process

Development and characterization of a high-solids deacetylation process

Rapid and Effective Oxidative Pretreatment of Woody Biomass at Mild Reaction Conditions and Low Oxidant Loadings

Otimização de parâmetros operacionais do pré-tratamento da palha de cana-de-açúcar

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