Soaking In Aqueous Ammonia Pretreatment Research Articles

Aqueous ammonia soaking pretreatment of spent coffee grounds for enhanced enzymatic hydrolysis: A bacterial cellulose production application

In the present work, aqueous ammonia soaking (AAS) was examined as a potential pretreatment stage of spent coffee grounds (SCG), to enhance their enzymatic hydrolysis. The studied parameters were treatment time (30–360 min), SCG solids loading (5–20% w/v), and temperature (40–80 °C). Each parameter was studied individually while keeping the other parameters constant. Following the AAS, the pretreated SCG were subjected to enzymatic hydrolysis using commercial preparations of cellulases and hemicellulases. The obtained hydrolysate was subsequently used as an alternative carbon source for the production of bacterial cellulose. Fourier-transform infrared spectroscopy (FT-IR), Confocal Laser Scanning Microscopy (CLSM), and Scanning Electron Microscopy (SEM) of the samples before and after pretreatment were performed in order to evaluate compositional and morphological changes of the biomass materials. Reducing sugars obtained from the ammonia-pretreated and saccharified samples were measured by HPLC. Optimization for total sugars present in the enzymatic hydrolysate was achieved at 120 min, 10% w/v solids concentration, 60 °C with the use of ∼28–30% v/v aqueous ammonia, where 8.34 ± 1.31 mgsugars/mLhydrolysate were obtained. The SCG hydrolysate was used as the sole carbon source for the growth of a Komagataeibacter sucrofermentans strain, and 2.04 ± 0.04 g/L of bacterial cellulose was therefrom produced.

Techno-economic analysis of furfural production with various pretreatment of oil palm empty fruit bunches using SuperPro Designer

Oil palm empty fruit bunches (OPEFB) are solid wastes that can be processed into several chemicals, one of which is furfural. Furfural can be used as a solvent and intermediate compound in many chemical industries. Nowadays, furfural needs in Indonesia are fulfilled through import, especially from China. Therefore, developing a furfural plant in Indonesia is required to fulfill the needs for furfural in Indonesia and surrounding countries. Based on that necessity, this study provides the preliminary study and simulation of furfural production from OPEFB by three kinds of pretreatment methods: soaking in aqueous ammonia (SAA), steam explosion (SE), and ammonia fiber expansion (AFEX). Simulation is conducted using SuperPro Designer Academic License to get the plant’s mass & energy balance and economic parameters. The plant will be built in Kawasan Industri Dumai, Pelintung, Riau. Then, by assuming 7920 hours annual operation time and 2000 kg OPEFB/h input rate, the simulations showed that furfural production with AFEX pretreatment is more economically feasible than with SAA and SE pretreatment. The value of profitability parameters as follows: Internal Rate of Return (IRR) = 49.77%, Net Present Value (NPV) at i = 9.6% = USD 39,210,000, and payback time = 1.75 years.

Life Cycle Perspectives of Using Non-Pelleted vs. Pelleted Corn Stover in a Cellulosic Biorefinery

Cellulosic biorefineries have attracted interest due to the growing energy security and environmental concerns related to fossil fuel-based energy and chemicals. Using pelleted biomass as a biorefinery feedstock can reduce their processing inputs while improving biomass handling and transportation. However, it is still questionable whether energy and emission savings from feedstock transportation and processing can justify pelletization. A life cycle assessment approach was used to compare energy consumption and greenhouse gas (GHG) emissions from pelleted and non-pelleted corn stover as a biorefinery feedstock. Operations considered were pelleting, transportation, and soaking in aqueous ammonia (SAA) pretreatment. Despite greater GHG emissions (up to 25 times higher than the transportation) generated from the pelleting process, the model showed a significant opportunity to offset and even reduce overall GHG emissions considering the pretreatment process benefits. Our process energy analysis showed that SAA pretreatment of pelleted biomass required significantly lower energy inputs (56%) due to the lower-severity pretreatment’s effectiveness. Higher pretreatment solid loadings are allowed when pelleted biomass is used and this reduces the process chemicals and water requirements by 56% and 49%, respectively. This study demonstrated that the SAA pretreatment of pelleted biomass might be a feasible option as the cellulosic biorefinery feedstock.

Comparative evaluation of biochemical methane potential of various types of Ugandan agricultural biomass following soaking aqueous ammonia pretreatment

The feasibility of pretreatment involving soaking in aqueous ammonia (SAA) for the anaerobic digestion (AD) of eight different types of agricultural biomass of Ugandan origin was investigated. Moderate pretreatment temperatures of 60 and 90°C were employed, and the NH3 concentration, solid-to-liquid ratio, and pretreatment time were fixed at 15.0% (w/w), 1:6, and 6h, respectively. The delignification efficiencies of the SAA pretreatment ranged from 51.1 to 76.6%, and the maximum value was observed for maize bran pretreated at 90°C. Biochemical methane potential experiments proved that the breaking of the complex bonds of lignin made fermentable sugars easily accessible to microorganisms. In all cases, the SAA pretreatment enhanced the methane potential of the eight types of Ugandan biomass compared with its untreated counterparts. The pretreated maize bran exhibited the highest methane yield of 291.5mL CH4/g COD, which is 83.1% of the theoretical conversion. SAA followed by AD is useful for employing Ugandan agricultural biomass as a renewable energy source.

On the Effect of Aqueous Ammonia Soaking Pre-Treatment on Continuous Anaerobic Digestion of Digested Swine Manure Fibers.

(1) Background: The continuously increasing demand for renewable energy sources renders anaerobic digestion as one of the most promising technologies for renewable energy production. Due to the animal production intensification, manure is being used as the primary feedstock for most biogas plants. Their economical profitable operation, however, relies on increasing the methane yield from the solid fraction of manure, which is not so easily degradable. The solid fraction after anaerobic digestion, the so-called digested fibers, consists mainly of hardly biodegradable material and comes at a lower mass per unit volume of manure compared to the solid fraction before anaerobic digestion. Therefore, investigation on how to increase the biodegradability of digested fibers is very relevant. So far, Aqueous Ammonia Soaking (AAS), has been successfully applied on digested fibers separated from the effluent of a manure-fed, full-scale anaerobic digester to enhance their methane productivity in batch experiments. (2) Methods: In the present study, continuous experiments at a mesophilic (38 °C) CSTR-type anaerobic digester fed with swine manure first and a mixture of manure with AAS-treated digested fibers in the sequel, were performed. Anaerobic Digestion Model 1 (ADM1) previously fitted on manure fed digester was used in order to assess the effect of the addition of AAS-pre-treated digested manure fibers on the kinetics of anaerobic digestion process. (3) Results and Conclusions: The methane yield of AAS-treated digested fibers under continuous operation was 49–68% higher than that calculated in batch experiments in the past. It was found that AAS treatment had a profound effect mainly on the disintegration/hydrolysis rate of particulate carbohydrates. Comparison of the data obtained in the present study with the data obtained with AAS-pre-treated raw manure fibers in the past revealed that hydrolysis kinetics after AAS pre-treatment were similar for both types of biomasses.

Hydrodynamic Analysis of Hydrolysis of the Rice Husk Cellulose by Using CFD Modeling

The importance of the rule and the demand of glucose trigger the seeking of the alternative materials to produce glucose. One of the alternatives used is the utilization of biomass such as the rice husk to produce glucose. Rice husk is the agricultural residue whose availability is very abundant. In this research, rice husk contained cellulose (42.2 %), hemicellulose (17.04 %), and lignin (20.46 %). First step to produce the glucose from rice husk was pretreatment stages (Soaking in Aqueous Ammonia pretreatment and Acid pretreatment). Furthermore it was followed by the acid hydrolysis step by using dilute H2SO4 solution. The concentration of H2SO4 used in this work was 1, 2, and 3 N with the various hydrolysis times of 30, 60, 90, 120, and 150 min. The result showed that increasing of hydrolysis time slightly increased glucose concentration. The highest glucose concentration was about 21.51% at H2SO4 concentration of 2 N and the hydrolysis time of 150 min. CFD modeling (ANSYS Fluent 16) was performed to investigate the hydrodynamic phenomena during hydrolysis. The hydrodynamic analysis showed that the best mixing occurred at H2SO4 concentration of 2 N for 150 min. It is a good agreement with the experimental finding.

Optimization of soaking in aqueous ammonia pretreatment for anaerobic digestion of African maize bran

In this study, maize bran biomass was subjected to soaking in aqueous ammonia (SAA) pretreatment to reduce and eliminate lignin, a major component that hinders biological digestibility. The effect of SAA pretreatment on the mesophilic anaerobic digestion of maize bran were investigated by using statistical techniques on batch anaerobic test. Response surface methodology by the central-composite design has verified the effects and the interactions of three variables, pretreatment temperature (10–110 °C), pretreatment time (1–11 h) and solid to liquid (S/L) ratio (0.068–0.307) on the responses: methane yield (MY), methane productivity rate (MPR), delignification and sugar recovery were monitored keenly. The optimal regions predicted via overlay plots for the multiple response falls within the following ranges: pretreatment temperatures between 55 and 70 °C, pretreatment time of 5 to 8 h and S/L ratio of 0.14 to 0.185. The optimal conditions were found at 72.5 °C, an S/L ratio of 0.14, and 7.02 h resulting to an MY of 293.8 mL/g COD, and an MPR of 106.0 mL CH4/g VSS-day. The model equations for the multiple responses were within p < 0.05 meaning it is significant and is fitted to the data sets. Validation experiments has confirmed that the pretreatment conditions with optimal responses presented are in close agreement comparing the ones obtained from the experiment and that as estimated by the model.

Quantifying reductions in soaking in aqueous ammonia pretreatment severity and enzymatic hydrolysis conditions for corn stover pellets

The benefits of using pelleted corn stover compared to loose corn stover with low severity soaking in aqueous ammonia pretreatment and reduced enzyme loadings were studied. Loose and pelleted corn stover were treated with the same set of pretreatment and hydrolysis conditions. A range of low to high severity pretreatment conditions and enzyme loadings were tested to determine conditions to achieve 90% glucose yields. Glucose yields from pelleted biomass reached 90% with reduced pretreatment severities, enzyme loadings, hydrolysis time, or various combinations of these. At the highest enzyme loadings, use of pelleted corn stover enabled reductions in hydrolysis time up to 58%. It also allowed 80% reduction in enzyme loading at higher pretreatment conditions. At moderate pretreatment levels, either enzyme loadings can be reduced by 40% or hydrolysis time by up to 48%. Using pelleted biomass as a biorefinery feedstock allows flexibility in production with different processing options.

A Demonstration of the Consistency of Maize Stover Pretreatment by Soaking in Aqueous Ammonia from Bench to Pilot-Scale

Soaking in aqueous ammonia (SAA) is a means of pretreating biomass at moderate temperatures and ammonia concentrations (15% w/w). To establish process consistency and scalability, sieved maize stover was pretreated at 50-ml, 300-ml, and 100-l scales. Each scale was carried out through different methods. Sealed reactor tubes were used for 50-ml pretreatment. Fabric dyeing apparatus was used for the 300-ml pretreatment and a commercial Littleford DVT reactor was used for 100-l pretreatment. For each scale, biomass washing and solid-liquid separations were scaled appropriately. Washed pretreated solids were analyzed for composition and recovery of dry biomass and carbohydrates calculated. Nearly 100% of the glucan content was recovered in pretreated solids at all three scales, indicating the viability of SAA pretreatment. Pretreated solids (15% w/w) were hydrolyzed in a 1-l twin Sigma blade mixer using Cellic CTec2 (15 FPU.g-glucan−1) followed by fermentation in shake flasks. Hydrolytic yields ranged 65–70% across scale treatments. In comparison, fermentative yields averaged 95% across scale treatments, indicating saccharification to be a rate-limiting step in effective bioconversion of lignocellulose.

Evaluation of Separate and Simultaneous Kinetic Parameters for Levulinic Acid and Furfural Production from Pretreated Palm Oil Empty Fruit Bunches

Palm oil empty fruit bunches (POEFBs) can be converted into levulinic acid (LA) and furfural, which are among the top building-block chemicals. The purpose of this study was to investigate separate and simultaneous kinetic model parameters for LA and furfural production from POEFBs, which were pretreated by soaking in aqueous ammonia (SAA). The highest LA yield, which was obtained at a reaction temperature of 170°C after 90 min in an acidic solution with a concentration of 1 M, was 52.1 mol%. The highest furfural yield was 27.94 mol%, which was obtained at a reaction temperature of 170°C after 20 min in an acidic solution with a concentration of 0.5 M. SAA pretreatment affected activation energy in glucose degradation reactions and favoured direct conversion of hemicellulose to furfural. The activation energy of LA production (EakHMF) increases with higher acid catalyst concentration, and the activation energy of furfural production (EakXYN) decreases with higher acid concentration. These trends in the activation energy occurred in both separate and simultaneous kinetic models. Simultaneous kinetic model is better to calculate kinetic parameters of LA and furfural production than separate kinetic models because the simultaneous kinetic model had a lower sum of square error (SSE) when estimating kinetic parameters.

Improving the efficiency of enzymatic hydrolysis of Eucalyptus residues with a modified aqueous ammonia soaking method

Abstract Eucalyptus residues from pulp mill were pretreated with aqueous ammonia soaking (AAS) method to improve the efficiency of enzymatic hydrolysis. The optimized condition of AAS was obtained by response surface methodology. Meanwhile, hydrogen peroxide was introduced into the AAS system to modify the AAS pretreatment (AASP). The results showed that a fermentable sugar yield of 64.96 % was obtained when the eucalypt fibers were pretreated at the optimal conditions, with 80 % of ammonia (w/w) for 11 h and keeping the temperature at 90 °C. In further research it was found that the addition of H2O2 to the AAS could improve the pretreatment efficiency. The delignification rate and enzymatic digestibility were increased to 64.49 % and 73.85 %, respectively, with 5 % of hydrogen peroxide being used. FTIR analysis indicated that most syringyl and guaiacyl lignin and a trace amount of xylan were degraded and dissolved during the AAS and AASP pretreatments. The CrI of the raw material was increased after AAS and AASP pretreatments, which was attributed to the removal of amorphous portion. SEM images showed that microfibers were separated and explored from the initial fiber structure after AAS pretreatment, and the AASP method could improve the destructiveness of the fiber surface.

Enhanced enzymatic hydrolysis of corncob by ultrasound-assisted soaking in aqueous ammonia pretreatment.

Ultrasound-assisted soaking in aqueous ammonia (USAA) pretreatment with 15wt% aqueous ammonia under low temperature (~ 60°C) and short-time (< 12min) low-frequency (20kHz, 60-650W) ultrasound has been investigated for enhancement of enzymatic hydrolysis of corncob. Operational parameters of energy density (2.93-17.07W/mL) and sonication time (0.34-11.66min) that affect cellulose recovery, delignification, and sugar recovery yield were studied and optimized. The maximum cellulose recovery, delignification and sugar recovery yield determined at the optimum conditions (energy density 10W/mL, sonication time 11.66min) were 83.8, 84.7, and 77.6%, respectively. The corncob pretreated using USAA has a lower hemicellulose content (28.9% vs 31.8%), a slightly lower crystallinity index value (42.7% vs 43.7%), and a larger surface cavity diameter (> 36μm vs < 20μm) than that pretreated using soaking in aqueous ammonia (SAA) pretreatment. The USAA pretreatment was proved to be a reliable and effective method for corncob pretreatment.

Process yield and economic trade-offs for enzymatic hydrolysis of alkaline pretreated corn stover

Response surface methodology was used to investigate the interaction of pH, temperature, and enzyme loadings on corn stover hydrolysis rates following soaking in aqueous ammonia pretreatment. Economic tradeoffs were estimated for cellulase and hemicellulase loadings under different hydrolysis conditions. Enzyme loadings had a more significant effect on rates than did pH or temperature. The effect of hydrolysis pH was independent of temperature and enzyme loadings, and the optimal pH for glucose and xylose yields were 4.5 and 4.3, respectively. Conducting hydrolysis at 50 °C rather than 37 °C enables either a 10% glucose yield increase, or a comparable yield with 40% and 65% reduction in cellulase and hemicellulase loadings, respectively. Although yield models showed that hydrolysis rates increase with higher enzyme loadings, economic models showed that optimal cellulase and hemicellulase loadings were as much as 47% and 23% lower, respectively, than the maximum loadings tested. Optimal enzyme loadings change with fluctuations in enzyme costs and ethanol price, but cellulase loadings were more sensitive to these changes than hemicellulase loadings. Enzyme loadings were also more sensitive to enzyme price at lower processing temperatures. Enzyme loadings can be adjusted to increase return based on enzyme costs, ethanol price, and process temperature.

Production of fermentable sugars from corn fiber using soaking in aqueous ammonia (SAA) pretreatment and fermentation to succinic acid using Escherichia coli AFP184

Conversion of corn fiber (CF), a by-product from the corn-to-ethanol conversion process, into fermentable sugar and succinic acid was investigated using soaking in aqueous ammonia (SAA) pretreatment followed by biological conversions, including enzymatic hydrolysis and fermentation using genetically engineered E. coli (AFP184). The SAA pretreatment (using a 15% w/w NH4OH solution at a solid-to-liquid ratio of 1: 10 at 60 °C for 24 h) removed 20-38% of lignin and significantly improved the digestibility of the treated solid (85-99% of glucan digestibility). Following the enzymatic hydrolysis, the sugar-rich hydrolysate was subjected to dilute sulfuric acid treatment (1 wt% sulfuric acid and 120 °C for 1 h), which hydrolyzed the oligosaccharides in the hydrolysate into fermentable monomeric sugars. The mixed sugar hydrolysates containing hexose and pentose obtained from the two-step hydrolysis and SAA pretreatment were fermented to succinic acid using a genetically engineered microorganism, Escherichia coli AFP184, for evaluating the fermentability. Engineered E. coli AFP184 effectively converted soluble sugars in the hydrolysate to succinic acid (20.7 g/L), and the production rate and yield were further enhanced with additional nutrients; the highest concentration of succinic acid was 26.3 g/L for 48 h of fermentation.

Delignification Kinetics of Corn Stover with Aqueous Ammonia Soaking Pretreatment

Soaking aqueous ammonia (SAA) pretreatment of corn stover was carried out at three temperatures (30, 50, and 70 oC) and three concentrations of ammonia solution (5, 15, and 25 wt.%). The delignification kinetic model, based on three first-order reactions, was applied to describe the kinetic behavior of lignin removal from corn stover during SAA pretreatment. The first, second, and third terms were based on the initial, bulk, and residual phases of delignification, respectively. The results showed that the model fitted well with the data obtained from the experiments. The activation energies for the delignification reactions were estimated as 61.05 and 59.46 kJ/mol in the bulk and residual phases, respectively. Delignification selectivity increased with increasing reaction temperature.

Understanding the Physicochemical Characteristics and the Improved Enzymatic Saccharification of Corn Stover Pretreated with Aqueous and Gaseous Ammonia

AbstractPhysicochemical characteristics of corn stover pretreated by soaking in aqueous ammonia (SAA) and low-moisture anhydrous ammonia (LMAA) were compared and investigated. The glucan digestibility of the treated biomass reached 90 % (SAA) and 84 % (LMAA). The LMAA pretreatment enhanced the digestibility by cleaving cross-linkages between cell wall components, whereas the SAA pretreatment additionally improved the digestibility by efficiently removing a major portion of the lignin under mild reaction conditions without significant loss of carbohydrates. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) revealed the structural and chemical transformations of lignin during the pretreatments. Both pretreatments effectively cleaved ferulate cell wall cross-linking that is associated with the recalcitrance of grass lignocellulosics toward enzymatic saccharification. Extracted lignin from SAA pretreatment was extensively depolymerized but retained “native” character, as evidenced by the retention of β-ether linkages.

The Effect of Aqueous Ammonia Soaking Pretreatment on Methane Generation Using Different Lignocellulosic Biomasses

In the present study aqueous ammonia soaking (AAS) has been tested as a pretreatment method for the anaerobic digestion of three lignocellulosic biomasses of different origin: one agricultural residue: sunflower straw, one perennial crop: grass and a hardwood: poplar sawdust. The methane production yield was evaluated in batch experiments at different organic loadings, in order to assess any inhibitory effects due to the pretreatment. The experiments showed that the increase of organic loading did not affect the final methane yield of either raw or AAS pretreated biomasses. Among the three biomasses tested, poplar sawdust exhibited the lowest methane yield, due to its high lignin content. AAS treatment led to an increase of the ultimate methane yields of all biomasses, with the increase in the case of poplar, sunflower straw and grass being 148.7, 37.7 and 26.2 %, respectively. AAS resulted in solubilization of hemicellulose and partial removal of cellulose for all biomasses. Higher cellulose degradation was observed in grass biomass, in which a different morphology than the other AAS treated samples, was shown in SEM images. No toxic compounds such as furaldehydes, were produced during AAS pretreatment.

Reduced pretreatment severity and enzyme loading enabled through switchgrass pelleting

This study investigated the effectiveness of low severity alkaline pretreatment conditions and reduced cellulase and hemicellulase loadings on glucose and xylose yields from pelleted switchgrass. Pelleting improved the efficacy of soaking in aqueous ammonia pretreatment enabling milder pretreatment and lower enzyme loadings to obtain high sugar yields. Although 80% glucose yields could be achieved with cellulase alone, hemicellulase addition improved yields from pelleted switchgrass to above 90% at cellulase loadings as low as 10 FPU g−1 glucan. Similar efficacy was found with higher cellulase loadings and reduced hemicellulase loading. Xylose yields greater than 80% were achieved with cellulase loadings greater than 14 FPU and 200 XU g−1 glucan. This study demonstrated that biomass pelleting can enable biorefineries to use less severe pretreatment conditions and reduced enzyme loadings while maintaining high hydrolysis yields. Models were developed to quantify the range of cellulase and hemicellulase loadings to achieve chosen glucose and xylose yields.

Detoxification of Corncob Acid Hydrolysate with SAA Pretreatment and Xylitol Production by ImmobilizedCandida tropicalis

Xylitol fermentation production from corncob acid hydrolysate has become an attractive and promising process. However, corncob acid hydrolysate cannot be directly used as fermentation substrate owing to various inhibitors. In this work, soaking in aqueous ammonia (SAA) pretreatment was employed to reduce the inhibitors in acid hydrolysate. After detoxification, the corncob acid hydrolysate was fermented by immobilized Candida tropicalis cell to produce xylitol. Results revealed that SAA pretreatment showed high delignification and efficient removal of acetyl group compounds without effect on cellulose and xylan content. Acetic acid was completely removed, and the content of phenolic compounds was reduced by 80%. Furthermore, kinetic behaviors of xylitol production by immobilized C. tropicalis cell were elucidated from corncob acid hydrolysate detoxified with SAA pretreatment and two-step adsorption method, respectively. The immobilized C. tropicalis cell showed higher productivity efficiency using the corncob acid hydrolysate as fermentation substrate after detoxification with SAA pretreatment than by two-step adsorption method in the five successive batch fermentation rounds. After the fifth round fermentation, about 60 g xylitol/L fermentation substrate was obtained for SAA pretreatment detoxification, while about 30 g xylitol/L fermentation substrate was obtained for two-step adsorption detoxification.

Enhanced methane productivity from manure fibers by aqueous ammonia soaking pretreatment

The necessity of increasing the methane productivity of manure based biogas plants has triggered the application of anaerobic digestion to the separated solid fraction of manure, with the challenge that its high lignocellulosic fibers content is difficult to digest and thus makes anaerobic digestion process slow and economically unfavourable. In the present study, aqueous ammonia soaking (AAS) was investigated as a pretreatment method to increase methane potential of swine manure fibers. 3days at 22°C were the optimal conditions among the ones tested (1, 3, and 5days at 22 and 55°C) for increasing the methane potential of manure fibers. AAS pretreatment exhibited a significant effect on methane production rate and potential. It was found that AAS for 3days at 22°C resulted at a 30–80% and 178% increase in methane yield from digested and raw manure fibers, respectively. Batch anaerobic digestion of AAS-treated digested manure fibers could stand loadings as high as 100g TS/l inoculum with no inhibition problems. Enzymatic hydrolysis tests applied to AAS-pretreated fibers resulted to 80% and 65% hydrolysis efficiency of glucan and xylan compared to insignificant numbers for non-pretreated fibers confirming thus that AAS effect on methane yield and production rate is due to the facilitation of hydrolysis step of anaerobic digestion process. This is attributed to AAS directly affecting the disintegration step and thus releasing carbohydrates, which can be further hydrolyzed, from the lignocellulosic matrix.