Soaking In Aqueous Ammonia Research Articles

Effect of Soaking in Aqueous Ammonia (SAA) Pretreatment on Switchgrass for Production of Cellulases Using Trichoderma reesei Rut C-30

<abstract> <bold><sc>Abstract.</sc></bold> Pretreatment plays an important role in the disintegration of phenolic compounds (in the form of lignin) from lignocellulosic feedstock. The effect of 4.5 wt% soaking in aqueous ammonia (SAA) on switchgrass was evaluated for cellulase production using Trichoderma reesei Rut C-30 at 27°C for 168 h. The cellulase production of SAA-treated switchgrass was compared with Solka-Floc and untreated switchgrass. Enzyme activities of 2.99, 1.34, and 0.37 FPU mL^-1 were observed for Solka-Floc, SAA-treated switchgrass, and untreated switchgrass, respectively, at 168 h of fermentation. Controlled environmental conditions had a significant effect on cellulase production using T. reesei. In a 7 L bioreactor (4 L working volume) using SAA-treated switchgrass and T. reesei with a controlled pH of 5 and aeration rate of 1 vvm (volumetric volume per minute), cellulase activity of 1.80 FPU mL^-1 was calculated at 168 h. The produced enzyme broth was evaluated for enzymatic saccharification of SAA-treated switchgrass. The enzymatic saccharification efficiency of T. reesei broth (with and without externally added β-glucosidase) was compared with the commercial enzyme Accellerase 1500 at 50°C for 72 h. Total polysaccharide conversions of 33, 49, and 43 wt% were observed with Accellerase 1500 (80 FPU g^-1 biomass), T. reesei Rut C-30 broth (4.75 FPU g^-1 biomass), and T. reesei Rut C-30 broth with externally added β-glucosidase (4.75 FPU g^-1 biomass + 45 pNPG g^-1 biomass), respectively, over 72 h of enzyme hydrolysis.

Application of a new xylanase activity from Bacillus amyloliquefaciens XR44A in brewer's spent grain saccharification.

BackgroundCellulases and xylanases are the key enzymes involved in the conversion of lignocelluloses into fermentable sugars. Western Ghat region (India) has been recognized as an active hot spot for the isolation of new microorganisms. The aim of this work was to isolate new microorganisms producing cellulases and xylanases to be applied in brewer's spent grain saccharification.Results93 microorganisms were isolated from Western Ghat and screened for the production of cellulase and xylanase activities. Fourteen cellulolytic and seven xylanolytic microorganisms were further screened in liquid culture. Particular attention was focused on the new isolate Bacillus amyloliquefaciens XR44A, producing xylanase activity up to 10.5 U mL−1. A novel endo-1,4-beta xylanase was identified combining zymography and proteomics and recognized as the main enzyme responsible for B. amyloliquefaciens XR44A xylanase activity. The new xylanase activity was partially characterized and its application in saccharification of brewer's spent grain, pretreated by aqueous ammonia soaking, was investigated.ConclusionThe culture supernatant of B. amyloliquefaciens XR44A with xylanase activity allowed a recovery of around 43% xylose during brewer's spent grain saccharification, similar to the value obtained with a commercial xylanase from Trichoderma viride, and a maximum arabinose yield of 92%, around 2-fold higher than that achieved with the commercial xylanase. © 2014 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Enhanced performances of microbial fuel cells using surface-modified carbon cloth anodes: A comparative study

In this study, performances of two-chamber microbial fuel cells (MFCs) with surface-modified carbon cloth anodes by four methods are compared including soaking in aqueous ammonia (CC-A), electrolysis in phosphate buffer (CC-P), electrolysis in nitric acid (CC-N) and electrolysis in nitric acid followed by soaking in aqueous ammonia (CC-NA). It is found that performances of all these modified anodes are better than that of the bare one. The MFC with the anode modified by CC-NA yield the maximum power density of 3.20 ± 0.05 W m−2, which is 58%, 36%, 35% and 28% higher than those of the MFC with untreated anode (CC-C, 2.01 ± 0.02 W m−2), and treated by the CC-A (2.35 ± 0.15), CC-N (2.38 ± 0.02 W m−2) and CC-P (2.50 ± 0.08 W m−2) methods, respectively. The active biomass and EIS analysis for the anodes indicated that the highest power output of the CC-NA MFC may primarily attributed to the enhanced electron transfer resulting from the existence of quinoid groups on the CC-NA surface, rather than the biomass effect. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopic analyses of the CC-NA anode further demonstrate that the formation of quinoid groups contributes to the improvement in the MFC performance by accelerating the electron transfer between electrochemically active bacteria (EAB) and the anode surface.

Effect of Aqueous Ammonia Soaking on the Methane Yield and Composition of Digested Manure Fibers Applying Different Ammonia Concentrations and Treatment Durations

The continuously increasing demand for renewable energy sources renders anaerobic digestion 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. Thus, their economical profitable operation relies on increasing the methane yield from manure, and especially of its solid fraction which is not so easily degradable. In the present study, aqueous ammonia soaking (AAS) at six different concentrations in ammonia (5%, 10%, 15%, 20%, 25% and 32%) and for 1, 3 and 5 days at 22 °C was applied on digested fibers separated from the effluent of a manure-fed, full-scale anaerobic digester. A methane yield increase from 76% to 104% was achieved during the first series of experiments, while the difference in reagent concentration did not considerably affect the methane yield. It was shown that the optimal duration was three days for both 5% and 25% w/w reagent concentrations in ammonia tested. Carbohydrates and phosphorus content remained unaffected, while a slight decrease in Klason lignin and non-soluble organic nitrogen content was observed after AAS. It is concluded that AAS is a very promising treatment resulting to an overall increase of the methane yield of digested manure fibers from 76% to 265% depending on the conditions and the batch of digested fibers used (an even higher increase of 190%–265% was achieved during the 2nd series of experiments, where different AAS durations were tested, compared to the 1st series were different ammonia concentrations were applied).

Pretreatment methods for bioethanol production.

Lignocellulosic biomass, such as wood, grass, agricultural, and forest residues, are potential resources for the production of bioethanol. The current biochemical process of converting biomass to bioethanol typically consists of three main steps: pretreatment, enzymatic hydrolysis, and fermentation. For this process, pretreatment is probably the most crucial step since it has a large impact on the efficiency of the overall bioconversion. The aim of pretreatment is to disrupt recalcitrant structures of cellulosic biomass to make cellulose more accessible to the enzymes that convert carbohydrate polymers into fermentable sugars. This paper reviews several leading acidic, neutral, and alkaline pretreatments technologies. Different pretreatment methods, including dilute acid pretreatment (DAP), steam explosion pretreatment (SEP), organosolv, liquid hot water (LHW), ammonia fiber expansion (AFEX), soaking in aqueous ammonia (SAA), sodium hydroxide/lime pretreatments, and ozonolysis are intensively introduced and discussed. In this minireview, the key points are focused on the structural changes primarily in cellulose, hemicellulose, and lignin during the above leading pretreatment technologies.

Investigation of commercial enzyme preparations for selective release of arabinose from corn fibre

AbstractBACKGROUNDLignocellulosic materials have great potential in the production of L‐arabinose in a new cost‐effective way. Selective enzymatic liberation of L‐arabinose from agricultural residues could be a promising method if purification of specific enzymes and extraction of pure polysaccharides could be omitted from the process. To achieve this goal, investigation of commercial multi‐component enzyme preparations for selective release of L‐arabinose from destarched corn fibre and soaking in aqueous ammonia (SAA) pretreated destarched corn fibres were performed.RESULTSHemicellulase NS22002 (Novozymes) has a relative xylanase activity of 1% (of measured highest) and 9%, and a relative arabinoxylan‐arabinofuranohydrolase (AX‐AFH) activity of 71% and 100% at pH 3 and 4, respectively. At pH 6 its relative xylanase and AX‐AFH activities are 93% and 52%, respectively. Hydrolyses of SAA pretreated destarched corn fibre with Hemicellulase NS22002 at pH 4 and 6 resulted in a large amount of hemicellulosic oligomers, considerable amount of monomer arabinose and negligible amount of monomer xylose and galactose in the supernatants. During the hydrolysis at pH 3 monomer sugars were not released and low amounts of hemicellulosic oligomers were solubilised.CONCLUSIONSAA pretreatment has been found to be an appropriate method to make the structure of destarched corn fibre accessible for hemicellulose‐degrading enzymes. Hemicellulase NS22002 has high endo‐xylanase activity over a broad pH range, and its α‐L‐arabinofuranosidase can release arabinose from solubilised hemicellulosic oligomers derived from corn fibre. Enzymatic hydrolysis of SAA pretreated destarched corn fibre using Hemicellulase NS22002 is suitable to solubilise the hemicellulose fraction, however it cannot selectively release arabinose monomers. © 2014 Society of Chemical Industry

Enhancing volatile fatty acid (VFA) and bio-methane production from lawn grass with pretreatment.

The bioconversion of fiber-based carbohydrates during anaerobic digestion (AD) is impeded due to the recalcitrant nature of the plant cell wall. Pretreatment of lignocellulose materials under mild conditions are needed to improve the digestibility at minimum cost. This study investigated the effects of different pretreatments, including ozone, soaking aqueous ammonia (SAA), combined ozone and SAA (OSAA), and size reduction to enhance volatile fatty acid (VFA) and bio-methane production when lawn grass was used as substrate. To study VFA production, methanogenesis was selectively inhibited by sodium 2-bromoethanesulfonate to decouple the relation between VFA and bio-methane. The enzymatic hydrolysis of SAA (residence time 24h at 50°C) and OSAA (10 min ozonation and 6h of SAA) in pretreatment of lawn grass sample resulted in 86.71% and 89.63% sugar recovery, respectively. The specific methane yields of the control, ozone, SAA, OSAA, and size-reduced grass samples were 402.5, 358.8, 481.0, 462.6, and 358.3 ml CH4/g volatile solid (VS), respectively.

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.

An economic and environmental evaluation for bamboo-derived bioethanol

The potential to obtain bioethanol from bamboo using three different pretreatment technologies (liquid hot water (LHW), dilute acid (DA) and soaking in aqueous ammonia (SAA)) is assessed via techno-economic and environmental analyses.

Pretreatment and Fractionation of Wheat Straw for Production of Fuel Ethanol and Value-added Co-products in a Biorefinery

An integrated process has been developed for a wheat straw biorefinery. In this process, wheat straw was pretreated by soaking in aqueous ammonia (SAA), which extensively removed lignin but preserved high percentages of the carbohydrate fractions for subsequent bioconversion. The pretreatment conditions included 15 wt% NH4OH, 1:10 solid:liquid ratio, 65 oC and 15 hours. Under these conditions, 48% of the original lignin was removed, whereas 98%, 83% and 78% of the original glucan, xylan, and arabinan, respectively, were preserved. The pretreated material was subsequently hydrolyzed with a commercial hemicellulase to produce a solution rich in xylose and low in glucose plus a cellulose-enriched solid residue. The xylose-rich solution then was used for production of value-added products. Xylitol and astaxanthin were selected to demonstrate the fermentability of the xylose-rich hydrolysate. <em>Candida mogii</em> and <em>Phaffia rhodozyma</em> were used for xylitol and astaxanthin fermentation, respectively. The cellulose-enriched residue obtained after the enzymatic hydrolysis of the pretreated straw was used for ethanol production in a fed-batch simultaneous saccharification and fermentation (SSF) process. In this process, a commercial cellulase was used for hydrolysis of the glucan in the residue and <em>Saccharomyces cerevisiae</em>, which is the most efficient commercial ethanol-producing organism, was used for ethanol production. Final ethanol concentration of 57 g/l was obtained at 27 wt% total solid loading.

Sweet Sorghum Biorefinery for Production of Fuel Ethanol and Value-Added Co-products

<abstract> <bold><sc>Abstract.</sc></bold> An integrated process has been proposed for a sweet sorghum biorefinery in which all carbohydrate components of the feedstock were used for production of fuel ethanol and industrial chemicals. In the first step, the juice was extracted from the stalks. The resultant bagasse was then pretreated using the soaking in aqueous ammonia (SAA) process, which did not result in significant loss of cellulose and hemicellulose, to enhance subsequent enzyme hydrolysis for production of fermentable sugars. Following pretreatment, the bagasse was hydrolyzed with a commercial enzyme product containing high hemicellulase activity (Accellerase XY). The xylose-rich solution obtained after solid/liquid separation was used for production of value-added co-products using suitable microorganisms. The value-added co-products produced to demonstrate the feasibility were astaxanthin and D-ribose. The residual solids were then hydrolyzed with a commercial enzyme product containing high cellulase activity (Accellerase 1500), with the juice extracted in the first step used as make-up water. By combining the sugar in the juice with the glucose released from the residual solids by enzyme hydrolysis, high ethanol concentrations could be achieved, which resulted in lower distillation cost than if pure water were used for enzyme hydrolysis and subsequent fermentation, as normally performed in cellulosic ethanol production.

Effects of the pretreatment method on enzymatic hydrolysis and ethanol fermentability of the cellulosic fraction from elephant grass

Elephant grass (Pennisetum purpureum) is a lignocellulosic material that has high potential for ethanol production in tropical countries due to their high availability and adaptability. Chemical and physicochemical pretreatments like alkaline delignification, diluted acid hydrolysis, steam explosion, alkaline peroxide and aqueous ammonia soaking were performed in order to determine their effect on the hydrolysis and the fermentability of the cellulosic fraction of this material. In an initial screening of the methods, the alkaline pretreatment with NaOH yielded the highest concentrations of reducing sugars (34.4g/L) and ethanol (15.1g/L). A more detailed study of the effect of the alkaline pretreatment conditions (temperature, solid to liquid ratio, NaOH concentration and residence time) on the fermentability of elephant grass was carried out. Results showed that under pretreatment conditions of 120°C for 1h with 2wt.%. NaOH and a solid to liquid ratio of 1: 20 (wt.) the highest yield of ethanol was obtained, i.e., 26.1g/L (141.5mg ethanol/g dry biomass, 95% of theoretical yield). Furthermore, this pretreatment allowed the removal of most of the lignin present in this material, i.e., 88% lignin removal. Besides, this pretreatment allowed a high recovery of the cellulosic fraction in the solid.

Enhancement of methane yield from wheat straw, miscanthus and willow using aqueous ammonia soaking

The increasing demand for methane production cannot be satisfied by the use of anaerobic digestion only from waste/wastewater treatment. Perennial energy crops, such as miscanthus and willow, as well as agricultural residues can be considered as options for increasing the methane production through biomass digestion, due to their high organic content and biomass yield. These materials present a great potential, which is only limited by the rigid lignocellulosic structure. In this case, it is possible to apply a pretreatment step in order to achieve increased biogas production. In the present study, aqueous ammonia soaking (AAS) has been investigated as a method to disrupt the lignocellulosic structure and increase the methane yield of wheat straw, miscanthus and willow. Among the three biomasses tested, wheat straw and miscanthus were the most promising in terms of methane production, yielding around 200 and 230 ml of methane per gram of total solids. In all three cases, AAS resulted to an increase in methane yield of 37–41%, 25–27% and 94–162% for wheat straw, miscanthus and willow, respectively. A comparison of the methane yields after 20 and 50 days of anaerobic digestion revealed that AAS affected positively the methane production rate as well. AAS also resulted to a low solubilization of sugars, with a 15.4% and 8.9% increase in soluble xylose concentration in miscanthus and willow, respectively, and a 5% solubilization of glucose in AAS-pretreated miscanthus.

Environmentally friendly pretreatment of plant biomass by planetary and attrition milling

This study evaluated the use of planetary and attrition milling as pretreatment processes for lignocellulosic biomass using rice straw. Planetary milling reduced the rice straw crystallinity from 0.48 to 0.11. Since the samples could be milled and enzymatically treated using the same media, loss of the biomass due to washing was effectively eliminated. In contrast, conventional sodium hydroxide and soaking in aqueous ammonia (SAA) processes showed a loss of 34.2% and 14.8%, respectively. Furthermore, milling produced significantly lower concentrations of soluble phenolics than the alkali treatments. Using a bioluminescent bioreporter strain that is sensitive to these phenolics, neither of the milled samples elicited a response while the sodium hydroxide and SAA samples led to a 25.8 and 4.7 -fold induction, respectively. Although planetary milling produced more reducing sugars than attrition milling before saccharification, both had similar monosaccharide yields, i.e., 0.38 and 0.34 g/g-biomass, respectively, when 40 g/l rice straw was treated.

Chestnut Shell as Unexploited Source of Fermentable Sugars: Effect of Different Pretreatment Methods on Enzymatic Saccharification

Chestnut shell (CS) is an agronomic residue mainly used for extraction of antioxidants or as adsorbent of metal ions. It also contains some polysaccharide that has not been considered as potential source of fermentable sugars for biofuel production until now. In this study, the effect of different pretreatment methods on CS was evaluated in order to obtain the greatest conversion of cellulose and xylan into fermentable sugars. Hot acid impregnation, steam explosion (acid-catalysed or not), and aqueous ammonia soaking (AAS) were selected as pretreatments. The pretreated biomass was subjected to saccharification with two enzyme cocktails prepared from commercial preparations, and evaluation of the best pretreatment and enzyme cocktail was based on the yield of fermentable sugars produced. As AAS provided the best result after preliminary experiments, enhancement of sugar production was attempted by changing the concentrations of ammonium hydroxide, enzymes, and CS. The optimal pretreatment condition was 10 % ammonium hydroxide, 70 °C, 22 h with CS at 5 % solid loading. After saccharification of the pretreated CS for 72 h at 50 °C and pH 5.0 with a cocktail containing cellulase (Accellerase 1500), beta-glucosidase (Accellerase BG), and xylanase (Accellerase XY), glucose and xylose yields were 67.8 and 92.7 %, respectively.

The effect of aqueous ammonia soaking on enzymatic hydrolysis of wheat straw

Enzymatic hydrolysis of wheat straw was performed following aqueous-ammonia soaking. The effects of various operating variables including pretreatment temperature (30, 50, and 70 °C), pretreatment time (15, 30, and 45 h), and ammonia concentration (10% and 30%) on the enzymatic digestibility were investigated. Enzymatic hydrolysis were performed at 5% (w/w) solid loading, 50 °C, and 150 rpm for 96 h, using Accellerase 1500 (30 FPU/g dry biomass). The best reaction conditions observed (50 °C, 45 h, and 30% ammonia) resulted in enzymatic hydrolysis yields of 76% for glucose and 81% for xylose. Total reducing sugars released during hydrolysis experiments were also determined. As the severity of the pretreatment was increased, higher reducing sugar release was observed. It was also found that total reducing sugars vary exponentially with the reciprocal of the pretreatment temperature. An empirical model was developed, which relates reducing sugar concentrations to pretreatment time and temperature.

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.

Maximum Production of Fermentable Sugars from Barley Straw Using Optimized Soaking in Aqueous Ammonia (SAA) Pretreatment

Soaking in aqueous ammonia (SAA) pretreatment was investigated to improve enzymatic digestibility and consequently to increase total fermentable sugar production from barley straw. Various effects of pretreatment process parameters, such as reaction temperature, reaction time, solid:liquid ratio, and ammonia concentration, were evaluated, and the optimum conditions for two of the most important factors, reaction temperature and time were determined using response surface methodology. Optimized reaction conditions were 77.6 °C treatment temperature, 12.1 h. treatment time, 15 wt.% ammonia concentration, and 1:8 solid-to-liquid ratio, which gave a sugar recovery yield of 71.5 % (percent of theoretical sugar recovered from the untreated barley straw) with enzyme loading of 15 FPU/g-glucan. In the optimization of the SAA pretreatment process, ammonia concentration, reaction temperature, and reaction time were determined to be the most significant factors correlated to subsequent enzyme digestibility. Based on tested conditions exhibiting high sugar recovery yields of >60 %, it appeared that reaction temperature affected total fermentable sugar production more significantly than reaction time.

Unraveling the structure of sugarcane bagasse after soaking in concentrated aqueous ammonia (SCAA) and ethanol production by Scheffersomyces (Pichia) stipitis

BackgroundFuel ethanol production from sustainable and largely abundant agro-residues such as sugarcane bagasse (SB) provides long term, geopolitical and strategic benefits. Pretreatment of SB is an inevitable process for improved saccharification of cell wall carbohydrates. Recently, ammonium hydroxide-based pretreatment technologies have gained significance as an effective and economical pretreatment strategy. We hypothesized that soaking in concentrated aqueous ammonia-mediated thermochemical pretreatment (SCAA) would overcome the native recalcitrance of SB by enhancing cellulase accessibility of the embedded holocellulosic microfibrils.ResultsIn this study, we designed an experiment considering response surface methodology (Taguchi method, L8 orthogonal array) to optimize sugar recovery from ammonia pretreated sugarcane bagasse (SB) by using the method of soaking in concentrated aqueous ammonia (SCAA-SB). Three independent variables: ammonia concentration, temperature and time, were selected at two levels with center point. The ammonia pretreated bagasse (SCAA-SB) was enzymatically hydrolysed by commercial enzymes (Celluclast 1.5 L and Novozym 188) using 15 FPU/g dry biomass and 17.5 Units of β-glucosidase/g dry biomass at 50°C, 150 rpm for 96 h. A maximum of 28.43 g/l reducing sugars corresponding to 0.57 g sugars/g pretreated bagasse was obtained from the SCAA-SB derived using a 20% v/v ammonia solution, at 70°C for 24 h after enzymatic hydrolysis. Among the tested parameters, pretreatment time showed the maximum influence (p value, 0.053282) while ammonia concentration showed the least influence (p value, 0.612552) on sugar recovery. The changes in the ultra-structure and crystallinity of native SCAA-SB and enzymatically hydrolysed SB were observed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The enzymatic hydrolysates and solid SCAA-SB were subjected to ethanol fermentation under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Scheffersomyces (Pichia) stipitis NRRL Y-7124 respectively. Higher ethanol production (10.31 g/l and yield, 0.387 g/g) was obtained through SSF than SHF (3.83 g/l and yield, 0.289 g/g).ConclusionsSCAA treatment showed marked lignin removal from SB thus improving the accessibility of cellulases towards holocellulose substrate as evidenced by efficient sugar release. The ultrastructure of SB after SCAA and enzymatic hydrolysis of holocellulose provided insights of the degradation process at the molecular level.

Structural and Thermal Characterization of Wheat Straw Pretreated with Aqueous Ammonia Soaking

Production of renewable fuels and chemicals from lignocellulosic feedstocks requires an efficient pretreatment technology to allow ready access of polysaccharides for cellulolytic enzymes during saccharification. The effect of pretreatment on wheat straw through a low-temperature and low-pressure soaking aqueous ammonia (SAA) process was investigated in this study using Fourier transform infrared (FTIR), pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS), solid and liquid state nuclear magnetic resonance (NMR), and thermogravimetry/differential thermogravimetry (TG/DTG) to demonstrate the changes in lignin, hemicellulose, and cellulose structure. After treatment of 60 mesh wheat straw particles for 60 h with 28-30% ammonium hydroxide (1:10 solid/liquid) at 50 °C, sugar recovery increased from 14% (untreated) to 67% (SAA treated). The FTIR study revealed a substantial decrease in absorbance of lignin peaks. Solid and liquid state NMR showed minimal lignin structural changes with significant compositional changes. Activation energy of control and pretreated wheat straw was calculated according to the Friedman and ASTM methods and found to be decreased for SAA-treated wheat straw, from 259 to 223 kJ/mol. The SAA treatment was shown to remove significant amounts of lignin without strongly affecting lignin functional groups or structure.