Optimization of alkaline pretreatment of coffee pulp for production of bioethanol

The use of lignocellulosic raw materials in bioethanol production has been intensively investigated in recent years. However, for efficient conversion to ethanol, many pretreatment steps are required prior to hydrolysis and fermentation. Coffee stands out as the most important agricultural product in Brazil and wastes such as pulp and coffee husk are generated during the wet and dry processing to obtain green grains, respectively. This work focused on the optimization of alkaline pretreatment of coffee pulp with the aim of making its use in the alcoholic fermentation. A central composite rotatable design was used with three independent variables: sodium hydroxide and calcium hydroxide concentrations and alkaline pretreatment time, totaling 17 experiments. After alkaline pretreatment the concentration of cellulose, hemicellulose, and lignin remaining in the material, the subsequent hydrolysis of the cellulose component and its fermentation of substrate were evaluated. The results indicated that pretreatment using 4% (w/v) sodium hydroxide solution, with no calcium hydroxide, and 25 min treatment time gave the best results (69.18% cellulose remaining, 44.15% hemicelluloses remaining, 25.19% lignin remaining, 38.13 g/L of reducing sugars, and 27.02 g/L of glucose) and produced 13.66 g/L of ethanol with a yield of 0.4 g ethanol/g glucose. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:451–462, 2014     

Enzyme hydrolysis and ethanol fermentation of dilute ammonia pretreated energy cane

This study is the first one ever to report on the use of high fiber sugarcane (a.k.a. energy cane) bagasse as feedstock for the production of cellulosic ethanol. Energy cane bagasse was pretreated with ammonium hydroxide (28% v/v solution), and water at a ratio of 1:0.5:8 at 160 °C for 1 h under 0.9-1.1 MPa. Approximately, 55% lignin, 30% hemicellulose, 9% cellulose, and 6% other (e.g., ash, proteins) were removed during the process. The maximum glucan conversion of dilute ammonia treated energy cane bagasse by cellulases was 87% with an ethanol yield (glucose only) of 23 g ethanol/100 g dry biomass. The enzymatic digestibility was related to the removal of lignin and hemicellulose, perhaps due to increased surface area and porosity resulting in the deformation and swelling of exposed fibers as shown in the SEM pictures.     

Composition of sugar cane,energy cane,and sweet sorghum suitable for ethanol production at Louisiana sugar mills

A challenge facing the biofuel industry is to develop an economically viable and sustainable biorefinery. The existing potential biorefineries in Louisiana, raw sugar mills, operate only 3 months of the year. For year-round operation, they must adopt other feedstocks, besides sugar cane, as supplemental feedstocks. Energy cane and sweet sorghum have different harvest times, but can be processed for bio-ethanol using the same equipment. Juice of energy cane contains 9.8% fermentable sugars and that of sweet sorghum, 11.8%. Chemical composition of sugar cane bagasse was determined to be 42% cellulose, 25% hemicellulose, and 20% lignin, and that of energy cane was 43% cellulose, 24% hemicellulose, and 22% lignin. Sweet sorghum was 45% cellulose, 27% hemicellulose, and 21% lignin. Theoretical ethanol yields would be 3,609 kg per ha from sugar cane, 12,938 kg per ha from energy cane, and 5,804 kg per ha from sweet sorghum.     

A study on the pretreatment of a sugarcane bagasse sample with dilute sulfuric acid

Experiments based on a 2³ central composite full factorial design were carried out in 200-ml stainless-steel containers to study the pretreatment, with dilute sulfuric acid, of a sugarcane bagasse sample obtained from a local sugar–alcohol mill. The independent variables selected for study were temperature, varied from 112.5°C to 157.5°C, residence time, varied from 5.0 to 35.0 min, and sulfuric acid concentration, varied from 0.0% to 3.0% (w/v). Bagasse loading of 15% (w/w) was used in all experiments. Statistical analysis of the experimental results showed that all three independent variables significantly influenced the response variables, namely the bagasse solubilization, efficiency of xylose recovery in the hemicellulosic hydrolysate, efficiency of cellulose enzymatic saccharification, and percentages of cellulose, hemicellulose, and lignin in the pretreated solids. Temperature was the factor that influenced the response variables the most, followed by acid concentration and residence time, in that order. Although harsher pretreatment conditions promoted almost complete removal of the hemicellulosic fraction, the amount of xylose recovered in the hemicellulosic hydrolysate did not exceed 61.8% of the maximum theoretical value. Cellulose enzymatic saccharification was favored by more efficient removal of hemicellulose during the pretreatment. However, detoxification of the hemicellulosic hydrolysate was necessary for better bioconversion of the sugars to ethanol.     

BIOETHANOL PRODUCTION FROM LEAFY BIOMASS OF MANGO (Mangifera indica) INVOLVING NATURALLY ISOLATED AND RECOMBINANT ENZYMES

The present study describes the usage of dried leafy biomass of mango (Mangifera indica) containing 26.3% (w/w) cellulose, 54.4% (w/w) hemicellulose, and 16.9% (w/w) lignin, as a substrate for bioethanol production from Zymomonas mobilis and Candida shehatae. The substrate was subjected to two different pretreatment strategies, namely, wet oxidation and an organosolv process. An ethanol concentration (1.21 g/L) was obtained with Z. mobilis in a shake-flask simultaneous saccharification and fermentation (SSF) trial using 1% (w/v) wet oxidation pretreated mango leaves along with mixed enzymatic consortium of Bacillus subtilis cellulase and recombinant hemicellulase (GH43), whereas C. shehatae gave a slightly higher (8%) ethanol titer of 1.31 g/L. Employing 1% (w/v) organosolv pretreated mango leaves and using Z. mobilis and C. shehatae separately in the SSF, the ethanol titers of 1.33 g/L and 1.52 g/L, respectively, were obtained. The SSF experiments performed with 5% (w/v) organosolv-pretreated substrate along with C. shehatae as fermentative organism gave a significantly enhanced ethanol titer value of 8.11 g/L using the shake flask and 12.33 g/L at the bioreactor level. From the bioreactor, 94.4% (v/v) ethanol was recovered by rotary evaporator with 21% purification efficiency.     

Enzymic saccharification of sugarcane bagasse pretreated by autohydrolysis-steam explosion

Pretreatment of bagasse by autohydrolysis at 200 degrees C for 4 min and explosive defibration resulted in the solubilization of 90% of the hemicellulose (a heteroxylan) and in the production of a pulp that was highly susceptible to hydrolysis by cellulases from Trichoderma reesei C-30 and QM 9414, and by a comercial preparation, Meicelase. Saccharification yields of 50% resulted after 24 h at 50 degrees C (pH 5.0) in enzymic digests containing 10% (w/v) bagasse pulps and 20 filter paper cellulase units (FPU). Saccharifications could be increased to more than 80% at 24 h by the addition of exogenous beta-glucosidase from Aspergillus niger. The crystallinity of cellulose in bagasse remained unchanged following autohydrolysis-explosion and did not appear to hinder the rate or extent of hydrolysis of cellulose. Autohydrolysis-exploded pulps extracted with alkali or ethanol to remove lignin resulted in lowere conversions of cellulose (28-36% after 25 h) than unextracted pulps. Alkali extracted pulps arising from autohydrolysis times of more than 10 min at 200 degrees C were less susceptible to enzymic hydrolysis than unextracted pulps and alkali-extracted pulps arising from short autohydrolysis times (e.g., 2 min at 200 degrees C). Autohydrolysis-explosion was as effective a pretreatment method as 0.25M NaOH (70 degrees C/2 h) both yielded pulps that resulted in high cellulose conversions with T. reesei cellulase preparations and Meicelase. Supplementation of T. reesei C-30 cellulose preparations with A. niger beta-glucosidases was effective in promoting the conversion of cellulose into glucose. A ration of FPU to beta-glucosidase of 1:1.25 was the minimum requirement to achieve more than 80% conversion of cellulose into glucose within 24 h. Other factors which influenced the extent of saccharification of autohydrolysis-exploded bagasse pulps were the enzyme-substrate ratio, the substrate concentration, and the saccharification mode.     

Hydrothermal treatment and ethanol pulping of sunflower stalks

The influence of temperature in the hydrothermal treatment of sunflower stalks on the composition of the liquid fraction obtained was examined. The remaining solid fraction was subjected to ethanol pulping in order to obtain pulp that was used to produce paper sheets. The pulp was characterized in terms of yield, kappa index, viscosity, and cellulose, hemicellulose and lignin contents; and the paper sheets in terms of breaking length, stretch, burst index and tear index. Hydrothermal treatment of the raw material at 190 degrees C provided a liquid phase with maximal hemicellulose-derived oligomers and monosaccharide (glucose, xylose and arabinose) contents (26.9 and 4.2 g/L, respectively). Pulping the solid fraction obtained by hydrothermal treatment at 180 degrees C, with 70% ethanol at a liquid/solid ratio of 8:1 at 170 degrees C for 120 min provided pulp with properties on a par with those of soda pulp from the sunflower stalks, namely: 36.3% yield, 69.1% cellulose, 12.6% hemicellulose, 18.2% lignin and 551 ml/g viscosity. Also, paper sheets obtained from the ethanol pulp were similar in breaking length (3.8 km), stretch (1.23%), burst index (1.15 kN/g) and tear index (2.04 m Nm(2)/g) to those provided by soda pulp.     

Efficient chemical and enzymatic saccharification of the lignocellulosic residue from <Emphasis Type="Italic">Agave tequilana</Emphasis> bagasse to produce ethanol by <Emphasis Type="Italic">Pichia caribbica</Emphasis>

Bagasse of Agave tequilana (BAT) is the residual lignocellulosic waste that remains from tequila production. In this study we characterized the chemical composition of BAT, which was further saccharified and fermented to produce ethanol. BAT was constituted by cellulose (42%), hemicellulose (20%), lignin (15%), and other (23%). Saccharification of BAT was carried out at 147°C with 2% sulfuric acid for 15 min, yielding 25.8 g/l of fermentable sugars, corresponding to 36.1% of saccharificable material (cellulose and hemicellulose contents, w/w). The remaining lignocellulosic material was further hydrolyzed by commercial enzymes, ~8.2% of BAT load was incubated for 72 h at 40°C rendering 41 g/l of fermentable sugars corresponding to 73.6% of the saccharificable material (w/w). Mathematic surface response analysis of the acid and enzymatic BAT hydrolysis was used for process optimization. The results showed a satisfactory correlation (R ² = 0.90) between the obtained and predicted responses. The native yeast Pichia caribbica UM-5 was used to ferment sugar liquors from both acid and enzymatic hydrolysis to ethanol yielding 50 and 87%, respectively. The final optimized process generated 8.99 g ethanol/50 g of BAT, corresponding to an overall 56.75% of theoretical ethanol (w/w). Thus, BAT may be employed as a lignocellulosic raw material for bioethanol production and can contribute to BAT residue elimination from environment.     

Valorization of cashew apple bagasse using acetic acid pretreatment: Production of cellulosic ethanol and lignin for their use as sunscreen ingredients

The present study focuses on the fractionation of cashew apple bagasse via a pretreatment using acetic acid as a delignifying agent and sulfuric acid as an external catalyst. As expected, the concentrations of both acids and the incubation time dramatically affected delignification and hemicellulose solubilization. Under the optimal pretreatment conditions, recycling of the spent liquor had no apparent impact on the chemical composition of the pretreated material, yield of sugar produced via enzymatic hydrolysis (∼37 g/L reducing sugars at 7.5% (w/v) solid loading), or yield of ethanol obtained via fermentation with Saccharomyces cerevisiae (∼16 g/L at 10% (w/v) solid loading). The lignin recovered from the spent liquor showed a good ultraviolet protective effect; the addition of 5% (w/w) of the biopolymer increased the sun protection factor of a commercial sunscreen lotion from 21.62 to 40.71. The combined use of hydrogen peroxide and ultraviolet radiation reduced the organosolv lignin color (absorbance at 450 nm was four times lower) owing to aromatic ring cleavage, but cosmetics containing whitened organosolv lignin had low sun protection factor values. In summary, the results obtained in this study demonstrate the utility of organic acid pretreatment in the valorization of lignocellulosic materials.     

Succession and activity of microorganisms in stored bagasse

Summary Fresh sugarcane bagasse was fermented under defined conditions and investigated regarding a microbial succession during fermentation, in view of the enzyme activities of microorganisms against the main bagasse components: sucrose, pectin, hemicellulose, cellulose, and lignin.Altogether, 400 pure cultures of microorganisms were obtained from 8 g bagasse during 6.5 days of storage. This flora consists of bacteria (74%), actinomycetes (6%), yeasts (13%), and fungi (7%). The yeasts dominate in early fermentation, followed by bacteria, and then by actinomycetes and fungi.This succession coincides with the enzymic activities of the isolated organisms during fermentation. At first, residual sugar is consumed predominantly by the yeasts. Then the bacteria degrade the pectin, the hemicellulose, and in parts, the cellulose. Later, the actinomycetes and the fungi imperfecti attack the hemicellulose, the cellulose, and, partly, the lignin within the bagasse fiber.These results are corroborated by investigations using bagasse from bulk storage.     

Biorefining of softwoods using ethanol organosolv pulping: preliminary evaluation of process streams for manufacture of fuel-grade ethanol and co-products

Pulps with residual lignin ranging from 6.4-27.4% (w/w) were prepared from mixed softwoods using a proprietary biorefining technology (the Lignol process) based on aqueous ethanol organosolv extraction. The pulps were evaluated for bioconversion using enzymatic hydrolysis of the cellulose fraction to glucose and subsequent fermentation to ethanol. All pulps were readily hydrolyzed without further delignification. More than 90% of the cellulose in low lignin pulps (< or =18.4% residual lignin) was hydrolyzed to glucose in 48 h using an enzyme loading of 20 filter paper units/g cellulose. Cellulose in a high lignin pulp (27.4% residual lignin) was hydrolyzed to >90% conversion within 48 h using 40 filter paper units/g. The pulps performed well in both sequential and simultaneous saccharification and fermentation trials indicating an absence of metabolic inhibitors. Chemical and physical analyses showed that lignin extracted during organosolv pulping of softwood is a suitable feedstock for production of lignin-based adhesives and other products due to its high purity, low molecular weight, and abundance of reactive groups. Additional co-products may be derived from the hemicellulose sugars and furfural recovered from the water-soluble stream.     

Search for optimum conditions of wheat straw hemicelluloses cold alkaline extraction process

A method for the selective extraction of hemicellulose from wheat straw involving cold alkaline extraction and subsequent separation by precipitation with ethanol is proposed. Wheat straw affords selective separation of the hemicellulose fraction from the cellulose and lignin fractions with the proposed method. The hemicellulose yield was optimized by using a 2n factor design to examine the influence of temperatures (temperature was designed between 20 and 40 °C), operation times (operation time was designed between 30 and 60 min) and alkali concentrations (alkali concentration was designed between 80 and 120 g L⁻¹). These conditions allowed 56.1% of all hemicellulose initially present in the raw material, and 59.1% of the lignin, to be extracted. Subsequent separation of hemicellulose in the liquid phase from the cold alkaline extraction by precipitation with ethanol provided a fraction containing 39.4% of all hemicellulose (45.2% hemicellulose in extract/total extract) and only 12% of all lignin in the raw material.     

Utilization of sugarcane bagasse cellulose for producing cellulose acetates: Novel use of residual hemicellulose as plasticizer

Sugarcane bagasse was fractionated to cellulose, hemicellulose and lignin by a proprietary steam explosion process, followed by downstream purifications, developed in our laboratory. The fractionated cellulose contained ～94% cellulose, about ～5% hemicellulose, traces of lignin (～0.2%), and ～1% ash. The cellulose was acetylated under heterogeneous conditions to obtain cellulose acetates. These were extensively characterized using FTIR, TGA, DSC, GPC, HPIC, WAXRD, and viscometry. The novel feature of this study was the utilization of the hemicellulose content (5%) of bagasse cellulose as an internal plasticizer. Through kinetic experimentation, we have demonstrated that the residual hemicellulose need not be considered as an impurity; rather it can be used in acetylated form as a plasticizer as well as a biodegradable additive for cellulose acetates made from slightly impure cellulose produced from non-wood origin. Our results therefore show how lignocellulosic agricultural wastes can be utilized to produce high value plastics.     

The Influence of Hemicellulose and Lignin Removal on the Enzymatic Digestibility from Sugarcane Bagasse

Sugarcane bagasse (SCB) was pretreated with liquid hot water (LHW) and aqueous ammonia (AA), with the objective of investigating the influence of hemicellulose and lignin removal on the enzymatic digestibility and sugar recovery. The experimental results show that LHW and aqueous ammonia have a good performance in terms of hemicellulose dissolution and lignin removal respectively. The biggest xylan recovery of 74.3 % was obtained for LHW pretreatment at 160 °C, 5 %?w/v for 20 min with the xylan dissolution of 83.1 %. And the biggest lignin removal of 84.0 % was obtained for aqueous ammonia pretreatment at 160 °C, 10 %?w/v for 60 min. Moreover, the aperture and surface area of the sample were enlarged by the liquid hot water, which improves the accessibility of the substrate to the enzyme. The lignin removal caused by aqueous ammonia pretreatment can reduce the absorption of enzyme. In addition, the correlation between the compositional change and the enzymatic digestibility indicates that the removal of hemicellulose was more effective than lignin for destruction of the hemicellulose–lignin–cellulose structure.     

Unpolluted fractionation of wheat straw by steam explosion and ethanol extraction

An unpolluted process of wheat straw fractionation by steam explosion coupled with ethanol extraction was studied. The wheat straw was steam exploded for 4.5 min with moisture of 34.01%, a pressure of 1.5 MPa without acid or alkali. Hemicellulose sugars were recovered by water countercurrent extraction and decolored with chelating ion exchange resin D412. The gas chromatography (GC) and high-performance liquid chromatography (HPLC) analysis results indicated that there were organic acids in the hemicellulose sugars and the ratio of monosaccharides to oligosaccharides was 1:9 and the main component, xylose, was 85.9% in content. The total recovery rate of hemicellulose was 80%. Water washed materials were subsequently extracted with ethanol. The optimum extraction conditions in this work were 40% ethanol, fiber/liquor ratio 1:50 (w/v), severity log(R)=3.657 (180 degrees C for 20 min), 0.1% NaOH. The lignin yield was 75% by acid precipitation and 85% ethanol solvent was recovered. The lignin was purified using Bj?rkman method. Infrared spectrometry (IR) results indicated that the lignin belonged to GSH (guaiacyl (G) syringyl (S) and p-hydroxyphenyl (H)) lignin and its purity rate reached 85.3%. The cellulose recovery rate was 94% and the results of electron spectroscopy for chemical analysis (ESCA) and infrared spectrometry (IR) showed that hemicellulose and lignin content decreased after steam explosion and ethanol extraction.     

Utilization of sugarcane bagasse for bioethanol production: sono-assisted acid hydrolysis approach

In this study, the production of sugar monomers from sugarcane bagasse (SCB) by sono-assisted acid hydrolysis was performed. The SCB was subjected to sono-assisted alkaline pretreatment. The cellulose and hemicellulose recovery observed in the solid content was 99% and 78.95%, respectively and lignin removal observed during the pretreatment was about 75.44%. The solid content obtained was subjected to sono-assisted acid hydrolysis. Under optimized conditions, the maximum hexose and pentose yield observed was 69.06% and 81.35% of theoretical yield, respectively. The hydrolysate obtained was found to contain very less inhibitors, which improved the bioethanol production and the ethanol yield observed was 0.17 g/g of pretreated SCB.     

氨基磺酸应用于甘蔗渣预处理的研究

本研究尝试将氨基磺酸应用于甘蔗渣预处理,探究其作为酸预处理试剂对甘蔗渣成分和酶解的影响。氨基磺酸预处理最优条件为浓度3%,温度121℃,预处理1 h。在该条件下,甘蔗渣的固体回收率为64.45%,半纤维素和木质素去除率分别为70.81%和25.10%,纤维素损失率仅7.56%。与硫酸、盐酸预处理相比,氨基磺酸的半纤维素和木质素去除率不如硫酸、盐酸预处理,但固体回收率更高,纤维素损失率低,能保留更多纤维素有效成分。进一步酶解显示,氨基磺酸预处理的纤维素转化率高于硫酸、盐酸预处理。氨基磺酸作为一种新的酸预处理试剂,在木质纤维素降解上有良好应用前景。     

Characterization of commercial cellulases and their use in the saccharification of a sugarcane bagasse sample pretreated with dilute sulfuric acid

This study aimed to correlate the efficiency of enzymatic hydrolysis of the cellulose contained in a sugarcane bagasse sample pretreated with dilute H₂SO₄ with the levels of independent variables such as initial content of solids and loadings of enzymes and surfactant (Tween 20), for two cellulolytic commercial preparations. The preparations, designated cellulase I and cellulase II, were characterized regarding the activities of total cellulases, endoglucanase, cellobiohydrolase, cellobiase, β-glucosidase, xylanase, and phenoloxidases (laccase, manganese and lignin peroxidases), as well as protein contents. Both extracts showed complete cellulolytic complexes and considerable activities of xylanases, without activities of phenoloxidases. For the enzymatic hydrolyses, two 2³ central composite full factorial designs were employed to evaluate the effects caused by the initial content of solids (1.19–4.81%, w/w) and loadings of enzymes (1.9–38.1 FPU/g bagasse) and Tween 20 (0.0–0.1 g/g bagasse) on the cellulose digestibility. Within 24 h of enzymatic hydrolysis, all three independent variables influenced the conversion of cellulose by cellulase I. Using cellulase II, only enzyme and surfactant loadings showed significant effects on cellulose conversion. An additional experiment demonstrated the possibility of increasing the initial content of solids to values much higher than 4.81% (w/w) without compromising the efficiency of cellulose conversion, consequently improving the glucose concentration in the hydrolysate.     

Sugarcane Internode Composition During Crop Development

Sugarcane sugar and bagasse can be utilized for the production of ethanol or other biofuels. A better understanding of the changes in composition with development along the stalk and with crop development will maximize the usage of sugarcane for this purpose. Two experiments were designed to elucidate internode composition changes during the growing season. In experiment 1, an internode of stalks of 5 modern cultivars were marked at the start of elongation, and then sampled every 1 to 2?weeks from July until October. Sugars were extracted and assayed, and a sequential detergent method was used to estimate hemicellulose, cellulose, and lignin contents. In experiment 2, internodes 1, 3, 5, 7, 9, and 11 down the stalk were sampled in late July (grand growth) and late September (ripening). Internode length, fresh weight, dry weight, water content, and sugar contents were determined as well as cell wall composition. Both experiments were repeated in 2?years. As internodes elongated, total sugar increased, and hemicellulose decreased as a proportion of neutral detergent fiber, while cellulose and lignin increased. After elongation, sucrose and lignin increased, and cellulose content decreased with internode age. The variability in cell wall composition among the five cultivars suggests that selection for desirable composition may be possible. In Experiment 2, hemicellulose contents were lower, and lignin and ash contents were higher at ripening than during grand growth. Delaying sugarcane harvest to maximize sucrose content may decrease bagasse suitability for cellulosic ethanol production because of the increased lignin content.     

添加剂对水稻秸秆实地混合厌氧发酵产甲烷系统的作用

为提高水稻秸秆利用效率,改进水稻秸秆实地混合厌氧发酵产甲烷技术,本研究开展了添加剂在混合厌氧发酵系统的应用研究。试验选取水稻秸秆和猪粪作为发酵原料,通过分别添加不同的浓度的吐温20和腐植酸,测定甲烷的产气量和浓度、秸秆的降解和土壤肥力的变化,以揭示添加剂类型及其浓度对水稻田实地甲烷生产系统的影响。结果表明:添加剂的掺入并未影响产气的动态变化趋势,但显著地促进产气和提高产气浓度,整体效果由高到低为腐植酸吐温20对照,其中经腐植酸处理的产气量和产气浓度对照相比分别提高了50. 73%和24. 55%。添加剂的掺入有利于水稻秸秆纤维素和半纤维素的降解,但对木质素没有显著影响;其中以0. 15 g/L腐植酸和0. 30 g/L吐温20的降解率最高,相较于对照其纤维素降解率均提高了22. 11%,半纤维素降解率分别提高了107. 13%和98. 39%。添加剂的掺入能显著增加土壤肥力,以0. 15 g/L腐植酸和0. 30 g/L吐温20处理水平的效果最优,相较于对照,其土壤有机质分别增加了29. 63%和23. 72%,全氮分别增加了52. 32%和42. 38%,全磷分别增加了83. 33%和57. 14%。