S-SI,a New Alkaline Protease Inhibitor from Streptomyces albogriseolus S-3253

This study investigated the production of ethanol from unutilized branches pruned from pear trees by steam explosion pretreatment. Steam pressures of 25, 35, and 45?atm were applied for 5?min, followed by enzymatic saccharification of the extracted residues with cellulase (Cellic CTec2). High glucose recoveries, of 93.3, 99.7, and 87.1%, of the total sugar derived from the cellulose were obtained from water- and methanol-extracted residues after steam explosion at 25, 35, and 45?atm, respectively. These values corresponded to 34.9, 34.3, and 27.1?g of glucose per 100?g of dry steam-exploded branches. Simultaneous saccharification and fermentation experiments were done on water-extracted residues and water- and methanol-extracted residues by Kluyveromyces marxianus NBRC 1777. An overall highest theoretical ethanol yield of 76% of the total sugar derived from cellulose was achieved when 100?g/L of water- and methanol-washed residues from 35?atm-exploded pear branches was used as substrate.     

Efficient conversion of sugarcane stalks into ethanol employing low temperature alkali pretreatment method

An alternative route for bio-ethanol production from sugarcane stalks (juice and bagasse) featuring a previously reported low temperature alkali pretreatment method was evaluated. Test-tube scale pretreatment-saccharification experiments were carried out to determine optimal LTA pretreatment conditions for sugarcane bagasse with regard to the efficiency of enzymatic hydrolysis of the cellulose. Free fermentable sugars and bagasse recovered from 2 kg of sugarcane stalks were jointly converted into ethanol via separate enzymatic hydrolysis and fermentation (SHF). Results showed that 98% of the cellulose present in the optimally pretreated bagasse was hydrolyzed into glucose after 72-h enzymatic saccharification using commercially available cellulase and β-glucosidase preparations at relatively low enzyme loading. The fermentable sugars in the mixture of the sugar juice and the bagasse hydrolysate were readily converted into 193.5 mL of ethanol by Saccharomyces cerevisiae within 12h, achieving 88% of the theoretical yield from the sugars and cellulose.     

Enhanced Bioethanol Production from Blue Agave Bagasse in a Combined Extrusion–Saccharification Process

This paper describes an improved process for bioethanol production using a recently developed combined extrusion–saccharification technology. Blue agave bagasse (BAB) was pretreated via a thermo-mechano-chemical process (co-rotational twin-screw, reactive extrusion) to increase the availability of cellulose and hemicellulose for enzymatic saccharification. Then, several commercial enzyme preparations, boosted with accessory enzymes (exoglucanase, endoglucanase, hemicellulase, xylanase, and β-glucosidase), were tested with extruded BAB at 5 % consistency in a stirred vessel. The enzyme blend that produced the highest saccharification yield was evaluated at different BAB consistencies. The obtained concentration of sugars increased up to 69.5 g/L (73 % yield) when a 20 % BAB mixture was used. When the enzyme blend was fed into the extruder and with a residence time of 2 min, the yield reached 15 % of the maximum theoretical of C6 sugars along this step. This extruded and pre-saccharified BAB was further hydrolyzed and used for fermentation. The pre-saccharification step significantly enhanced cellulose degradation and ethanol production. Our results indicate that the enzymatic saccharification of BAB, coupled with reactive extrusion, produces an excellent substrate for bioethanol production.     

The effects of four different pretreatments on enzymatic hydrolysis of sweet sorghum bagasse

Four pretreatment processes including ionic liquids, steam explosion, lime, and dilute acid were used for enzymatic hydrolysis of sweet sorghum bagasse. Compared with the other three pretreatment approaches, steam-explosion pretreatment showed the greatest improvement on enzymatic hydrolysis of the bagasse. The maximum conversion of cellulose and the concentration of glucose obtained from enzymatic hydrolysis of steam explosion bagasse reached 70% and 25 g/L, respectively, which were both 2.5 times higher than those of the control (27% and 11 g/L). The results based on the analysis of SEM photos, FTIR, XRD and NMR detection suggested that both the reduction of crystallite size of cellulose and cellulose degradation from the Iα and Iβ to the Fibril surface cellulose and amorphous cellulose were critical for enzymatic hydrolysis. These pretreatments disrupted the crystal structure of cellulose and increased the available surface area, which made the cellulose better accessible for enzymatic hydrolysis.     

Enhanced enzymatic hydrolysis of sugarcane bagasse by N-methylmorpholine-N-oxide pretreatment

The cellulose dissolution solvent used in Lyocell process for cellulose fiber preparation, N-methylmorpholine-N-oxide (NMMO) monohydrate, was demonstrated to be an effective agent for sugarcane bagasse pretreatment. Bagasse of 20wt% was readily dissolved in NMMO monohydrate at 130 degrees C within 1h. After dissolution, bagasse could be regenerated by rapid precipitation with water as a porous and amorphous mixture of its original components. The regenerated bagasse exhibited a significant enhancement on enzymatic hydrolysis kinetic. Not only the reducing sugars releasing rate but also hydrolysis yield was enhanced at least twofold as compared with that of untreated bagasse. The cellulose fraction of regenerated bagasse was nearly hydrolyzed to glucose after 72h hydrolysis with Cellulase AP3. The recycled NMMO demonstrated the same performance as the fresh one on bagasse pretreatment for hydrolysis enhancement. The regenerated bagasse was directly used in simultaneous saccharification and fermentation (SSF) for ethanol production by Zymomonas mobilis. No negative effect on ethanol fermentation was observed and ethanol yield approximately 0.15 g ethanol/g baggasse was achieved.     

Optimization of steam explosion as a method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification

The technique of autohydrolysis steam explosion was examined as a means for pretreatment of sugarcane bagasse. Treatment conditions were optimized so that following enzymatic hydrolysis, pretreated bagasse would give 65.1 g sugars/100 g starting bagasse. Released sugars comprised 38.9 g glucose, 0.6 g cellobiose, 22.1 g xylose, and 3.5 g arabinose, and were equivalent to 83% of the anhydroglucan and 84% of the anhydroxylan content of untreated bagasse. Optimum conditions were treatment for 30 S with saturated steam at 220 degrees C with a water-to-solids ratio of 2 and the addition of 1 g H(2)SO(4)/100 g dry bagasse. Bagasse treated in this manner was not inhibitory to fermentation by Saccharomyces uvarum except at low inoculum levels when fermentation time was extended by up to 24 h. Pretreated saccharified bagasse was inhibitory to Pachysolen tannophilus and this was attributed to the formation of acetate from the hydrolysis of acetyl groups present in hemicellulose. The major advantage of the pretreatment is the achievement of high total sugar yield with moderate enzyme requirement and only minor losses due to sugar decomposition.     

Evaluation of steam explosion pre-treatment for enzymatic hydrolysis of sunflower stalks

Sunflower stalks, a largely available and cheap agricultural residue lacking of economic alternatives, were subjected to steam explosion pre-treatment, the objective being to optimize pre-treatment temperature in the range 180-230°C. Enzymatic hydrolysis performed on the pre-treated solids by a cellulolytic complex (Celluclast 1.5L) and analysis of filtrates were used to select the best pre-treatment temperature. Temperature selection was based on the susceptibility to enzymatic hydrolysis of the cellulose residue and both the cellulose recovery in the solid and the hemicellulose-derived sugars recoveries in the filtrate. After 96h of enzymatic action, a maximum hydrolysis yield of 72% was attained in the water-insoluble fiber obtained after pre-treatment at 220°C, corresponding to a glucose concentration of 43.7g/L in hydrolysis media. Taking into account both cellulose recovery and hydrolysis yield, the maximum value of glucose yield referred to unpretreated raw material was also found when using steam pre-treated sunflower stalks at 220°C, obtaining 16.7g of glucose from 100g of raw material. With regard to the filtrate analysis, most of the hemicellulosic-derived sugars released during the steam pre-treatment were in oligomeric form, the highest recovery being obtained at 210°C pre-treatment temperature. Moreover, the utilisation of hemicellulosic-derived sugars as a fermentation substrate would improve the overall bioconversion of sunflower stalks into fuel ethanol.     

Feasibility of Manufacturing Cellulose Nanocrystals from the Solid Residues of Second-Generation Ethanol Production from Sugarcane Bagasse

The reuse of the solid residues generated in the production of second-generation (2G) ethanol to obtain high-value products is a potential strategy for improving the economic and environmental viability of the overall process. This study evaluated the feasibility of using the residual solids remaining after the enzymatic hydrolysis of sugarcane bagasse for the production of cellulose nanocrystals (CNC), a valuable bionanomaterial. To this end, sugarcane bagasse subjected to steam explosion (SEB) or liquid hot water (LHWB) pretreatment was hydrolysed using different loadings of a commercial cellulase cocktail. Samples of SEB and LHWB were hydrolysed enzymatically, resulting in glucose releases close to 40 g/L, which would be suitable for producing 2G ethanol by microbial fermentation. The solid residues after the enzymatic hydrolysis step presented cellulose contents of up to 54 %, indicating that a significant amount of recalcitrant crystalline cellulose remained available for subsequent use. These solid residues were purified and submitted to acid hydrolysis, resulting in the successful formation of CNC with crystallinity close to 80 %, lengths of 193–246 nm and diameters of 14–18 nm. The CNC produced presented morphology, dimensions, physical-chemical characteristics, thermal stability and crystallinity within the ranges reported for this type of material. Moreover, the enzyme loading or the type of hydrothermal pretreatment process employed here showed no significant effects on the CNC obtained, indicating that these variables could be flexibly adjusted according to specific interests.     

湿氧化爆破稻秆的同步糖化发酵条件研究

探讨了木质纤维素经过湿氧化爆破后在同步糖化发酵过程中酵母产乙醇的基本规律.采用单因素方法对湿氧化爆破条件、酶系组成和添加量以及预酶解时间和温度进行了优化.不同湿氧化爆破预处理条件下的稻秆对同步糖化发酵工艺的影响较大,在预处理温度160 ℃,进氧压力为4×105 Pa,碱用量为6%(w/w),反应时间为20 min的条件...     

Characterization of the steam-exploded spent Shiitake mushroom medium and its efficient conversion to ethanol

Spent Shiitake mushroom medium was subjected to steam explosion followed by simultaneous saccharification and fermentation (SSF) using Meicelase and Saccahromyces cerevisiae AM12. Water extraction of the medium exposed to steam at 20 atm for 5 min enhanced the saccharification rate by about 20% compared to steam-exploded medium before water extraction and resulted in the production of 23.8 g/l ethanol from a substrate concentration of 100 g/l. This corresponded to 87.6% of the theoretical ethanol yield, i.e., 15.9 g ethanol was obtained from 100 g of spent Shiitake mushroom medium. Spent Shiitake mushroom medium subjected to steam explosion and then water extraction appears to be a candidate for efficient bioconversion to ethanol.     

Enhanced saccharification kinetics of sugarcane bagasse pretreated in 1-butyl-3-methylimidazolium chloride at high temperature and without complete dissolution

Dissolution of bagasse with 1-butyl-3-methylimidazolium chloride at high temperatures (110-160 °C) is investigated as a pretreatment process for saccharification and fermentation based biofuel production. Material balances are reported and used along with enzymatic saccharification data to identify optimum pretreatment conditions (150 °C for 90 min). At all pretreatment temperatures, dissolved and reprecipitated material is enriched in cellulose, has a low crystallinity and the cellulose component is easily and quantitatively hydrolysed (100%, 3h, 15 FPU). At pretreatment temperatures ≤ 150 °C, the undissolved material has only slightly lower crystallinity than the starting. At pretreatment temperatures ≥ 150 °C, the undissolved material has low crystallinity and when combined with the dissolved material has a saccharification rate and extent similar to completely dissolved material. Complete dissolution is not necessary to maximise saccharification efficiency at temperatures ≥ 150 °C.     

Surface carbohydrate analysis and bioethanol production of sugarcane bagasse pretreated with the white rot fungus, Ceriporiopsis subvermispora and microwave hydrothermolysis

Effects of pretreatments with a white rot fungus, Ceriporiopsis subvermispora, and microwave hydrothermolysis of bagasse on enzymatic saccharification and fermentation were evaluated. The best sugar yield, 44.9 g per 100 g of bagasse was obtained by fungal treatments followed by microwave hydrothermolysis at 180 °C for 20 min. Fluorescent-labeled carbohydrate-binding modules which recognize crystalline cellulose (CjCBM3-GFP), non-crystalline cellulose (CjCBM28-GFP) and xylan (CtCBM22-GFP) were applied to characterize the exposed polysaccharides. The microwave pretreatments with and without the fungal cultivation resulted in similar levels of cellulose exposure, but the combined treatment caused more defibration and thinning of the plant tissues. Simultaneous saccharification and fermentation of the pulp fractions obtained by microwave hydrothermolysis with and without fungal treatment, gave ethanol yields of 35.8% and 27.0%, respectively, based on the holocellulose content in the pulp. These results suggest that C. subvermispora pretreatment could be beneficial part of the process to produce ethanol from bagasse.     

Ethanol production from alkaline peroxide pretreated enzymatically saccharified wheat straw

Wheat straw used in this study contained 44.24 +/- 0.28% cellulose and 25.23 +/- 0.11% hemicellulose. Alkaline H(2)O(2) pretreatment and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to fermentable sugars. The maximum yield of monomeric sugars from wheat straw (8.6%, w/v) by alkaline peroxide pretreatment (2.15% H(2)O(2), v/v; pH 11.5; 35 degrees C; 24 h) and enzymatic saccharification (45 degrees C, pH 5.0, 120 h) by three commercial enzyme preparations (cellulase, beta-glucosidase, and xylanase) using 0.16 mL of each enzyme preparation per g of straw was 672 +/- 4 mg/g (96.7% yield). During the pretreatment, no measurable quantities of furfural and hydroxymethyl furfural were produced. The concentration of ethanol (per L) from alkaline peroxide pretreated enzyme saccharified wheat straw (66.0 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 37 degrees C in 48 h was 18.9 +/- 0.9 g with a yield of 0.46 g per g of available sugars (0.29 g/g straw). The ethanol concentration (per L) was 15.1 +/- 0.1 g with a yield of 0.23 g/g of straw in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 37 degrees C in 48 h.     

亚硫酸盐甘蔗渣浆酶解液发酵制备乙醇

以亚硫酸盐甘蔗渣浆酶解液作为原料,利用C. shehatae发酵制取燃料乙醇。结果表明：还原糖最适初始质量浓度为葡萄糖140 g/L、木糖60 g/L、酶解液总糖80 g/L。利用初始葡萄糖55.06 g/L、木糖11.18 g/L、纤维二糖4.51 g/L的亚硫酸盐甘蔗渣浆酶解液发酵,经18 h获得乙醇22.98 g/L。乙醇得率为67.23%,葡萄糖利用率为99.27%,木糖利用率为32.96%,C. shehatae适合作为蔗渣为原料的乙醇发酵菌株。     

Ethanol production from lignocellulosic biomass of energy cane

Ethanol produced from lignocellulosic biomass is a renewable alternative to diminishing petroleum based liquid fuels. The release of many new sugarcane varieties by the United States Department of Agriculture to be used as energy crops is a promising feedstock alternative. Energy cane produces large amounts of biomass that can be easily transported, and production does not compete with food supply and prices because energy cane can be grown on marginal land instead of land for food crops. The purpose of this study was to evaluate energy cane for lignocellulosic ethanol production. Energy cane variety L 79-1002 was pretreated with weak sulfuric acid to remove lignin. In this study, 1.4 M sulfuric acid pretreated type II energy cane had a higher ethanol yield after fermentation by Klebsiella oxytoca without enzymatic saccharification than 0.8 M and 1.6 M sulfuric acid pretreated type II energy cane. Pretreated biomass was inoculated with K. oxytoca for cellulose fermentation and Pichia stipitis for hemicellulose fermentation under simultaneous saccahrification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) conditions. For enzymatic saccharification of cellulose, the cellulase and ??-glucanase cocktail significantly increased ethanol production compared to the ethanol production of fermented acid pretreated energy cane without enzymatic saccharification. The results revealed that energy cane variety L 79-1002 produced maximum cellulosic ethanol under SHF (6995 mg/L) and produced 3624 mg/L ethanol from fermentation of hemicellulosic sugars.     

沙柳原料高浓度底物酶解发酵乙醇工艺

为了提高沙柳生物转化过程的经济可行性,考察了沙柳原料经过蒸爆、超微粉碎+稀酸、超微粉碎+稀碱预处理后高浓度底物补料酶解的效果,并对其高浓度水解糖液进行了乙醇发酵。结果表明:蒸爆处理法水解效果最好,通过补料酶解,底物质量分数可以达到30%,酶解液中总糖质量浓度达到132 g/L,葡萄糖质量浓度105 g/L;超微粉碎+稀酸预处理原料底物质量分数可以达到22%,酶解液中总糖质量浓度达到123 g/L,葡萄糖质量浓度73 g/L;超微粉碎+稀碱预处理原料底物质量分数可以达到22%,酶解液中总糖质量浓度133 g/L,葡萄糖质量浓度77 g/L。3种预处理使沙柳原料的酶解糖液都可以较好地被酿酒酵母利用发酵产乙醇,蒸爆处理原料的酶解糖液乙醇发酵效果最好,乙醇质量浓度达到47 g/L。     

Ethanol from lignocellulosic materials by a simultaneous saccharification and fermentation process (SFS) with Kluyveromyces marxianus CECT 10875

Simultaneous saccharification and fermentation (SSF) process for ethanol production from various lignocellulosic woody (poplar and eucalyptus) and herbaceous (Sorghum sp. bagasse, wheat straw and Brassica carinata residue) materials has been assayed using the thermotolerant yeast strain Kluyveromyces marxianus CECT 10875. Biomass samples were previously treated in a steam explosion pilot plant to provide pretreated biomass with increased cellulose content relative to untreated materials and to enhance cellulase accessibility. SSF experiments were performed in laboratory conditions at 42 °C, 10% (w/v) substrate concentration and 15 FPU/g substrate of commercial cellulase. The results indicate that it is possible to reach SSF yields in the range of 50–72% of the maximum theoretical SSF yield, based on the glucose available in pretreated materials, in 72–82 h. Maximum ethanol contents from 16 to 19 g/l were obtained in fermentation media, depending on the material tested.     

Enzymatic hydrolysis and simultaneous saccharification and fermentation of alkali/peracetic acid-pretreated sugarcane bagasse for ethanol and 2,3-butanediol production

The enzymatic digestibility of alkali/peracetic acid (PAA)-pretreated bagasse was systematically investigated. The effects of initial solid consistency, cellulase loading and addition of supplemental β-glucosidase on the enzymatic conversion of glycan were studied. It was found the alkali-PAA pulp showed excellent enzymatic digestibility. The enzymatic glycan conversion could reach about 80% after 24 h incubation when enzyme loading was 10 FPU/g solid. Simultaneous saccharification and fermentation (SSF) results indicated that the pulp could be well converted to ethanol. Compared with dilute acid pretreated bagasse (DAPB), alkali-PAA pulp could obtain much higher ethanol and xylose concentrations. The fermentation broth still showed some cellulase activity so that the fed pulp could be further converted to sugars and ethanol. After the second batch SSF, the fermentation broth of alkali-PAA pulp still kept about 50% of initial cellulase activity. However, only 21% of initial cellulase activity was kept in the fermentation broth of DAPB. The xylose syrup obtained in SSF of alkali-PAA pulp could be well converted to 2,3-butanediol by Klebsiella pneumoniae CGMCC 1.9131.     

Ethanol production from wheat straw by recombinant Escherichia coli strain FBR5 at high solid loading

Ethanol production by a recombinant bacterium from wheat straw (WS) at high solid loading by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) was studied. The yield of total sugars from dilute acid pretreated WS (150 g/L) after enzymatic saccharification was 86.3 ± 1.5 g/L. The pretreated WS was bio-abated by growing a fungal strain aerobically in the liquid portion for 16 h. The recombinant Escherichia coli strain FBR5 produced 41.1 ± 1.1 g ethanol/L from non-abated WS hydrolyzate (total sugars, 86.6 ± 0.3 g/L) in 168 h at pH 7.0 and 35 °C. The bacterium produced 41.8 ± 0.0 g ethanol/L in 120 h from the bioabated WS by SHF. It produced 41.6 ± 0.7 g ethanol/L in 120 h from bioabated WS by fed-batch SSF. This is the first report of the production of above 4% ethanol from a lignocellulosic hydrolyzate by the recombinant bacterium.     

Effect of dilute acid pretreatment on the saccharification and fermentation of rye straw

This research shows the effect of dilute acid pretreatment with various sulfuric acid concentrations (0.5–2.0% [wt/vol]) on enzymatic saccharification and fermentation yield of rye straw. After pretreatment, solids of rye straw were suspended in Na citrate buffer or post-pretreatment liquids (prehydrolysates) containing sugars liberated after hemicellulose hydrolysis. Saccharification was conducted using enzymes dosage of 15 or 25 FPU/g cellulose. Cellulose saccharification rate after rye straw pretreatment was enhanced by performing enzymatic hydrolysis in sodium citrate buffer in comparison with hemicellulose prehydrolysate. The maximum cellulose saccharification rate (69%) was reached in sodium citrate buffer (biomass pretreated with 2.0% [wt/vol] H₂SO₄). Lignocellulosic complex of rye straw after pretreatment was subjected to separate hydrolysis and fermentation (SHF) or separate hydrolysis and co-fermentation (SHCF). The SHF processes conducted in the sodium citrate buffer using monoculture of Saccharomyces cerevisiae (Ethanol Red) were more efficient compared to hemicellulose prehydrolysate in respect with ethanol yields. Maximum fermentation efficiency of SHF processes obtained after rye straw pretreatment at 1.5% [wt/vol] H₂SO₄ and saccharification using enzymes dosage of 25 FPU/g in sodium citrate buffer, achieving 40.6% of theoretical yield. However, SHCF process using cocultures of pentose-fermenting yeast, after pretreatment of raw material at 1.5% [wt/vol] H₂SO₄ and hydrolysis using enzymes dosage of 25 FPU/g, resulted in the highest ethanol yield among studied methods, achieving 9.4 g/L of ethanol, corresponding to 55% of theoretical yield.