自絮凝颗粒酵母发酵菊芋汁生产乙醇

分别采用分批和连续发酵方式,对自絮凝颗粒酵母Saccharomyces cerevisiae flo发酵菊芋汁生产乙醇的条件进行了优化. 与先酶解菊芋汁后再用自絮凝酵母发酵的分步糖化发酵相比,分批发酵过程中同时加入菊粉酶和自絮凝酵母的同步糖化发酵乙醇得率高,发酵时间短. 当菊芋汁总糖浓度分别为105和179 g/L时,同步糖化发酵的最高乙醇浓度达50和82.5 g/L,比分步糖化发酵高6.4%和13.8%. 在连续发酵过程中应用同步糖化发酵法,当稀释率为0.02 h-1时,乙醇浓度约为90 g/L时达到稳定状态,乙醇得率达到理论值的90%,生产强度达2.12 g/(L×h).     

Ethanol production by co-fermentation of hexose and pentose from food wastes using Saccharomyces coreanus and Pichia stipitis

To improve the conversion rate of a saccharification liquid from food wastes containing pentoses and hexoses into bioethanol, after selecting Saccharomyces coreanus and Pichia stipitis, the respective fermentation and co-fermentation properties were investigated. In the fermentation using S. coreanus, the result under anaerobic condition was better than under aerobic conditions. In the anaerobic fermentation, the concentration of the reducing sugar and glucose remaining after 24 hrs was 9.09 and 1.88 g/L, respectively, with 40.59 g/L of ethanol produced; the ethanol productivity was 1.69 g/L-h. Also, even with the fermentation using P. stipitis, the reducing sugars and glucose were rapidly reduced, with a marked production of ethanol, but the ethanol produced was lower than those under anaerobic and aerobic conditions with the use of S. coreanus. Therefore, for the production of a high concentration of bioethanol from food wastes, ethanol fermentation was induced using S. coreanus until the middle of the fermentation, with P. stipitis used during the latter stage of the fermentation, where the circumstance favored its use, and thus, the carbon source not converted by S. coreanus was later converted to ethanol. As a result, both ethanol production of 48.63 g/L and productivity of 2.03 g/L-h increased over those of the anaerobic fermentation using S. coreanus.     

高底物浓度纤维乙醇同步糖化发酵工艺的比较

引言日益加剧的能源危机和环境污染,正迫使人们寻求新的可再生替代能源。纤维乙醇作为一种重要的生物质替代能源,经过近40多年的发展,已经具备了实现工业化生产的潜力。为了进一步降低纤     

木薯干原料同步糖化发酵生产乙醇

提出了用木薯干为原料,同步糖化发酵(SSF)开发燃料乙醇的新工艺. 对各个影响条件进行了研究,获得了最佳的工艺条件：原料粉碎粒度0.45 mm,加水比2.8, 100℃下蒸煮30 min,a-淀粉酶、糖化酶的添加量分别为10, 180 U/g, 30℃下发酵48 h. 并与普通的先糖化后发酵(SHF)生产模式进行了对比,认为SSF具有工艺简单、能耗低、发酵迅速、醪液酒精度高等众多优点,值得工业推广.     

Sago starch saccharification and simultaneous ethanol fermentation by amyloglucosidase and Zymomonas mobilis

Simultaneous saccharification and ethanol fermentation (SSF) of sago starch was studied using amyloglucosidase (AMG) and Zymomonas mobilis. The optimal concentration of AMG and operating temperature for the SSF process were found to be 0.5% (v/w) and 35°C, respectively. Under these conditions with 150 g dm^?3 sago starch as a substrate, the final ethanol concentration obtained was 69.2 g dm^?3 and ethanol yield, Y_P/S, 0.50 g g^?1 (97% of theoretical yield). Sago starch in the concentration range of 100–200 g dm^?3 was efficiently converted into ethanol. When compared to a two-step process involving separate saccharification and fermentation stages, the SSF reduced the total process time by half.     

木薯酒精渣的预处理及补料同步糖化发酵制取乙醇

木薯酒精渣的处置是制约木薯燃料乙醇大规模产业化的问题之一。本文立足于探索木薯酒精渣利用途径,分析了木薯酒精渣的主要成分,对比了氨水、氢氧化钠、氨水组合稀硫酸3种预处理方式对于木薯酒精渣纤维素和木素含量及纤维素酶水解效率的影响,分析了处理前后木薯酒精渣的表面结构及纤维素结晶度,并以氨水处理后的木薯酒精渣为底物,进行了同步糖化发酵。结果表明,3种预处理方法中组合预处理能更好地增加纤维素含量和提高纤维素酶水解效率,与未处理原料相比,组合预处理后纤维素含量增加了111.26%,木素下降了35.05%,酶水解72h纤维素转化率从42.10%增加到61.71%。氨水预处理后,原料的木素含量降低,处理后木薯酒精渣的表面变得更加粗糙,纤维素结晶度有所增加,以氨水处理后的木薯酒精渣为底物进行分批补料同步糖化发酵,当初始底物浓度为100.0g/L,分别在20h、40h、60h进行补料至最终底物浓度为400.0g/L时,发酵120h乙醇浓度达到51.0g/L。     

Ethanol production from sweet sorghum residual

In this work, the ethanol production from sweet sorghum residue was studied. Sweet sorghum residue was hydrolyzed with phosphoric acid under mild conditions. The liquid hydrolysate was fermented by Pachysolen tannophilus, and the hydrolysis residue was fermented by the simultaneous saccharification and fermentation (SSF) using Saccharomyces cerevisiae with cellulase (60 FPU/g dry materials). Orthogonal experiments were carried out to investigate the effects of main reaction condition factors, such as temperature, acid concentration, time and dry-matter content, on the reducing sugar yield. The results show that the optimal reaction conditions should be 120°C, 80 g/L, 80 min and 10%, respectively. Under these conditions, 0.3024 g reducing sugar/g dry material was obtained. The liquid hydrolysate was then fermented by P.tannophilus with the highest ethanol concentration of 14.5 g/L. At a water-insoluble solid concentration of 5%, 5.4 g/L ethanol was obtained after 12 h of SSF. The total ethanol yield was 0.147 g/g dry material, which would be beneficial for the application of ethanol production from sweet sorghum residue. __________ Translated from Journal of Beijing University of Chemical Technology, 2007, 34(6): 637-639, 652 [译自: 北京化工大学学报]     

耐热酿酒酵母FE-B的分离筛选及应用研究

从米酒酒曲中筛选出来一株乙醇发酵菌株,命名为FE-B,经鉴定为酿酒酵母,CGMCC保藏号为2735。FE-B在28,36和40℃都能生长,28 h左右达到稳定期时培养物的菌体浓度分别为4.24,3.95和3.23 g(DCW)/L。FE-B在28,36和42℃发酵24 h,发酵液中的乙醇浓度分别为8.0%,8.1%和3.3%。FE-B在温度≤41℃,酶加入量25 IU/g(秸秆干基),固含量10%条件下进行同步糖化与发酵,乙醇产生速率随温度上升而递增,当温度为41℃时,72 h后体系中乙醇浓度可达2.11%,纤维素水解率87.6%,具有很好的应用前景。     

Different process configurations for bioethanol production from pretreated olive pruning biomass

BACKGROUND: In Mediterranean countries, olive tree pruning provides a widely available renewable agricultural residue with, currently, no industrial application. This residue could provide feedstock for the bioethanol industry. In the present study, olive tree pruning biomass pretreated with both ‘liquid hot water’ and ‘dilute‐sulfuric acid’ was tested as a substrate for ethanol production. Three different process configurations, separate hydrolysis and fermentation (SHF), simultaneous saccharification, fermentation and prehydrolysis (PSSF), and simultaneous saccharification and fermentation (SSF), were compared at different water‐insoluble solids concentrations. RESULTS: High ethanol concentration of about 3.7% (v/v) was obtained by separate hydrolysis and fermentation or prehydrolysis and simultaneous saccharification and fermentation of liquid hot water pretreated at 23% (w/w) substrate loading. CONCLUSION: The nature of the pretreated residue allows high substrate concentration (≥17% w/w) to be used in the enzymatic hydrolysis step. Substrate loading of 17% DM has been shown to provide a compromise between hydrolysis efficiency and glucose concentrations for the same enzyme/substrate ratio. Prehydrolysis prior to simultaneous saccharification and fermentation facilitated SSF performance at high substrate loading on liquid hot water pretreated olive pruning residue. This effect was not observed with dilute‐acid pretreated substrate. Copyright © 2011 Society of Chemical Industry     

Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.     

Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.     

蒸汽爆破麦草同步糖化发酵转化乙醇的研究

近年来对木质生物资源同步糖化发酵转化乙醇的研究较多,但是,麦草同步糖化发酵转化乙醇的最佳工艺条件还未确定。文中采用正交试验设计的方法,对在混合酶(纤维素酶Celluclast 1.5 1,β-葡萄糖苷酶Novozym 188)与酿酒酵母菌作用下,稀硫酸催化的蒸汽爆破麦草原料同步糖化发酵转化乙醇的工艺条件进行研究,详细讨论了反应温度、底物质量浓度、发酵液pH值、纤维素酶浓度对乙醇质量浓度和得率的影响。结果表明,工艺条件对乙醇质量浓度和得率的影响程度由高到低依次为:底物质量浓度、纤维素酶浓度、发酵液pH值、反应温度。最佳工艺条件为反应温度35℃,底物质量浓度100 g/L,发酵液pH值5.0,纤维素酶浓度30 FPU/g。在此条件下,随着反应时间的延长,乙醇质量浓度持续上升。反应72 h后,乙醇质量浓度和得率分别达到22.7 g/L和65.8%。     

表面活性剂对麦草同步糖化发酵转化乙醇的影响

研究了5种非离子型表面活性剂(BSA, Tween-20, Tween-80, PEG-4000, PEG-6000)促进麦草同步糖化发酵的效果. 结果表明,5种表面活性剂均能促进麦草同步糖化发酵,以Tween-20效果最为显著. 反应体系中添加Tween-20可降低酶用量而保持乙醇浓度基本相同. 在pH 5.0、温度37℃、底物浓度50 g/L及Celluclast 1.5 l用量25 FPU/g、Novozym 188用量15 IU/g的反应体系中,添加0.03 g/g Tween-20,反应72 h,乙醇浓度达到18.7 g/L,比未添加表面活性剂的体系提高了14.0%,反应时间缩短了12 h.     

Comparison of bioethanol production of simultaneous saccharification & fermentation and separation hydrolysis & fermentation from cellulose-rich barley straw

Cellulose rich barley straw, which has a glucan content of 62.5%, followed by dilute acid pretreatment, was converted to bioethanol by simultaneous saccharification and fermentation (SSF). The optimum fractionation conditions for barley straw were an acid concentration of 1% (w/v), a reaction temperature of 158 °C and a reaction time of 15 min. The maximum saccharification of glucan in the fractionated barley straw was 70.8% in 72 h at 60 FPU/gglucan, while the maximum digestibility of the untreated straw was only 18.9%. With 6% content WIS (water insoluble solid) for the fractionated barley straw, 70.5 and 83.2% of the saccharification yield were in SHF and SSF (representing with glucose equivalent), respectively, and a final ethanol concentration of 18.46 g/L was obtained under the optimized SSF conditions: 34 °C with 15 FPU/g-glucan enzyme loading and 1 g dry yeast cells/L. The results demonstrate that the SSF process is more effective than SHF for bioethanol production by around 18%.     

Continuous simultaneous saccharification and fermentation of raw starch in a membrane reactor

A kinetic model for simultaneous saccharification and fermentation (SSF) of raw starch is proposed. The model includes the effect of ethanol on an active site for saccharification and the decay of a raw starch affinity site. The kinetic parameters were determined by using the experimental results of a batch saccharification and a long-term repeated-batch SSF of raw sweet potato starch. From analysis of the experimental results it is concluded that two subsites took part in ethanol inhibition, and that the inactivation of the raw starch affinity site was induced by adsorption of glucoamylase onto raw starch. The proposed kinetic model successfully predicted the progress of continuous SSF in a membrane reactor.     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

Bioethanol production from wheat straw by the thermotolerant yeast Kluyveromyces marxianus CECT 10875 in a simultaneous saccharification and fermentation fed-batch process

Solid content in the simultaneous saccharification and fermentation (SSF) broth should be as high as possible in order to reach higher ethanol concentration. In this work, several feeding strategies for ethanol production from steam-exploded wheat straw by Kluyveromyces marxianus CECT 10875 have been studied with the aim of obtaining higher ethanol concentrations. Previous fermentability tests as well as SSF processes showed the difficulty of using the slurry for ethanol production under the studied conditions. Notwithstanding, fed-batch SSF processes with water-insoluble solids (WIS) fraction resulted in better configuration, reaching the highest ethanol concentration (36.2 g/L) with an initial WIS content of 10% (w/v) and 4% (w/v) of substrate addition at 12 h, which meant 20% more ethanol when compared with batch SSF.     

Simultaneous saccharification and fermentation of alkaline-pretreated corn stover to ethanol using a recombinant yeast strain

Bio-ethanol converted from cheap and abundant lignocellulosic materials is a potential renewable resource to replace depleting fossil fuels. Simultaneous saccharification and fermentation (SSF) of alkaline-pretreated corn stover for the production of ethanol was investigated using a recombinant yeast strain Saccharomyces cerevisiae ZU-10. Low cellobiase activity in Trichoderma reesei cellulase resulted in cellobiose accumulation. Supplementing the simultaneous saccharification and fermentation system with cellobiase greatly reduced feedback inhibition caused by cellobiose to the cellulase reaction, thereby increased the ethanol yield. 12 h of enzymatic prehydrolysis at 50 °C prior to simultaneous saccharification and fermentation was found to have a negative effect on the overall ethanol yield. Glucose and xylose produced from alkaline-pretreated corn stover could be co-fermented to ethanol effectively by S. cerevisiae ZU-10. An ethanol concentration of 27.8 g/L and the corresponding ethanol yield on carbohydrate in substrate of 0.350 g/g were achieved within 72 h at 33 °C with 80 g/L of substrate and enzyme loadings of 20 filter paper activity units (FPU)/g substrate and 10 cellobiase units (CBU)/g substrate. The results are meaningful in co-conversion of cellulose and hemicellulose fraction of lignocellulosic materials to fuel ethanol.     

木质纤维生物质同步糖化发酵(SSF)生产乙醇的研究进展

综述了有关木质纤维生物质原料同步糖化发酵生产乙醇的最新研究进展和未来发展方向:同步糖化发酵是一种用于从木质纤维原料生产乙醇的工艺过程,此工艺的优点是酶水解与发酵同时进行,可以减少最终产物对酶水解的抑制作用,并减少投资成本,是最具发展潜力和优势的工艺之一。近年来在优化预处理工艺、降低纤维素酶成本以及己糖戊糖协同发酵等方面的研究都取得了长足的进步,其中以小麦秸秆为原料进行同步糖化发酵所得到的乙醇浓度接近40g/L。     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.