Process Research on Separate Hydrolysis and Fermentation(SHF) and Simultaneous Saccharification and Fermentation(SSF) of Ethanol Production by Lignocellulose

[ Objective] The research aimed to explore the efficiency of ethanol production under the optimal conditions of separate hydrolysis and fermentation （SHF） and simultaneous saccharification and fermentation （SSF）. [ Method ] Under the optimal conditions of hydrolysis and fermenta- tion, SHF and SSF process were designed respectively. SHF process was conducted under the optimal conditions of hydrolysis and fermentation separately, while SSF process was carried out at the optimum temperature of hydrolysis and fermentation. [ Result] In SHF process, the efficiency of ethanol production was similar during both supematant and mixture fermentation, and yeast was more active during the mixture fermentation. In SSF process, the efficiency of ethanol production was higher at 35 ℃, and the production of xylose was higher than that in hydrolysis process. [ Conclusion] Under the experimental conditions, the efficiency of ethanol production during simultaneous saccharification and fermentation was higher than that during separate hydrolysis and fermentation.

Simultaneous saccharification and fermentation of steam-pretreated lespedeza stalks for the production of ethanol

Lespedeza stalks were subjected to steam pretreatment at 210℃ for some steaming time before simultaneous saccharification and fermentation （SSF）. Cellulose-derived glucose was extensively utilized by yeast during SSE The ethanol yields after steam pretreatment of the lespedeza stalks at 210℃ were 59.3%, 72.8% and 62.2% of the theoretically expected values when the steaming times were 2, 4 and 6 min, respectively. The highest yield from α-cellulose was 92.7% of the theoretical value. Steam explosion pretreatment of lespedeza stalks increased ethanol yields by a factor of 4.4, from 16.4% （untreated） to 72.8% （steam explosion pretreated）.

Optimization of rice wine fermentation process based on the simultaneous saccharification and fermentation kinetic model

Chinese rice wine making is a typical simultaneous saccharification and fermentation （SSF） process. During the fermentation process, temperature is one of the key parameters which decide the quality of Chinese rice wine. To optimize the SSF process for Chinese rice wine brewing, the effects of temperature on the kinetic parameters of yeast growth and ethanol production at various temperatures were determined in batch cultures using a mathematical model. The kinetic parameters as a function of temperature were evaluated using the software Origin8.0. Combing these functions with the mathematical model, an appropriate form of the model equations for the SSF considering the effects of temperature were developed. The kinetic parameters were found to fit the experimental data satisfactorily with the developed temperature-dependent model. The temperature profile for maximizing the ethanol production for rice wine fermentation was determined by genetic algorithm. The optimum temperature profile began at a low temperature of 26℃ up to 30 h. The operating temperature increased rapidly to 31.9 ℃, and then decreased slowly to 18℃ at 65 h. Thereafter, the temperature was maintained at 18 ℃ until the end of fermentation. A maximum ethanol production of 89.3 g.L 1 was attained. Conceivably, our model would facilitate the improvement of Chinese rice wine production at the industrial scale.

Optimization Studies in Simultaneous Saccharification and Fermentation of Wheat Bran Flour into Ethanol

The effects of process variables in Simultaneous Saccharification and Fermentation (SSF) of wheat bran flour were studied in bulk fermentation using a coculture of Aspergillus niger - Kluveromyces marxianus. The effect of substrate density, pH, temperature, and enzyme concentration on wheat bran was predicted by designing experiments in which a single parameter is varied keeping other variables at a constant level. The above parameters were optimized for a batch culture in a fermentor. Optimal values for substrate concentration, pH, temperature, and enzyme concentration during processing were 200 g/l, 5.5, 65°C, and 7.5 IU, respectively. In pre-treatment experiments, the concentration of enzymes and the pre-treatment temperature are highly correlated. The influence of pH, temperature, and substrate density on ethanol production was investigated. Temperature pH was determined as optimal, 32°C and 5.5, respectively. After 48 hours of fermentation at optimum pH, a solution of wheat bran containing a maximum of 6% starch produces a maximum of 22.9 g/l ethanol.

Simultaneous Saccharification and Fermentation of Alkali-Acid Pretreated Sugarcane Trash to Ethanol

The Simultaneous Saccharification and Fermentation （SSF） of alkali-acid pretreated sugarcane trash to ethanol was optimized using commercial cellulase and Saccharomyces cerevisiae TISTR 5596 cells. Substrate concentration （12.5% w/v, 15% w/v, 17.5% w/v and 20% w/v）, enzyme loading （25 FPU/g Dry Substrate （DS）, 50 FPU/g DS and 75 FPU/g DS）, and temperature （30 ~C, 35 ~C and 40 ~C） were evaluated. The SSF optimal conditions for alkali-acid pretreated sugarcane trash were 20% w/v of substrate concentration, enzyme loading 50 FPU/g DS, temperature 35 ~C, initial pH 5.0 and yeast inoculum 107 cells/mL. Under the above optimal conditions, ethanol concentration was possible to reach in the range between 50.14 g/L and 55.08 g/L at 96 hrs and 144 hrs, respectively. This study could establish the effective utilization of sugarcane trash for bioethanol production using optimized fermentation parameters.

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.Experi-ments 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 fungalα-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 200g/L,5.5,65℃ and 7.5IU,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℃ and 5.5,respectively.The wheat bran flour solution equivalent to 6%(w/V)initial starch concentration gave the highest ethanol concentrationof 23.1g/Lafter 48hoffermentation 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 fermenta-tion 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 sweet potato powder for the production of ethanol under conditions of very high gravity

Due to its merits of drought tolerance and high yield,sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production.Very high gravity(VHG)technology is an effective strategy for improving the efficiency of ethanol fermentation from starch materials.However,this technology has rarely been applied to sweet potatoes because of the high viscosity of their liquid mash.To overcome this problem,cellulase was added to reduce the high viscosity,and the optimal dosage and treatment time were 8 U/g(sweet potato powder)and 1 h,respectively.After pretreatment by cellulase,the viscosity of the VHG sweet potato mash(containing 284.2 g/L of carbohydrates)was reduced by 81%.After liquefaction and simultaneous saccharification and fer-mentation(SSF),thefinal ethanol concentration reached 15.5%(v/v),and the total sugar conversion and ethanol yields were 96.5%and 87.8%,respectively.

Study of simultaneous saccharification and fermentation for steam exploded wheat straw to ethanol

Although simultaneous saccharification and fermentation(SSF)has been investigated extensively,the optimum condition for SSF of wheat straw has not yet been determined.Dilute sulfuric acid impregnated and steam explosion pretreated wheat straw was used as a substrate for the production of ethanol by SSF through orthogonal experiment design in this study.Cellulase mixture(Celluclast 1.5 1 and β-glucosidase Novozym 188)were adopted in combination with the yeast Saccharomyces cerevisiae AS2.1.The effects of reaction temperature,substrate concentration,initial fermentation liquid pH value and enzyme loading were evaluated and the SSF conditions were optimized.The ranking,from high to low,of influential extent of the SSF affecting factors to ethanol concentration and yield was substrate concentration,enzyme loading,initial fermentation liquid pH value and reaction temperature,respectively.The optimal SSF conditions were:reaction temperature,35℃;substrate concentration,100 g·L^(-1);initial fermentation liquid pH,5.0;enzyme loading,30 FPU·g21.Under these conditions,the ethanol concentration increased with reaction time,and after 72 h,ethanol was obtained in 65.8%yield with a concentration of 22.7 g·L^(-1).

Feasibility Study of Ethanol Production from Food Wastes by Consolidated Continuous Solid-State Fermentation

To save the cost and input energy for bioethanol production, a consolidated continuous solid-state fermentation (CCSSF) system composed of a rotating drum reactor, a humidifier and a condenser has been developed. In this research, the feasibility of using this system for production of ethanol from food wastes was carried out. The ethanol conversion of bread crust and rice grain (uncooked rice) as substrates reached up to 100.9% ± 5.1% and 108.0% ± 7.9% (against theoretical yield), respectively. Even for bread crust, a processed starchy material which contained lower carbohydrate content than rice grain, the amount of ethanol obtained in a unit of CCSSF per year was higher due to easy saccharification and fermentation. The salt contained in potato chips directly affected yeast activity resulting to low ethanol conversion (80.7% ± 4.7% against theoretical yield).

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。

木质纤维生物量一步法(SSF)转化成乙醇的研究进展

该文综述了木质纤维生物量一步法 (SSF)转化成乙醇的研究进展 ,总结了SSF法的优点 ,提出了现阶段SSF法存在的问题以及在今后研究中需要解决的问题 .

高浓度红薯醪SSF燃料乙醇过程中底物抑制的调节

红薯干经粉碎、液化处理后得到淀粉含量为230g/kg的高浓度红薯醪,利用工业酵母Saccharomyces cereviseATCC 6508同步糖化发酵(SSF)生产燃料乙醇。通过改变糖化酶的添加剂量调节发酵过程中糖化速率,控制醪液中葡萄糖浓度的变化。发酵前期严格控制底物抑制对细胞生长速率的影响,通过较高的细胞浓度保障发酵后期发酵速率,减轻产物抑制对发酵过程的影响。实验发现在0.2、0.4、0.6和0.8g/kg(糖化酶/红薯干粉)糖化酶添加量下,发酵过程中葡萄糖浓度被严格控制在强烈抑制的浓度水平以下(100g/kg),1.0g/kg剂量下醪液中葡萄糖浓度长时间高于100g/kg,底物抑制严重;发酵后期在0.2、0.4和0.6g/kg剂量下,由于糖化酶活性降低,糖化速率成为发酵速率的限制因素。综合分析糖化酶的最佳剂量为0.8g/kg,该剂量下既能严格控制底物抑制水平,同时保持发酵后期较高糖化速率,发酵终点乙醇浓度达118.23g/kg(16.12%,v/v),发酵时间为72h。

厨余垃圾同步糖化发酵产纤维素乙醇的工艺优化

为提高纤维素乙醇产率,以未经腐烂的果皮和蔬菜垃圾作为原料,采用酿酒酵母与纤维素酶作为催化添加剂进行同步糖化发酵,结合单因素实验和正交实验,优化了利用厨余垃圾同步糖化发酵产生纤维素乙醇的工艺条件。结果表明:在单因素实验中,采用SSF(同步糖化发酵)工艺时,纤维素酶酶加量、酵母用量、发酵温度和初始pH等因素均能使乙醇产率升高,差异不显著;在正交试验中,采用SSF工艺时,对乙醇产率影响的因素从强到弱为发酵温度>纤维素酶酶加量>酵母用量,且在纤维素酶酶加量30 mg、酵母用量10 mL、初始pH=5、发酵温度45℃、发酵72 h条件下,乙醇浓度最高,可达6.43 g/L,产率为0.089 g/(L·h)。研究发现,采用SSF工艺,为提高乙醇产率、实现废弃物资源化、缓解能源短缺压力等方面提供了新的方向。

玉米酒精的浓醪同步糖化发酵工艺研究

以我国目前玉米酒精生产工艺为基础,通过选择液化[拌料干物浓度(dry solid,DS)、液化pH、液化时间、耐高温α-淀粉酶剂量、液化温度]和同步糖化发酵(葡萄糖淀粉酶剂量、酵母接种量、发酵温度等)等过程主要控制参数建立实验室玉米酒精发酵方法。实验确定液化条件为拌料DS 25%、液化pH 5.6、液化时间120 min、耐高温α-淀粉酶剂量40 U/g、液化温度88℃,此时液化醪黏度(91.2±2.8)mPa·s、还原糖为(11.65±0.03)g/100 g,符合同步发酵玉米酒精的液化指标要求。实验确定同步糖化发酵条件为葡萄糖淀粉酶剂量150 U/g、酵母接种量3%、发酵温度32℃,在该条件下酒精发酵过程稳定,CO 2失重数据最大标准差为0.38,占相应CO 2平均失重仅为2.96%;在发酵成熟醪中乙醇含量为(12.58±0.04)g/100 mL,发酵效率为97.71%,粮酒转化率为2.425 t/t,实验结果符合我国玉米酒精生产的实际情况。因此该方法可以为酒精生产工艺的优化及原辅料的选择提供数据参考。

基于常压室温等离子体诱变技术选育耐高温马克斯克鲁维酵母菌株及其代谢机制解析

为达到同步糖化发酵(simultaneous saccharification and fermentation,SSF)中菌株高温耐受能力提升的目的,该文以实验室保藏的马克斯克鲁维酵母(Kluyveromyces marxianus)GX-UN120为出发菌株,采用常压室温等离子体(atmospheric and room temperature plasma,ARTP)诱变技术,结合高温胁迫筛选获得1株具有较好耐高温能力和产乙醇能力的菌株GX-UN127。结果表明,诱变菌株GX-UN127在48℃培养72 h,OD_(600)可达到1.27(原始菌株无法生长)。同时,当以100 g/L麸皮为原料,45℃SSF 12 h,诱变菌株GX-UN127发酵乙醇的产量可达7.6 g/L,较出发菌株提升15.2%。在此基础上,结合生理指标和代谢组学进一步探究诱变菌株耐受高温的生理机制,研究表明半胱氨酸和蛋氨酸代谢、谷胱甘肽代谢、精氨酸和脯氨酸代谢、甘油磷脂代谢等代谢途径与诱变菌株GX-UN127的更强高温耐受性密切相关。此诱变选育耐高温马克斯克鲁维酵母菌株的方案可行,为该类菌株进行SSF生产燃料乙醇提供理论支持。

表达漆酶的重组酿酒酵母菌株同步糖化发酵产乙醇特性研究

将来源于硬毛拴菌(Trametes trogii CICC 2689)的lcc1基因通过Di-CRISPR技术整合到酿酒酵母Y6中以实现漆酶的稳定表达,考察漆酶在酚类抑制剂及同步糖化发酵中的抗逆作用。结果显示:平板拮抗和液体摇瓶实验中,重组菌株Y6/Lac的生长状况、对数期生长速率及延滞期较对照菌株Y6均表现出相应优势;同时Y6/Lac对碱木质素的降解率提高41%,同步糖化发酵产乙醇效率提高14%。

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0.45mm,加水比2.8,100℃下蒸煮30min,α?淀粉酶、糖化酶的添加量分别为10,180U/g,30℃下发酵48h.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.

菊芋原料同步糖化发酵生产丁二酸

对菊芋原料发酵生产丁二酸进行了研究,用Actinobacillus succinogenes和Aspergillusniger同步糖化发酵,发现同步糖化发酵效果优于糖化后再发酵,在同步糖化发酵过程中还原糖质量浓度始终保持在10～40 g/L,可以避免高浓度的还原糖对A.succinogenes的抑制。5 L搅拌罐中同步糖化补料分批发酵96 h产丁二酸98.2 g/L,对消耗糖产率95.4%,生产强度1.02g/（L.h）。

汽爆玉米秸秆同步糖化发酵产乙醇的工艺优化

该文对同步糖化发酵玉米秸秆生产纤维乙醇的工艺条件进行了研究,分别利用单因素试验和正交试验考察了影响发酵的工艺条件。结果显示:温度37℃、pH值4.8、底物15%(质量分数)、表面活性剂Tween-200.15%(质量分数)、纤维素酶用量30U/g、酵母用2%的葡萄糖溶液活化,接种量5‰(相对底物干质量)、培养基的组成:KH2PO42.5g/L,(NH4)2SO42.0g/L,MgSO4·7H2O0.15g/L,CaCl20.35g/L、发酵时间60h为同步糖化发酵(SSF)生产乙醇的最优工艺条件,该条件下乙醇的体积分数为2.85%,乙醇得率达理论值的88.12%。