糠醛渣纤维乙醇同步糖化发酵过程研究

以过碱化处理的糠醛渣为原料,采用正交试验法进行同步糖化发酵(SSF)转化乙醇工艺条件及过程研究.通过考察反应温度、pH、纤维素酶用量和表面活性剂浓度来优化同步糖化发酵转化工艺条件.在正交优化条件基础上,进行了5 L发酵罐试验,并同步分析表征了发酵过程中还原糖浓度、乙醇浓度、酵母细胞数、纤维素含量及其结构变化.同步糖化发酵转化糠醛渣生成乙醇的优化条件为:反应温度38℃,pH 4.2,纤维素酶用量20 FPU/(g纤维素),吐温-20质量分数0.15%,酵母接种量10%.发酵罐中同步糖化发酵糠醛渣生成乙醇的转化率达到72.33%,过程分析表明反应时间为27 h时,糠醛渣糖化发酵产乙醇的转化率达到最高,比其他纤维原料的反应转化时间大大缩短.同步糖化发酵过程中,糠醛渣纤维素含量逐步降低,纤维索表观结晶度呈下降趋势,纤维素微晶尺寸减小.     

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%。     

Span-20和Tween-80对发酵液中Nisin泡沫分离的影响

研究了微量非离子表面活性剂Tween-80和Span-20对发酵液中乳链菌肽(Nisin)泡沫分离的影响. 结果表明,发酵液泡沫分离时泡沫层轴向气泡直径、连续通气过程的泡沫层高度、泡沫层平均持气量等均因添加活性剂而明显变化. 不同体系气泡大小为,含0.2 g/L Span-20发酵液>含0.5 g/L Span-20发酵液>发酵液>含0.2 g/L Tween-80发酵液>含0.5 g/L Tween-80发酵液;Tween-80的加入破坏了气泡表面的网状结构,因而泡沫层持气量较高;连续通气时,2种表面活性剂都会引起泡沫层高度降低,但Tween-80会增加泡沫层的稳定性. 当Tween-80浓度达0.5 g/L时,Nisin的收率大幅度提高,原因是分离过程中Nisin失活率减少.     

Tween80对稻草水解及同步糖化与发酵产乳酸的影响

在生物转化纤维原料产乳酸的过程中,酶解纤维原料产还原糖是限速步骤。为了获得较高的产物产率,需较高的酶用量,这使大规模酶解废弃纤维原料的成本很高。对吐温80在酶解稻草纤维素产糖,以及耐高温乳酸菌同步糖化发酵稻草产乳酸过程中的作用进行了考察。初步结果表明,吐温80加入可使保持同等程度的水解率所需的酶用量降低,添加0.2 g/g底物的吐温80到酶用量10 FPU/g体系,水解120 h的糖产率为292.2 mg/g,比不加表面活性剂体系的糖产率增加了11%;添加0.7 g/L的吐温80进行同步糖化与发酵72 h,能使乳酸产量提高24.2%。     

木薯酒精渣同步糖化发酵制乙醇的工艺研究

研究了利用木薯酒精厂废渣为原料发酵生产乙醇的方法,结果表明:经过简单的机械粉碎后,通过同步糖化发酵生产乙醇是可行的。发酵条件为:木薯酒精渣经粉碎后取粒径小于0.85mm的部分,初始料水比1∶8,纤维素酶添加量为每克木薯渣(干重)30FPU,发酵过程中在24h内分批将剩余木薯渣加入至总料水比达到1∶2.5,利用5L发酵罐进行同步糖化发酵,发酵液中乙醇质量浓度达到52g/L,木薯酒精渣到乙醇的收率达到13%。纤维素酶的添加量对发酵效果影响显著,当达到每克木薯渣(干重)50FPU时,发酵液中乙醇质量浓度可达65g/L,乙醇收率达到16%。     

非离子表面活性剂对木质纤维素酶解的促进作用

纤维素酶单位酶活力较低、酶用量较高及酶自身易失活等因素依然是木质纤维素工业生产能源和生物基产品的瓶颈性问题。本文尝试在木质纤维素基质水解时添加一些非离子型表面活性剂以减少纤维素酶用量,并对这些非离子型表面活性剂促进酶解效率提高的原因进行了初步探讨。研究发现,添加非离子性表面活性剂能提高木质纤维素的酶解,添加浓度为0.05 g/g底物,常压甘油自催化预处理麦草经过添加两种非离子表面活性剂Tween-80和PEG 6000后葡萄糖产量分别可提高20%左右;非离子表面活性剂对不含木质素的原料酶解产糖也有较大的提高,以滤纸为底物时葡萄糖产量提高近90%,以微晶纤维素为底物时分别提高70%以上;添加非离子表面活性剂使得酶解体系中扩散系数k升高,异相反应效率提高,酶促反应动力学Km值明显减小,显著提高底物对纤维素酶的亲和力。     

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).     

糠醛渣直接同步糖化发酵生产乙醇过程比较研究

以糠醛渣为原料,直接同步糖化发酵(SSF)生产乙醇,并与水洗糠醛渣生产乙醇进行对比。通过考察不同条件来优化同步糖化发酵生产工艺条件,并分析表征了SSF过程中乙醇浓度和副产物浓度变化。优化条件为:糠醛渣底物质量分数10%,纤维素酶用量12%,无患子皂素质量浓度0.5g/L,酵母接种量7g/L,同步糖化发酵乙醇得率达到其理论得率的93.1%。与水洗糠醛渣相比,糠醛渣直接SSF过程可将原料吸附的5.50%葡萄糖部分转化为乙醇。水洗糠醛渣SSF生产乙醇所产生的副产物要远低于糠醛渣直接生产所产生的副产物,添加无患子皂素可有效抑制糠醛渣同步糖化发酵过程中副产物的产生。     

表面活性剂对复合刷镀液中纳米WC分散性的影响

研究了在(Ni-P)-纳米WC复合刷镀液中添加阴离子型表面活性剂SDS、阳离子型表面活性剂PEI、非离子型表面活性剂OP对分散体系分散效果的影响.结果表明:表面活性剂能有效阻止复合刷镀液中微粒的絮凝、团聚,其用量对复合刷镀液分散效果有显著的影响.当阴离子型表面活性剂SDS的质量浓度为0.2g/L,阳离子型表面活性剂PEI为O.8g/L时,刷镀液中沉降粉体体积最小,添加非离子型表面活性剂OP的分散体系分散效果较差.     

橡子粉同步液化糖化产燃料乙醇的发酵条件优化

以除去单宁的橡子粉为原料,应用活性干酵母同步液化糖化发酵(SLSF)制备燃料乙醇,并通过单因素试验和正交试验优化发酵条件。结果表明,同步液化糖化发酵技术适用于橡子粉发酵制备燃料乙醇;发酵的最佳条件为:除去单宁的橡子粉20 g,料液比为1:3(g:mL),淀粉酶100 U/g,糖化酶3 750 U/g,活性干酵母1.50%;在30 ℃静止发酵120 h,发酵液中的乙醇质量浓度达到106.5 g/L,橡子淀粉的乙醇转化率达到89.36 %。采用橡子粉发酵法制备燃料乙醇与以玉米等粮食作物为原料制备的燃料乙醇质量浓度相当,可以替代粮食作物生产燃料乙醇。     

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.     

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.     

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。     

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%.     

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.     

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 l and ?-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°C; substrate concentration, 100 g·L^-1; initial fermentation liquid pH, 5.0; enzyme loading, 30 FPU·g^-1. 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.     

Direct ethanol production from rice straw by coculture with two high-performing fungi

To develop efficient and economical direct ethanol production from fine rice straw crashed mechanically, two high-performing fungi, which can secret hyperactive cellulases and/or ferment effectively various sugars, were selected from some strains belong to Mucor circinelloides preserved in our laboratory. The simultaneous saccharification and fermentation (SSF) by coculture with these fungi was investigated. The screening of high-performing fungi resulted in the selection of NBRC 4572 as an ethanol-producing fungus and NBRC 5398 as a cellulase-secreting fungus. The strain 4572 produced ethanol aerobically from glucose and xylose in high yields of 0.420 g/g at 36 h and 0.478 g/g at 60 h, respectively, but secreted fairly low cellulases. On the other hand, the strain 5398 also produced ethanol from glucose in yield of 0.340 g/g though it had a little growth in xylose culture. However, it secreted hyperactive cellulases that are essential for hydrolysis of rice straw in culture and the maximum activities of endo-β-glucanase and β-glucosidase were 2.11 U/L and 1.47 U/L, respectively. In SSF of rice straw by coculture with two fungi selected, the ethanol production reached 1.28 g/L after 96 h when the inoculation ratio of the strain 5398 to the strain 4572 was 9.     

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 l 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°C; substrate concentration, 100 g·L⁻¹; initial fermentation liquid pH, 5.0; enzyme loading, 30 FPU·g⁻¹. 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. __________ Translated from Chemical Engineering (China), 2007, 35(12): 42–45 [译自: 化学工程]     

表面活性剂对去血渍复合酶中蛋白酶活性的影响

研究了3种类型8种常用表面活性剂LAS,K12,AES,AOS,TX-10,6501,CAB以及AEO9对去血渍复合酶中蛋白酶活性的影响,表面活性剂浓度设定为0.2~0.8 g/L。结果表明:阴离子表面活性剂LAS,K12,AES和AOS在一般洗涤浓度0.2~0.5 g/L下对蛋白酶活性无明显影响,但在0.8 g/L的高浓度时表现出一定的抑制作用,其中LAS的抑制作用最大;非离子表面活性剂TX-10,6501和AEO9以及两性离子表面活性剂CAB在0.2~0.5 g/L浓度下的激活作用比较明显,这种激活作用随着浓度的继续增大至0.8 g/L而逐渐减弱。总体来说,阴离子表面活性剂在0.2~0.5 g/L浓度下能与去血渍复合酶中蛋白酶良好配伍,而非离子表面活性剂和两性离子表面活性剂在整个实验浓度下都能与去血渍复合酶中蛋白酶良好配伍。