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1.
研究纤维素酸水解产生的4种副产物乙酸、甲酸、糠醛、5-羟甲基糠醛及发酵产物乙醇对Kluyveromyces marxianus 1727共发酵葡萄糖和木糖的影响。结果表明:5.0 g/L乙酸和1.0 g/L甲酸对葡萄糖和木糖共发酵具有明显的抑制作用;1.0 g/L糠醛和5-羟甲基糠醛基本不影响K.marxianus 1727发酵葡萄糖,且能够被K.marxianus1727转化为毒性相对较低的物质。由于5-羟甲基糠醛的转化速率慢,对K.marxianus 1727发酵木糖的抑制程度大于糠醛。乙醇对K.marxianus 1727发酵木糖具有抑制作用,当乙醇质量浓度大于20 g/L时,生物量及木糖利用率约是对照的44%和70%。  相似文献   

2.
为了客观评判耐高温东方伊萨酵母HN-1利用木质纤维素水解液生产燃料乙醇的潜力,本文采用单因素试验和响应面中心组合试验研究了木质纤维素水解液有毒副产物甲酸钠(1.0-5.0 g/L)、乙酸钠(2.5-8.0 g/L)、糠醛(0.2-2.0 g/L)、5-羟甲基糠醛(0.1-1.0 g/L)和香草醛(0.5-2.0 g/L)对其乙醇发酵的影响。结果表明,木质纤维素水解液有毒副产物对东方伊萨酵母HN-1乙醇发酵的影响较小,除添加2 g/L香草醛或添加1 g/L 5-羟甲基糠醛可使乙醇产量分别降低20.38%和11.2%外,其他抑制物的添加对乙醇的生成未有显著影响。但是,当副产物浓度较高时,可以显著抑制菌体生长,添加1-5 g/L甲酸钠、2.5-8.0 g/L乙酸钠、0.4-2 g/L糠醛或0.5-2 g/L香草醛,发酵36 h时菌体细胞干重分别较对照下降了25.04%-37.02%、28.83%-43.82%、20.06%-37.60%和26.39%-52.64%。中心组合试验结果表明各抑制物交互作用对乙醇的生成影响不显著。该研究表明木质纤维素水解液副产物对东方伊萨酵母HN-1乙醇发酵的影响较小,适合用于纤维乙醇发酵。  相似文献   

3.
为实现利用秸秆水解产生的五碳糖发酵产壳聚糖,以米根霉为研究对象,研究水解温度、水解时间、酸浓度等不同预处理方式获得的半纤维素水解液对米根霉发酵产壳聚糖的影响。结果表明:水解温度、水解时间对水解液中木糖含量以及甲酸、乙酸、糠醛等抑制剂浓度具有显著影响,并进一步影响后续发酵产壳聚糖的生成量。利用响应曲面对稀酸水解预处理条件进行优化,获得最佳工艺条件:H_2SO_413.6 g/L,99.5℃,水解时间1.91 h,在此条件下预测壳聚糖发酵产量为0.79 g/L,实验验证产量为0.82 g/L,占菌体生物量的15%~18%。研究结果为秸秆资源的高效利用及发酵生产壳聚糖提供新思路。  相似文献   

4.
发酵性丝孢酵母HWZ004利用水稻秸秆水解液发酵产油脂   总被引:3,自引:0,他引:3  
为高效利用水稻秸秆中的纤维素和半纤维素产油脂,采用稀酸预处理和酶水解两步法对水稻秸秆进行水解,然后以水解液为碳源,培养发酵性丝孢酵母Trichosporon fermentans HWZ004产微生物油脂。结果表明,经简单overliming法脱毒后水稻秸秆水解液中乙酸、糠醛和5-羟甲基糠醛的浓度分别为0.4 g/L、0.1 g/L和0.05 g/L。只需添加少量氮源和微量CuSO4?5H2O,该水解液即可满足T. fermentans HWZ004发酵产油脂的要求。发酵最适接种量、初始pH和温度分别是5.0%、7.0和25 ℃。T. fermentans HWZ004在优化条件下培养7 d的生物量、油脂含量和油脂产量分别是26.4 g/L,52.2%和13.8 g/L;油脂得率系数为17.0,大大高于驯化前菌株T. fermentans CICC 1368在脱毒水稻秸秆半纤维素水解液中的对应值 (11.9)。所产油脂的脂肪酸组成与植物油相似,不饱和脂肪酸含量达70%以上,宜作为生物柴油的生产原料。  相似文献   

5.
半纤维素水解液抑制物对微生物细胞的毒性限制了其在丁醇发酵中的应用,旨在探讨其对产丁醇共生体系TSH06的抑制作用并为其应用于丁醇发酵奠定基础。通过稀酸水解半纤维素制得水解液,采用P2培养基稀释的半纤维素水解液为底物,分别利用NaOH和氨水调节培养基pH值,结合实时荧光定量PCR方法来研究水解液对产丁醇共生体系TSH06的抑制作用。以NaOH调节pH抑制菌体的生长,氨水调节pH菌体可生长发酵。产丁醇菌株TSH06可以在50%稀释度以下的水解液中发酵生长,并且能够耐受并降解抑制物糠醛与5-羟甲基糠醛,最终丁醇产量达到4.16-5.16 g/L,低于P2培养基中的丁醇产量(8.83 g/L)。稀释水解液中,48 h之后乙酸浓度在3.18-4.16 g/L,远大于P2培养基中的乙酸浓度(低于2 g/L)。相对于P2培养基,在50%水解液中培养的TSH06有机酸生成途径关键基因的基因转录水平明显提高,而有机酸返耗途径以及丁醇生成途径的关键基因的基因转录水平则明显下降。水解液中过多的乙酸抑制了产酸期到产溶剂期的转化,而酸的累积使得菌体在底物被完全消耗之前就趋于衰退死亡,从而造成丁醇产量的降低与底物的不完全利用。  相似文献   

6.
木质纤维素预处理过程中产生的有毒副产物严重影响了纤维素乙醇发酵,提高酿酒酵母抑制物耐受性是提高纤维素乙醇发酵效率的有效方法。文中通过过表达LCB4基因,研究了重组菌株S288C-LCB4在乙酸、糠醛和香草醛胁迫下的细胞生长和乙醇发酵性能。结果表明,LCB4过表达菌株在分别含有10 g/L乙酸、1.5 g/L糠醛和1 g/L香草醛的平板中生长均优于对照菌株;在分别含有10 g/L乙酸、3 g/L糠醛和2 g/L香草醛的液体乙醇发酵过程中,重组菌株S288C-LCB4乙醇发酵产率分别为0.85 g/(L·h)、0.76 g/(L·h)和1.12 g/(L·h),比对照菌株提高了34.9%、85.4%和330.8%;且糠醛和香草醛胁迫下发酵时间分别缩短了30 h和44 h。根据发酵终点发酵液代谢物分析发现重组菌株比对照菌株产生了更多甘油、海藻糖和琥珀酸,这些物质有利于增强菌株的抑制物耐受性。综上所述,LCB4基因过表达可显著提高酿酒酵母S288C在乙酸、糠醛和香草醛胁迫下的乙醇发酵性能。  相似文献   

7.
为了解产酸克雷伯氏菌对木质纤维素水解液中主要抑制物的耐受和代谢,考察了产酸克雷伯氏菌发酵生产2,3-丁二醇(2,3-butanediol,2,3-BDO)过程中对3种发酵抑制物乙酸、糠醛和5-羟甲基糠醛(5-hydroxymethylfurfural HMF)的耐受以及抑制物浓度的变化,检测了糠醛和HMF的代谢产物.结果表明:产酸克雷伯氏菌对乙酸、糠醛和HMF的耐受浓度分别为30 g/L、4 g/L和5 g/L.并且部分乙酸可作为生产2,3-丁二醇的底物,在0~30 g/L浓度范围内可提高2,3-丁二醇的产量.发酵过程中产酸克雷伯氏菌可将HMF和糠醛全部转化,其中约70%HMF被转化为2,5-呋喃二甲醇,30%HMF和全部糠醛被菌体代谢.研究表明在木质纤维素水解液生产2,3-丁二醇的脱毒过程中可优先考虑脱除糠醛,一定浓度的乙酸可以不用脱除.  相似文献   

8.
选择乙酸根、糠醛、5-羟甲基糠醛、苯酚、香草酸和丁香醛等6种典型木质纤维素酸解副产物,考察它们对D-乳酸生产菌Sporolactobacillus sp.Y2-8生长及发酵的影响。实验结果表明:酚类物质抑制作用最强烈,0.25 g/L丁香醛已经完全抑制了菌体的生长和D-乳酸的发酵;苯酚和香草酸在低浓度(≤1.0 g/L)时抑制作用较小,但质量浓度达到3 g/L时对D-乳酸产量的抑制率分别为99%和70%;3 g/L糠醛和5-羟甲基糠醛对产物的抑制率分别为60%与20%,抑制作用小于酚类;乙酸根的影响最小,10 g/L的乙酸钠对菌体的生长和发酵几乎无抑制作用;当抑制物混合时,存在着相互促进作用,抑制作用更强烈。  相似文献   

9.
以树干毕赤酵母和酿酒酵母为发酵菌株,酸性蒸汽爆破玉米秸秆预水解液和纯糖模拟液为C源,采用固定化酵母细胞的方法,研究了酸爆玉米秸秆预水解液初始pH、N源种类及其浓度、3种发酵模式对树干毕赤酵母戊糖发酵的影响。结果表明:玉米秸秆预水解液适合发酵的初始pH范围为6.0~7.0;1.0 g/L的(NH4)2SO4作为N源,在40 g/L葡萄糖和25 g/L木糖培养基中发酵24 h,糖利用率达到99.47%,乙醇质量浓度为24.72 g/L,优于尿素和蛋白胨作为N源;3种模式的发酵体系中,以游离树干毕赤酵母和固定化酿酒酵母发酵性能最好,糖利用率和乙醇得率分别为99.43%和96.39%。  相似文献   

10.
王丹  王洪辉  王競  汪楠  张杰  邢建民 《生物工程学报》2013,29(10):1463-1472
利用可再生生物质特别是木质纤维素水解液来生产平台化合物丁二酸,是目前研究的热点。虽然许多研究者相继报道了木质纤维素水解液对菌株生长和丁二酸生产存在一定抑制作用,但并没有水解液中各种抑制物对菌株影响的相关动力学研究及机理研究。我们选择了两种代表性木质纤维素水解液抑制物,即糠醛和5-羟甲基糠醛,系统研究了它们对大肠杆菌的生长和丁二酸生产的影响。结果表明:糠醛和5-羟甲基糠醛的初始抑制浓度均为0.8 g/L。当糠醛浓度大于6.4 g/L,5-羟甲基糠醛浓度大于12.8 g/L时,菌株生长完全受到抑制。在最高耐受浓度下,糠醛的存在使菌株生物量比对照菌株下降77.8%,丁二酸产量下降36.1%。5-羟甲基糠醛的存在使菌株生物量比对照菌株降低13.6%,丁二酸产量降低18.3%。糠醛和5-羟甲基糠醛具有明显的协同作用。体外酶活测定表明丁二酸生产途径中关键酶磷酸烯醇式丙酮酸羧化酶、苹果酸脱氢酶、富马酸还原酶均受糠醛和5-羟甲基糠醛抑制。研究结果对丁二酸生产用纤维素水解液的预处理和脱毒工艺开发具有指导作用,有利于实现丁二酸发酵生产的工业化。  相似文献   

11.
Hemicellulose liquid hydrolyzate from dilute acid pretreated corn stover was fermented to ethanol using Pichia stipitis CBS 6054. The fermentation rate increased with aeration but the pH also increased due to consumption of acetic acid by Pichia stipitis. Hemicellulose hydrolyzate containing 34 g/L xylose, 8 g/L glucose, 8 g/L Acetic acid, 0.73 g/L furfural, and 1 g/L hydroxymethyl furfural was fermented to 15 g/L ethanol in 72 h. The yield in all the hemicellulose hydrolyzates was 0.37–0.44 g ethanol/g (glucose + xylose). Nondetoxified hemicellulose hydrolyzate from dilute acid pretreated corn stover was fermented to ethanol with high yields, and this has the potential to improve the economics of the biomass to ethanol process.  相似文献   

12.
A batch reactor was used to investigate the dilute acid hydrolysis reaction of alpha-cellulose and sugar decomposition reactions. Varying the sulfuric acid concentration from 0.07 to 5.0% for reaction temperatures between 180 and 220°C significantly affected glucose yields, which ranged from about 70% to below 10%. Increasing the reaction temperature enhanced this effect. Similar experimental results were obtained for the decomposition of xylose. For sugar decomposition reactions, less than 0.3 g/L of furfural and 5-hydroxymethylfurfural (5-HMF) were produced from glucose and xylose in the absence of sulfuric acid at 190°C and 15 min of reaction time, but adding a small amount of sulfuric acid (0.5%) dramatically increased the decomposition rate and led to the formation of four undesireable products: formic acid, 5-HMF, acetic acid, and furfural. In both hydrolysis and fermentation reactions formic acid, acetic acid, and 5-HMF severely inhibited ethanol fermentation, while furfural had less of an inhibition effect.  相似文献   

13.
A systematic study was conducted characterizing the effect of furfural, 5-hydroxymethylfurfural (5-HMF), and acetic acid concentration on the production of xylitol and ethanol by a novel endophytic yeast, Rhodotorula mucilaginosa strain PTD3. The influence of different inhibitor concentrations on the growth and fermentation abilities of PTD3 cultivated in synthetic nutrient media containing 30?g/l xylose or glucose were measured during liquid batch cultures. Concentrations of up to 5?g/l of furfural stimulated production of xylitol to 77?% of theoretical yield (10?% higher compared to the control) by PTD3. Xylitol yields produced by this yeast were not affected in the presence of 5-HMF at concentrations of up to 3?g/l. At higher concentrations of furfural and 5-HMF, xylitol and ethanol yields were negatively affected. The higher the concentration of acetic acid present in a media, the higher the ethanol yield approaching 99?% of theoretical yield (15?% higher compared to the control) was produced by the yeast. At all concentrations of acetic acid tested, xylitol yield was lowered. PTD3 was capable of metabolizing concentrations of 5, 15, and 5?g/l of furfural, 5-HMF, and acetic acid, respectively. This yeast would be a potent candidate for the bioconversion of lignocellulosic sugars to biochemicals given that in the presence of low concentrations of inhibitors, its xylitol and ethanol yields are stimulated, and it is capable of metabolizing pretreatment degradation products.  相似文献   

14.
发酵抑制物对絮凝酵母戊糖发酵的影响   总被引:1,自引:0,他引:1  
将絮凝剂加入酵母溶液中,使酵母絮凝成颗粒以此作为固定化酵母进行戊糖发酵。研究了常见发酵抑制物(甲酸、乙酸、糠醛和乳酸等)对絮凝酵母发酵木糖的影响。结果表明:在60.0g/L木糖发酵液中,经过24h发酵,木糖利用率达94.6%,当分别添加抑制物甲酸、乙酸、糠醛、乙醇和乳酸时,聚氧乙烯絮凝酵母分别对其的耐受浓度为0.5、0.5、1.0、30.0和8.0g/L。当抑制物添加量超过各自的耐受浓度后,对絮凝酵母发酵会产生明显的抑制作用。  相似文献   

15.
Several compounds that are formed or released during hydrolysis of lignocellulosic biomass inhibit the fermentation of the hydrolysate. The use of a liquid extractive agent is suggested as a method for removal of these fermentation inhibitors. The method can be applied before or during the fermentation. For a series of alkanes and alcohols, partition coefficients were measured at low concentrations of the inhibiting compounds furfural, hydroxymethyl furfural, vanillin, syringaldehyde, coniferyl aldehyde, acetic acid, as well as for ethanol as the fermentation product. Carbon dioxide production was measured during fermentation in the presence of each organic solvent to indicate its biocompatibility. The feasibility of extractive fermentation of hydrolysate was investigated by ethanolic glucose fermentation in synthetic medium containing several concentrations of furfural and vanillin and in the presence of decanol, oleyl alcohol and oleic acid. Volumetric ethanol productivity with 6 g/L vanillin in the medium increased twofold with 30% volume oleyl alcohol. Decanol showed interesting extractive properties for most fermentation inhibiting compounds, but it is not suitable for in situ application due to its poor biocompatibility. Biotechnol. Bioeng. 2009;102: 1354–1360. © 2008 Wiley Periodicals, Inc.  相似文献   

16.
Mucor indicus fermented dilute-acid lignocellulosic hydrolyzates to ethanol in fed-batch cultivation with complete hexose utilization and partial uptake of xylose. The fungus was tolerant to the inhibitors present in the hydrolyzates. It grew in media containing furfural (1 g/l), hydroxymethylfurfural (1 g/l), vanillin (1 g/l), or acetic acid (7 g/l), but did not germinate directly in the hydrolyzate. However, with fed-batch methodology, after initial growth of M. indicus in 500 ml enzymatic wheat hydrolyzate, lignocellulosic hydrolyzate was fermented with feeding rates 55 and 100 ml/h. The fungus consumed more than 46% of the initial xylose, while less than half of this xylose was excreted in the form of xylitol. The ethanol yield was 0.43 g/g total consumed sugar, and reached the maximum concentration of 19.6 g ethanol/l at the end of feeding phase. Filamentous growth, which is regarded as the main obstacle to large-scale cultivation of M. indicus, was avoided in the fed-batch experiments.  相似文献   

17.
Steam-exploded (SE) poplar wood biomass was hydrolyzed by means of a blend of Celluclast and Novozym cellulase complexes in the presence of the inhibiting compounds produced during the preceding steam-explosion pretreatment process. The SE temperature and time conditions were 214 degrees C and 6 min, resulting in a log R(0) of 4.13. In enzymatic hydrolysis tests at 45 degrees C, the biomass loading in the bioreactor was 100 g(DW)/L (dry weight) and the enzyme-to-biomass ratio 0.06 g/g(DW). The enzyme activities for endo-glucanase, exo-glucanase, and beta-glucosidase were 5.76, 0.55, and 5.98 U/mg, respectively. The inhibiting effects of components released during SE (formic, acetic, and levulinic acids, furfural, 5-hydroxymethyl furfural (5-HMF), syringaldehyde, 4-hydroxy benzaldehyde, and vanillin) were studied at different concentrations in hydrolysis runs performed with rinsed SE biomass as model substrate. Acetic acid (2 g/L), furfural, 5-HMF, syringaldehyde, 4-hydroxybenzaldehyde, and vanillin (0.5 g/L) did not significantly effect the enzyme activity, whereas formic acid (11.5 g/L) inactivated the enzymes and levulinic acid (29.0 g/L) partially affected the cellulase. Synergism and cumulative concentration effects of these compounds were not detected. SSF experiments show that untreated SE biomass during the enzymatic attack gives rise to a nonfermentable hydrolysate, which becomes fermentable when rinsed SE biomass is used. The presence of acetic acid, vanillin, and 5-HMF (0.5 g/L) in SSF of 100 g(DW) /L biomass gave rise to ethanol yields of 84.0%, 73.5%, and 91.0% respectively, with respective lag phases of 42, 39, and 58 h.  相似文献   

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