两株高效代谢木质纤维素稀酸水解物产乙醇的酵母特性及耐毒研究

对实验室筛选出的两株高效代谢木质纤维素稀酸水解液产乙醇的酵母菌Y1(Candida tropicalis)和Y4(Issatchenkiaorientalis)的乙醇发酵特性及耐毒能力进行了的研究。以未经任何脱毒处理的木质纤维素稀酸水解液为发酵底物进行乙醇发酵(原位脱毒乙醇发酵)。结果表明,Y1和Y4均能在24h内将水解液中所有的葡萄糖消耗完,乙醇产率分别为0.49g/g和0.45g/g,分别达到了理论值的96.1%和86.0%。在含有不同浓度梯度的糠醛及5-羟甲基糠醛的模拟水解液中,Y1和Y4能耐受的最高糠醛浓度均为5.0g/L,最高的5-羟甲基糠醛浓度均大于7.0g/L,当两种抑制剂等量混合时,两株菌能耐受的最高浓度为4.0g/L。两株菌均有较好的乙醇发酵及耐毒能力。该研究结果为木质纤维素水解液的原位脱毒发酵生产然料乙醇奠定了基础。     

酵母菌复合培养物对木质纤维素稀酸水解液原位脱毒乙醇发酵

为了解决木质纤维素稀酸水解产物中发酵抑制剂对微生物的抑制作用以及木糖的乙醇发酵问题,该研究用本实验室开发的能高效代谢葡萄糖产乙醇并代谢糠醛和5-羟甲基糠醛的2株酵母菌种Saccharomyces cerevisiae Y5和Ismtchenkia/orientalis Y4分别与Pichia.stipitis CBS6054组成2个复合菌种,用复合菌种对木质纤维素稀酸水解产物进行原位脱毒乙醇发酵.结果证明,复合菌种S.cerevisiae Y5,P.stipitis CBS6054显示出了很好的代谢稀酸水解液中的葡萄糖和木糖产乙醇并快速代谢糠醛和5-羟甲基糠醛的能力,乙醇产率为0.43g/g(达到理论值的85.1%).该复合培养物可作为木质纤维索稀酸水解产物不需任何脱毒处理直接进行乙醇发酵的复合菌种.     

高耐毒性酿酒酵母的紫外诱变选育

木质纤维素生产乙醇已成为世界各国研究开发的热点.但在酿酒酵母对木质纤维素稀酸水解产物的乙醇发酵中,对水解产物中的毒性物质非常敏感.菌种对水解液毒性物质耐受力相对较低是影响木质纤维素乙醇发酵工业化的主要因素之一.利用紫外线对酿酒酵母进行诱变,得到2株高效耐水解液中毒性物质突变株k和n.2株突变株发酵未脱毒的木屑稀酸水解产物的乙醇产量分别达到理论值的71.0%和61.3%,为进一步提高酿酒酵母耐毒性的研究和木质纤维素稀酸水解生产乙醇的工业化提供了基础.     

木质纤维素稀酸水解液乙醇发酵的新方法

为了降低木质纤维素水解液发酵抑制剂对乙醇发酵的负影响,采用混合菌种对木质纤维素稀酸水解液乙醇发酵方式进行了研究。对批式发酵、补料批式发酵和间隔补料批式发酵3种发酵方式进行了比较。实验结果表明,间隔补料批式发酵可以有效地减弱水解液中抑制因子对菌种的影响,乙醇产量明显高于其他两种发酵方式,利用酿酒酵母(Saccaromyces cerevisiae 2.535)和嗜鞣管囊酵母(Pachysolen tannophilis ATCC 32728)混合发酵,乙醇产量最终达到14.4g/L,乙醇产率(Yp/s)为0.47g/g,相当于最大理论产率的92.2%。利用酿酒酵母和重组大肠杆菌混合菌种发酵,乙醇产量达到了14.5g/L。对木质纤维素稀酸水解液采用间隔补料批式乙醇发酵方法,可进一步减少抑制剂对乙醇发酵的影响,使发酵顺利进行。     

稀酸和氨相结合预处理柳枝稷

为了提高柳枝稷中纤维素和半纤维素糖的转化率,降低水解液中抑制剂的浓度,采用稀酸低温水解和氨浸泡相结合的方法对柳枝稷进行预处理.通过对酸、氨浓度、液固比、反应时间、温度的研究,确定两步法预处理的最佳条件.经两步预处理和Celluclast 1.5L,Novozyme 188酶解,总纤维素(葡萄糖)转化率为85.99%;半纤维素(木糖)的转化率为66.99%;总糖转化率为77.26%,稀酸水解液中抑制剂的浓度较低,乙酸为2.20g,L,糠醛为1.37g/L,检测不到5-羟甲基糠醛.研究结果为利用柳枝稷制取燃料乙醇提供了新途径.     

改进的柳枝稷预处理方法及乙醇发酵研究

为了提高柳枝稷中纤维素和半纤维素糖的转化率,降低水解液中抑制剂的浓度,首先,用稀酸在温和条件下对柳枝稷进行水解,然后用碱对酸水解后的固体物进行预处理,接着用纤维素酶酶解并分别对稀酸水解液和酶解液进行乙醇发酵.结果表明:纤维素转化率达到94.26%,半纤维素转化率为60.93%,稀酸水解液乙醇发酵的乙醇产率为0.441g乙醇/g糖,达到最高理论值的86.47%.酶解液乙醇发酵的乙醇产率为0.486g乙醇/g葡萄糖,达到最高理论值的95.29%.     

木质纤维素稀酸水解液游离细胞乙醇发酵

为了对木质纤维素稀酸水解液进行游离细胞乙醇发酵,采用了混合菌种与不同发酵方式对稀酸水解液的乙醇发酵进行了研究。通过对1#菌和2#菌以及1#菌和3#菌两组混合菌种的驯化,得到了能耐受一定浓度的发酵抑制因子并产生较高乙醇产量的菌株。用1#菌和2#菌混合菌种以及1#菌和3#菌混合菌种进行批式发酵,72h内乙醇产率分别为0.49g/g和0.45g/g,达到了理论产率的96.1%和88.5%。对补料批式发酵进行的初步研究也取得了比较好的结果。     

生产纤维素乙醇的原生质体融合菌株的构建

为了获得耐发酵抑制剂、耐乙醇并利用木糖的纤维素乙醇生产菌种,以实验室保藏菌种Saccharomyces cerevisiae Y5和Pichia stipitis CBS6054为亲本,采用双亲灭活原生质体融合技术,选育出了共代谢葡萄糖和木糖,且耐受发酵抑制剂的酵母菌株Y10-F.该菌在以木糖为唯一碳源的培养基中培养96h,木糖的利用率达到58.8％,乙醇浓度为5.2g/L.在外加6.0、8.0g/L乙醇的培养液中,Y10-F的生长优于亲株.外加3.0g/L的糠醛时,Y10-F的延滞期较亲本Y5和CBS6054分别缩短了6h和18h.对融合菌株Y10-F进行了汽爆法预处理玉米秸秆的酶解液发酵实验,具有较好的耐毒和产乙醇能力.     

燃料酒精生产中对木质纤维素稀酸水解液的脱毒处理

用稀酸水解农业废弃物秸秆、木材加工废物等木质纤维素产生糖，再将这些糖发酵成燃料酒精，是利用农林废弃物等生物质生产清洁燃料的途径之一。为使木质纤维素产生糖，通常采用理化结合的方法，在高温、高压和催化剂稀酸的作用下水解木质纤维素，例如，用稀酸140-160℃或者更高温度处理木质纤维素即可得到含糖水解液。在该水解过程中，虽然含有葡萄糖、木糖、阿拉伯糖等可发酵产酒精的混合糖，但由于反应条件剧烈，还会含有许多对酒精发酵微生物有毒性作用的抑制物，称之为发酵抑制剂，这些发酵抑制剂浓度随水解反应条件的剧烈程度和木质纤维素的种类不同而不同。水解液中的抑制剂主要有：糠醛、羟甲基糖醛、乙酸、酚类化合物、丁香酸、羟基苯甲酸、香草醛及其它有毒化合物。     

水稻脆性秸秆发酵产纤维乙醇的研究

以水稻脆性秸秆为原料进行了发酵产乙醇的研究。用水稻脆性秸秆比用作对照的普通秸秆的半纤维素和木质素含量分别高17%和5%,纤维素含量低15%。采用浓度为2%(w/v)的硫酸进行秸秆预处理后,脆性秸秆稀酸水解液中葡萄糖含量为普通秸秆的1.38倍;每克脆性秸秆产生的木糖和阿拉伯糖比普通秸秆分别高出12.0 mg和3.9 mg;两种秸秆酸水解液中副产物乙酸、糠醛和5-羟甲基糠醛的浓度差异不显著。经过纤维素酶进一步处理后,每克脆性秸秆得到的总还原糖量为(541.2±8.0)mg,比普通秸秆高出41.9 mg。Escherichia coli SZ470利用酸预处理且酶促糖化的两种秸秆发酵72 h后,脆性秸秆发酵的乙醇产量可达(10.9±0.4)g/L,为普通秸秆的1.1倍。     

一株酵母菌高温驯化与同步糖化发酵研究

对实验室筛选出的一株耐高温酵母菌Y8(Candida maltosa)进行高温驯化,对驯化后菌株的高温产乙醇特性及同步糖化发酵进行研究。结果表明,与原菌株Y8相比,经驯化的菌株Y8-5(Candida maltosa)在高温条件下的生长发酵能力得到进一步提高。在46℃,4%葡萄糖情况下,其发酵性能均能接近正常发酵温度(30℃)下酵母的发酵水平。46℃、以3%(w/v)玉米秸秆、30PFU/g酶,用该菌株进行同步糖化和发酵,得到13.93g/L的乙醇,达到理论产率的88.2%。菌株Y8-5显示了较好的耐高温性能和乙醇发酵特性,为同步糖化发酵技术生产燃料乙醇提供了高温菌种的应用基础。     

Visible-light-induced hydrogen production over Pt-Eosin Y catalysts with high surface area silica gel as matrix

A new system for the production of hydrogen, constructed using silica gel as a matrix, Eosin Y as a photosensitizer, and Pt as a cocatalyst, has been reported. It was found that the rate of photosensitized hydrogen evolution in the presence of silica gel is enhanced about 10-fold relative to the homogeneous phase, i.e. in the absence of silica gel. The pH value of the solution and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 7 and 3.60 × 10⁻⁴ mol dm⁻³ (E/S = 1/3) to 7.24 × 10⁻⁴ mol dm⁻³ (E/S = 1/1), respectively. Triethanolamine (TEOA) as an electron donor, the rate of hydrogen evolution and the apparent quantum efficiency in the silica gel system under visible-light irradiation (λ ≥ 420 nm) can reach about 43 μmol h⁻¹ and 10.4%, respectively. In addition, the roles of silica gel, Pt and TEOA, respectively; and the probable mechanism of photosensitized hydrogen evolution have been discussed.     

Hydrogen-rich gas production from ethanol steam reforming over Ni/Ga/Mg/Zeolite Y catalysts at mild temperature

In order to reduce the coke formation over a conventional Ni/γ-Al₂O₄ catalyst and increase the activity at low temperature, we used the impregnation approach to synthesize MgO (30.0 wt.%)/Zeolite Y catalysts loaded with bimetallic Ni(10.0 wt.%)/Ga(10.0–30.0 wt.%) and study the steam-reforming reactions of ethanol. The Ga-loaded catalyst impregnated between the Ni and Mg components exhibits significantly higher reforming reactivity compared to the conventional Ni/Mg/Zeolite Y catalyst. The main products from steam reforming over the Ni/Ga/Mg/Zeolite Y catalyst are only H₂ and CH₄ at above 550 °C, and the catalytic performances differ according to the amount of Ga. The H₂ production and ethanol conversion are maximized at 87% and 100%, respectively, over Ni(10)/Ga(30)/Mg(30)/Zeolite Y at 700 °C for 1 h at CH₃CH₂OH:H₂O = 1:3 and a gas hourly space velocity (GHSV) of 6740 h⁻¹, and the high performance is maintained for up to 59 h.     

Ce(Ⅳ)Y分子筛对FCC汽油的选择性吸附脱硫的研究

采用草酸对NaY分子筛进行脱铝,然后用经过脱铝的NaY分子筛与硝酸铈溶液进行液相离子交换,经过焙烧制得Ce(Ⅳ)Y分子筛。在室温(25℃)、剂油比为1∶3、吸附时间为6h的条件下,用Ce(Ⅳ)Y和NaY分子筛对FCC汽油(硫含量为135μg/g)进行静态吸附脱硫,利用微库仑综合分析仪对吸附剂处理过的FCC汽油进行硫含量的测定,结果表明经过改性的Ce(Ⅳ)Y分子筛脱硫率为85.1%,比NaY分子筛的脱硫率高34.4个百分点。利用频率响应仪(FR)和智能重量分析仪(IGA)研究了Ce(Ⅳ)Y分子筛与噻吩类硫化物的作用机理。结果表明:Ce(Ⅳ)Y分子筛不但能够脱除噻吩、2-甲基噻吩、3-甲基噻吩、四氢噻吩等硫化物,而且能够脱除一部分NaY分子筛较难脱除的二甲基类噻吩硫化物,噻吩与Ce(Ⅳ)Y分子筛之间形成的稳定的化学键是S-M(σ)键和π络合的共同作用。     

Effect of Y element on cyclic stability of A2B7 -type La–Y–Ni-based hydrogen storage alloy

The La_3-xY_xNi_9.7Mn_0.5Al_0.3 (x = 1, 1.5, 1.75, 2, 2.25, 2.5) alloys were prepared by magnetic suspension induction melting method and annealed at 1273 K for 24 h. The alloys were tested using electrochemical measurements, X-ray diffraction (XRD) and scanning electron microscope with energy-dispersive X-ray diffraction spectroscope (SEM-EDS). With the increase of Y content, the main phase of the alloys changed from Gd₂Co₇ phase to Ce₂Ni₇ phase, and Ce₂Ni₇ phase increased gradually. The maximum discharge capacity of alloys increased from 279.3 mA h/g (x = 1) to 383.8 mA h/g (x = 2.5). The high-rate dischargeabilitiy at the discharge current density of 1200 mA/g increased from 56.98% (x = 1) to 83.76% (x = 2.5). The maximum capacity retention rate first increased from 50.13% (x = 1) to 69.43% (x = 2), and then decreased to 21.35% (x = 2.5). The results showed that the structural stability of the alloys was improved due to the increase of Y content. However, with the increase of Y content, the corrosion, pulverization, and the dissolution of Al element aggravated, which deteriorated the cyclic stability of the alloy electrodes.     

Effect of element substitution and surface treatment on low temperature properties of AB3.42-type La–Y–Ni based hydrogen storage alloy

The low-temperature performance (LTP) of AB_3.42-type La–Y–Ni hydrogen storage alloy was studied by methods of element substitution and surface treatment. The effect of Mn-additive on LTP of La_1·3Ce_0·5Y_4·2Ni_19.5-xMn_xAl (x = 0, 0.2, 0.5) was systematically investigated. Electrochemical studies showed that Mn-additive deteriorated the LTP of the alloy by reducing platform pressure, deteriorating kinetic performance and forming more oxides on the alloy surface. RE-substitution and hot alkali-ultrasonic treatment of La_1.3RE_0.5Y_4·2Ni_19·5Al (RE = Ce, Sm, Nd) alloys were applied to further optimize the LTP. The maximum discharge capacity and capacity retention at the 100th cycle of La_1·3Ce_0·5Y_4·2Ni_19·5Al alloy were 252.1 mA h/g and 87.1% at 243 K, respectively. Furthermore, the LTP of RE-substitution alloys at 243 K was conspicuously improved by surface treatment, which were raised from 214.7 mA h/g to 301.1 mA h/g by Sm-substitute, from 220.9 mA h/g to 303.9 mA h/g by Nd-substitute and from 252.1 mA h/g to 254.8 mA h/g by Ce-substitute.     

Interactions of Y and Cu on Mg2Ni type hydrogen storage alloys: A study based on experiments and density functional theory calculation

Evolution of microstructure and hydrogen storage performances were studied in a Y substituted Mg₂₄Ni₁₀Cu₂ hydrogen storage alloy. Interactions of Y and Cu on the phase structure and hydrogen storage properties were explore. Substitution by Y refined the microstructure and yield existence of YMgNi₄. Furthermore, Y addition promoted the replacement of Cu for Ni in the Mg₂Ni.The study of the alloy's dehydrogenation performance and mechanism showed that the addition of Y did not alter the mechanism of random nucleation and subsequent growth, but reduced the activation energy of the dehydrogenation of the alloy from 77.4 kJ/mol to 67.6 kJ/mol. The thermodynamic energy of the dehydrogenation was also improved, and the enthalpy change (ΔH) and entropy change (ΔS) of the Mg₂NiH₄ phase decreased from 67.1 J/K/mol H₂ and 123.1 J/K/mol H₂ to 61.1 J/K/mol H₂ and 115.4 J/K/mol H₂, respectively. Furthermore, the density functional theory calculation showed that the addition of Y promoted the substitution of Cu for Ni, further reduced the stability of the main hydride Mg₂NiH₄, facilitated the release of hydrogen, and reduced the ΔH and ΔS of the hydride dehydrogenation.     

Tuning hydrogen storage thermodynamic properties of ZrFe2 by partial substitution with rare earth element Y

ZrFe₂ delivers the advantages of high hydrogen storage capacity and easy activation, but its de-/hydriding pressure is too high for practical application. In this work, we alloyed ZrFe₂ with Y to obtain a single C15 Laves phase structure by the proper annealing process. The microstructure and hydrogen storage properties of Zr_1-xY_xFe₂ (x = 0.1–0.4) compounds were investigated. The results show that the cell volume increases and the dissociation pressure decreases with increasing Y content for the Zr–Y–Fe–H system. The Y alloying is beneficial for increasing hydrogen storage capacity despite the worsening plateau slope and hysteresis. The Zr_0·6Y_0·4Fe₂ exhibits the highest hydrogen absorption capacity of 1.77 wt%, while the Zr_0·8Y_0·2Fe₂ shows a dehydriding enthalpy of 25.06 kJ/mol H₂ and dehydriding entropy of 116.53 J/mol·K H₂, corresponding to the dissociation pressure of 59 atm at 298 K that is suitable for high-pressure hydrogen storage applications.     

Biodiesel production by esterification of oleic acid over zeolite Y prepared from kaolin

Zeolite Y, with a Si/Al ratio 3.1, was prepared using Iraqi kaolin and tested as a catalyst in the liquid-phase esterification of oleic acid (a simulated free fatty acid frequently used as a model reaction for biodiesel production). XRD confirmed the presence of the characteristic faujasite structure of zeolite Y, and further analysis was conducted using BET adsorption, FTIR spectroscopy, XRF, DLS particle size and SEM. A range of experimental conditions were employed to study the reaction; alcohol/oleic acid molar ratio, temperature, and catalyst mass loading. The optimum conditions for the reaction were observed at 70 °C, 5 wt% catalyst loading and 6:1 ethanol to oleic acid molar ratio. The oleic acid conversion using the zeolite prepared from kaolin was 85% after 60 min, while the corresponding value for a commercial sample of HY zeolite was 76%. Our findings show that low Si/Al ratio zeolite Y is a suitable catalyst for esterification, which is in contrast to the widespread view of the unsuitability of zeolites, in general, for such applications.