Understanding the correlation between calcination temperature and performance in low-temperature methanation over Ni-Zr/Al2O3 catalysts

Low-temperature methanation of CO in the continuous stirred tank reactor (CSTR) over Zr doped Ni/Al₂O₃ catalyst calcined at different temperatures (673, 723, and 823 K) was investigated. XRD, TPR, XPS, ICP, SEM, and S-TPR techniques were employed to characterize the fresh and spent catalysts. Based on the characterization results, it was found that low-temperature (673 K) calcination could effectively prohibit the formation of NiAl₂O₄ spinel, thereby resulting in more reducible NiO particles, which were the essential precursor of methanation active sites over the catalyst surface. Thus, the highest CO conversion of 93.6% was achieved over the 25N3ZA-673 catalyst. In addition, the deactivation rate of 25N3ZA-673 was relatively slow in comparison to 25N3ZA-823 due to the presence of more reducible NiO. The formed nickel carbonyl species (Ni[CO]_x), which quickly decomposed at a higher reaction temperature, was closely related to the catalyst deactivation. Therefore, 25N3ZA-673 possessed much better stability at 593 K than that at 553 K.     

Renewable hydrogen production from steam reforming of glycerol (SRG) over ceria-modified γ-alumina supported Ni catalyst

Excess crude glycerol derived as a by-product from biodiesel industry prompts the need to valorise glycerol to value-added chemicals. In this context, catalytic steam reforming of glycerol (SRG) was proposed as a promising and sustainable alternative for producing renewable hydrogen (H₂). Herein, the development of nickel (Ni) supported on ceria-modified mesoporous γ-alumina (γ-Al₂O₃) catalysts and their applications in catalytic SRG (at 550–750 °C, atmospheric pressure and weight hourly space velocity, WHSV, of 44,122 ml·g⁻¹·h⁻¹ (STP)) is presented. Properties of the developed catalysts were characterised using many techniques. The findings show that ceria modification improved Ni dispersion on γ-Al₂O₃ catalyst support with highly active small Ni particles, which led to a remarkable catalytic performance with the total glycerol conversion (ca. 99%), glycerol conversion into gaseous products (ca. 77%) and H₂ yield (ca. 62%). The formation rate for H₂ production (14.4 × 10⁻⁵ mol·s⁻¹·g⁻¹, TOF (H₂) = 3412 s⁻¹) was significantly improved with the Ni@12Ce-Al₂O₃ catalyst, representing nearly a 2-fold increase compared with that of the conventional Ni@Al₂O₃ catalyst. In addition, the developed catalyst also exhibited comparatively high stability (for 12 h) and coke resistance ability.     

γ-聚谷氨酸对带鱼鱼糜凝胶特性的影响

γ-聚谷氨酸作为一种新型可食用的食品添加剂,可显著提高带鱼鱼糜的凝胶强度(P<0.05),且对鱼糜的白度值影响较小。响应面优化试验结果表明,采用两段加热方式,γ-聚谷氨酸添加量0.54‰、第1段加热温度52.6℃,加热时间39min时,鱼糜凝胶强度最高,为281.66g.cm。在各影响因素中,γ-聚谷氨酸添加量对凝胶强度的影响最大,其次是第1段加热温度,加热时间影响最小。SDS-PAGE电泳图谱和扫描电镜图谱显示γ-聚谷氨酸与鱼糜蛋白质可相互作用,从而提高鱼糜凝胶强度。经两段式加热的鱼糜凝胶强度显著高于一段加热方式(P<0.05),但二者在肌原纤维蛋白SDS-PAGE电泳图谱上无明显差异,说明γ-聚谷氨酸对二者肌原纤维蛋白质的组成没有影响。     

大豆发芽过程中异黄酮、γ-氨基丁酸等成分含量变化的研究

研究了大豆发芽期间氨基酸、γ-氨基丁酸、大豆异黄酮、水分、总糖、可溶性蛋白质以及粗脂肪的含量变化.结果表明,大豆发芽48h时总游离氨基酸含量明显增加,水解氨基酸的含量略有增加但变化不明显;总糖、粗脂肪含量降低;水分含量升高;γ-氨基丁酸、大豆异黄酮等功能性因子含量都有明显提高,其中,发芽48h的大豆中γ-氨基丁酸的含量是干大豆的700%,发芽48h的大豆中大豆异黄酮的含量是干大豆的191.2%.     

利用廉价原料生产聚谷氨酸的研究

目的 降低聚谷氨酸的生产成本.方法 从聚谷氨酸发酵所需的氮源和碳源出发,分别研究了小麦水解蛋白、豆饼粉、豆粕粉、玉米蛋白、玉米浆等有机氮源和甘蔗糖蜜、甜菜糖蜜、葡萄糖蜜、玉米糖蜜等碳源对聚谷氨酸发酵产量的影响,在此基础上通过单因素实验优化了玉米浆、硫酸铵、甜菜蜜、谷氨酸钠的添加量,最后通过发酵罐发酵比较了优化后的工艺与...     

γ-氨基丁酸对香菇采后品质的影响

为了探讨γ-氨基丁酸（γ-aminobutyric acid, GABA）对采后香菇品质的影响,本文研究了不同浓度的GABA处理对香菇外观和营养品质的影响。结果表明,不同浓度的GABA处理能够不同程度的降低香菇的失重率、相对电导率和丙二醛含量,抑制香菇的呼吸作用、较好的保持香菇的L*值和硬度,同时促进抗坏血酸、总酚和蛋白质的积累。从呼吸强度来看,GABA处理仅在贮藏前期（9 d）抑制香菇的呼吸作用,其中5.0 g·L?1 GABA处理的效果最好;从失重率、L*值、硬度等外观品质以及抗坏血酸、总酚、蛋白质等品质指标来看,5.0 g·L?1 GABA处理的效果最好;从相对电导率和丙二醛含量来看,2.5 g·L?1 GABA处理的效果最好,但是与5.0 g·L?1 GABA处理之间无显著差异。综合考虑GABA对香菇各项指标的影响,确定其最佳处理浓度为5.0 g·L?1。以上结果表明GABA可以通过抑制呼吸,减缓细胞膜的透性的增大,减少香菇的失水进而较好的保持香菇的硬度和色度;同时能够通过促进抗坏血酸、总酚和蛋白质的积累来保持香菇的营养品质。     

从酸菜液中筛选产γ-氨基丁酸的菌株

从腌制的酸菜液中,采用乳酸菌分离纯化法,经初筛、复筛得到一株产γ-氨基丁酸的菌株,编号为LpL-0212,对菌株进行形态学观察和生理生化实验及16S rDNA、atpA基因序列分析鉴定,鉴定该菌株为Enterococcus faecium。在含2%谷氨酸钠的TYG发酵培养基中静置培养24h,经薄层层析定性、高效液相色谱法测定,发酵液中的γ-氨基丁酸含量可达到102.37μmol/L。     

补料发酵枯草芽孢杆菌合成γ-聚谷氨酸的研究

在5L自动发酵罐中,通过分批发酵和补料分批发酵,对枯草芽孢杆菌(Bacillus subtilis HCUL-B-115)生物合成γ-聚谷氨酸(γ-PGA)进行研究,以达到高产的目的。结果表明：在分批发酵过程中,在通入空气条件下搅拌转速由150r/min提高至250r/min,发酵结束时γ-PGA产量从11.30g/L提高到30.86g/L;在补料分批发酵过程中,在通入空气条件下,搅拌转速采用250r/min,当糖质量浓度在20g/L以下时,每次补加50mL 糖质量浓度200g/L的玉米糖化液则菌体大量生长,γ-PGA产量提高到52.20g/L。     

γ-氨基丁酸检测方法的比较

本文对检测γ-氨基丁酸的纸层析法、高效液相色谱法和氨基酸分析仪法进行了全面的比较研究.结果表明纸层析法检测γ-氨基丁酸,在使用展开剂V（正丁醇）∶V（冰醋酸）∶V（水）=4∶1∶3的条件下,具有简单、快速等优点,但精密度较低.高效液相色谱法以邻苯二甲醛作为衍生剂,用反相C18柱为分离柱,精密度较高,准确度较好,但是操作过程相对繁琐.氨基酸分析仪法采用茚三酮柱后衍生,稳定性好、灵敏度高、操作简便,但要求样品氨基酸浓度在100nmol/mL范围内,使用费用高.     

米糠中产γ-氨基丁酸细菌分离及其接种发酵研究

利用薄层层析初步筛选出米糠中产γ-氨基丁酸（GABA）能力较强的菌株,对其16S rDNA序列进行分析,确定菌株种类;用氨基酸自动分析仪进一步筛选出高产GABA菌株;将高产GABA菌株接种到米糠进行发酵试验。结果表明,陈米糠更有利于分离到高产GABA菌株;筛选到产量较高的菌株16S rDNA序列分别与屎肠球菌（Enterococcus faecium）、棉子肠球菌（Enterococcus raffinosus）、大肠埃希氏菌（Escherichia coli）、短乳杆菌（Lactobacillus brevis）和宋内志贺杆菌（Shigella sonnei）相似性最高;接种单菌种发酵不能明显提高米糠中GABA含量,但混合接种地衣芽孢杆菌（Bacillus licheniformis）DY和乳酸菌L-44A可以使其含量达到184.6 mg/100 g（干质量）;利用蛋白酶处理米糠后接种乳酸菌L-44A可以使米糠中GABA含量达到245.8 mg/100 g（干质量）。