The growth of oleaginous Rhodotorula glutinis in an internal-loop airlift bioreactor by using mixture substrates of rice straw hydrolysate and crude glycerol

The conversion of lignocellulosic biomass (LCB) to microbial oils is attracting a growing amount of attention. However, the growth of the oleaginous yeast Rhodotorula glutinis on LCB hydrolysate (mainly rice straw) only will lead to a low lipid mass fraction, in the range of 10–20%. This study shows that the addition of crude glycerol to the LCB hydrolysate medium can efficiently raise the lipid mass fraction to the range of 30–40%. Crude glycerol is a by-product in the biodiesel production process. The use of renewable LCB hydrolysate and crude glycerol would greatly reduce the substrate cost for microbial oil production using R. glutinis. In addition, the results of experiments show that a low-cost airlift bioreactor is a more suitable fermentation process for the growth of R. glutinis than the use of a conventional agitation tank. When using mixed carbon sources of LCB hydrolysate with 30 kg m⁻³ of reducing sugars and 30 kg m⁻³ of crude glycerol, a maximal cell mass of 21.4 kg m⁻³ and lipid mass fraction of 58.5 ± 6.2 were achieved in an internal loop airlift bioreactor, and this process may have the potential to be applied in scale-up production.     

环氧氯丙烷下游产品生产现状及市场前景

论述了环氧氯丙烷的主要下游产品环氧树脂、合成甘油、氯醇橡胶等的生产现状、市场前景等,指出:我国氯碱行业应该重视这些环氧氯丙烷下游精细化工产品的开发,以促进我国环氧氯丙烷的发展。     

以葡萄糖为辅助底物发酵生产1,3-丙二醇的研究

采用Klebsiellapneumoniae对葡萄糖作为辅助底物发酵生产 1 ,3 丙二醇进行了研究。结果表明葡萄糖单独作为底物发酵时不生成 1 ,3 丙二醇。以葡萄糖和甘油为混合底物时 ,则可以显著提高菌体浓度 ,但是 1 ,3 丙二醇浓度和甘油到 1 ,3 丙二醇转化率没有提高。在甘油为底物的批式发酵过程中 ,通过流加葡萄糖作为辅助底物可以提高甘油到 1 ,3 丙二醇的摩尔转化率 ,同时可缩短发酵时间。通过选择合适的葡萄糖流加速率 ,较以甘油为单一底物的发酵结果 ,1 ,3 丙二醇的摩尔转化率最高可达0 649,提高了 53 4% ;生产强度为 1 0 0 5g/ (L·h) ,提高了 1 39 9%。     

Single-phase gold/palladium catalyst: The nature of synergistic effect

The liquid phase oxidation of glycerol with oxygen has been studied using mono and bimetallic catalysts based on Au and Pd metals supported on activated carbon, in order to study the effect of the metal on the distribution of the products and on activity of catalysts. It was found that by using bimetallic catalysts (Au–Pd) a strong synergistic effect was shown. By using a preformed nucleating centre we were able to obtain a single alloyed phase, which allowed us to address the synergistic effect to the presence of alloyed Au/Pd. The advantage of using this latter catalyst lies not only in the high activity but also in a prolonged catalyst life. Although a partial leaching of palladium and assembling of the particles have been revealed by ICP and HRTEM respectively, activity after 10 re-cycles decreased less than expected (about 10%).     

复合固体超强酸SO42-/ZrO2-TiO2催化合成三醋酸甘油酯

采用复合固体超强酸SO₄^2-/ZrO₂-TiO₂为催化剂，甘油和冰醋酸为原料，结合醋酸精馏回流工艺，合成了三醋酸甘油酯（TCG）。通过对合成工艺改进，免除了有毒带水剂的使用。使TCG合成更安全，更经济和环保。催化剂制备和TCG合成最佳工艺条件为：硫酸浸渍液浓度（0.5～0.55） mol·L^－1，焙烧温度（550～600） ℃，催化剂用量（占总投料量质量分数）2.5％～3.0%。投料比n（甘油）∶n（醋酸）=1∶ 5.5，反应温度130 ℃，反应时间3.0 h，产品收率达92.6%，催化剂可重复使用6次，易于再生。     

Synthesis of hyperbranched P poly(glycerol-diacid) oligomers

Novel oligomeric prepolymers were synthesized by acid-catalyzed condensation of glycerol with iminodiacetic, azelaic, or succinic acid. The prepolymers were obtained, on average, in 62% yield and were characterized by ¹³C NMR, ¹H NMR, matrix-assisted laser desorption ionization-time of flight-mass spectrometry, and gel permeation chromatography. The synthesized oligomers had an average M.W. of 1543 Daltons (average polydispersity (PD)=1.34, average degree of polymerization (DOP)=5.5). Hyperbranching was evident in the oligomers produced when using azelaic acid and succinic acid as co-monomers with glycerol, whereas the reaction between iminodiacetic acid and glycerol resulted in linear products bearing cyclic urethane structures.     

A Possible Industrial Solution to Ferment Lignocellulosic Hydrolyzate to Ethanol: Continuous Cultivation with Flocculating Yeast

The cultivation of toxic lignocellulosic hydrolyzates has become a challenging research topic in recent decades. Although several cultivation methods have been proposed, numerous questions have arisen regarding their industrial applications. The current work deals with a solution to this problem which has a good potential application on an industrial scale. A toxic dilute-acid hydrolyzate was continuously cultivated using a high-cell-density flocculating yeast in a single and serial bioreactor which was equipped with a settler to recycle the cells back to the bioreactors. No prior detoxification was necessary to cultivate the hydrolyzates, as the flocks were able to detoxify it in situ. The experiments were successfully carried out at dilution rates up to 0.52 h⁻¹. The cell concentration inside the bioreactors was between 23 and 35 g-DW/L, while the concentration in the effluent of the settlers was 0.32 ± 0.05 g-DW/L. An ethanol yield of 0.42–0.46 g/g-consumed sugar was achieved, and the residual sugar concentration was less than 6% of the initial fermentable sugar (glucose, galactose and mannose) of 35.2 g/L.     

Separation of 1,3-propanediol from glycerol-based fermentations of Klebsiella pneumoniae by alcohol precipitation and dilution crystallization

The separation of 1,3-propanediol from the glycerol-based fermentation broth of Klebsiella pneumoniae plays an important role during the microbial production of 1,3-propanediol. In this paper, the separation of 1,3-propanediol from fermentative broth by a combination of ultrafiltration and alcohol dilution crystallization was investigated. The broth was first filtered by ultrafiltration, and 99% of cells, 89.4% of proteins and 69% of nucleic acids were removed. The obtained broth was further condensed by vacuum distillation, and then alcohol was added. The macromolecular impurities, such as nucleic acids, polysaccharides and proteins, were precipitated, and inorganic and organic salts were crystallized. The optimal volume ratio of alcohol added to the condensed fermentation broth was determined to be 2:1. As a result, proteins, nucleic acids and electric conductivity decreased by 97.4%, 89.7% and 95.8%, respectively, compared with the fermentative broth. The influences of pH and water content in condensed broth on alcohol precipitation and dilution crystallization were also investigated. The experimental results indicated that alcohol precipitation and dilution crystallization was feasible and effective for the separation of 1,3-propanediol from actual fermentation broth. Translated from The Chinese Journal of Process Engineering, 2006, 6(3): 454–457 [译自: 过程工程学报]     

有机酸对产丙二醇菌生长和生产的影响

为提高克雷伯氏肺炎杆菌厌氧发酵生产1,3-丙二醇的能力,在发酵过程中添加有机酸(OA),考察其对菌体生长、1,3-丙二醇及其他副产物合成的影响。实验表明:添加OA可促进菌体生长,加入质量浓度为0.2~0.5g/L的OA,菌体生长的菌液在590 nm处吸光度(OD)值比参照值高出30%;加入过量的OA(>1.0 g/L),则菌体生长受到抑制,OD值比参照值低37%;添加OA可促进单位细胞合成1,3-丙二醇,加入质量浓度为0.2~0.5g/L的OA,单位菌体的1,3-丙二醇质量浓度比参照高3.8%~17.5%;添加OA能提高甘油转化为1,3-丙二醇的转化速率,加入0.2~0.5 g/L的OA,甘油转化为1,3-丙二醇的最大转化速率达0.81 h-1。在15 L罐上批式发酵48 h,1,3-丙二醇最终质量浓度达42.9 g/L,甘油转化为1,3-丙二醇的平均转化率达64%。     

Selective hydrogenolysis of glycerol to propylene glycol on Cu–ZnO catalysts

Hydrogenolysis of biomass-derived glycerol is an alternative route to sustainable production of propylene glycol. Cu–ZnO catalysts were prepared by coprecipitation with a range of Cu/Zn atomic ratio (0.6–2.0) and examined in glycerol hydrogenolysis to propylene glycol at 453–513 K and 4.2 MPa H₂. These catalysts possess acid and hydrogenation sites required for bifunctional glycerol reaction pathways, most likely involving glycerol dehydration to acetol and glycidol intermediates on acidic ZnO surfaces, and their subsequent hydrogenation on Cu surfaces. Glycerol hydrogenolysis conversions and selectivities depend on Cu and ZnO particle sizes. Smaller ZnO and Cu domains led to higher conversions and propylene glycol selectivities, respectively. A high propylene glycol selectivity (83.6%), with a 94.3% combined selectivity to propylene glycol and ethylene glycol (also a valuable product) was achieved at 22.5% glycerol conversion at 473 K on Cu–ZnO (Cu/Zn = 1.0) with relatively small Cu particles. Reaction temperature effects showed that optimal temperatures (e.g. 493 K) are required for high propylene glycol selectivities, probably as a result of optimized adsorption and transformation of the reaction intermediates on the catalyst surfaces. These preliminary results provide guidance for the synthesis of more efficient Cu–ZnO catalysts and for the optimization of reaction parameters for selective glycerol hydrogenolysis to produce propylene glycol.