张国玲,杜伟,刘德华

油脂酵母具有高产油能力,并且所积累油脂的主要成分与植物油脂相似,可作为生物柴油制备的原料.本文对影响酵母油脂合成的关键酶、基因、碳源以及酵母油脂在生物柴油制备中的研究进展进行了综述,认为ATP∶柠檬酸裂解酶和苹果酸酶是酵母油脂合成代谢途径中的关键酶,另外,LRO1、DGA1和ARE基因也被认为同油脂合成有着紧密联系.对酵母油脂用于生物柴油生产的前景进行了展望:利用廉价碳源如甘油、能源作物以及木质纤维素水解液等培养酵母,可有效降低生产成本.在不同催化方法下,酵母油脂均可用于制备生物柴油,这对进一步研究生物柴油的生产应用有着重要意义.     

酵母油脂及用于生物柴油制备研究进展

油脂酵母具有高产油能力,并且所积累油脂的主要成分与植物油脂相似,可作为生物柴油制备的原料。本文对影响酵母油脂合成的关键酶、基因、碳源以及酵母油脂在生物柴油制备中的研究进展进行了综述,认为ATP∶柠檬酸裂解酶和苹果酸酶是酵母油脂合成代谢途径中的关键酶,另外,LRO1、DGA1和ARE基因也被认为同油脂合成有着紧密联系。对酵母油脂用于生物柴油生产的前景进行了展望：利用廉价碳源如甘油、能源作物以及木质纤维素水解液等培养酵母,可有效降低生产成本。在不同催化方法下,酵母油脂均可用于制备生物柴油,这对进一步研究生物柴油的生产应用有着重要意义。     

产油酵母利用廉价原料合成油脂的研究进展

利用微生物油脂生产的生物柴油是替代传统化石燃料的绿色可再生能源,产油酵母是极具潜力的产油微生物。然而利用葡萄糖作为碳源成本较高,限制了微生物油脂合成技术的规模化应用,因而寻找廉价原料至关重要。本文基于产油酵母合成油脂的代谢机理,重点介绍了产油酵母利用4种廉价原料,即木质纤维素、粗甘油、有机废水和挥发性脂肪酸合成微生物油脂的研究进展。针对这些来自工农业副产物的廉价原料,分别讨论了其复杂成分对产油酵母生长和油脂合成产生的促进或抑制作用,分析总结了高效预处理、基因工程改造菌体以及微生物共培养等解决方案。通过以上分析,阐明了产油酵母利用廉价原料合成油脂的优点,提出了针对复杂成分和高有机质浓度的抑制性问题的解决方法,理清了未来研究的方向,有助于进一步推动廉价原料用于产油酵母生产油脂及可再生能源技术的发展。     

微生物合成2,3-丁二醇的代谢工程

2,3-丁二醇（2,3-BD）是一种重要的微生物代谢产物,广泛应用于食品、医药、化工等多个领域。微生物合成2,3-BD的效率不高一直制约着其生物制造工业化进程,应用代谢工程的理论和方法优化微生物的代谢途径有望解决这一问题。本文全面总结了近年来微生物合成2,3-BD研究过程中的菌株改造和构建技术,包括过表达合成途径中的关键酶编码基因、敲除旁路代谢途径关键酶编码基因、应用辅因子工程手段对天然菌株代谢网络进行重新设计和合理改造,以及利用合成生物学技术在模式菌株中构建全新的代谢途径,实现2,3-BD的高效生物合成。最后,本文对未来的研究方向进行了展望,提出了进一步利用先进的合成生物学方法构建高效细胞工厂的指导性建议。     

微生物合成2,3-丁二醇的代谢工程

2,3-丁二醇(2,3-BD)是一种重要的微生物代谢产物,广泛应用于食品、医药、化工等多个领域。微生物合成2,3-BD的效率不高一直制约着其生物制造工业化进程,应用代谢工程的理论和方法优化微生物的代谢途径有望解决这一问题。本文全面总结了近年来微生物合成2,3-BD研究过程中的菌株改造和构建技术,包括过表达合成途径中的关键酶编码基因、敲除旁路代谢途径关键酶编码基因、应用辅因子工程手段对天然菌株代谢网络进行重新设计和合理改造,以及利用合成生物学技术在模式菌株中构建全新的代谢途径,实现2,3-BD的高效生物合成。最后,本文对未来的研究方向进行了展望,提出了进一步利用先进的合成生物学方法构建高效细胞工厂的指导性建议。     

产油微生物利用废弃物积累油脂的研究进展

微生物油脂是一种应用前景广阔的新型油脂资源, 具有制备功能性油脂和生物柴油的优点, 因此越来越受到人们的重视。但微生物油脂生产时所用原料成本高, 导致微生物油脂的产业化发展受到制约。因此寻找廉价易得的发酵基质将促进微生物油脂生产的工业化进程, 同时解决了日益严峻的能源与环境安全问题。本文简述了各种工业废水、剩余活性污泥及餐厨废弃物等废弃物的特点, 总结了产油微生物利用该类废弃物生产油脂的研究现状及可能存在的发酵工艺及经济成本问题, 指出了未来的发展方向是开发附加值产品及廉价高效的絮凝剂以降低油脂成本、探究利用微生物前期处理降解剩余污泥中的毒性物质、探讨酶与酸碱联合水解餐厨废弃物的工艺等。     

微生物合成植物天然产物的细胞工厂设计与构建

植物天然产物结构多样,具有丰富的生理活性与功能。利用微生物细胞工厂生产来源稀缺、获取难度大的植物天然产物具有经济可行、环境友好等优势。本文系统介绍了萜烯、黄酮以及生物碱的生物合成途径及其关键酶,阐述了差异转录组学、同功酶挖掘等途径解析与重构的方法。指出关键酶改造、途径动态调控、代谢区室化与代谢网络再平衡是增大外源途径代谢通量、抑制副产物合成、降低产物毒性与菌株代谢负担、提高目标产物合成能力的有效策略。提出了解析合成植物天然产物关键酶在微生物中的催化特异性机制、开发外源途径的高效组装方法等进一步提高微生物细胞工厂生产效率的建议。     

3株油脂酵母产油特性的对比研究

微生物油脂可作为生物柴油和其他油脂基化学品的原料,明确产油菌株的产油规律和所产油脂脂肪酸组成是确定其开发潜力的关键。在葡萄糖限氮培养基中对比了3株产油酵母的油脂积累能力,圆红冬孢酵母皮状丝孢酵母禾本红酵母;采用GC-MS分析了3株产油酵母的脂肪酸组成,3株产油酵母油脂均以C16和C18为主,可作为生物柴油的原料油脂。     

微生物油脂制取生物燃料研究进展

随着化石燃料短缺和环境污染问题的日益严重,可再生能源的重要性不断凸显.其中,生物燃料受到越来越多的关注.利用微生物制取生物燃料是当下流行的技术路线之一.微生物油脂因原料来源广泛、生产工艺简单等优势,国内外学者对其进行了广泛深入的研究.本文总结了产油微生物菌体培育技术、微生物菌体破壁技术和微生物制备生物燃料技术,为产油微...     

提高微藻产油能力的研究进展

现阶段微藻产油是公认最有潜力的产油方式，因此提高产油微藻的油脂合成量一直是近年来研究的热点。从两个方面重点介绍了提高藻细胞油脂含量的方法，即通过选择合适的培养条件和培养模式来增加产量，同时也详细阐述了在不同条件及模式下，对藻细胞产物含量合成的具体影响。综述了目前提高微藻油脂合成量的主要方式，为进一步提高生物柴油产量奠定了基础。     

Mutant forms of {beta}-galactosidase with an altered requirement for magnesium ions

By random approaches we have previously isolated many variantsof Escherichia coli ß-galactosidase within a shortcontiguous tract near the N-terminus (residues 8–12 ofwildtype enzyme), some of which have increased stability towardsheat and denaturants. The activity of these mutants was originallyanalysed and quantitated in situ in activity gels without theaddition of magnesium ions to the buffer system. We now showthat the improved stability is only observable under such conditionsof limiting magnesium ion concentrations or in the presenceof appropriate concentrations of a metal chelator. In the presenceof EDTA, purified preparations of one of these mutant enzymeswere much more resistant to denaturants than wild-type, butthis differential was completely nullified in the presence of1 mM Mg²⁺. However, the stability of this mutant enzyme in EDTAwas lower than that shown by it, or the wild-type enzyme, inthe presence of magnesium ions. In addition, certain alterationswithin another N-terminal tract (residues 27–31 of wild-type)resulted in enzymes with greater dependence on Mg²⁺ than naturalß-galactosidase. We conclude that a small number ofresidue changes in a large protein can profoundly modulate therequirement for metal ion stabilization, allowing partial abrogationof this need in certain cases. Thus, some enzymes which requiredivalent metal ions for structural purposes only may be engineeredtowards metal independence.     

A Fluorescence-Based Assay for Quantitative Analysis of Phospholipid:Diacylglycerol Acyltransferase Activity

Phospholipid:diacylglycerol acyltransferase (PDAT) catalyzes the acyl-CoA-independent triacylglycerol (TAG) biosynthesis in plants and oleaginous microorganisms and thus is a key target in lipid research. The conventional in vitro PDAT activity assay involves the use of radiolabeled substrates, which, however, are expensive and demand strict regulation. In this study, a reliable fluorescence-based method using nitrobenzoxadiazole-labeled diacylglycerol (NBD-DAG) as an alternative substrate was established and subsequently used to characterize the enzyme activity and kinetics of a recombinant Arabidopsis thaliana PDAT1 (AtPDAT1). We also demonstrate that the highly toxic benzene used in typical PDAT assays can be substituted with diethyl ether without affecting the formation rate of NBD-TAG. Overall, this method works well with a broad range of PDAT protein content and shows linear correlation with the conventional method with radiolabeled substrates, and thus may be applicable to PDAT from various plant and microorganism species.     

Comparison of Nile Red and Cell Size Analysis for High‐Throughput Lipid Estimation Within Oleaginous Yeast

With growing interest in oleaginous yeast as producers of future fuels and bulk chemicals, a robust, high‐throughput method for estimating lipid production is required. Although the lipophilic dye Nile red is frequently used to assay large samples of yeast and microalgae, inconsistent stain permeability between species and strains limits its effectiveness for some microorganisms. In this study, the oleaginous yeast Metschnikowia pulcherrima is used to develop a fluorescence‐free, cell‐size‐based image analysis method for estimating lipid production, which is then compared with an optimized Nile red method across several experimental scenarios. Cell size analysis (CSA) outperforms Nile red in all scenarios, correlating well with lipid extraction data when screening multiple strains, screening a subset of strains grown in different conditions, and tracking the lipid accumulation of a culture over time. Stain permeability is shown to vary significantly among the strains trialled, with lipid droplet size and cell wall thickness having a deleterious effect in the permeability of high‐lipid‐accumulating cells. CSA can also allow culture population dynamics to be monitored, providing key process information of cell size distribution in response to changing media compositions. Practical Applications: Nile red is currently the go‐to method for high‐ throughput lipid screening; however, staining inconsistencies in some organisms caused by varying cell morphology makes it challenging to optimize a robust protocol. Although fluorescence‐free methods exist (Raman spectroscopy, Fourier‐transform infrared spectroscopy, GCMS), the need for extensive sample preparation and specialist equipment restricts their widespread adoption. The CSA method presented here offers an accurate, robust, and cheap alternative for the study of microorganisms where fluorescence‐based avenues are not feasible. Furthermore, the population dynamics collected during CSA can easily be applied to bioreactor style processing, where tracking size distributions can provide real time information of culture status. This additional information is valuable even if fluorescence screening is a possibility.     

Mass and energy balance for analysis of oleaginous yeast growth

Mass and energy balance method was used to analyze the variation of theoretical biomass yield and oxygen yield based on the intracellular lipid accumulation in oleaginous yeasts. Maximum biomass yield decreases with the increase of lipid content. For the oxygen yield, however, the trend is obscure because it depends not only on lipid content, but also on energetic yield. Attention is drawn to the possibility that data consistency in continuous culture of the oleaginous yeast may be checked by the method of mass and energy balance.     

Combined effects of sucrose and copper(II) ions on the growth and copper(II) bioaccumulation properties of Candida sp

A microbiological process using Candida sp was developed for the removal of copper(II) ions in the presence of molasses as nutrient. The combined effects of sucrose (in molasses) and copper(II) ions on the growth and copper(II) bioaccumulation properties of adapted Candida cells was tested under laboratory conditions as a function of initial pH and single‐sucrose and dual‐sucrose and copper(II) ion concentrations. The optimum pH value for maximum growth and metal ion accumulation was determined as 4.0 for the microorganism. At a constant copper(II) concentration, growth and copper(II) bioaccumulation increased with increasing concentrations of molasses sucrose up to 15 gdm⁻³. Although increased initial copper(II) concentration increased the copper(II) uptake capacity of the microorganism, inhibition by copper(II) ions of the growth of Candida sp was observed at all the concentrations of copper(II) at all the sucrose concentrations studied. The non‐competitive inhibition kinetics (assuming copper(II) ions as the toxic inhibitory component) were used to define the relationship between the specific growth rate and molasses sucrose and copper(II) concentrations and model parameters were determined by using experimental data. © 2000 Society of Chemical Industry     

Seed-mediated growth of palladium nanocrystals: the effect of pseudo-halide thiocyanate ions

In synthesis in a solution phase, adsorbates such as halides can interact selectively with different metal crystal facets and affect the final morphology of nanocrystals. Pseudo-halide thiocyanate ions (SCN-) can also adsorb on the metal surface, but they have never been used for the synthesis of shape-controlled colloidal metal nanocrystals. In this study, we first investigated the effect of SCN- on the morphology of palladium nanocrystals through a seed-mediated growth method. The presence of 1 μM SCN- in the growth solutions could lead to the formation of palladium polyhedra: truncated rhombic dodecahedra enclosed by twelve {110}, eight {111} and six {100} facets. The products were nanocubes enclosed with six {100} facets if cetyltrimethylammonium bromide (CTAB) was the only capping agent. Meanwhile, the mechanism of the effect of SCN- on the morphology of Pd nanocrystals is discussed.     

添加剂对电解铜箔作用机理及作用效果的研究进展

电解铜箔作为锂离子电池负极集流体和活性材料的载体,其性能直接影响电池的容量和循环寿命。添加剂的引入是电解铜箔制备工艺中性能调控的重要方式。通过向电解液中引入添加剂可以改变铜沉积的反应电位,影响镀层的微观结构和形貌,有利于提升电解铜箔的某种性能。多种添加剂共同作用时可以提升铜箔的综合性能。本文根据特征基团分类,综述了含硫有机物、含氮有机物、聚醚类化合物、卤素离子、稀有元素这五类常用添加剂对电解铜箔的作用以及不同添加剂间的相互作用和改性优化方式。通过对各添加剂作用机理和效果的分析比较,总结了目前研究中在机理与性能关联性、机理解释矛盾、机理研究的有效手段、添加剂配方生产应用等方面存在的局限性,并指出未来的研究将向着作用机理深入化、添加剂结构配方优化等方向前进。     

Lipid and fatty acid biosynthesis by Rhodotorula minuta

Demand for fatty acids is increasing at an annual rate of 17%, due to their increased use in the oleochemical and transport industries. Presently, vegetable oils are the major source of fatty acids, whereas lipids with fatty acids similar to those of some vegetable oils have been reported to be synthesized by oleaginous microorganisms. In the present study, the culturing conditions for the oleaginous yeast Rhodotorula minuta IIP-33 have been optimized. In contrast to the lipid accumulation characteristics of most oleaginous yeasts, a carbon-to-nitrogen ratio of 30 was favorable for maximal accumulation of lipids (48%) with 22.5% conversion of glucose as carbon substrate. The lipids contained fatty acids in the C₇–C₁₈ range, the relative composition of which varied with culture temperature.