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。     

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.     

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。     

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。     

金属离子对产油微生物油脂积累影响的研究进展

利用产油微生物合成含量丰富的油脂,对于解决石化能源日益紧缺问题,改善人类生活水平具有重要意义.金属离子能影响产油微生物生长形态、细胞内外渗透压和油脂合成关键酶活力等,对产油微生物油脂合成有重要的调控作用.本文首先介绍了产油微生物的产油机制,随后重点阐述了金属离子对产油微生物油脂积累的影响及其分子机理,最后对进一步探讨金属离子在产油微生物发酵过程中的作用研究提出一些建议.文章指出由于产油微生物油脂合成途径不尽相同,在工业上利用产油微生物生产油脂时,应从该微生物油脂合成的主要途径入手,找出该途径中的关键酶,随后充分考虑不同微生物对金属离子的耐受性、不同金属离子对微生物形态和胞内关键酶活力的影响,以及不同金属离子之间对同种关键酶的活性中心是否存在竞争或协同的关系等,从而制定可行的金属离子添加控制策略.     

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...     

初始还原糖浓度对2株酵母利用玉米秸秆水解液产油的影响

试验利用皮状丝孢酵母、圆红冬孢酵母以玉米秸秆稀酸水解液为原料,在不添加任何外加营养物质的条件下,研究了玉米秸秆水解液初始还原糖浓度对2株产油酵母生长和产油的影响,结果表明2株酵母适宜的还原糖浓度均为82g/L左右;圆红冬孢酵母生物量和油脂产量分别为21.19 g/L和5.81 g/L,皮状丝孢酵母生物量和油脂产量分别可达34.32 g/L和1.28 g/L。     

大连化物所实现葡萄糖和木糖生产油脂

中国科学院大连化学物理所赵家保研究员领导的生物质高效转化研究组在生物质能源研究中,首次实现葡萄糖和木糖同步利用生产油脂。这一重要研究成果已于日前发布在权威杂志（（BiotechnologyforBiofuels））上。该研究组多年来致力于将生物质转化为生物柴油的研究。通过筛选,赵家保团队发现部分产油酵母可同步利用葡萄糖和木糖在胞内积累油脂,菌体油脂含量达到59％;直接利用玉米秸秆水解液培养,该产油酵母葡萄糖体油脂含量达到39％。     

微生物丙三醇的生产及研究进展

丙三醇通常是由油脂皂化，水解和丙烯合成来进行生物的化工产品，由微生物生产是新的研究开发领域。生产丙三醇的微生物有醇酒酵母，细菌、耐渗透压酵母、单细胞藻类。微生物合成丙三醇在生物原料、生产机制、提取等方面各具特点。虽然目前微生物途径丙三醇产业化潜力仍面临较大竞争压力，但从近来对微生物丙三醇的研究进展看，可以预见随着对丙三醇消费的不断增加和产品成本的降低，因地制宜发展微生物生产丙三醇前景是好的。     

生物酶法转化酵母油脂合成生物柴油

以一株高产油脂圆红冬孢酵母菌(Rhodosporidum toruloides Y4#)干菌粉为原料,利用酸热法提取了该酵母油脂,并对所得油脂进行了分析. 进一步利用该酵母油脂为原料分别研究了无溶剂体系中三步甲醇法及在叔丁醇介质体系中脂肪酶催化合成生物柴油,发现脂肪酶可以有效转化该酵母油脂制备生物柴油. 在优化反应条件下,生物柴油得率可达90%左右,略低于相同条件下利用精制大豆油合成生物柴油的得率.     

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.     

Lipids of oleaginous yeasts. Part II: Technology and potential applications

The process of lipid accumulation in the oleaginous yeasts cultivated in various fermentation configurations when either sugars and related compounds or hydrophobic substances are used as substrates is presented and kinetic models describing both de novo and ex novo lipid accumulation are analyzed. Technological aspects related with single cell oil (SCO) produced by oleaginous yeasts are depicted. The influence of culture parameters upon lipid production process is presented. Lipid production has been studied in batch, fed‐batch, and continuous cultivation systems using yeasts belonging to the species Lipomyces starkeyi, Rhodosporidium toruloides, Apiotrichum curvatum, Candida curvata, Cryptococcus curvatus, Trichosporon fermentans, and Yarrowia lipolytica. The potentiality of yeasts to produce SCO as starting material of 2nd generation biodiesel is indicated and discussed. Of significant importance is also the utilization of yeast lipids as substitutes of high added value exotic fats (e.g., cocoa butter). Lipid produced by the various yeasts presents, in general, similar composition with that of common vegetable oils being composed of unsaturated fatty acids, whereas cocoa butter is principally composed of saturated fatty acids, consequently the various strategies that are followed in order to increase the cellular saturated fatty acid content of the yeast lipid are presented and comprehensively discussed.     

Production of lipid from N‐acetylglucosamine by Cryptococcus curvatus

N‐Acetylglucosamine (GlcNAc), the monomeric constituent of chitin, is rarely used as a carbon source for fermentation technology. In this study, we demonstrate that the oleaginous yeast Cryptococcus curvatus ATCC 20509 can produce intracellular lipid during the cultivation process and total lipid content can reach 54% on a GlcNAc‐based medium. Culture of C. curvatus under various conditions indicated that lipid accumulation also occurred at a relatively broad range of temperatures as well as relatively high initial GlcNAc concentrations. Fatty acid analysis indicated that the product was rich in palmitic acid, stearic acid, and oleic acid, closely resembling the composition of palm oil. More importantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our data suggested that GlcNAc could be used as a feedstock for industrial biotechnology and that C. curvatus ATCC 20509 is a strain capable of accumulating high intracellular lipid using this nitrogen‐rich renewable material. Practical applications: Microbial lipid is a versatile material, especially for biodiesel production. Stable and abundant renewable raw substrates remain to be explored for large‐scale production of microbial lipid. The present work reports lipid production using N‐acetylglucosamine (GlcNAc) by the oleaginous yeast Cryptococcus curvatus ATCC 20509 to yield up to 54% intracellular lipid content. More significantly, the lipid sample produced at 22 °C had a total saturated fatty acid content of 54.2 wt%, suggesting that it may be explored as cocoa‐butter equivalent. Our technology provides the opportunity to effectively convert GlcNAc, available from one of the most abundant renewable materials chitin, into lipid. This procedure should prove valuable in terms of renewable energy production as well as environmental pollution control.     

Role of flow cytometry for the improvement of bioprocessing of oleaginous microorganisms

Oleaginous microorganisms, such as yeast, fungi, microalgae and bacteria, represent a key segment of second generation feed-stock materials and are considered to synthesize a wide range of industrially important chemical compounds. Oleaginous microorganisms possess a broad varieties of chemical compounds such as carotenoids, pigments, carbohydrates, chlorophyll, and storage-material lipids. Oleaginous microorganisms have been recognized as promising sources for the synthesis of unsaturated, especially polyunsaturated fatty acids (PUFA). So far, a variety of high-throughput screening methodologies (HTMs) have been employed for the development of bioprocessing of oleaginous microorganisms for sustainable production of industrially valuable compounds. Of HTMs, flow cytometry (FC) and sorters (FACS) have received substantial interest as better HTMs because of their ability to screen large numbers of cells within seconds, and interrogate and isolate living cells at single-cell level. Forward and side scattering signals of FC are used to determine the physiological state of the cell while different channels available in the FC facilitate the detection of signals produced from fluorophores. Simultaneous measurement of physiological characteristics along with specific compound accumulation at single-cell level enables the possibility of separating a particular phenotype with specific properties from a population. Different microbial strain development strategies in combination with FACS produced improved phenotypes with desired properties. This review first summarizes the FACS methodologies suitable for oleaginous microorganisms and the significant progress that has been achieved in oleaginous microorganisms using FACS, and highlights the important, advanced and future prospects of FACS methodologies that are suitable for the development of bioprocessing in oleaginous microorganisms. © 2018 Society of Chemical Industry     

Lipids of oleaginous yeasts. Part I: Biochemistry of single cell oil production

In the first part of this review, the biochemistry of lipid accumulation in the oleaginous microorganisms is depicted. Lipid biosynthesis form sugars and related substrates is a secondary anabolic activity, conducted after essential nutrient (usually nitrogen) depletion in the medium. Due to this exhaustion, the carbon flow is directed towards the accumulation of intracellular citric acid that is used as acetyl‐CoA donor in the cytoplasm. Acetyl‐CoA generates cellular fatty acids and subsequently triacylglycerols. Lipid accumulation from hydrophobic substrates is a growth associated process, being independent from nitrogen exhaustion in the medium. Medium fatty acids are incorporated with various incorporation rates and are either dissimilated for growth needs or become “substrate” for intracellular biotransformations. “New” fatty acid profiles (in both extra‐ and intracellular lipids) that did not previously exist in the medium are likely to be produced. Oleaginous microorganisms consume their own storage lipids when their metabolic abilities cannot be saturated by the extracellular carbon source. Reserve lipid breakdown is independent from the type of the carbon source used for lipid accumulation. In most cases it is accompanied by lipid‐free biomass production. Lipid mobilization is a specific process, as preferential degradation of the neutral lipid fractions is observed.     

基于消耗碳氮比进行底物分配和油脂得率预测

微生物油脂作为胞内代谢产物,其脂肪酸组成和植物油类似,是生物柴油和油脂工业理想替代原料。为了进一步了解底物中碳氮比对油脂合成的影响,通过恒化培养的方法,研究了圆红冬孢酵母在不同稀释率条件下,消耗碳氮比和底物在油脂和非油生物量之间的分配以及和油脂得率之间的关系。通过碳、氢、氧和氮的化学反应计量学分析,并根据不同稀释率稳态时所消耗C/N比,构建了底物碳在油脂和非油生物量之间的分配模型。利用实验数据确定了模型参数:最大油脂碳得率Y_L^max为0.51 mol C·(mol C)^-1,最大菌体碳得率Y_L^max为0.52 mol C·(mol C)^-1,促使油脂合成的临界C/N比为12.1 mol C·(mol C)^-1。利用该分配模型预测不同消耗C/N比的油脂得率,预测值为实验值的 95.2%～116.7%,表明模型可靠性较好。     

Environment-Friendly Synergistic Abiotic Stress for Enhancing the Yield of Lipids from Oleaginous Yeasts

The microbial lipids isolated from oleaginous yeasts are a potential alternative to tree borne oils. There is a need to optimize and enhance the production of lipid by various stress approaches. In the present study, yeasts are subjected to physico-chemical stresses, and growth, as well as lipid concentration at different time intervals are monitored. It is found that the nanoparticles (NP) such as Ag-NP and Zn-NP have an inhibitory effect on yeast growth. Most yeast strains show an increase in growth and lipid accumulation when ionic liquid (1-ethyl-3-methylimidazolium acetate) ([EMIM][OAc]) and table salt (NaCl) stress are applied. Lipid is chemically characterized using gas chromatography furnished with flame ionization detector (GC-FID), GC/MS, and NMR techniques. It contains a higher percentage of saturated fatty acids (SFA: 74.3%), monounsaturated fatty acids (19.1%) with low amounts of polyunsaturated fatty acids (1.9%). The thermo-stability study reveals that the lipid have higher volatility (380–410 °C) as closely compared with coconut oil, and much lower with respect to the winged bean oil (430–470 °C). The melting point of the lipids (37 °C) is determined through differential scanning calorimetry (DSC). The DSC and physico-chemical properties are supported that the yeast lipids may use as a cocoa-butter substitute. Production of lipid under NaCl stress (200 × 10⁻³ m ) is more than 60.4% higher as compared to the control. However, the combined stress effect of NaCl (200 × 10⁻³ m ) and 15 × 10⁻³ m of [EMIM][OAc] results in more than 96.4% yield of lipid. The exchange of inorganic and organic ions in combined treatment forces the microbial cells to accumulate more amounts of lipid, which may form a lipid-emulsion layer to protect the cell from osmosis. It is interestingly observed that the stress cells shift the flux to accumulate a significantly improved percentage of SFA, which could be provided better protection cover due to its expanded structure, less reactive characteristics, and completely insoluble nature in ionic-aqueous solvent. Practical applications: Oleaginous yeast is multiplied in a very limited space, and easily scalable for sustainable production of lipid to meet its commercial demand. This novel approach for enhancing the yield of lipid with the application of synergistic stress in between NaCl and the green solvent (ionic liquid) is being reported for the first time. This lipid has potential alternative applications as cocoa-butter.     

Microbial lipid production as biodiesel feedstock from N‐acetylglucosamine by oleaginous microorganisms

BACKGROUND: The byproducts from shrimp processing are heads and shells which contain a wealth of carbon and could be converted into oils via oleaginous microorganisms. The objective of this investigation was to determine the feasibility of using oleaginous microorganisms to convert N‐acetylglucosamine (GlcNAc), the major carbohydrate of the hydrolysate of shrimp processing waste, to triacylglycerols as a biodiesel feedstock. RESULTS: Screening experiments were conducted among Rhodotorula glutinis, Rhodococcus opacus and Cryptococcus curvatus using GlcNAc as sole carbon and energy source at 30 °C. All three microorganisms were found to grow well on GlcNAc, but the lipid contents in the cells were consistently low (lower than 5%) in the growth phase. However, lipid accumulation by C. curvatus was greatly enhanced upon entering the death phase in the absence of GlcNAc and the lipid content increased to 28.4% at 167.7 h. This indicated that C. curvatus was the optimal tested microorganism for the production of microbial oils from GlcNAc. Phosphate was further evaluated on the growth and lipid production by C. curvatus from GlcNAc. Results indicated that the yields of both biomass during growth phase and lipids at death phase increased with the increase of the ratio of C to P. But the fatty acid profiles of the accumulated lipids did not change significantly. CONCLUSION: Results indicated that shrimp processing waste could be utilized to produce oils as a biodiesel feedstock. The results could be applied to maximize production of oils from shrimp processing waste. Copyright © 2011 Society of Chemical Industry