Extracellular RNase produced by Yarrowia lipolytica

Production of extracellular RNase(s) by Yarrowia lipolytica CX161-1B was examined in media between pHs 5 and 7. RNase production occurred during the exponential growth phase. High-molecular-weight nitrogen compounds supported the highest levels of RNase production. Several RNases were detected in the supernatant medium. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the RNases had estimated molecular weights of 45,000, 43,000, and 34,000. It was found that Y. lipolytica secretes only one RNase (the 45,000-molecular-weight RNase) and that the 43,000 and 34,000-molecular-weight RNases are degradation products of this RNase. The alkaline extracellular protease secreted by Y. lipolytica was shown to have a major role in the 45,000- to 43,000-molecular-weight conversion, and it was demonstrated that the 45,000-molecular-weight RNase could be purified from a mutant which does not produce the alkaline extracellular protease. Purification of the RNase from a wild-type strain resulted in purification of the 43,000-molecular-weight RNase. This RNase was a glycoprotein with a molecular weight of 44,000 as estimated by gel filtration, an isoelectric point of pH 4.8, and a pH optimum between 6.5 and 7.0.     

Pilot plant production of rhamnolipid biosurfactant by Pseudomonas aeruginosa

Rhamnolipid biosurfactants were continuously produced with Pseudomonas aeruginosa on the pilot plant scale. Production and downstream processing elaborated on the laboratory scale were adapted to the larger scale. Differences in performance resulting from the scale-up are discussed. A biosurfactant concentration of approximately 2.25 g liter-1 was achieved. The biosurfactant yield on glucose was 77 mg g-1 h-1, and the productivity was 147 mg liter-1 h-1, corresponding to a daily production of 80 g of biosurfactant. The first enrichment step consisted of an adsorption chromatography which was followed by an anion-exchange chromatography. The resulting product was 90% pure, and the overall recovery of active material was above 60% with the downstream processing used.     

Biosynthesis of biotin vitamers by Yarrowia lipolytica

The hydrocarbon utilizing yeast Yarrowia lipolyyica NCYC 1421 produces biotin and its vitamers when grown on glucose in biotin-free media. Levels of production can be influenced by the medium composition. Growth in the presence of longchained fatty acids greatly increases biotin vitamer production. The biotin vitamers produced are normally dethiobiotin and 7-keto, 8-aminopelargonic acid. The addition of succinic acid at 0.5 g per litre causes the vitamer 7, 8-diaminopelargonic acid to be produced at high levels. The biotin antagonist α-dehydrobiotin inhibits the growth of Yarrowia lipolytica . Mutants can be readily isolated which show resistance to α-dehydrobiotin, but these do not produce greater amounts of biotin or its vitamers.     

Pilot plant production of rhamnolipid biosurfactant by Pseudomonas aeruginosa.

Rhamnolipid biosurfactants were continuously produced with Pseudomonas aeruginosa on the pilot plant scale. Production and downstream processing elaborated on the laboratory scale were adapted to the larger scale. Differences in performance resulting from the scale-up are discussed. A biosurfactant concentration of approximately 2.25 g liter-1 was achieved. The biosurfactant yield on glucose was 77 mg g-1 h-1, and the productivity was 147 mg liter-1 h-1, corresponding to a daily production of 80 g of biosurfactant. The first enrichment step consisted of an adsorption chromatography which was followed by an anion-exchange chromatography. The resulting product was 90% pure, and the overall recovery of active material was above 60% with the downstream processing used.     

Perspectives of nervonic acid production by Yarrowia lipolytica

Biotechnology Letters - Nervonic acid (cis-15-tetracosenoic acid, 24:1Δ15) is a long chain monounsaturated fatty acid, mainly exists in white matt er of the human brains. It plays an important...     

Selectivity in citric acid production by Yarrowia lipolytica

This experimental study reports about production selectivity in the fermentation of glucose to citric acid by Yarrowia lipolytica as a function of substrate concentration. Batch runs featuring biomass growth and one or two citric acid production phases were carried out in a 15-l stirred tank fermentor. The presented results demonstrate that working at high initial substrate concentration in the production phase is beneficial both in terms of a higher production rate of citric acid, the desired metabolite (reaching 0.077 h(-1)) and of a higher utilization degree of the employed carbon source (yield up to 0.384 g(c.a.)/g(glucose)). The production rate of isocitric acid, the major undesired metabolite, was found to be practically constant over the tested initial substrate concentration range.     

Production of 1-decanol by metabolically engineered Yarrowia lipolytica

Medium-chain alcohols are used to produce solvents, surfactants, lubricants, waxes, creams, and cosmetics. In this study, we engineered the oleaginous yeast Yarrowia lipolytica to produce 1-decanol from glucose. Expression of a fatty acyl-CoA reductase from Arabidopsis thaliana in strains of Y. lipolytica previously engineered to produce medium-chain fatty acids resulted in the production of 1-decanol. However, the resulting titers were very low (<10 mg/mL), most likely due to product catabolism. In addition, these strains produced small quantities of 1-hexadecanol and 1-octadecanol. Deleting the major peroxisome assembly factor Pex10 was found to significantly increase 1-decanol production, resulting in titers exceeding 500 mg/L. It also increased 1-hexadecanoland and 1-octadecanol titers, though the resulting increases were less than those for 1-decanol. These results demonstrate that Y. lipolytica can potentially be used for the industrial production of 1-decanol and other fatty alcohols from simple sugars.     

解脂耶氏酵母表达系统研究进展

解脂耶氏酵母（Yarrowia lipolytica）是非常规酵母中具代表性的一种,它底物广泛,尤其能利用有机酸（柠檬酸、异柠檬酸）,蛋白类（蛋白酶、脂肪酸、酯酶、磷酸酶、α-甘露糖苷酶、RNase）。烷烃类廉价物质作为底物分泌大量的代谢产物,自上世纪40年代被发现以来,越来越受到研究者的重视,并于上世纪90年代被开发成为一种新的酵母表达系统,用于42种异源蛋白的高效表达。综述了解脂耶氏酵母表达系统及其特点,有利于研究者从转录和翻译的水平研究异源蛋白在此菌中的表达分泌路径以及寻找到调控型启动子。     

Yarrowia lipolytica lipase production enhanced by increased air pressure

Aims: To study the cellular growth and morphology of Yarrowia lipolytica W29 and its lipase and protease production under increased air pressures. Methods and Results: Batch cultures of the yeast were conducted in a pressurized bioreactor at 4 and 8 bar of air pressure and the cellular behaviour was compared with cultures at atmospheric pressure. No inhibition of cellular growth was observed by the increase of pressure. Moreover, the improvement of the oxygen transfer rate (OTR) from the gas to the culture medium by pressurization enhanced the extracellular lipase activity from 96·6 U l^?1 at 1 bar to 533·5 U l^?1 at 8 bar. The extracellular protease activity was reduced by the air pressure increase, thereby eliciting further lipase productivity. Cell morphology was slightly affected by pressure, particularly at 8 bar, where cells kept the predominant oval form but decreased in size. Conclusions: OTR improvement by total air pressure rise up to 8 bar in a bioreactor can be applied to the enhancement of lipase production by Y. lipolytica. Significance and Impact of the Study: Hyperbaric bioreactors can be successfully applied for yeast cells cultivation, particularly in high‐density cultures used for enzymes production, preventing oxygen limitation and consequently increasing overall productivity.     

Substrate utilization by recombinant Yarrowia lipolytica growing on sucrose

We report the study of the dynamics of substrate utilization by the genetic modified strain Yarrowia lipolytica H222-S4(p67ICL1) T5. In contrast to its wild-type equivalent, this recombinant strain is able to excrete the sucrose cleaving enzyme invertase. Both the sucrose degradation rate and the glucose and fructose consumption rate have been investigated. In all experiments, satisfied amounts of invertase were produced so that all sucrose was cleaved into its monomers. While glucose and fructose as sole carbon sources were consumed with the same uptake rate, a clear preference for glucose uptake was detected in cultivations with sucrose as sole carbon source or mixed substrates when compared with fructose. Nevertheless, no real diauxie could be observed because of partly simultaneous consumption of both monosaccharides. Fructose being present in the cultivation medium at the beginning of the fermentation led to the retardation of glucose uptake. This effect was observed for various fructose starting concentrations in the range of 5–85 g/l.     

Engineering Yarrowia lipolytica for Campesterol Overproduction

Campesterol is an important precursor for many sterol drugs, e.g. progesterone and hydrocortisone. In order to produce campesterol in Yarrowia lipolytica, C-22 desaturase encoding gene ERG5 was disrupted and the heterologous 7-dehydrocholesterol reductase (DHCR7) encoding gene was constitutively expressed. The codon-optimized DHCR7 from Rallus norvegicus, Oryza saliva and Xenapus laevis were explored and the strain with the gene DHCR7 from X. laevis achieved the highest titer of campesterol due to D409 in substrate binding sites. In presence of glucose as the carbon source, higher biomass conversion yield and product yield were achieved in shake flask compared to that using glycerol and sunflower seed oil. Nevertheless, better cell growth rate was observed in medium with sunflower seed oil as the sole carbon source. Through high cell density fed-batch fermentation under carbon source restriction strategy, a titer of 453±24.7 mg/L campesterol was achieved with sunflower seed oil as the carbon source, which is the highest reported microbial titer known. Our study has greatly enhanced campesterol accumulation in Y. lipolytica, providing new insight into producing complex and desired molecules in microbes.     

Lipase location in Yarrowia lipolytica cells

Lipase production by Yarrowia lipolytica was growth associated and, at the beginning of cultivation, it was mainly cell-bound. Lipase release into the culture medium started when about 50% of the carbon source (olive oil or glucose) was consumed reaching its maximum concentration in the late stationary phase.     

基因工程微生物合成鼠李糖脂表面活性剂的研究进展

鼠李糖脂是一类重要的生物表面活性剂。相比于化学合成的表面活性剂,其具有更优秀的理化性质及环境友好等特点,被广泛应用于微生物采油、环境污染修复等工程中。目前,鼠李糖脂的工业生产主要采用铜绿假单胞菌这一具有致病性的天然合成菌株,与此同时,受菌株遗传背景的限制,优化发酵过程等方法在产量提升方面遇到了一些瓶颈问题。利用基因工程方法对菌株进行改良有望进一步提高鼠李糖脂生产的安全性、产量、产物性能等多项指标,因此受到了越来越广泛的关注。本文综述了近年来利用基因工程方法优化鼠李糖脂生物合成的最新进展,讨论了异源合成、代谢通路改造、基因表达优化、蛋白质工程、底盘工程等多种策略的应用,并展望了一系列可行的研究方向。     

Preparation of dodecanol-tolerant strains of Yarrowia lipolytica

Dodecanol (1% v/v) and dodecanoic acid (1% w/v) inhibited growth of Yarrowia lipolytica in complex media supplemented with glucose but dodecanedioic acid (1% w/v) was not toxic. Dodecanol-tolerant strains were prepared from the wild type strain H222 as well as the acyl-CoA oxidase deleted (deltaPOX2, POX3, POX5) strain MTLY35. These strains grew in rich media containing up to 10% (v/v) dodecanol. Dodecanol-tolerant strains remained dodecanol tolerant after they had been cultured in rich media without dodecanol. No significant amount of dodecanedioic acid was accumulated by the dodecanol-tolerant strains when grown on glucose in the presence of dodecanol.     

Production of brown tyrosine pigments by the yeast Yarrowia lipolytica

AIMS: To study the mechanism of production of brown pigments from tyrosine in the yeast Yarrowia lipolytica. METHODS AND RESULTS: Pigment formation was followed during growth in tyrosine medium, and the presence of the pigment precursor in the medium was assessed by evaluating pigment formation after removing the cells at different times of incubation. It was observed that the pigment precursor accumulated outside the cells during the exponential phase of growth, but pigment formation only occurred during the stationary phase of growth and resulted from the oxidation of the precursor. Pigment formation was repressed by glucose and L-glutamine, and promoted by lactic acid, L-asparagine and glycine. Spectra of 1H and 13C-NMR revealed that the brown pigment was derived from tyrosine and was a polymer composed of a core of aromatic residues. CONCLUSION: The results indicate that pigments result from the extracellular accumulation and auto-oxidation of an intermediate of tyrosine catabolism. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the mechanism of pigment production from tyrosine in a yeast species.     

Synthesis of rhamnolipid biosurfactant and mode of hexadecane uptake by Pseudomonas species

Background  

Microorganisms have devised ways by which they increase the bioavailability of many water immiscible substrates whose degradation rates are limited by their low water solubility. Hexadecane is one such water immiscible hydrocarbon substrate which forms an important constituent of oil. One major mechanism employed by hydrocarbon degrading organisms to utilize such substrates is the production of biosurfactants. However, much of the overall mechanism by which such organisms utilize hydrocarbon substrate still remains a mystery.     

解脂亚罗酵母P12单倍体的制备

[背景]目前解脂亚罗酵母在实验研究和工业生产方面的应用越来越广泛,但相较于常规酵母而言,解脂亚罗酵母缺乏简便有效的遗传转化体系,致使其在基因表达调控方面存在较大困难.同时,酵母的染色体倍性也会对基因敲除效果产生影响,选择单倍体细胞作为功能基因改造的受体可以避免等位基因之间相互作用的影响,解决多倍体细胞基因敲除不完全的问...