Transport of L-glucose by Rhodotorula glutinis

The kinetics of L-glucose transport by Rhodotorula glutinis were studied over a 720-fold range of sugar concentrations. Analysis of the saturation isotherm revealed the presence of a one-carrier system for L-glucose in the plasma membrane of Rhodotorula glutinis. This carrier exhibited a km of 3.7 +/- 0.3 mM. D-Ribose was found to be a competitive inhibitor with a Ki of 19 +/- 1 mM. The results suggest that L-glucose is transported by the high-Km, D-ribose carrier. L-Glucose was transported against a concentration gradient and the transport was inhibited by the proton conductor 2,4-dinitrophenol.     

Production of carotenoids by strains of Rhodotorula glutinis cultured in raw materials of agro-industrial origin

The production of carotenoids by strains of Rhodotorula glutinis on different raw materials of agro-industrial origin (grape must, glucose syrup, beet molasses, soybean flour extract, maize flour extract) was investigated. Maximum yield (5.95 mg/l of total carotenoids culture fluid, 630 μg/g dry cell weight) was obtained with a particular strain of Rhodotorula glutinis after a batch culture of 120 h in a substrate containing concentrated rectified grape must as the sole carbohydrate source. In all experiments, the major pigments forming carotenoids (β-carotene, torulene, torularhodin) were quantified.     

Carotenoid Biosynthesis in Rhodotorula glutinis

It was determined that lycopene could be cyclized directly by Rhodotorula glutinis. It was also shown the the temperature effect (i.e., increased beta-carotene synthesis in response to lower incubation temperatures) in R. glutinis was controlled by changes in enzyme concentration.     

影响黏红酵母黏附牙鲆肠黏液的因素研究

目的研究pH、温度、二价阳离子对黏红酵母黏附作用的影响以及不同生长阶段的黏红酵母对牙鲆肠黏液的黏附特点。方法以牙鲆肠黏液作为黏附模型,采用MTT比色法测定黏红酵母在上述影响因素作用下的黏附能力。结果在10~30℃黏红酵母对牙鲆肠黏液的黏附随温度升高而增强,中性偏酸的环境有利于黏红酵母的黏附;Ca2 能显著增加黏红酵母的黏附,但Mg2 促黏附作用不明显;处于对数生长期的黏红酵母对牙鲆肠黏液的黏附能力最强,其次是延滞期的酵母,而稳定期和衰亡期的黏红酵母黏附能力显著减弱。结论黏红酵母对牙鲆肠黏液的黏附作用不仅受多种环境因子的影响,也受其自身生理状态的影响,其黏附作用具有可控性,这对黏红酵母在牙鲆肠道内黏附、定植的调控有一定的参考价值。     

Transport and metabolism of 2-deoxy-D-glucose by Rhodotorula glutinis

2-Deoxy-D-glucose transport by Rhodotorula glutinis is an active process. The intracellular concentration of free deoxyglucose after 15 min incubation of Rhodotorula cells with this sugar was 230 times the extracellular concentration. Although cell extracts at this time contained more 2-deoxy-D-glucose 6-phosphate than deoxyglucose, pulse-labelling experiments demonstrated that deoxyglucose is transported as the free sugar and subsequently phosphorylated. After transport, Rhodotorula cells metabolize deoxyglucose. The major metabolites during 30-90 min incubations were determined to be 2-deoxy-D-glucose 6-phosphate, 2-deoxy-D-glucitol, 2-deoxy-D-gluconate and 2,2'-dideoxy-alpha, alpha'-trehalose. Rhodotorula glutinis also degrades deoxyglucose to CO2. The concentrations of intermediates in this pathway were too low to detect and resolve in extracts of control cells. In 2,4-dinitrophenol-poisoned cells, however, it appears that deoxyglucose degradation is restricted largely to loss of C-1 as CO2 and it was possible to identify 1-deoxy-D-ribulose 5-phosphate as an intermediate presumably arising from metabolism of deoxyglucose by the oxidative portion of the hexose monophosphate pathway.     

Synthesis of intracellular and extracellular metabolites by Rhodotorula glutinis

A close relationship has been established between the production of extracellular and intracellular lipids and polysaccharides by Rhodotorula glutinis. Their synthesis depended on the pH of the medium. The composition and dynamics of polyol content in the cells, and the presence of acids typical of exolipids in the composition of intracellular lipids under certain conditions, suggest that the components of extracellular lipids are synthesized within the yeast cell.     

Biosorption of uranium by magnetically modified Rhodotorula glutinis

Adsorption of uranium from aqueous solution onto the magnetically modified yeast cell, Rhodotorula glutinis, was investigated in a batch system. Factors influencing sorption such as initial solution pH, biomass dosage, contact time, temperature, initial uranium concentration and other common cations were analyzed. Sorption isotherm, kinetic and thermodynamic studies of uranium on magnetically modified R. glutinis were also carried out. The temperature dependent equilibrium data agreed well with the Langmuir model. Kinetic data obtained at different temperatures were simulated using pseudo-first-order and pseudo-second-order kinetic models, the pseudo-second-order kinetic model was found to describe the data better with correlation coefficients near 1.0. The thermodynamic parameters, ΔH°, ΔS° and ΔG° were calculated from the sorption data gained at different temperatures. These thermodynamic parameters showed that the sorption process was endothermic and spontaneous. All results indicated that magnetically modified R. glutinis can be a potential sorbent for uranium wastewater treatment.     

耐乙酸粘红酵母合成油脂

乙酸是木质纤维素在水解过程中的主要副产物,高浓度的乙酸严重影响产油微生物的生长和油脂合成。本文研究了粘红酵母对乙酸的耐受性及其利用乙酸合成微生物油脂的能力。结果表明,在初始葡萄糖、木糖浓度分别为6 g/L和44 g/L的混合糖培养基中,乙酸浓度低于10 g/L时,不会对菌体生长产生抑制作用,油脂合成还得到了促进。当乙酸添加量为10 g/L时,生物量、油脂产量、油脂含量较对照组分别提高了21.5%、171.2%和121.6%。进一步研究表明,粘红酵母具备利用乙酸合成油脂的能力,当以乙酸为唯一碳源,浓度为25 g/L时,油脂产量达到3.20 g/L,油脂质量得率为13%。微生物油脂成分分析表明,粘红酵母以乙酸为底物制得的油脂可以作为制备生物柴油的油脂原料,其主要成分为棕榈酸、硬脂酸、油酸、亚油酸和亚麻酸,其中饱和脂肪酸和不饱和脂肪酸含量分别为40.9%和59.1%。由于粘红酵母具有利用乙酸合成微生物油脂的能力,在以木质纤维素水解液为原料生产微生物油脂的脱毒过程中,一定浓度的乙酸可以不必脱除。     

Effect of glucose on pyruvate utilization by Rhodotorula glutinis

Summary The utilization of glucose and pyruvate by the yeast Rhodotorula glutinis in a medium containing both carbon sources has been studied. Glucose is readily consumed whereas the uptake of pyruvate is completely blocked by the presence of the sugar.The content of pyruvate kinase and phosphoenolpyruvate carboxykinase in R. glutinis cells growing on glucose plus pyruvate are drastically affected with time by the disappearance of the sugar from the culture medium. After complete exhaustion of glucose, the level of pyruvate kinase drops sharply down to a minimum whereas that of phosphoenolpyruvate carboxykinase rises abruptly up to a maximum.Feeding experiments with labelled compounds show that glucose affects the utilization of the amino acids alanine and aspartate, and conversely that the amino acids influence the utilization of the sugar. Glucose breakdown and its incorporation into polysaccharides is controlled by the amino acids and gluconeogenesis from the amino acids is controlled by the sugar.     

Uptake of disaccharides by the aerobic yeast Rhodotorula glutinis

Sucrose (and raffinose), trehalose, maltose, cellobiose, and lactose were examined for their transport into Rhodotorula glutinis. Melibiose and lactose were found not to be transported at all. Sucrose, raffinose and trehalose are split by periplasmic hydrolases prior to the penetration of their monosaccharide components into cells, the hydrolysis being the rate-limiting factor for the uptake process. Maltose and cellobiose appear to use specific uptake systems. Experiments with protoplasts of Rhodotorula glutinis support the conclusions that sucrose and trehalose are not consumed in the absence of exoenzymes.     

Kinetics of D-glucose and 2-deoxy-D-glucose transport by Rhodotorula glutinis

The yeast Rhodotorula glutinis (Rhodosporidium toruloides) is capable of accumulative transport of a wide variety of monosaccharides. Initial velocity studies of the uptake of 2-deoxy-D-glucose were consistent with the presence of at least two carriers for this sugar in the Rhodotorula plasma membrane. Non-linear regression analysis of the data returned maximum velocities of 0.8 +/- 0.2 and 2.0 +/- 0.2 nmol/min per mg (wet weight) and Km values of 18 +/- 4 and 120 +/- 20 microM, respectively, for the two carriers. Kinetic studies of D-glucose transport also revealed two carriers with maximum velocities of 1.1 +/- 0.4 and 2.4 +/- 0.4 nmol/min per mg (wet weight) and Km values of 12 +/- 3 and 55 +/- 12 microM. As expected, 2-deoxy-D-glucose was a competitive inhibitor of D-glucose transport. Ki values for the inhibition were 16 +/- 8 and 110 +/- 40 microM. These Ki values were in good agreement with the Km values for 2-deoxy-D-glucose transport. D-Xylose, the 5-deoxymethyl analog of D-glucose, appears to utilize the D-glucose/2-deoxy-D-glucose carriers. This pentose was observed to be a competitive inhibitor of D-glucose (Ki values = 0.14 +/- 0.06 and 5.6 +/- 1.6 mM) and 2-deoxy-D-glucose (Ki values = 0.15 +/- 0.07 and 4.6 +/- 1.2 mM) transport.     

粘红酵母和酿酒酵母联合处理味精废水

为了解决味精废水中高NH4+浓度抑制油脂微生物的生长和油脂积累问题,采用粘红酵母和酿酒酵母联合处理味精废水的方法:首先利用酿酒酵母降解味精废水(MSG)中NH4+,然后将处理后的废水进一步发酵培养合成油脂。研究结果表明:用经酿酒酵母预处理过的味精废水作为粘红酵母的培养基发酵时,粘红酵母的生物量为33.3 g/L,油脂产率为18.16%,COD降解率为50.6%,NH4+的降解率为93.9%。比粘红酵母单独处理味精废水,NH4+的降解率提高了6.14倍,生物量、油脂产率和COD降解率分别提高了8.1%、30.06%和9.58%。     

Invertase from a strain of Rhodotorula glutinis

An invertase (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26) from Rhodotorula glutinis was purified by ammonium sulfate fractionation, gel filtration and anion exchange chromatography. Invertase molecular weight was estimated to be 100 kDa by analytical gel filtration and 47 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Molecular mass determinations indicated that the native enzyme exists as a homodimer. It is a glycoprotein that contains 19% carbohydrate. The enzyme attacks beta-D-fructofuranoside (raffinose, stachyose and sucrose) from the fructose end. It has a K(m) of 0.227 M and a V(max) of 0.096 micromol/min with sucrose as a substrate. Invertase activity is stable between pH 2.6 and 5.5 for 30 min, maximum activity being observed at pH 4.5. The activation energy was 6520 cal/mol. The enzyme is stable between 20 and 60 degrees C. Mg(2+) and Ca(2+) ions stimulated invertase activity 3-fold, while Fe(2+), K(+), Co(2+), Na(+) and Cu(2+) increased activity about 2-fold. The transfructosylation reaction could not be observed. This enzyme is of particular interest since it appears to have a high hydrolytic activity in 1 M sucrose solution. This fact would make the enzymatic hydrolysis process economically efficient for syrup production using by-products with high salt and sugar contents such as sugar cane molasses.     

Regulation of ornithine transcarbamylase in Rhodotorula glutinis

The regulation of ornithine transcarbamylase (OTC) of Rhodotorula glutinis has been studied, by growing the yeasts in different carbon and nitrogen sources and estimating the enzyme level in crude yeasts extracts.The results show a nutritional repression of OTC by arginine, when added to the culture media as carbon, nitrogen or carbon and nitrogen sources. On the other hand ornithine does not exert any effect in the same experimental conditions.