Enrichment of wheat bran byRhodotorula gracilis through solid-state fermentation

The potential oil-producing yeast Rhodotorula gracilis was found to produce higher yields of biomass (13.7 g/L) and lipids (20.3%) in a nitrogen-limited and economically cheaper medium (molasses without yeast extract) in a submerged fermentation system. But, when the yeast was grown on four different wheat bran media by solid-state fermentation technique, different media combinations affected the percent increase in biomass, protein, oil production, fatty acid profile and degree of saturation and unsaturation. The initial lipid content in the control medium was 3.5% while in a medium with wheat bran, molasses, and minerals it was 69.8%. The yeast did not produce alpha-amylase, amyloglucosidase and cellulolytic enzymes for the breakdown of wheat bran. The yeast produced red carotenoids, a precursor of vitamin B12 and some oligounsaturated fatty acids in the fermented product.     

Thiamin uptake in Euglena gracilis

Thiamin uptake has been investigated in Euglena gracilis Z. This protozoon possessed an active transport system for thiamin with a Km value of 17 nM and a Vmax value of 7.8 pmol per 10(6) cells per min. Thiamin uptake was dependent on pH and temperature, but not on exogenous glucose as an energy source. Oxythiamin and pyrithiamin were competitive inhibitors with Ki values of 33 nM and 15 nM, respectively. Thiamin monophosphate, thiamin pyrophosphate, thiamin triphosphate, heteropyrithiamin, quinolinothiamin, thiamin chloride and amprolium inhibited uptake. Inhibition of thiamin uptake by various metabolic inhibitors and anaerobiosis suggest that thiamin uptake requires an energy source generated by respiration and glycolysis.     

Mercury uptake and removal by Euglena gracilis

The uptake and removal of mercury (added as HgCl2) from the culture medium by Euglena gracilis was studied. In cultures initiated in the light, cells accumulated a small fraction of the added heavy metal (5-13%). Mercury was both biologically and nonbiologically volatilized, and cell growth was partially inhibited; under these conditions the glutathione content was 3.2 nmol/10(6) cells. In contrast, in cultures initiated in the dark, mercury uptake by cells was two to three times higher, biological volatilization remained unchanged and nonbiological volatilization and growth were negligible; the glutathione content diminished to 1.4 nmol/10(6) cells. Biological mercury volatilization depended on cell density and metal concentration, but was light-independent. Thus, volatilization of mercury by Euglena appeared not to be an effective mechanism of resistance, whereas a high intracellular level of glutathione and a low mercury uptake seemed necessary for successful tolerance.     

Production of levanase byRhodotorula sp.

Rhodotorula sp. produced a high yield of levanase (12.5 nkat/mL) in shake flasks in basal medium containing 1% maltose as the sole carbon source. Among the different carbon sources used, maltose was found to be the best for levanase production. The optimum temperature and pH for levanase production were 30°C and 6, respectively. In a batch reactor the enzyme productivity was higher (500 nkat L⁻¹ h⁻¹) than in shaken flasks (347 nkat L⁻¹ h⁻¹).     

Accumulation of lipid byRhodotorula glutinis in continuous culture

Summary Rhodotorula glutinis accumulated 35% (w/w) lipid when grown nitrogen-limited in a chemostat at a dilution rate (D) of 0.02^–1 . At D = 0.10 h^–1, the lipid content was only 15% (w/w). Dual limitation of nitrogen and phosphate increased neither the amount of lipid produced nor the lipid yield (14g lipid per 100g glucose consumed). The fatty acid composition was unchanged by the growth rate.     

Anomalous kinetics of sucrose uptake in maize scutellum slices1

Abstract The kinetics of sucrose uptake into maize scutellum slices showed that the uptake mechanism had a saturable component with a Km of l.5mol m^?3 sucrose. Nevertheless, uptake rate was constant (zero order) over extended periods of time until the bathing solution was nearly depleted of sucrose. It is concluded that these anomalous uptake kinetics reflect sucrose influx across the plasmalemma because of the following results: (a) Efflux of sucrose into buffer was negligible compared with uptake rate, (b) When slices were incubated in fructose, sucrose was synthesized and there was a net release of sucrose to the bathing solution until a steady-state was reached when influx and efflux were equal in magnitude. After the steady-state was reached, efflux of sucrose from the slices was nearly the same in magnitude as the estimated rate of uptake that would have occurred from bathing solutions initially containing the steady-state sucrose concentration, (c) Exchange of sucrose between bathing solution and slices was negligible compared with uptake rate, (d) Pretreatment of slices with uranyl nitrate abolished sucrose uptake, but uptake rate was re-established in these slices after treatment with HCl (pH 2). Uptake rate was set by the initial sucrose concentration of the bathing solution, and was not influenced by the level of endogenous sucrose or by the rate at which the sucrose concentration of the bathing solution declined. Abrupt increases in sucrose concentration during the uptake period increased the rate of uptake only if the concentration was increased above that at the start of the uptake period. Following abrupt decreases in sucrose concentration, there was a lag of about 30 min before uptake rate decreased greatly. If slices were washed and replaced in a fresh sucrose solution during the uptake period, a new uptake rate was set to correspond to the new initial sucrose concentration. It is suggested that the sucrose carrier has a transport site with a relatively low Km (much below 1.5mol m^?3) and that the measured Km (1.5mol m^?3) is that of a site that binds sucrose and thereby controls the rate of uptake. The low Km suggested for the transport site would explain the zero order kinetics but a model of the uptake mechanism that includes the control site cannot, as yet, be constructed from the data.     

Synthesis of L-phenylalanine analogs byRhodotorula glutinis. Bioconversion of cinnamic acids derivatives

The synthesis of L-alpha aromatic amino acids by amination of forty-one derivatives of cinnamic acid and related compounds is tested with the yeastRhodotorula glutinis.     

Aneusomaty inOrobanche gracilis

InOrobanche gracilis Sm. (collected in Vienna, Lower Austria, and N. Italy) the somatic chromosome numbers were found to be inter-and intra-individually variable. Most plants yielded counts of around the tetraploid level (2n = 73−91), a few of around the hexaploid level (2n = 112−116). Only 36% of the plants were eusomatic, only 24% eutetraploid (2n = 76). Depending on the variable somatic chromosome number, gametophytic numbers are also variable. Univalents, multivalents, and anaphase anomalies were of regular occurrence during meiosis of plants with more than 2n = 76 chromosomes. This is the first report of variable polyploid chromosome numbers (4x = 76, 6x = 114) inOrobanche sect.Orobanche. Aneusomaty is due to a constitutional tendency to nondisjunction during mitosis. The supernumerary chromosomes are considered to represent A- (= normal) rather than B-chromosomes. A possible causality between the chromosomal and the morphological variation, and the adaptive significance of this phenomenon are discussed.     

Microspectrophotometry ofEuglena gracilis

The paraflagellar bodies (PFBs) of isolated flagella ofEuglena gracilis were investigated microspectrophotometrically using a visible- and infrared-light microscope with image analyzer and microspectrophotometer. Flagella with attached PFBs were separated from the cell bodies by a short exposure to near-UV light. Fluorescence-emission spectra (excitation at 365 nm) of single PFBs had maxima near 470 and 520 nm, indicating the presence of pterins and flavins. No fluorescence was associated with the flagella themselves. Pterin- and flavin-like fluorescence emission was also found in blue-fluorescing vesicles distributed throughout the entire cell body ofEuglena. Their characterization by microfluorimetry was greatly aided by the use of chlorophyll-free mutants in which the signal-to-noise ratio was distinctly enhanced because of the lack of chlorophyll fluorescence. Our finding of flavin-like fluorescence associated with PFB strengthens similar earlier reports in the literature. The occurrence of pterin-like fluorescence in the PFB lends further support to our earlier proposal that pterins as well as flavins may function as photoreceptor pigments for near-UV and blue light.     

Anomalous oxygen uptake from isolated chloroplasts inhibited in photosystem II and without external electron donors.

Light induced modulated signal of oxygen uptake by isolated chloroplasts in the presence of methyl viologen, when Photosystem II activity was inhibited and in the absence of any electron donors, was detected by a modulated oxygen Pt electrode, polarized negatively. Evidence is brought to show that an electrochemical process which takes place on the surface of the negatively polarized Pt-cathode produces an intermediate which serves as an electron donor to Photosystem I. Atempts to identify this intermediate show that it may be very probably the superoxide radical generated by the electrochemical reduction of oxygen which continuously diffuses from the external circulating medium to the electrode.     

Heteroxanthin in Euglena gracilis

Summary 1. From a large scale preparation of Euglena gracilis, strain Z, besides the acetylenic pigments diatoxanthin and diadinoxanthin and the allene neoxanthin, an additional acetylenic xanthophyll has been isolated. 2. Mass and IR spectra and chemical reactions showed typical patterns of heteroxanthin from Vaucheria. 3. The pigment was transformed into diadinochrome-isomers with acidified acetone. 4. A partial synthesis of heteroxanthin from diadinoxanthin by LiAlH₄-reduction is described, confirming the structure proposed by Strain. 5. The identity of heteroxanthin with the trollein—like pigment described for Euglena is discussed.     

Antimutagenicity in Euglena gracilis

The genotoxic effect of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) and furadantine (Fu) was significantly decreased by standard antimutagens (ascorbic acid, α-tocopherol, chlorophyllin and sodium selenite) in the unicellular flagellate Euglena gracilis. The effects of these compounds were verified also by a bacterial test in which three strains of Salmonella typhimurium, TA97, TA100 and TA102, were used. The above compounds were antimutagenic in strains of bacteria used, except for chlorophyllin which had no effect on strain TA102.     

Proteolysis in Euglena gracilis

Endoproteolytic activities (EC 3.4.22. and 23.) of cell-free extracts of Euglena gracilis, measured by autolysis and azocaseinolysis, vary considerably during the culture growth cycle. They are high in the lag phase, drop sharply up to the mid-logarithmic phase, and then rise again reaching the initial high levels in the stationary phase. This pattern has been observed for both the soluble and the particulate proteolytic activities of four cell types differing with regard to the developmental state of the chloroplast: dark-grown, light-induced, and light-grown wild-type cells, as well as light-grown apoplastic W₃BUL mutant cells, all on a glucose-based medium. Therefore, the activity of the main intracellular proteinases is neither directly nor indirectly light-regulated, but seems to be controlled by the availability of nutrients. Endogenous inhibitors of proteinases could not be detected. Cysteine proteinase activity has been found in the soluble and the particulate fractions, but aspartic proteinase activity in the latter ones only. Different cysteine proteinases may be present in the two fractions, during the different growth phases, and in the four cell types studied.Abbreviations CBB Coomassie Brilliant Blue G-250 - DFP diisopropyl fluorophosphate - EDTA disodium ethylendiaminetetraacetic acid - E-64 l-transepoxysuccinyl-leucyl-amido(4-guanidino)butane - Iog phase logarithmic growth phase - MET 2-mercaptoethanol - PMSF phenylmethylsulfonyl fluoride - Z benzyloxycarbonyl Paper I of this series is Krauspe and Scheer (1986). A preliminary publication appeared (Krauspe et al. 1982)