Hemolytic activity of Rhizopus nigricans and Rhizopus arrhizus

Rhizopus nigricans andR. arrhizus were cultured in modified Sabouraud broth and synthetic dextrose-glutamate medium for periods of two to eight weeks. The culture filtrates and extracts of fungous mats were examined for the presence ofin vitro hemolytic activity. The culture filtrates exhibited little hemolytic activity but all fungous mat extracts produced hemolysis of sheep, rabbit, guinea pig and human erythrocytes. Guinea pig erythrocytes were in general most readily hemolyzed and sheep erythrocytes least readily hemolyzed.

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Zusammenfassung Rhizopus nigricans undR. arrhizus sind in modifizierter Sabouraud's Brühe und in synthetischem Dextroseglucamate-Nährboden für zwei bis acht Wochen gezüchtet worden. Das Kulturfiltrat und der Extrakt des Pilzmyzeliums sind für das Vorhandensein der in-vitro hämolytischen Aktivität untersucht. Das Kulturfiltrat zeigte eine geringe hämolytische Aktivität, jedoch verursachten alle Pilzmyzeliumextrakte eine Hämolyse in Erythrozyten von Schaf, Kaninchen, Meerschweinchen und Menschen. Meerschweinchenerythrozyten sind im allgemeinen am leichtesten, Schaferythrozyten am wenigsten hämolysiert.

     

Lipids of Rhizopus arrhizus Fischer

The lipids of Rhizopus arrhizus Fischer mycelia and sporangiospores were extracted, isolated, and separated by thin-layer, liquid, and gas chromatography. Structural confirmations of the compounds were made by a gas chromatographmass spectrometer combination. The n-heptane fraction contained squalene (1%) as a major hydrocarbon constituent. Other major lipid classes detected were free fatty acids, naturally occurring methyl esters of fatty acids, triglycerides, sterols, and polar lipids. The polar lipids (44.4%) were found in the highest concentrations, and the triglycerides (22.1%), sterols (16.7%), and free fatty acids (11.7%) were present in lesser concentrations. This is the first report of naturally occuring methyl esters of long-chain fatty acids being present in fungal mycelium. There appears to be a preference for incorporation of unsaturated acids into the complex lipids, with the exception of the triglycerides. The major saturated fatty acids in the mycelium were palmitic (C(16)) and arachidic (C(20)), whereas the major unsaturated acids were oleic (C(18:1)) and linoleic (C(18:2)), respectively.     

Biosorption of radionuclides by Rhizopus arrhizus

The sorption of various radionuclides viz. 233U, 239Pu, 241Am, 144Ce, 147Pm, 152+154Eu and 95Zr from aqueous nitrate medium has been studied using biomass Rhizopus arrhizus. The biosorption of 233U and 239Pu was found to be maximum at pH 6-7 whereas for other trivalent actinides and fission products viz. 241Am, 144Ce, 147Pm, 152+154Eu and tetravalent 95Zr, it was more effective at pH 2. This biomass is a promising sorbant for the treatment of radioactive effluents from nuclear industry. © Rapid Science Ltd. 1998     

Chiral synthesis of alpha-phenylpyridylmethanols with Rhizopus arrhizus

The bioreduction of 2-benzoylpyridine (1a) with Rhizopus arrhizus afforded (S)-(+)-alpha-phenyl-2-pyridylmethanol (2a) in 82% enantiomeric excess (e.e.) while the asymmetric hydrolysis of its racemic acetate resulted in the antipode (R)-(-)-2a with 24% optical purity.     

Influence of Exogenous Fatty Acids on Cottonseed Germination

Effects of exogenous free fatty acid application on percentage germination and radicle length were investigated with more chill sensitive (Pima S-4) and less chill sensitive (Pima S-5) cottonseed (Gossypium barbadense L.) at chilling (14°C) and optimal (34°C) temperatures. Of the organic solvents able to solubilize free fatty acids, aqueous solutions as high as 5% dimethyl sulfoxide did not adversely affect germination at 34°C. Palmitic, oleic and linoleic acids (120 μM) were solubilized in 5% DMSO. At 14°C, percent germination of fatty acid treated Pima S-5 significantly increased, while no difference was observed for Pima S-4. Conversely, radicle length of fatty acid treated Pima S-4 significantly increased especially with oleate and linoleate, while no difference was detected for Pima S-5. Fatty acid supplementation influenced neither germination nor radicle length for Pima S-4 and Pima S-5 at 34°C.     

Biochemical Studies of Bacterial Sporulation and Germination XV. Fatty Acids in Growth, Sporulation, and Germination of Bacillus megaterium

The levels of fatty acids and their distribution were determined in cultures of Bacillus megaterium during growth, sporulation, and germination. Branched-chain pentadecanoates (br-C15) were the principal fatty acids of log-phase cells. Synthesis of branched-chain tetradecanoates (br-C14) during sporulation increased the relative proportion of these branched fatty acids in sporulating cells and in mature spores. The log-phase distribution was reestablished during outgrowth of the spore. The ratio of br-C15 to br-C14 could be radically altered by addition of their respective amino acid precursors, isoleucine and valine, without seriously affecting the sporulation process. The fatty acid composition of each of the purified phospholipids from log-phase cells was the same, indicating that each phospholipid receives a portion of the fatty acid pool present in the cell at the time of its synthesis. Similarly, the fatty acids of each of the spore phospholipids resembled those of the spore extract. Phospholipids accounted for two-thirds of the fatty acids of the log-phase but only one-third of those of the spore.     

Interaction between Antheridogens and Fatty Acids in Fern Spore Germination

Certain fatty acids in the C₅ to C₁₈ range, at concentrations as low as 10⁻⁵ M, were found to inhibit the germinations of spores of the sensitive fern, Onoclea sensibilis L. The addition of gametophytic culture flltrates of the bracken fern, Pteridium aquilinum (L.) Kuhn, containing antheridogen A, was found to overcome this inhibition and allow the spores to germinate and the gametophytes to develop in a normal fashion. Some fatty acids were found to increase the antheridium-inducing potency of antheridogen A as much as 10-fold. An effect similar to this may promote the diecious reproduction of ferns.     

Zn biosorption by Rhizopus arrhizus and other fungi

Biosorption of zinc ions by inactivated fungal mycelia was studied. Of the six fungal species, Rhizopus arrhizus, Mucor racemosus, Mycotypha africana, Aspergillus nidulans, Aspergillus niger and Schizosaccharomyces pombe, R. arrhizus exhibited the highest capacity (Q ^max = 213 μmol g⁻¹ dry weight). Further experiments with different cellular fractions of R. arrhizus showed that Zn was predominantly bound to cell-wall chitin and chitosan (Q ^max = 312 μmol g⁻¹ dry weight). Adsorption data were best modelled by the Langmuir isotherm, although they can be modelled by the Freundlich equation as well at relatively low aqueous concentrations. Biosorption generally decreased with increase in biosorbent particle size and its concentration. Low pH reduced Zn sorption, because of the strong competition from hydrogen ions for binding sites on fungi. The presence of ligands reduced metal uptake, chiefly by forming metal complexes of a less biosorbable nature. Received: 2 November 1998 / Received revision: 12 January 1999 / Accepted: 17 January 1999     

The mechanism of uranium biosorption by Rhizopus arrhizus

Biosorption of elements is a little understood phenomenon exhibited by some types of even nonliving microbial biomass. A common fungus Rhizopus arrhizus has been reported to take up uranium from aqueous solutions to the extent of 180 mg U(6+)/g. The mechanism of uranium sequestering by this type of biomass was studied by using experimental techniques such as electron microscopy, x-ray energy dispersion analysis, IR spectroscopy, and supporting evidence was obtained for a biosorption mechanism consisting of at least three processes. Uranium coordination and adsorption in the cell-wall chitin structure occur simultaneously and rapidly whereas precipitation of uranylhydroxide within the chitin microcrystalline cell-wall structure takes place at a lower rate. Interference of Fe(2+) and Zn(2+) coions with uranium biosorption is indicated.     

Uptake of Metal Ions by Rhizopus arrhizus Biomass

Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La³⁺, Mn²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Hg²⁺, Pb²⁺, UO₂²⁺, and Ag⁺. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups.     

少根根霉(Rhizopus arrhizus)脂肪酶基因在毕赤酵母中的分泌表达

利用PCR技术从少根根霉中扩增出脂肪酶基因(包括前导序列和成熟肽),并将其连接到酵母分泌表达载体pPIC9K中,转化毕赤酵母GS115。利用抗生素G418从重组阳性克隆中筛选得到高拷贝的转化子。在5 L的发酵罐中,当碳源耗尽后开始流加甲醇诱导脂肪酶的表达,经过96 h培养后发酵液上清液中重组脂肪酶(rRAL)的表达量约为90 mg/L。rRAL经过超滤,SP-Sepharose离子交换层析和Butyl-Sepharose疏水层析纯化。纯化后的蛋白在SDS-PAGE上为单一条带,表观分子量为32 kDa,比酶活为1 543 U/mg。N-端序列分析表明rRAL是经过加工后的产物。同时没有发现全长的Rhizopus arrhizus脂肪酶(RAL)被分泌表达。     

The mechanism of thorium biosorption by Rhizopus arrhizus

Inactive cells of Rhizopus arrhizus have been documented to exhibit a high thorium biosorptive uptake (170 mg/g) from aqueous solutions. The mechanism of thorium sequestering by this biomass type was investigated following the same method as for the uranium biosorption mechanism. The thorium sequestering mechanism appeared somewhat different from that of uranium. Experimental evidence is presented which indicates that, at optimum biosorption pH (4), thorium coordinates with the nitrogen of the chitin cell wall network and, in addition, more thorium is absorbed by the external section of the fungal cell wall. At pH 2 the overall thorium uptake is reduced. The kinetic study of thorium biosorption revealed a very rapid rate of uptake. Unlike uranium at optimum solution pH, Fe(2+) and Zn(2+) did not interfere significantly with the thorium biosorptive uptake capacity of R. arrhizus.     

Inhibition of Soybean Lipoxygenase-1 by Sucrose Esters of Fatty Acids

The effect of sucrose esters of fatty acids with carbon numbers from 8 to 16 on soybean Iipoxygenase-1 (L-1) was investigated. The sucrose esters inhibited L-1 and the inhibitory effect increased with an increase in the carbon number of the fatty acid up to 12, being constant above 12. Kinetic studies showed that two molecules of the sucrose ester bound to. L-1 and inhibited it competitively. Based on the behavior of pK_i dependence on the carbon chain length of the sucrose esters, the dodecyl group appeared to be optimum to bind L-1. The results suggest that sucrose esters bind to the catalytic site of L-1 by hydrophobic interaction of the fatty acid and lead to the loss of activity. Sucrose esters, which are widely used as an emulsifier, can be an effective inhibitor of enzymatic lipid peroxidation in food processing.     

Changes in Volatile Fatty Acids and Free Amino Acids during Air-Tobacco Stalks

In our searching program for novel sorbicillin related compounds, three novel compounds, spirosorbicillinols A (1), B (2), and C (3), were isolated from the fermentation broth of the USF-4860 strain isolated from a soil sample. The planar structures of compounds 1–3 were determined from spectroscopic evidence and degradation reaction, and that of 1 was the same as that of 2. The relative stereochemistries of compounds 1–3 were determined by ¹H-¹H coupling constants, the elucidation of HMBC and NOESY spectra in detail. 1 and 2 were stereoisomers at C8 position, each other. We propose that compounds 1 and 2 were formed by exo and endo intermolecular Diels-Alder reaction between sorbicillinol as a diene and scytolide (proposed precursor-1) as a dienophile, respectively. Similarly, we propose that compound 3 was formed by an endo intermolecular Diels-Alder reaction between sorbicillinol and proposed precursor-2.