An early evolutionary origin for the minor spliceosome

The minor spliceosome is a ribonucleoprotein complex that catalyses the removal of an atypical class of spliceosomal introns (U12-type) from eukaryotic messenger RNAs. It was first identified and characterized in animals, where it was found to contain several unique RNA constituents that share structural similarity with and seem to be functionally analogous to the small nuclear RNAs (snRNAs) contained in the major spliceosome. Subsequently, minor spliceosomal components and U12-type introns have been found in plants but not in fungi. Unlike that of the major spliceosome, which arose early in the eukaryotic lineage, the evolutionary history of the minor spliceosome is unclear because there is evidence of it in so few organisms. Here we report the identification of homologues of minor-spliceosome-specific proteins and snRNAs, and U12-type introns, in distantly related eukaryotic microbes (protists) and in a fungus (Rhizopus oryzae). Cumulatively, our results indicate that the minor spliceosome had an early origin: several of its characteristic constituents are present in representative organisms from all eukaryotic supergroups for which there is any substantial genome sequence information. In addition, our results reveal marked evolutionary conservation of functionally important sequence elements contained within U12-type introns and snRNAs.

Valine pathway is more crucial than phenyl propanoid pathway in regulating capsaicin biosynthesis in Capsicum frutescens mill

Capsaicin, a pungency factor alkaloid of Capsicum fruits, is biosynthesized by enzymatic condensation of vanillylamine, a phenyl propanoid intermediate, and 8-methyl-nonenoic acid, a fatty acid derivative from the leucine/valine pathway by capsaicin synthase. Biotic elicitors, such as aqueous mycelial extracts of Rhizopus oligosporus and Aspergillus niger, and abiotic elicitors, such as salicylic acid and methyl jasmonate, were incorporated to cell-suspension cultures of Capsicum frutescens. The maximum elicitation of capsaicinoids to the extent of 6-folds was noticed when mycelial extracts of R. oligosporus were incorporated to cell-suspension cultures. The phenyl propanoid intermediates were elicited to the extent of 3-4-fold, whereas the levels of 8-methyl-nonanoic acid increased 6-fold in R. oligosporus mycelial-extract-treated cultures. The enzymatic assays of caffeic acid O-methyl transferases, keto acyl synthase, and capsaicin synthase were performed in elicited and nonelicited cell-suspension cultures. These enzymes were overexpressed in R. oligosporus mycelial-extract-treated suspension cultures, which was also confirmed by reverse transcriptase polymerase chain reaction studies. This is the first paper on the overexpression of 8-methyl-nonanoic acid leading to capsaicin biosynthesis using elicitors.

Adsorption behavior of rhodamine B on Rhizopus oryzae biomass

The removal of a carcinogenic dye rhodamine B (C. I. 45170) from wastewater by biomass of different moulds and yeasts is described. Among all of the fungal species tested, the biomass of Rhizopus oryzae MTCC 262 is found to be the most effective. Dye adsorption reaches maximum with the biomass harvested from the early stationary phase of growth. The optimum temperature and pH for adsorption are observed to be 40 degrees C and 7.0, respectively. The adsorption rate is very fast initially and attains equilibrium after 5 h. The adsorption isotherm follows the Langmuir isotherm model satisfactorily within the studied dye concentration range. Of the different metabolic inhibitors tested, 2,4-ditrophenol (DNP) and N,N'-dicyclohexylcarbodiimide (DCCD) decrease dye adsorption by approximately 30% suggesting the role of energy metabolism in the process. Spectrophotometric study indicates that the removal of rhodamine B by R. oryzae biomass involves an adsorption process. Scanning (SEM) and transmission (TEM) electron microscopic investigations have been carried out to understand the probable mechanism of the dye-biomass interaction.

Characterisation of an acid trehalase produced by the thermotolerant fungus Rhizopus microsporus var. rhizopodiformis: biochemical properties and immunochemical localisation

An acid trehalase from Rhizopus microsporus var. rhizopodiformis was purified to apparent homogeneity. The molecular weight by SDS-PAGE (60 kDa) or Sephacryl S-200 filtration (105 kDa) suggested a homodimer. The carbohydrate content was 72%. Endoglycosidase H digestion resulted in one sharp band of 51.5 kDa in SDS-PAGE. pH and temperature optima were 4.5 and 45 degrees C, respectively. The isoelectric point was 6.69 and activation energy was 1.14 kcal mol(-1). The enzyme was stable for 1 h at 50 degrees C and decayed at 60 degrees C (t50 of 1.3 min.). Apparent KM for trealose was 0.2mM. Immunolocalisation studies showed the enzyme tightly packed at the surface of the cells.

Hydroxylation of the sesterterpene leucosceptrine by the fungus Rhizopus stolonifer

The microbial transformation of leucosceptrine (1), the first member of class leucosesterterpenes, by Rhizopus stolonifer afforded two metabolites, 1alpha-hydroxyleucosceptrine (2), and 8alpha-hydroxyleucosceptrine (3).

Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared. The resin stabilized the initial electrochemical potential to -405+/-5 mV corresponding to 2 micro gl(-1) of lead concentration in solution. The amounts of lead sorbed by R. arrhizus biomass and diatomite were 0.9 mmol g(-1) (C(e)=5.16 x 10(-2)mM) and 0.052 mmol g(-1) (C(e)=5.97 x 10(-2) mM), respectively. Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites. The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity.

Lead biosorption study with Rhizopus arrhizus using a metal-based titration technique

Acid-base and metal-based potentiometric titration methods were used to analyze sorption mechanisms of lead by Rhizopus arrhizus fungal biomass. Biosorption was not considered globally but as the result of successive sorption reactions on various binding sites with different selectivities. Precipitation occurred rapidly when lead concentration increased. Lead was sorbed essentially by carboxylic groups and by phosphates and sulfonates (less abundant) of the organic matter. The lead affinity to carboxylic, sulfonate and phosphate binding sites depended on the association coefficient with proton or counter-ion and on the spatial distribution of the surface sites promoting the formation of mono- or bi-dentate complexes. Chemical bonds and binding sites were confirmed using microscopic and spectroscopic techniques (IR, MET-EDAX). It appeared that although the total organic acidity was reached, number of ionized and free carboxylic groups were not involved in lead sorption reactions. In spite of lead speciation in the solution, surface micro-precipitation was observed and the two processes, surface adsorption and micro-precipitation, are sequential and possibly overlapping. At low concentrations (<10(-6) M) adsorption is the dominant phenomenon and beyond (>10(-5) M) surface clusters appeared before the predicted solution precipitation phenomenon.

Pathogenic fungus harbours endosymbiotic bacteria for toxin production

A number of plant pathogenic fungi belonging to the genus Rhizopus are infamous for causing rice seedling blight. This plant disease is typically initiated by an abnormal swelling of the seedling roots without any sign of infection by the pathogen. This characteristic symptom is in fact caused by the macrocyclic polyketide metabolite rhizoxin that has been isolated from cultures of Rhizopus sp.. The phytotoxin exerts its destructive effect by binding to rice beta-tubulin, which results in inhibition of mitosis and cell cycle arrest. Owing to its remarkably strong antimitotic activity in most eukaryotic cells, including various human cancer cell lines, rhizoxin has attracted considerable interest as a potential antitumour drug. Here we show that rhizoxin is not biosynthesized by the fungus itself, but by endosymbiotic, that is, intracellular living, bacteria of the genus Burkholderia. Our unexpected findings unveil a remarkably complex symbiotic-pathogenic relationship that extends the fungus-plant interaction to a third, bacterial, key-player, and opens new perspectives for pest control.

Creation of Rhizopus oryzae lipase having a unique oxyanion hole by combinatorial mutagenesis in the lid domain

Combinatorial libraries of the lid domain of Rhizopus oryzae lipase (ROL; Phe88Xaa, Ala91Xaa, Ile92Xaa) were displayed on the yeast cell surface using yeast cell-surface engineering. Among the 40,000 transformants in which ROL mutants were displayed on the yeast cell surface, ten clones showed clear halos on soybean oil-containing plates. Among these, some clones exhibited high activities toward fatty acid esters of fluorescein and contained non-polar amino acid residues in the mutated positions. Computer modeling of the mutants revealed that hydrophobic interactions between the substrates and amino acid residues in the open form of the lid might be critical for ROL activity. Based on these results, Thr93 and Asp94 were further combinatorially mutated. Among 6,000 transformants, the Thr93Thr, Asp94Ser and Thr93Ser, Asp94Ser transformants exhibited a significant shift in substrate specificity toward a short-chain substrate. Computer modeling of these mutants suggested that a unique oxyanion hole, which is composed of Thr85 Ogamma and Ser94 Ogamma, was formed and thus the substrate specificity was changed. Therefore, coupling combinatorial mutagenesis with the cell surface display of ROL could lead to the production of a unique ROL mutant.

Rapid identification of microbial VOCs from tobacco molds using closed-loop stripping and gas chromatography/time-of-flight mass spectrometry

Several microbial volatile organic compounds (MVOCs) that can serve as potential chemical markers for microbial contamination in tobacco have been identified. Four different fungal species, Aspergillus niger (AN), A. ornatus (AO), Pencillium chrysogenum (PC) and Rhizopus stolonifer (RS), commonly reported in moldy tobacco were cultured and screened for MVOCs. Because the MVOCs emitted by a microbial species are substrate specific, the fungal strains were separately grown on potato dextrose agar (PDA) and tobacco products. MVOCs from the mold cultures grown on PDA and tobacco products were extracted using closed-loop stripping analysis (CLSA) and identified by gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS). Some of the prominent tobacco mold markers identified by this method include: 1-octen-3-ol; 2-octen-1-ol; 2-methyl-1-butanol; 3-methyl-1-butanol; 1-octene and 2-pentanone. In particular, 1-octen-3-ol was detected in all the mold cultures and moldy tobacco samples analyzed. Olfactory evaluation of 1-octen-3-ol indicated a characteristic musty odor and the odor threshold was determined to be approximately 200 ng/ml. The limits of detection for 1-octen-3-ol using GC/TOF-MS and GC/mass selective detector (MSD) in the full-scan mode and selected ion monitoring (SIM) mode were investigated. The CLSA-GC/TOF-MS demonstrates a fast, sensitive and semi-quantitative analytical technique for screening tobacco materials for the presence of mold via chemical markers of microbial contamination.

A cholesterol biosynthesis inhibitor fromRhizopus oryzae

A bile acid derivative, methyl cholate (1), was isolated from EtOAc extract of the fungus Rhizopus oryzae as a cholesterol biosynthesis inhibitor. It showed moderate inhibitory activity on cholesterol biosynthesis in human Chang liver cells. Compound 1 exhibited inhibitory effect on the later step of cholesterol biosynthesis, indicating that its action mode is different from that of statins that act on the HMG-CoA reductase.

Improved microbiological hydroxylation of sesquiterpenoids: semisynthesis, structural determination and biotransformation studies of cyclic sulfite eudesmane derivatives

Two new cyclic sulfite eudesmane derivatives have been investigated. Their (R) and (S) sulfur configuration and the structural arrangement of their "A" rings have been assigned by means of their 13C and 1H NMR chemical shifts and have been confirmed by single-crystal X-ray analyses. Microbial-transformation of these epimer cyclic sulfites and their dihydroxyeudesmane precursor have been studied using the hydroxylating fungus Rhizopus nigricans. Increased biocatalysis rates and considerable differences in the biotransformation of both cyclic sulfite eudesmanes have been found. Promising 8alpha,11-dihydroxy derivatives have been isolated from the (S)-diastereomer bioconversion.

Increased pyruvate efficiency in enzymatic production of (R)-phenylacetylcarbinol

Loss of substrate, pyruvate, a limitation for enzymatic batch production of (R)-phenylacetylcarbinol (PAC), resulted from two phenomena: temperature dependent non-enzymatic concentration decrease due to the cofactor Mg2+ and formation of by-products, acetaldehyde and acetoin, by pyruvate decarboxylase (PDC). In the absence of enzyme, pyruvate stabilization was achieved by lowering the Mg2+ concentration from 20 to 0.5 mM. With 0.5 mM Mg2+ Rhizopusjavanicus and Candida utilis PDC produced similar levels of PAC (49 and 51 g 1(-1), respectively) in 21 h at 6 degrees C; however C. utilis PDC formed less by-product from pyruvate and was more stable during biotransformation. The process enhancements regarding Mg2+ concentration and source of PDC resulted in an increase of molar yield (PAC/consumed pyruvate) from 59% (R. javanicus PDC, 20 mM Mg2+) to 74% (R. javanicus PDC, 0.5 mM Mg2+) to 89% (C. utilis PDC, 0.5 mM Mg2+).

Studies on chromium(VI) adsorption-desorption using immobilized fungal biomass

The aim of this study was to investigate the Cr(VI) biosorption potential of immobilized Rhizopus nigricans and to screen a variety of non-toxic desorbing agents, in order to find out possible application in multiple sorption-desorption cycles. The biomass was immobilized by various mechanisms and evaluated for removal of Cr(VI) from aqueous solution, mechanical stability to desorbents, and reuse in successive cycles. The finely powdered biomass, entrapped in five different polymeric matrices viz. calcium alginate, polyvinyl alcohol (PVA), polyacrylamide, polyisoprene, and polysulfone was compared for biosorption efficiency and stability to desorbents. Physical immobilization to polyurethane foam and coir fiber was less efficient than polymer entrapment methods. Of the different combinations (%, w/v) of biomass dose compared for each matrix, 8% (calcium alginate), 6% (polyacrylamide and PVA), 12% (polyisoprene), and 10% (polysulfone) were found to be the optimum. The Cr sorption capacity (mg Cr/g sorbent) of all immobilized biomass was lesser than the native, powdered biomass. The Cr sorption capacity decreased in the order of free biomass (119.2) > polysulfone entrapped (101.5) > polyisoprene immobilized (98.76) > PVA immobilized (96.69) > calcium alginate entrapped (84.29) > polyacrylamide (45.56), at 500 mg/l concentration of Cr(VI). The degree of mechanical stability and chemical resistance of the immobilized systems were in the order of polysulfone > polyisoprene > PVA > polyacrylamide > calcium alginate. The bound Cr(VI) could be eluted successfully using 0.01 N NaOH, NaHCO3, and Na2CO3. The adsorption data for the native and the immobilized biomass was evaluated by the Freundlich isotherm model. The successive sorption-desorption studies employing polysulfone entrapped biomass indicated that the biomass beads could be regenerated and reused in more than 25 cycles and the regeneration efficiency was 75-78%.

Microbial transformation of ginsenoside Rb1 by Rhizopus stolonifer and Curvularia lunata

Of 49 microbial strains screened for their capabilities to transform ginsenoside Rb1, Rhizopus stolonifer and Curvularia lunata produced four key metabolites: 3-O-[beta-D-glucopyranosyl-(1,2)-beta-D-glucopyranosyl]-20-O-[beta-D-glucopyranosyl]-3beta,12beta, 20(S)-trihydroxydammar-24-ene (1), 3-O-[beta-D-glucopyranosyl-(1,2)-beta-D-glucopyranosyl]-20-O-[beta-D-glucopyranosyl]-3beta,12beta, 20(S)-trihydroxydammar-24-ol (2), 3-O-[beta-D-glucopyranosyl-(1,2)-beta-D-glucopyranosyl]-3beta, 12beta, 20(S)-trihydroxydammar-24-ene (3), and 3-O-beta-D-glucopyranosyl-3beta, 12beta, 20(S)-trihydroxydammar-24-ene (4), identified by TOF-MS, 1H- and 13C-NMR spectral data. Metabolites 1, 3 and 4 were from the incubation with R. stolonifer, and 1 and 2 from the incubation with C. lunata. Compound 2 was identified as a new compound.

A new solution for an old problem: the regiochemical distribution of the acyl chains in galactolipids can be established by electrospray ionization tandem mass spectrometry

Electrospray ionization-quadrupole ion trap mass spectrometry (ESI-QITMS), either in positive- or in negative-ion mode, has been used to establish the chemical structures (chain length, degree of unsaturation, positional distribution) of the fatty acids attached to the primary (sn-1) and secondary (sn-2) hydroxyl groups of the glycerol moiety of natural monogalactosyl- (MGDG) and digalactosyldiacylglycerols (DGDG), isolated from the freshwater dinoflagellate Glenodinium sanguineum and from a marine diatom belonging to the genus Chaetoceros. Fragmentation by collision-induced dissociation of a single component in MGDG and DGDG mixtures, separated by high-performance liquid chromatography (HPLC) and detected on-line by tandem positive-ion ESI-MS, leads to a clear-cut determination of the positional distribution of the sn-glycerol-bound fatty acyl chains. Reversed-phase liquid chromatography allowed a partial resolution of the component mixture before ESI-MS/MS analysis. These results were validated by comparison with ESI-MS data obtained for the sn-2 lysoglyceroglycolipids synthesized via regiospecific enzymatic hydrolysis of the corresponding diacylglycerols by Rhizopus arrhizus lipase.

Evaluation of two types of polyurethane for the immobilisation of Rhizopus oryzae for copper uptake

Previous studies have shown that Rhizopus oryzae strain IM 057412 grown in reticulated polyurethane foam demonstrated the same heavy metal adsorption capacity as the free biomass. Immobilisation in other types of polymers was shown to reduce the biomass uptake capacity because of mass transfer limitations due to the restricted porosity of the immobilisation matrices. For practical purposes the growing of biomass in polyurethene support particles to use as a commercial adsorbent is not viable or financially sound. The current work describes a different approach in which dried non-viable cells of R. oryzae were incorporated into two types of polyurethane carrier matrix during the production process. The polymers used were a conventional hydrophobic polyurethane and a hydrophilic polyurethane, Hypol 2002. Oven-dried and powdered particles (D<150 microm) of R. oryzae were immobilised by mixing the biomass with each of the polymers prior to the reaction in which the polymer was expanded to form a foam; consequently the biomass was uniformly dispersed throughout the porous matrix. The resulting fungi-polyurethane matrices were then cut into cubes (approximately = 4-6 mm dimension) and their adsorptive properties studied with respect to copper. Experiments were conducted in shake flasks to establish the equilibrium time for the reaction for both free and immobilied biomass. The biomass immobilised in Hypol gave the same adsorptive capacity as that of free biomass when compared on a weight basis, but biomass immobilised in conventional polyurethane foam showed no adsorption. To assess fully the effect of pH on copper and to eliminate precipitation as a removal mechanism experiments were conducted at different pHs and different copper concentrations. In each case the solution pH was maintained by acid or base addition in response to measurements using a standard calomel electrode. It was shown that at pH 5 copper concentrations above 100 mg l(-1) were likely to precipitate. The amount of precipitation was accounted for within the high concentration adsorption isotherm experiments by using a mass balance approach. Results showed that the adsorption of the Hypol immobilised biomass followed the Langmuir adsorption isotherm model and showed the copper adsorption capacity of the matrix to be between 10 and 13 mg g(-1). The copper attached to the immobilised biomass could easily be desorbed by increasing the acidity, allowing the matrix to be used in repetitive sorption-desorption cycles. There was a small decrease in the adsorption capacity after the first desorption cycle that could be explained by a partial loss of biomass as detected by loss of total organic carbon (TOC).

Total synthesis of rhizoxin D, a potent antimitotic agent from the fungus Rhizopus chinensis

Rhizoxin D (2) was synthesized from four subunits, A, B, C, and D representing C3-C9, C10-C13, C14-C19, and C20-C27, respectively. Subunit A was prepared by cyclization of iodo acetal 21, which set the configuration at C5 of 2 through a stereoselective addition of the radical derived from dehalogenation of 21 at the beta carbon of the (Z)-alpha,beta-unsaturated ester. Aldehyde 29 was obtained from phenylthioacetal 24 and condensed with phosphorane 30, representing subunit B, in a Wittig reaction that gave the (E,E)-dienoate 31. This ester was converted to aldehyde 33 in preparation for coupling with subunit C. The latter in the form of methyl ketone 55 was obtained in six steps from propargyl alcohol. An aldol reaction of 33 with the enolate of 55 prepared with (+)-DIPCl gave the desired beta-hydroxy ketone 56 bearing a (13S)-configuration in a 17-20:1 ratio with its (13R)-diastereomer. After reduction to anti diol 57 and selective protection as TIPS ether 58, the C15 hydroxyl was esterified to give phosphonate 59. An intramolecular Wadsworth-Emmons reaction of aldehyde 62, derived from delta-lactone 60, furnished macrolactone 63, which was coupled in a Stille reaction with stannane 68 to give 2 after cleavage of the TIPS ether.

Enhanced separation of filamentous fungi by ultrasonic field: possible usage in repeated batch processes

Usage of ultrasonic field-based filters in retention of filamentous fungal cells was assessed using Rhizopus arrhizus NRRL 1526 as a model organism. Effects of operating conditions, such as power input, harvest pump flow rate, run time and stop time, on the system's separation efficiency (SE) were evaluated by modulating the variables according to a Central Composite Design (CCD). The standard pump with which the ultrasonic filter was equipped was shown to be unsuitable and was, therefore, substituted for with a prime rate reverse pump that made possible separation and recycle of the mycelial biomass. The operating conditions were optimised (run time, 300 s; stop time, 3 s; power input, 6 W; harvest pump flow rate, 4 l per day) and a repeated batch process (three batches for a total of 192 h) was performed during which the SE was maintained always higher than 88%.

Studies on enhancement of Cr(VI) biosorption by chemically modified biomass of Rhizopus nigricans

This study reports the biosorption of Cr(VI) by chemically modified biomass of Rhizopus nigricans and the possible mechanism of Cr complexation to the adsorbent. The cell wall of this fungus possesses strong complexing property to effectively remove Cr(VI) anions from solution and wastewater. The mechanism of Cr adsorption by R. nigricans was ascertained by chemical modifications of the dead biomass followed by FTIR spectroscopic analysis of the cell wall constituents. Treatment of the biosorbent with mild alkalies (0.01 N NaOH and ammonia solution) and formaldehyde (10%, w/v) deteriorated the biosorption efficiency. However, extraction of the biomass powder in acids (0.1 N HCl and H2SO4), alcohols (50% v/v, CH3OH and C2H5OH) and acetone (50%, v/v) improved the Cr uptake capacity. Reaction of the cell wall amino groups with acetic anhydride reduced the biosorption potential drastically. Blocking of the-COOH groups by treatment with water soluble carbodiimide also resulted in initial lag in Cr binding. Biomass modification experiments conducted using Cetyl Trimethyl Ammonium Bromide (CTAB), Polyethylenimine (PEI), and Amino Propyl Trimethoxy Silane (APTS) improved the biosorption efficiency to exceptionally high levels. The FTIR spectroscopic analysis of the native, Cr bound and the other types of chemically modified biomass indicated the involvement of amino groups of Rhizopus cell wall in Cr binding. The adsorption data of the native and the most effectively modified biomass were evaluated by the Freundlich and the Langmuir adsorption isotherms and the possible adsorption phenomena are also discussed.

Efficient and selective microbial esterification with dry mycelium of Rhizopus oryzae

The use of dry mycelium of Rhizopus oryzae as biocatalyst for ester production in organic solvent has been studied. Mycelia with notable carboxylesterase activity were produced when different Tweens (20, 40, 60 and 80) were employed as main carbon source for the growth. Dry mycelium of four strains of Rhizopus oryzae proved effective for efficiently catalysing the synthesis of different flavour esters (hexylacetate and butyrate, geranylacetate and butyrate) starting from the corresponding alcohol and free acid, including acetic acid. The esterification of the racemic mixture of 2-octanol and butyric acid proceeded with high enantioselectivity (R-ester produced with enantiomeric excess > or =97%) when Rhizopus oryzae CBS 112.07 and Rhizopus oryzae CBS 260.28 were employed.

Regioselective enzymatic acylations of polyhydroxylated eudesmanes: semisynthesis, theoretical calculations, and biotransformation of cyclic sulfites

Different lipase enzymes have been tested in order to perform regioselective acetylations on the eudesmane tetrol from vulgarin. High yields (95%) of 1,12-diacetoxy derivative (4) were achieved in 1 h with Candida antarctica lipase (CAL). However, only the 12-acetyl derivative (6) was obtained in similar yield with Mucor miehei (MML) or Candida cylindracea (CCL) lipases. The enzymatic protection at C-1 and C-12 has been used to form eudesmane cyclic-sulfites between C-6 and C-4 atoms. The R/S-sulfur configuration has been assigned by means of the experimental and theoretical (13)C and (1)H NMR chemical shifts. The theoretical shifts were calculated using the GIAO method, with a MM+ geometry optimization followed by a single-point calculation at the B3LYP/6-31G(*) level (B3LYP/6-31G(*)//MM+). Moreover, B3LYP/6-31G(*) geometry optimizations were carried out to test the B3LYP/6-31G(*)//MM+ results, for the deacetylated sulfites (12 and 15). In addition to the delta(C) and delta(H) shifts, the (3)J(HH) coupling constants were also calculated and compared with the experimental values when available. Finally, different reactivities have been checked in both sulfites by biotransformation with Rhizopus nigricans. While the R-sulfite gave 2 alpha- and 11 beta-hydroxylated metabolites, the S-sulfite yielded only regioselective deacetylations. Furthermore, both sulfites showed different reactivities in redox processes.

[Determination of lactic acid in fermentation broth of Rhizopus oryzae by reversed-phase high performance liquid chromatography (RP-HPLC)]

A method for determining lactic acid in fermentation broth of Rhizopus oryzae by RP-HPLC is described. The operating conditions were Wakosil-II 5 C18 RS column(4.6 mm i.d. x 150 mm, 5 microns) at room temperature, 0.01 mol/L phosphoric acid solution (pH 2.5) as mobile phase with a flow rate of 1.0 mL/min and UV detection at 210 nm. The retention time of lactic acid was 3.820 min. This method is simple, rapid and accurate. The results will not be affected by other components in the broth. The relative standard deviation was 0.22% (n = 5), and the recovery was over 99%.

Biotransformations with Rhizopus arrhizus and Geotrichum candidum for the preparation of (S)-atenolol and (S)-propranolol

(+/-)-Atenolol/(+/-)-propranolol and their acetates were incubated with the fungus Rhizopus arrhizus and Geotrichum candidum separately for different time intervals to afford (S)-atenolol/(S)-propranolol in good optical yield. The time and pH for this biotransformation was optimised. The present biodegradations using Rhizopus arrhizus and Geotrichum candidum provides a simple and useful method to obtain (S)-atenolol and (S)-propranolol which are active enantiomers of the beta-adrenergic blockers.

Glucosamine content of tempe mould, Rhizopus oligosporus

The glucosamine content of Rhizopus oligosporus NRRL 2710 mycelium grown in different media was determined. In Sabouraud dextrose broth the glucosamine content ranged from 51 g (kg dry biomass)(-1) for mycelial pellets less than 5 mm diameter to 107 g kg(-1) for pellets 16-35 mm diameter. Mycelium grown on Sabouraud dextrose agar contained 111 g glucosamine (kg dry biomass)(-1) while that grown on soymilk agar, used to simulate growth on soybeans in tempe, contained 82 g kg(-1). The estimation of glucosamine was reproducible, with a mean coefficient of variation of 4% for mycelial pellets and 11% for mycelium from agar media. It is suggested that a conversion factor of 12 g dry biomass (g glucosamine)(-1) is applicable to determine fungal biomass in tempe fermentation.