Fabrication and characterization of Rhizochitosan and its incorporation with platelet concentrates to promote wound healing

Composite dressing composed of Rhizochitosan and Regenplex™ to promote wound healing were assessed. Rhizochitosan was fabricated by deacetylation of Rhizochitin, which obtained by simply depigmenting sporangium-free mycelial mattress produced from Rhizopus stolonifer F6. Physicochemical characterizations of Rhizochitosan demonstrated that it contained 13.5% chitosan with a water-absorption ability of 35-fold dry weight and exhibiting hydrogel nature after hydration. In a wound-healing study on SD rats with full-thickness injury, the composite dressing had a better healing effect than those for each individual components and control group and wound even healed as functional tissue instead of scar tissue. The underlying mechanism of the composite beneficial to wound remodeling is likely attributable to a more reduction level of matrix metalloproteinase (MMP)-9 expression in early stage and a higher MMP-2 expression level in a later stage of healing process. Conclusively, the composite dressing demonstrated to be highly beneficial to the healing of full-thickness injury wound.

Rhizopus oligosporus and Lactobacillus plantarum Co-Fermentation as a Tool for Increasing the Antioxidant Potential of Grass Pea and Flaxseed Oil-Cake Tempe

Tempe-type fermentation originating from Indonesia can enhance the antioxidant activity of plant material. However, this biological potential depends on substrates and applied microorganisms. This study aimed to determine whether co-fermentation with Rhizopus oligosporus and Lactobacillus plantarum improved antioxidant activity of tempe obtained from grass pea seeds with flaxseed oil-cake addition (up to 30%). For this purpose, substances reacting with Folin-Ciocalteu reagent and free radicals scavenging potential were measured in water-soluble fractions and dialysates from simulated in vitro digestion. Additionally, the water-soluble phenolic profile was estimated. The higher level of water-extractable compounds with antioxidant activity was determined in co-fermentation products than in fungal fermentation products. Moreover, the fermentation process with the use of L. plantarum contributed to a greater accumulation of some phenolic acids (gallic acid, protocatechuic acid) in tempe without having a negative effect on the levels of other phenolic compounds determined in fungal fermented tempe. During in vitro digestion simulating the human digestive tract, more antioxidant compounds were released from products obtained after co-fermentation than fungal fermentation. An addition of 20% flaxseed oil-cake and the application of bacterial-fungal co-fermentation, can be considered as an alternative tool to enhance the antioxidant parameters of grass pea tempe.

In Situ Ring Contraction and Transformation of the Rhizoxin Macrocycle through an Abiotic Pathway

A Rhizopus sp. culture containing an endosymbiont partner ( Burkholderia sp.) was obtained through a citizen-science-based soil-collection program. An extract prepared from the pair of organisms exhibited strong inhibition of Ewing sarcoma cells and was selected for bioassay-guided fractionation. This led to the purification of rhizoxin (1), a potent antimitotic agent that inhibited microtubule polymerization, along with several new (2-5) and known (6) analogues of 1. The structures of 2-6 were established using a combination of NMR data analysis, while the configurations of the new stereocenters were determined using ROESY spectroscopy and comparison of GIAO-derived and experimental data for NMR chemical shift and ³ J_HH coupling values. Whereas compound 1 showed modest selectivity for Ewing sarcoma cell lines carrying the EWSR1/ FLI1 fusion gene, the other compounds were determined to be inactive. Chemically, compound 2 stands out from other rhizoxin analogues because it is the first member of this class that is reported to contain a one-carbon-smaller 15-membered macrolactone system. Through a combination of experimental and computational tests, we determined that 2 is likely formed via an acid-catalyzed Meinwald rearrangement from 1 because of the mild acidic culture environment created by the Rhizopus sp. isolate and its symbiont.

Monohexosylceramides from Rhizopus Species Isolated from Brazilian Caatinga: Chemical Characterization and Evaluation of Their Anti-Biofilm and Antibacterial Activities

Monohexosylceramides (CMHs) are highly conserved fungal glycosphingolipids playing a role in several cellular processes such as growth, differentiation and morphological transition. In this study, we report the isolation, purification and chemical characterization of CMHs from Rhizopus stolonifer and R. microspores. Using positive ion mode ESI-MS, two major ion species were observed at m/z 750 and m/z 766, respectively. Both ion species consisted of a glucose/galactose residue attached to a ceramide moiety containing 9-methyl-4,8-sphingadienine with an amidic linkage to a hydroxylated C16:0 fatty acid. The antimicrobial activity of CMH was evaluated against Gram positive and Gram negative bacteria using the agar diffusion assay. CMH from both Rhizopus species inhibited the growth of Bacillus terrae, Micrococcus luteus (M. luteus) and Pseudomonas stutzeri (P. stutzeri) with a MIC₅₀ of 6.25, 6.25 and 3.13 mg/mL, respectively. The bactericidal effect was detected only for M. luteus and P. stutzeri, with MBC values of 25 and 6.25 mg/mL, respectively. Furthermore, the action of CMH on the biofilm produced by methicillin-resistant Staphylococcus aureus (MRSA) was analyzed using 12.5 and 25 mg/mL of CMH from R. microsporus. Total biofilm biomass, biofilm matrix and viability of the cells that form the biofilm structure were evaluated. CMH from R. microsporus was able to inhibit the MRSA biofilm formation in all parameters tested.

N-Glycosylation Engineering to Improve the Constitutive Expression of Rhizopus oryzae Lipase in Komagataella phaffii

Our previous studies demonstrated that the N-glycans in Rhizopus chinensis lipase (RCL) was important for its secretion. In order to improve the secretion of Rhizopus oryzae lipase (ROL) under the control of the GAP promoter in Komagataella phaffii, two extra N-glycosylation sites were introduced in ROL according to the position of the N-glycosylation sites of RCL by sequence alignment. The results indicated that the secretion level of ROL was strongly improved by N-glycosylation engineering, and the highest value of extracellular enzyme activity was increased from 0.4 ± 0.2 U/mL to 207 ± 6 U/mL in a shake flask. In the 7-L fermenter, the extracellular enzyme activity of the mutant (2600 ± 43 U/mL) and the total protein concentration (2.5 ± 0.2 g/L) were 218- and 6.25-fold higher than these of the parent, respectively. This study presents a strategy for constitutive recombinant expression of ROL using the GAP promoter combined with N-glycosylation engineering, providing a potential enzyme for application in the food industry.

Immunomodulatory Properties of Filamentous Fungi Cultivated through Solid-State Fermentation on Rapeseed Meal

Water extracts from solid-state fermentation (SSF) on rapeseed meal using filamentous fungi exhibit interesting immunomodulatory activities in vitro. Immunomodulation was determined by the capacity of the compounds to activate blood neutrophils and to influence cytokine production in human peripheral blood mononuclear cells (PBMC) and mouse bone marrow-derived macrophages (BMDM). Among the strains tested, Aspergillus sojae mycelium and SSF extracts were the most promising in terms of enhancing the immune response. The filamentous fungus was also successfully cultivated in a pre-pilot bioreactor with forced aeration. The results indicated that the extracts not only activated blood neutrophils but also significantly modulated IL-1β cytokine levels with lipopolysaccharide (LPS)-stimulated PBMC and BMDM without any cytotoxicity in immune cells. IL-1β was down-regulated in a dose-dependent manner in the presence of A. sojae crude mycelium and SSF extract with PBMC, which indicated that there was an anti-inflammatory activity, whereas IL-1β secretion was up-regulated in the presence of stimulated BMDM with the highest concentration that was tested (100 μg/mL). The non-fermented rapeseed had no effect at the same concentration. SSF culture, as a natural product, may be a good source for the development of functional feed with an immunostimulating effect or could potentially be used in medicinal applications.

Metabolism of Quercetin and Naringenin by Food-Grade Fungal Inoculum, Rhizopus azygosporus Yuan et Jong (ATCC 48108)

Rhizopus azygosporus Yuan et Jong (ATCC 48108), a starter culture for fermented soybean tempeh, produces β-glucosidases that cleave flavonoid glycosides into aglycones during fermentation. However, recent data suggest that fermentation of a flavonoid glycoside-rich extract with this strain did not result in the production of aglycones. Thus, in this paper, flavonoid metabolism of this strain was investigated. Incubation of flavonoid aglycones, naringenin and quercetin, with R. azygosporus resulted in the production of flavonoid glucosyl-, hydroxyl-, and sulfo-conjugated derivatives. Naringenin was completely metabolized within 96 h into eriodictyol sulfate and eriodictyol glucoside, whereas quercetin was partially metabolized into quercetin glucoside, diglucoside, sulfate, and glucosyl-sulfate. Most of these metabolites were found to be excreted by the fungi into the culture medium. Toxicity analysis revealed that incubation with both quercetin and naringenin did not exert inhibitory effects on fungal growth. This study presents an interesting mechanism of fungal detoxification of flavonoids in foods.

Efficient production of (2)H, (13)C, (15)N-enriched industrial enzyme Rhizopus chinensis lipase with native disulfide bonds

BACKGROUND

In order to use most modern methods of NMR spectroscopy to study protein structure and dynamics, isotope-enriched protein samples are essential. Especially for larger proteins (>20 kDa), perdeuterated and Ile (δ1), Leu, and Val methyl-protonated protein samples are required for suppressing nuclear relaxation to provide improved spectral quality, allowing key backbone and side chain resonance assignments needed for protein structure and dynamics studies. Escherichia coli and Pichia pastoris are two of the most popular expression systems for producing isotope-enriched, recombinant protein samples for NMR investigations. The P. pastoris system can be used to produce (13)C, (15)N-enriched and even (2)H,(13)C, (15)N-enriched protein samples, but efficient methods for producing perdeuterated proteins with Ile (δ1), Leu and Val methyl-protonated groups in P. pastoris are still unavailable. Glycosylation heterogeneity also provides challenges to NMR studies. E. coli expression systems are efficient for overexpressing perdeuterated and Ile (δ1), Leu, Val methyl-protonated protein samples, but are generally not successful for producing secreted eukaryotic proteins with native disulfide bonds.

RESULTS

The 33 kDa protein-Rhizopus chinensis lipase (RCL), an important industrial enzyme, was produced using both P. pastoris and E. coli BL21 trxB (DE3) systems. Samples produced from both systems exhibit identical native disulfide bond formation and similar 2D NMR spectra, indicating similar native protein folding. The yield of (13)C, (15)N-enriched r27RCL produced using P. pastoris was 1.7 times higher that obtained using E. coli, while the isotope-labeling efficiency was ~15 % lower. Protein samples produced in P. pastoris exhibit O-glycosylation, while the protein samples produced in E. coli were not glycosylated. The specific activity of r27RCL from P. pastoris was ~1.4 times higher than that produced in E. coli.

CONCLUSIONS

These data demonstrate efficient production of (2)H, (13)C, (15)N-enriched, Ile (δ1), Leu, Val methyl-protonated eukaryotic protein r27RCL with native disulfides using the E. coli BL21 trxB (DE3) system. For certain NMR studies, particularly efforts for resonance assignments, structural studies, and dynamic studies, E. coli provides a cost-effective system for producing isotope-enriched RCL. It should also be potential for producing other (2)H, (13)C, (15)N-enriched, Ile (δ1), Leu, Val methyl-protonated eukaryotic proteins with native disulfide bonds.

Antibacterial Effects of Biosynthesized Silver Nanoparticles on Surface Ultrastructure and Nanomechanical Properties of Gram-Negative Bacteria viz. Escherichia coli and Pseudomonas aeruginosa

Understanding the interactions of silver nanoparticles (AgNPs) with the cell surface is crucial for the evaluation of bactericidal activity and for advanced biomedical and environmental applications. Biosynthesis of AgNPs was carried out through in situ reduction of silver nitrate (AgNO3) by cell free protein of Rhizopus oryzae and the synthesized AgNPs was characterized by UV-vis spectroscopy, high resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), ζ-potential analysis, and FTIR spectroscopy. The HRTEM measurement confirmed the formation of 7.1 ± 1.2 nm AgNPs, whereas DLS study demonstrated average hydrodynamic size of AgNPs as 9.1 ± 1.6 nm. The antibacterial activity of the biosynthesized AgNPs (ζ = -17.1 ± 1.2 mV) was evaluated against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. The results showed that AgNPs exhibited concentration dependent antibacterial activity and 100% killing of E. coli and P. aeruginosa achieved when the cells were treated with 4.5 and 2.7 μg/mL AgNPs, respectively for 4 h. Furthermore, the intracellular reactive oxygen species (ROS) production suppressed the antioxidant defense and exerted mechanical damage to the membrane. AgNPs also induced surface charge neutralization and altered of the cell membrane permeability causing nonviability of the cells. Atomic force microscopy (AFM) studies depicted alteration of ultrastructural and nanomechanical properties of the cell surface following interaction with AgNPs, whereas FTIR spectroscopic analysis demonstrated that cell membrane of the treated cells underwent an order-to-disorder transition during the killing process and chemical composition of the cell membrane including fatty acids, proteins, and carbohydrates was decomposed following interaction with AgNPs.

[Effects of pellet characteristics on L-lactic acid fermentation by Rhizopus oryzae]

OBJECTIVE

Effects of pellet morphology, diameter, density, and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO3.

METHODS

Different initial spore concentrations were inoculated in the preculture medium with different peptone and CaCO3 concentrations, and cultivated at 30 degrees C for 36 h. Representative pellets were chosen for interior structure analysis and L-lactic acid production.

RESULTS

Inoculum size was the most important factor determining pellet formation and diameter. Peptone concentration had the greatest effect on pellet density. L-lactic acid production depended heavily on pellet density but not on pellet diameter. Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure. This structure greatly decreased production. The production of L-lactic acid increased until the density reached a certain level (50 - 60 kg/m3) , which the compact part distributed homogeneously in the thick outer layer of the pellet, and loose in the central layer. Homogeneously structured, denser pellets limited mass transfer. CaCO, concentration only had a slight influence on pellet diameter and density.

CONCLUSION

This work provides the insight into pellet structure and its relationship with productivity.

In vitro antimalarial studies of novel artemisinin biotransformed products and its derivatives

Biotransformation of antimalarial drug artemisinin by fungi Rhizopus stolonifer afforded three sesquiterpenoid derivatives. The transformed products were 1α-hydroxyartemisinin (3), 3.0%, a new compound, 10β-hydroxyartemisinin, 54.5% (4) and deoxyartemisinin (2) in 9% yield. The fungus expressed high-metabolism activity (66.5%). The chemical structures of the compounds were elucidated by 1D, 2D NMR spectrometry and mass spectral data. The major compound 10β-hydroxyartemisinin (4) was chemically converted to five new derivatives 5-9. All the compounds 3-9 were subjected for in vitro anti-malarial activity. 10β-Hydroxy-12β-arteether (8), IC50 at 18.29nM was found to be 10 times better active than its precursor 4 (184.56nM) and equipotent antimalarial with natural drug artemisinin whereas the α-derivative 9 is 3 times better than 4 under in vitro conditions. Therefore, the major biotransformation product 4 can be exploited for further modification into new clinically potent molecules. The results show the versatility of microbial-catalyzed biotransformations leading to the introduction of a hydroxyl group at tertiary position in artemisinin in derivative (3).

Optimization of marine waste based-growth media for microbial lipase production using mixture design methodology

Lipase production by Staphylococcus xylosus and Rhizopus oryzae was investigated using a culture medium based on a mixture of synthetic medium and supernatants generated from tuna by-products and Ulva rigida biomass. The proportion of the three medium components was optimized using the simplex-centroid mixture design method (SCMD). Results indicated that the experimental data were in good agreement with predicted values, indicating that SCMD was a reliable method for determining the optimum mixture proportion of the growth medium. Maximal lipase activities of 12.5 and 23.5 IU/mL were obtained with a 50:50 (v:v) mixture of synthetic medium and tuna by-product supernatant for Staphylococcus xylosus and Rhizopus oryzae, respectively. The predicted responses from these mixture proportions were also validated experimentally.

Heterologous expression systems for lipases: a review

The production of heterologous lipases is one of the most promising strategies to increase the productivity of the bioprocesses and to reduce costs, with the final objective that more industrial lipase applications could be implemented. In this chapter, an overview of the most common microbial expression systems for the overproduction of microbial lipases is presented. Prokaryotic system as Escherichia coli and eukaryotic systems as Saccharomyces cerevisiae and Pichia pastoris are analyzed and compared in terms of productivity, operational, and downstream processing facilities. Finally, an overview of heterologous Candida rugosa and Rhizopus oryzae lipases, two of the most common lipases used in biocatalysis, is presented. In both cases, P. pastoris has been shown as the most promising host system.

Identification of prenylated pterocarpans and other isoflavonoids in Rhizopus spp. elicited soya bean seedlings by electrospray ionisation mass spectrometry

Phytoalexins from soya are mainly characterised as prenylated pterocarpans, the glyceollins. Extracts of non-soaked and soaked soya beans, as well as that of soya seedlings, grown in the presence of Rhizopus microsporus var. oryzae, were screened for the presence of prenylated flavonoids with a liquid chromatography/mass spectrometry (LC/MS)-based screening method. The glyceollins I-III and glyceollidins I-II, belonging to the isoflavonoid subclass of the pterocarpans, were tentatively assigned. The formation of these prenylated pterocarpans was accompanied by that of other prenylated isoflavonoids of the subclasses of the isoflavones and the coumestans. It was estimated that approx. 40% of the total isoflavonoid content in Rhizopus-challenged soya bean seedlings were prenylated pterocarpans, whereas 7% comprised prenylated isoflavones and prenylated coumestans. The site of prenylation (A-ring or B-ring) of the prenylated isoflavones was tentatively annotated using positive-ion mode MS by comparing the (1,3) A(+) retro-Diels-Alder (RDA) fragments of prenylated and non-prenylated isoflavones. Furthermore, the fragmentation pathways of the five pterocarpans in negative-ion (NI) mode were proposed, which involved the cleavage of the C-ring and/or D-ring. The absence of the ring-closed prenyl (pyran or furan) gave exclusively -H(2) O(x,y) RDA fragments, whereas its presence gave predominantly the common RDA fragments.

Simultaneous copper, cobalt and phenol removal from aqueous solutions by alternating biosorption and biodegradation

A strategy for removal of heavy metals and phenol from wastewaters is proposed. It involves consecutive cation biosorption by fungi, phenol biodegradation by the yeast association Candida sp. 2326 + Candida sp. 2327 and regeneration. Copper and cobalt removal from aqueous solutions containing 80-120 mg/L phenol by biosorption, using Rhizopus archizus cells immobilized onto poly (vinyl alcohol), was investigated by conducting a series of batch experiments. The removal efficiencies were 81% for Cu and 5% for Co. The residual concentrations of Cu (1.9 mg/L) and of Co (9.5 mg/L) did not change the biodegradation dynamics of phenol. A quantitative biodegradation of 120 mg/L phenol proceeded within 22 h. After biodegradation of phenol, the removal efficiencies achieved by biosorption after regeneration were 90% for Cu and 44% for Co. It was found that copper and cobalt form positively charged complexes with phenol. This complex formation hinders the retention of Cu and Co by the biosorbent and reduces the uptake of their cations.

Effect of salinity on metal-complex dye biosorption by Rhizopus arrhizus

In this study the biosorption of Yellow RL, a metal-complex anionic dye, by dried Rhizopus arrhizus, a filamentous fungus, was investigated as a function of initial solution pH, initial dye concentration and initial salt (sodium chloride) concentration. The fungus exhibited the maximal dye uptake at pH 2 in the absence and in the presence of salt. Dye uptake increased with the dye concentration up to 1000 mg l(-1) and diminished considerably in the presence of increasing concentrations of salt up to 50 g l(-1). The fungus biosorbed 85.4 mg dye g(-1)of dried biomass at 100 mg l(-1) initial dye concentration in the absence of salt. When 50 g l(-1) salt was added to the biosorption medium, this value dropped to 60.8 mg g(-1) resulting in 28.8% reduction in biosorption capacity. The Redlich-Peterson and Langmuir-Freundlich were the most suitable adsorption models for describing the biosorption equilibrium data of the dye both individually and in salt containing medium. The pseudo-second-order and saturation type kinetic models depicted the biosorption kinetics accurately for all cases studied. Equilibrium and kinetic constants varied with the level of salt were expressed as a function of salt concentration.

Microbial synthesis of multishaped gold nanostructures

The development of methodologies for the synthesis of nanoparticles of well-defined size and shape is a challenging one and constitutes an important area of research in nanotechnology. This Full Paper describes the controlled synthesis of multishaped gold nanoparticles at room temperature utilizing a simple, green chemical method by the interaction of chloroauric acid (HAuCl4 x 3H20) and cell-free extract of the fungal strain Rhizopus oryzae. The cell-free extract functions as a reducing, shape-directing, as well as stabilizing, agent. Different shapes of gold nanocrystals, for example, triangular, hexagonal, pentagonal, spherical, spheroidal, urchinlike, two-dimensional nanowires, and nanorods, are generated by manipulating key growth parameters, such as gold ion concentration, solution pH, and reaction time. The synthesized nanostructures are characterized by UV/Vis and Fourier-transform infrared spectroscopy, transmission electron microscopy, and energy dispersive X-ray analysis studies. Electron diffraction patterns reveal the crystalline nature of the nanoparticles and a probable mechanism is proposed for the formation of the different structural entities.

Structural determination of aspericins A-C, new furan and pyran derivates from the marine-derived fungus Rhizopus sp. 2-PDA-61, by 1D and 2D NMR spectroscopy

Three new furan and pyran derivatives named aspericins A-C (1-3), as well as a known asperic acid (4), have been isolated from the marine-derived fungus Rhizopus sp. 2-PDA-61. The complete (1)H and (13)C NMR assignments for the new compounds were carried out using (1)H, (13)C, DEPT, COSY, HMQC, HMBC, and NOESY NMR experiments. Compounds 1-3 were evaluated for their cytotoxic activities on P388, A549, HL-60, and BEL-7420 cell lines by the MTT and SRB methods.

Purification and characterization of a new Rhizopuspepsin from Rhizopus oryzae NBRC 4749

A secretory aspartic protease (also termed as rhizopuspepsin) was purified from Rhizopus oryzae NBRC 4749 by ion exchange chromatography with a yield of 45%. The enzyme was a nonglycoprotein with a molecular mass of 37 kDa as determined by SDS-PAGE analysis. N-terminal sequence and LC-MS/MS analyses revealed that this rhizopuspepsin corresponded to the hypothetical protein RO3G_12822.1 in the R. oryzae genome database. Comparison of genomic and cDNA genes demonstrated that the rhizopuspepsin contained two introns, whereas only one intron was reported in other rhizopuspepsin genes. Phylogenetic analysis also indicated that this rhizopuspepsin was distinct from other rhizopuspepsins. The temperature and pH optima for the purified rhizopuspepsin were 50 degrees C and pH 3.0, respectively, and a half-life of about 3.5 h was observed at 40 degrees C. The enzyme preferentially cleaved the peptides with hydrophobic and basic amino acids in the P1 site but had no activity for the Glu, Pro, Trp, and aliphatic amino acids containing the beta-branch side chain.

A novel technology for biosorption and recovery hexavalent chromium in wastewater by bio-functional magnetic beads

The goal of this study was to develop an applied technique for the removal and recovery of heavy metal in wastewater. It is novel that the Cr(VI) could be adsorbed and recovered by bio-functional magnetic beads. Furthermore, the magnetic separation technology would make their separation more convenient. The beads were constituted by the powder of Rhizopus cohnii and Fe(3)O(4) particles coated with alginate and polyvinyl alcohol (PVA). The parameters effecting Cr(VI) removal were obtained: the optimum pH 1.0 and optimum temperature 28 degrees C. The biosorption took place mainly in form of Cr(VI) and R. cohnii biomass played a key role in Cr(VI) adsorption. The model of Langmuir isotherm and Lagergren could be better used to fit the sorption process and kinetics, respectively. The beads still maintained predominant characteristics of adsorption, recovery and magnetism after five cycles for adsorption-desorption. The mechanism of adsorption was gained by Fourier transform infrared spectroscopy (FTIR), raman spectroscopy (RS) and scanning electron microscopy (SEM). The groups of -NH(3)(+), -NH(2)(+)-, and NH- played an important role in the Cr(VI) adsorption. Consequently, the beads exhibited the superior performances in Cr(VI) cleanup, separation and recovery and the perspective potential in application.

Six new ergosterols from the marine-derived fungus Rhizopus sp

Six new ergosterols, including 3beta-hydroxyl-(22E, 24R)-ergosta-5,8,22-trien-7,15-dione (1), 3beta-hydroxyl-(22E, 24R)-ergosta-5,8,14,22-tetraen-7-one (2), 3beta,15beta-dihydroxyl-(22E, 24R)-ergosta-5,8(14),22-trien-7-one (3), 3beta,15alpha-dihydroxyl-(22E, 24R)-ergosta-5,8(14),22-trien-7-one (4), 3beta-hydroxyl-(22E, 24R)-ergosta-5,8(14),22-trien-7,15-dione (5), and 5alpha,8alpha-epidioxy-23,24(R)-dimethylcholesta-6,9(11),22-trien-3beta-ol (6), have been isolated from the marine-derived fungus Rhizopus sp., along with four known ones (7-10). The structures of the new compounds were determined on the basis of extensive spectroscopic data. All compounds were evaluated for their cytotoxic activities on P388, A549, HL-60, and BEL-7420 cell lines by the MTT and SRB methods.

Chromium(VI) biosorption by dried Rhizopus arrhizus: effect of salt (NaCl) concentration on equilibrium and kinetic parameters

Some industrial wastewaters contain high quantities of salts besides heavy metal ions. The presence of salt ions leads to high ionic strength, which may significantly affect the performance of the biosorption process so the effect of salts on the biosorption of heavy metal ions should be investigated. In this study the biosorption of chromium(VI) from saline solutions on dried Rhizopus arrhizus was studied as a function of pH, initial chromium(VI) and salt (NaCl) concentrations in a batch system. The biosorption capacity of R. arrhizus strongly depended on solution pH and maximum chromium(VI) sorption capacity of sorbent was obtained at pH 2.0 both in the absence and in the presence of increasing concentrations of salt. Chromium(VI)-salt biosorption studies were performed at this pH value. Equilibrium uptakes of chromium(VI) increased with increasing chromium(VI) concentration up to 250mgl(-1) and decreased considerably by the presence of increasing concentrations of salt. At 100mgl(-1), initial chromium(VI) concentration, dried R. arrhizus biosorbed 78.0mgg(-1) of chromium(VI) in 72h without salt medium. When salt concentration was raised to 50gl(-1), this value dropped to 64.0mgg(-1) of chromium(VI) at the same conditions resulting in 17.9% decrease of biosorption capacity. The equilibrium sorption data were analysed by using Freundlich, Langmuir, Redlich-Peterson and Langmuir-Freundlich (Sips), the two and three parameters adsorption models, using non-linear regression technique and isotherm constants were evaluated depending on salt concentration. The Langmuir-Freundlich (Sips) was the best suitable adsorption model for describing the biosorption of chromium(VI) individually and in salt-containing medium. Pseudo-first-order, pseudo-second-order and saturation type kinetic models described the biosorption kinetics accurately at all chromium(VI) concentrations in the absence and in the presence of changing concentrations of salt. Isotherm and saturation type kinetic constants varied due to the level of salt were expressed as a function of initial salt concentration.

Application of response surface methodology for the biosorption of copper using Rhizopus arrhizus

Response surface methodology was used to study the cumulative effect of the various parameters namely, initial copper ion concentration, pH, temperature, biomass loading and to optimize the process conditions for the maximum removal of copper. For obtaining the mutual interaction between the variables and optimizing these variables, a 2(4) full factorial central composite design using response surface methodology was employed. The analysis of variance (ANOVA) of the quadratic model demonstrates that the model was highly significant. The model was statistically tested and verified by experimentation. A maximum copper removal of 98% was obtained using the biosorption kinetics of copper under optimum conditions.

Continuous fixed bed biosorption of reactive dyes by dried Rhizopus arrhizus: determination of column capacity

A continuous fixed bed study was carried out by using dried Rhizopus arrhizus as a biosorbent for the removal of three reactive dyes; Gemacion (Procion) Red H-E7B (GR), a monoclorotriazine mono-azo type reactive dye; Gemazol Turquise Blue-G (GTB), a vinyl sulfone mono-azo type reactive dye and Gemactive (Reactive) Black HFGR (GB), a vinyl sulfone di-azo type reactive dye from aqueous solution. The effect of operating parameters such as flow rate and inlet dye concentration on the sorption characteristics of R. arrhizus was investigated at pH 2.0 and at 25 degrees C for each dye. Data confirmed that the total amount of sorbed dye decreased with increasing flow rate and increased with increasing inlet dye concentration for each dye. The column biosorption capacity of dried R. arrhizus was 1007.8 mg g(-1) for GR dye, 823.8 mg g(-1) for GTB dye and 635.7 mg g(-1) for GB dye at the highest inlet dye concentration of approximately 750 mg l(-1) and at the minimum flow rate of 0.8 ml min(-1). Thomas and Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the biosorption capacity of the column for each dye useful for process design. Both models were found suitable for describing the whole dynamic behavior of the column with respect to flow rate and inlet dye concentration.

Microbial transformation of (-)-guaiol and antibacterial activity of its transformed products

Microbial transformation of the sesquiterpene (-)-guaiol (1) [1(5)-guaien-11-ol] was investigated using three fungi, Rhizopus stolonifer, Cunninghamella elegans, and Macrophomina phaseolina. Fungal transformation of 1 with Rhizopus stolonifer yielded a hydroxylated product, 1-guaiene-9 beta,11-diol (2). In turn, Cunninghamella elegans afforded two mono- and dihydroxylated products, 1-guaiene-3beta,11-diol (3) and 1(5)-guaiene-3beta,9 alpha,11-triol (4), while Macrophomina phaseolina produced two additional oxidative products, 1(5)-guaien-11-ol-6-one (5) and 1-guaien-11-ol-3-one (6). All metabolites were found to be new compounds as deduced on the basis of spectroscopic techniques. Compounds 1-6 were evaluated for their activity against several bacterial strains.

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.