Purification and characterization of a ß-glucosidase from aspergillus niger and its application in the hydrolysis of geniposide to genipin.

An extracellular ß-glucosidase from Aspergillus niger Au0847 was purified to homogeneity by precipitation with ammonium sulfate, anion exchange, and gel filtration. The purified protein was composed of two subunits with molecular masses of 110 and 120 kDa. Au0847 ß-glucosidase exhibited relatively high thermostability and pH stability, and its highest activity was obtained at 65°C and pH 4.6, respectively. As a potential metalloprotein, its enzymatic activity was potently stimulated by manganese ion and DTT. The ß-glucosidase displayed avid affinity and high catalytic efficiency for geniposide. Au0847 ß-glucosidase has potential value as an industrial enzyme for the hydrolysis of geniposide to genipin.

Improving Aspergillus niger tannase yield by N+ ion beam implantation

This work aimed to improve tannase yield of Aspergillus niger through N+ ion beam implantation in submerged fermentation. The energy and dose of N+ ion beam implantation were investigated. The results indicated that an excellent mutant was obtained through nine successive implantations under the conditions of 10 keV and 30-40 (×2.6×10(13)) ions/cm², and its tannase yield reached 38.5 U/mL, which was about five-time higher than the original strain. The study on the genetic stability of the mutant showed that its promising performance in tannase production could be stable. The studies of metal ions and surfactants affecting tannase yield indicated that manganese ions, stannum ions, xylene and SDS contained in the culture medium had positive effects on tannase production under submerged fermentation. Magnesium ions, in particular, could enhance the tannase yield by the mutant increasing by 42%, i.e. 53.6 U/mL. Accordingly, low-energy ion implantation could be a desirable approach to improve the fungal tannase yield for its commercial application.

Morphological changes induced by class III chitin synthase gene silencing could enhance penicillin production of Penicillium chrysogenum.

Chitin synthases catalyze the formation of ß-(1,4)-glycosidic bonds between N-acetylglucosamine residues to form the unbranched polysaccharide chitin, which is the major component of cell walls in most filamentous fungi. Several studies have shown that chitin synthases are structurally and functionally divergent and play crucial roles in the growth and morphogenesis of the genus Aspergillus although little research on this topic has been done in Penicillium chrysogenum. We used BLAST to find the genes encoding chitin synthases in P. chrysogenum related to chitin synthase genes in Aspergillus nidulans. Three homologous sequences coding for a class III chitin synthase CHS4 and two hypothetical proteins in P. chrysogenum were found. The gene which product showed the highest identity and encoded the class III chitin synthase CHS4 was studied in detail. To investigate the role of CHS4 in P. chrysogenum morphogenesis, we developed an RNA interference system to silence the class III chitin synthase gene chs4. After transformation, mutants exhibited a slow growth rate and shorter and more branched hyphae, which were distinct from those of the original strain. The results also showed that the conidiation efficiency of all transformants was reduced sharply and indicated that chs4 is essential in conidia development. The morphologies of all transformants and the original strain in penicillin production were investigated by light microscopy, which showed that changes in chs4 expression led to a completely different morphology during fermentation and eventually caused distinct penicillin yields, especially in the transformants PcRNAi1-17 and PcRNAi2-1 where penicillin production rose by 27 % and 41 %, respectively.

Morphology engineering of Penicillium chrysogenum by RNA silencing of chitin synthase gene.

Chitin synthases, that catalyze the formation of chitin the major component of cell walls in most filamentous fungi, play crucial roles in the growth and morphogenesis. To investigate the roles of chitin synthase in Penicillium chrysogenum, we developed an RNAi system to silence the class III chitin synthase gene chs4. After transformation, mutants had a slow growth rate and shorter but highly branched hyphae. All transformants either were unable to form conidia or could form only a few. Changes in chs4 expression could lead to a completely different morphology and eventually cause distinct penicillin yields. In particular, the yield of one transformant was 41 % higher than that of the original strain.

Characterization of bioimprinted tannase and its kinetic and thermodynamics properties in synthesis of propyl gallate by transesterification in anhydrous medium.

Tannase has been extensively applied to synthesize gallic acid esters. Bioimprinting technique can evidently enhance transesterification-catalyzing performance of tannase. In order to promote the practical utilization of the modified tannase, a few enzymatic characteristics of the enzyme and its kinetic and thermodynamics properties in synthesis of propyl gallate by transesterification in anhydrous medium have been studied. The investigations of pH and temperature found that the imprinted tannase holds an optimum activity at pH 5.0 and 40 °C. On the other hand, the bioimprinting technique has a profound enhancing effect on the adapted tannase in substrate affinity and thermostability. The kinetic and thermodynamic analyses showed that the modified tannase has a longer half-time of 1,710 h at 40 °C; the kinetic constants, the activation energy of reversible thermal inactivation, and the activation energy of irreversible thermal inactivation, respectively, are 0.054 mM, 17.35 kJ mol(-1), and 85.54 kJ mol(-1) with tannic acid as a substrate at 40 °C; the free energy of Gibbs (ΔG) and enthalpy (ΔH) were found to be 97.1 and 82.9 kJ mol(-1) separately under the same conditions.

[Induced synthesis of hydroxyapatite by Aspergillus niger].

OBJECTIVE: The research objective is to induce hydroxyapatite (HAP) synthesis by using fungus. METHODS: We used the PDA (Potato Dextrose Agar Medium) liquid medium containing different concentrations of Na2HPO4 and CaCO3 to study the way Aspergillus niger synthesize HAP, to observe the induced mineral crystal structure and to analyze the induced mineral type with transmission electron microscopy (TEM) and X-ray diffraction (XRD). RESULTS: The main results are as follows: (1) A. niger can induce HAP synthesis in PDA liquid medium with the proper concentration of Na2HPO4 and CaCO3. (2) The reaction of A. niger inducing HAP synthesis depends on the time of the response system. Longer time is more advantageous in producing HAP. The main reason for A. niger inducing HAP crystals formation are as follows: fungal metabolism produces the acidic substances to dissolve CaCO, and the growth mycelia absorbing Ca2+ lead to Ca2+ enriched on the surface, to promote the production of secondary mineral apatite and further transform into HAP in the mycelia spheres. CONCLUSION: A. niger can inducing HAP crystals formation in PDA liquid medium containing Na2HPO4 and CaCO3. Considering the importance of HAP in bio-medicine materials and its costly prices, our method for HAP bio-induction is of the temperate response condition, simple preparation craft, and lower cost, which has the potential application prospect.

Status, ecology, and conservation of the Himalayan griffon Gyps himalayensis (Aves, Accipitridae) in the Tibetan plateau.

The dramatic population crashes of 3 species of Gyps vulture have raised concerns about the status of their lesser-known congeners. Among these is the Himalayan griffon, G. himalayensis, an iconic vulture of the Tibetan plateau. The continued existence of this scavenger has not only ecological but also cultural implications because of their unique role in the centuries-old sky burial tradition that is followed by nearly 5 million Tibetan people. A lack of baseline information of the Himalayan griffon limits our ability to take conservation measures. The presented data, which were collected during 1996 and 2004 to 2007, indicate that this species is still widespread throughout the plateau and has not experienced a major population decline, likely as a result of protection by Tibetan Buddhism and limited disturbances from human activities largely due to the remoteness of the plateau. Both site and road counts showed that open meadow habitats had the highest griffon abundance, followed by alpine shrub and forest habitats. Estimates based on road transect counts showed that 229,339 Himalayan griffons (+/- 40,447) occupy the 2.5 million km2 Tibetan plateau. In contrast, the maximum carrying capacity of the plateau, on the basis of the total biomass of potential food resources, is 507,996 griffons, with meadow habitats accounting for about 76% of the total population. Griffons depend largely on livestock carcasses for food and forage in groups averaging 5.5 (range 1-100) individuals. Domestic yaks provide about 64% of the griffons' diet, while wild ungulates and human corpses provide 1% and 2%, respectively. Compared with its lowland congeners, this, the only high-elevation Gyps species, had both low population density and small group size, a likely response to the harsh environmental conditions. Although griffon abundance appears relatively stable in their fairly pristine environment, precautionary measures, including investigation of threats, monitoring of population dynamics, and establishment of modern conservation consciousness among Tibetan Buddhists, should be carried out to ensure that this abundance continues.