Thermotolerant Emericella nidulans NK-62 was isolated from bird nesting material and was tested for its ability to produce xylanase. The fungus when grown on a medium containing wheat bran (2% w/v) supplemented with Czapek's mineral salt solution at 45 °C for 7 days produced 362 IU/ml of xylanase (EC 3.2.1.8). The specific activity of E. nidulans NK-62 xylanase was found to be 275 IU/mg of total protein. The enzyme was found to be active over a broad temperature and pH range with 60 °C as optimum temperature for enzyme activity. The enzyme was stable at 50 °C and its half-life at 55 °C was 45 min. -xylosidase (EC 3.2.1.37) and carboxymethylcellulase (EC 3.2.1.4) activities, 0.018 and 0.21 IU/ml respectively, were also noticed. The fungus was screened for its ability to produce xylanase on four different lignocellulosic substrates. It produced 318.9 IU/ml of cellulase-free xylanase on corn cobs. The fungus could also utilize lentil bran (seed husk of Lens esculentus) and meal of groundnut shells to produce 84.8 and 17.3 IU/ml xylanase respectively. 相似文献
Eighty‐eight fungi isolated from soil and decaying organic matter were screened for mannanolytic activity. Twenty‐eight fungi produced extracellular mannanase on locust bean gum as evidenced by zone of hydrolysis produced on mannan agar gel. Six prominent producers, including four Fusarium species namely Fusarium fusarioides NFCCI 3282, Fusarium solani NFCCI 3283, Fusarium equiseti NFCCI 3284, Fusarium moniliforme NFCCI 3287 with Cladosporium cladosporioides NFCCI 3285 and Acrophialophora levis NFCCI 3286 produced the β‐mannanase in the range of 84–140 nkat/mL. All these grew well on particulate substrates in solid‐state fermentation (SSF), producing relatively higher titers on mannan‐rich palm kernel cake (PKC) and copra meal. Two high yielding strains, F. equiseti (1747 nkat/gds) and A. levis (897 nkat/gds) were selected for statistical optimization of mannanase on PKC. Interaction of two critical solid state fermentation parameters, pH and moisture on mannanase production by these two molds was studied by response surface method. Optimized production on PKC resulted in three‐ to fourfold enhancement in enzyme yield was observed in case of F. equiseti (5945 nkat/gds) and A. levis (4726 nkat/gds). HPLC analysis of mannan hydrolysate indicated that F. equiseti and A. levis mannanase performed efficient hydrolysis of konjac gum (up to 99%) with exclusive mannooligosaccahride (DP of 4) production. A seminative SDS‐PAGE revealed that A. levis and F. solani produced three isoforms, F. moniliforme produced two isoforms while F. fusarioides, F. equiseti, and C. cladosporioides produced a single enzyme. 相似文献
The gene encoding NADP+-dependent isocitrate dehydrogenase (IDH; EC 1.1.1.42) of a psychrophilic bacterium, Psychromonas marina, was cloned and sequenced. The open reading frame of the gene encoding IDH of P. marina (PmIDH) was 2229 bp in length and corresponded to a polypeptide composed of 742 amino acids. The molecular mass of IDH was calculated as 80,426 Da. The deduced amino acid sequence of PmIDH exhibited high degrees of homology with the monomeric IDH from other bacteria such as Colwellia maris (62% identity) and Azotobacter vinelandii (AvIDH) (64%). His-tagged PmIDH overexpressed in Escherichia coli cells was purified and characterized. The optimum temperature of PmIDH activity was about 35 °C; however, the enzyme lost 74% of the activity after incubation for 10 min at 30 °C, indicating that this enzyme is thermolabile. Chimeric enzymes produced through domain swapping between PmIDH and mesophilic AvIDH were constructed and their optimum temperatures and thermostability were determined. The results suggest that regions 2 and 3, especially region 3, of the two IDHs are involved in their catalytic activities and optimum temperature and thermostability for activity.
The thermophilic fungi Thermomyces lanuginosus, Malbranchea cinnamomea, Myceliophthora fergusii and the thermotolerant Aspergillus terreus were cultivated on various carbon sources, and hemicellulolytic and cellulolytic enzyme profiles were evaluated. All fungi
could grow on locust bean galactomannan (LBG), Solka floc, wheat bran and pectin, except T. lanuginosus, which failed to utilize LBG for growth. Different levels of cellulase and hemicellulase activities were produced by these
fungal strains. Depending on the carbon source, variable ratios of thermostable hydrolytic enzymes were obtained, which may
be useful in various applications. All strains were found to secrete xylanolytic and mannanolytic enzymes. Generally, LBG
was the most efficient carbon source to induce mannanase activities, although T. lanuginosus was able to produce mannanase only on wheat bran as a carbon source. Xylanolytic activities were usually highest on wheat
bran medium, but in contrast to other investigated fungi, xylanase production by M. fergusii was enhanced on pectin medium. Preliminary thermostability screening indicated that among the investigated species, thermotolerant
glycosidases can be found. Some of the accessory activities, including the α-arabinosidase activity, were surprisingly high.
The capability of the produced enzymes to improve the hydrolysis of lignocellulosic pretreated substrate was evaluated and
revealed potential for these enzymes. 相似文献
This study documents indigenous knowledge of breeds of cattle, sheep and goats in southwestern Niger, and includes both pastoralists
and agropastoralists. Our study included sheep and goats in view of the increasing importance of small ruminants in livestock
production systems in the Sahel since the drought of the 1970s and 1980s. This study was carried out under the Desert Margins
Program (DMP) project on arresting land degradation and the conservation of biodiversity in desert margins of sub-Saharan
Africa, partly funded by the Global Environment Facility (GEF). 相似文献
Inulinase production by Penicillium sp. NFCC 2768 isolated from the rhizosphere soil of dahlia was studied on media containing inulin-rich plant extracts. The maximum inulinase activity (64.54 nkat/ml) was observed with the tuber extract of dahlia (Dahlia pinnata). The fungus produced substantial inulinase activity on asparagus root powder (45.23 nkat/ml) and garlic extracts (41.32 nkat/ml). The apparent molecular weight of the purified inulinase was 68 kDa. The optimum pH and temperature for enzyme activity were 5.0 and 50°C, respectively. Mn2+ and Ca2+ were found to enhance the inulinase activity, while Hg2+ was found to be a strong inhibitor. Inulinase liberated fructose, glucose, sucrose, kestose (GF2), nystose (GF3), and inulooligosaccharides (IOS). This study suggested the use of dahlia tuber extract and asparagus root powder as suitable substrates for inulinase production by the newly isolated Penicillium sp. NFCC 2768, and its application in the generation of fructose and IOS. 相似文献
Metallothioneins (MTs) are low molecular weight ubiquitous metalloproteins with high cysteine (thiol) content. The intracellular concentration of zinc (Zn) is tightly regulated and MT plays a crucial role in it. The present study investigates the relationship between the Zn status (as a function of Zn concentration and time) in the rat liver and the occurrence of hepatic MT. For dose dependent study, four experimental groups, one control and three receiving different levels of metal supplementation, were chosen [Group 1 control and Group 2, Group 3, Group 4 receiving subcutaneous dose of 10, 50 and 100 mg of Zn/kg body weight (in the form of ZnSO4·7H2O), respectively]. For the time dependent expression of MT, again four experimental groups, i.e. Group 5 control and Group 6, Group 7, Group 8 receiving 50 mg of Zn/kg body weight (in the form of ZnSO4·7H2O) subcutaneously and sacrificed at different time intervals after last injection i.e. 6, 18, 48 h, respectively were chosen. Isolation of MT was done by using combination of gel filtration and ion exchange chromatography while characterization of MT fraction was carried in the wavelength range 200–400 nm. Expression of MT was studied by using Western blot analysis. The results revealed that the MT expression increases with increasing the dose of Zn administered and maximum at 18 h after last Zn injection. Accumulation of MT with increase dose would help in maintaining the intracellular Zn concentration by its sequestration which further reduces the possibility of undesirable binding of Zn to other proteins significantly and maintains Zn homeostasis. The maximum expression of MT at 18 h is indicative of its half life. 相似文献