Production of cellulase using a mutant strain of Trichoderma reesei growing on lactose in batch culture

The production of cellulases in batch culture was studied using a mutant strain of Trichoderma reesei C-5 growing on lactose. Growth kinetic parameters on 2% lactose were studied and the comparative results for growth and enzyme productivities at two different lactose levels are discussed. The cellulase synthesis rate depended on the lactose concentration in the medium. Although growth was favoured at a higher lactose level, the volumetric enzyme productivity did not increase in proportion and the specific enzyme productivity decreased to a certain extent, indicating that partial catabolic inhibition at higher lactose concentrations may be possible. However, it was noted that the mutant strain was highly depressed and capable of synthesising active cellulases on lactose.     

Detection and identification of ferricrocin produced by ectendomycorrhizal fungi in the genusWilcoxina

The ectendomycorrhizal fungiWilcoxina mikolae isolates CSY-14 and RMD-947 andW. rehmii isolate CSY-85 were grown in pure culture under iron-limiting conditions. All three isolates tested positive for siderophore formation using both the ferric perchlorate assay and a sensitive HPLC iron-binding assay. A peptide siderophore was isolated from the culture medium by HPLC and shown to contain the amino acids serine, glycine and ornithine in a 1:2:3 ratio. This siderophore was identified as ferricrocin on the basis of electrospray mass spectroscopy and its co-chromatography in two different HPLC systems with ferricrocin isolated fromAspergillus fumigatus. Ferricrocin was the only siderophore isolated from theseWilcoxina cultures. This is the first report of siderophore formation by ectendomycorrhizal fungi.     

Presence and nature of a glycocalyx-like coat on the external vesicular membrane of cysticercus cellulosae. A high resolution histochemical study.

Three histochemical techniques were used to demonstrate the presence of mucosubstances on the exposed surface of the vesicular membrane of $\text{Cysticercus cellulosae.}$ Using Alcian blue staining, electron micrographs revealed electron dense deposits of lanthanum confined to the entire exposed surface of the microthriches. Using concanavalin A, the results showed a discontinuous thin layer of electron dense deposits along the same exposed surface as the Alcian blue technique. Using colloidal iron hydroxide labelling, the electron micrographs showed the presence of negative charges along only the tips of the microthriches. This distribution of the negative charges is discussed and possible explanations are proposed. The conclusion from these results on both the presence of a surface glycocalyx-like coat rich in both acidic and neutral carbohydrates and the presence of a negative surface potential suggest that the exposed surface of $\text{Cysticercus cellulosae}$ may have important roles in the host-parasite interrelationships.     

Nigericin forms highly stable complexes with lithium and cesium

Nigericin is a monocarboxylic polyether molecule described as a mobile K⁺ ionophore unable to transport Li⁺ and Cs⁺ across natural or artificial membranes. This paper shows that the ion carrier molecule forms complexes of equivalent energy demands with Li⁺, Cs⁺, Na⁺, Rb⁺, and K⁺. This is in accordance with the similar values of the complex stability constants obtained from nigericin with the five alkali metal cations assayed. On the other hand, nigericinalkali metal cation binding isotherms show faster rates for Li⁺ and Cs⁺ than for Na⁺, K⁺, and Rb⁺, in conditions where the carboxylic proton does not dissociate. Furthermore, proton NMR spectra of nigericin-Li⁺ and nigericin-Cs⁺ complexes show wide broadenings, suggesting strong cation interaction with the ionophore; in contrast, the complexes with Na⁺, K⁺, and Rb⁺ show only clear-cut chemical shifts. These latter results support the view that nigericin forms highly stable complexes with Li⁺ and Cs⁺ and contribute to the explanation for the inability of this ionophore to transport the former cations in conditions where it catalyzes a fast transport of K⁺>Rb⁺>Na⁺.Part of the results of this paper were presented at the 14th International Congress of Biochemistry in Prague, Czechoslovakia.     

Glucose oxidase immobilized electrode for potentiometric estimation of glucose

Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1 urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix, pH and temperature. An improvement in the performance of the electrode has been achieved by coimmobilizing 2 urea and metal ions such as Mg²⁺ and Mn²⁺. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1–5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function.     

DNA synthesis and nuclear division during formation of infection structures by bean rust uredospore germlings

Plectonema boryanum can grow in the dark with ribose, sucrose, mannitol, maltose, glucose, or fructose. Cell doubling times with 10 mM substrate are the following: 5 days with ribose, 6 days with sucrose or mannitol, 10 days with maltose, 12 days with glucose, and 13 days with fructose; with ribose plus 0.1% casamino acids it is 2.5 days. Dark-grown cells appear morphologically similar to light-grown cells. Cells grown in the dark for several years remain pigmented and resume photoautotrophic growth when placed in the light. Dim light (85 lux) increases the growth rate with ribose and with ribose plus casamino acids to nearlytwice that of the dark rate. In moderate light, growth takes place with ribose even in the presence of 1x10^-5 M DCMU.