Spectrophotometric titrations of ferricytochrome C with ferrohexacyanide in the pH range 5 to 7

Spectrophotometric titrations were conducted on the system horse heart ferricytochromec plus ferrohexacyanide in the pH range 5 to 7 and at temperatures 8, 18, 22 and 28°C. A difference extinction coefficient for reducedvs. oxidized cytochromec at 550 nm of 21 mmol^–1cm^–1 was used in part of the evaluations. On the assumption that only one electron-transferlinked proton dissociation is effective for both ferro- and ferricytochromec in this pH range, various possible models are developed with only three conforming with the experimental pH dependence of the spectrophotometric equilibrium constant. The data conform best to a model with protonic dissociation constants between pH 5 and 7 such that the reduced cytochromec species is at least a factor of 3 more acidic than the one for oxidized cytochromec (with pK_H 6). This interpretation holds least for the data at 22°C, which points to a structural rearrangement at about this temperature (Czerlinski and Bracokova, 1973; Zabinski and Czerlinski, 1974; Zabinski, et al., 1974). While the extinction coefficient of ferrocytochromec shows no significant change with pH and temperature, the one for ferricytochromec does: it is about 5% larger at pH 5 than at pH 7 (550 nm). Graphs for the absorption change of ferricytochromec (pH 7 as reference) document the details over the wavelength range 500 to 750 nm.     

Production of dextranase byLipomyces starkeyi

Summary The optimal growth rate ofLipomyces starkeyi, with dextran as sole carbon source, was found within the pH range 2.5–4.0, and temperature between 25–30°C. This yeast was unable to grow above 33°C. Dextranase production optima paralleled growth optima, except at pH 2.5. Decrease in enzyme yield at this pH could not be attributed to poor yeast growth or enzyme stability.     

pH influence on ethanol production and retained biomass in a passively immobilizedZymomonas mobilis system

Summary A broad pH range of 4.5–7.5 for maximum ethanol productivity and ethanol yield was observed with a passively immobilizedZ. mobilis system. Total retained biomass (as suspended flocs and entrapped cells) was >50 g/l for medium pH values between 4.0–8.0. The entrapped cells to suspended flocs ratio was highest at pH 4.0, whereas at pH above 5.2 it was close to 1.0. The observed enhancement of cell immobilization on the packing support at low pH seemed to be related to formation of bacterial filaments.     

Higher culture pH is preferable for inclusion body formation of recombinant salmon growth hormone inEsherichia coli

Summary Higher culture pH of 7.6 was shown to be preferable for the inclusion body formation of salmon growth hormone (SGH) inEscherichia coli harboring a recombinant plasmid. High-level formation of SGH inclusion bodies was achieved at 33°C (pH 7.6). Growth inhibition by soluble SGH was also observed.     

Growth conditions of a pectinolyticAspergillus fumigatus for degumming of natural fibres

Summary Optimum growth conditions forA. fumigatus strain 4 when citric pectin was the sole carbon source were at a temperature of 45°C, pH 4.0 and an incubation time from 36 to 42h. Under these conditions no cellulase activity was found. When orange pulp was the sole carbon source, optimum polygalacturonase activities were found when the fungus was cultured for 36 h at 45°C and a pH 3.0 to 4.5.     

Selection of preculture conditions for solid state fermentation of sugar beet pulp

Summary For the protein upgrading of sugar-beet pulp in solid state fermentation byTrichoderma reesei andFusarium oxysporum, serveral conditions were studied to prepare an economical preculture for large scale process. The best performance was shown by a preculture obtained in 24 h from 1.5 % molasses solution at pH 4.5–5.0 with 1.0 % milled beet pulp.     

Langmuir adsorption isotherm forSulfolobus acidocaldarius on coal particles

Summary Sulfolobus acidocaldarius attachment to coal particles was observed in 20% coal slurry at 72°C and pH 2.0. The rate and extent of attachment were determined and the data fit the Langmuir adsorption model. The results compared qualitatively with selected adsorption data from other investigators forThiobacillus ferrooxidans.     

The animal ether phospholipid platelet-activating factor stimulates acidification of the incubation medium by cultured soybean cells

Addition of the animal ether phospholipid platelet-activating factor, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine, (PAF) stimulates medium acidification in cultured soybean (Glycine max L.) cells. The pH of the medium after 8–10 hours is on the average one pH unit lower than in controls. With fusicoccin an average pH difference of 1.7 units is reached. Phospholipids, glycerol, 1-oleyl-2-acetyl-sn-glycerol, 1-0-hexadecyl-sn-glycerol, and triolein at the same concentrations as PAF had no stimulatory effect on medium acidification. The detergents CHAPS and deoxycholate lead to alkalinization of the medium whereas lysophosphatidylcholine (LPC), a detergent with structural similarity to PAF, shows no effect.Abbreviations CHAPS (3-((3-cholamylopropyl) dimethylamino)-1-propanesulfonate) - DOC deoxycholic acid - FC fusicoccin - LPC lysophosphatidylcholine - OAG 1-oleyl-2-acetyl-sn-glycerol - PAF platelet-activating factor = 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine - IAA indole-3-acetic acid     

The effect of pH on production of citric and gluconic acid from beet molasses using continuous culture

Summary The effect of pH on the production of citric and gluconic acid, from beet molasses byAspergillus niger, was studied using continuous culture. At pH values above 2.5 gluconic acid was the major product, citric acid being the predominant product at low pH values. The optimum specific activities of citrate synthase, aconitase, NAD-linked isocitrate dehydrogenase, and NADP-linked isocitrate dehydrogenase occurred at pH 4 and of glucose oxidase at pH 5.     

Cell removal from fermentation broth by flocculation + sedimentation

Summary Cell separation by flocculation+sedimentation ofStreptoccocus equisimilis cultivation for hyaluronate lyase recovery, was investigated as a function of the pH of the fermentation broth, using three different cationic flocculants. The polyelectrolyte Superfloc N-100 appears to be the best of the three flocculants tested; after treatmen of pH 6.0 and 120 min free sedimentation, the cells are sedimented at 20% of the initial volume and 80% of the volume remained as a clear supernatant without loss of enzyme activity.     

Xylanase ofChaetomium cellulolyticum: Its nature of production and hydrolytic potential

Summary Maximum xylanase production byChaetomium cellulolyticum was obtained in the culture supernatant after 30 h of growth at 37°C in basal medium containing 1% xylan at pH maintained between 6.5 and 7.5. Addition of 0.05% Tween 80 to the medium increased the enzyme production considerably. Xylanase production was found to be growth associated. The optimal conditions for enzymatic hydrolysis of xylan were found to be pH 6.0 and 50°C. During enzymatic hydrolysis, xylose, xylobiose and other xylooligosaccharides were liberated from xylan. The pH values for xylanase production and for xylan hydrolysis were closely related to the utilization of hemicelluloses of aspen wood for fungal protein production by this organism as reported in our earlier work.     

The isomaltulose synthesising enzyme ofSerratia plymuthica

Summary An intracellular enzyme was located inSerratia plymuthica which produced isomaltulose from sucrose. The enzyme was purified giving a preparation with a specific activity of 1,285. It has pH and temperature optima of 6.0 and 30°C, respectively. The enzyme was stable retaining 100% activity after 2 weeks at 30°C. It had an isoelectric point at pH 9.0, a Mr of 79,500 and the Km for sucrose was 65.3mM. The enzyme converted 40% (w/v) sucrose to isomaltulose with an efficiency of 87%.     

Some characteristics of the cellulase of Aspergillus candidus

Summary The effects of pH, temperature and substrate concentration on the cellulase (B-1,4-endoglucanase) activity ofA. candidus were studied. Maximum enzyme activities were obtained when the concentration of the substrate (CMC) was 6 mg per ml, at pH 4, and temperature 50 C. The enzyme retained 85% of its original activity under optimal conditions of pH and temperature after 36 hours of incubation. The Km constant of the reaction was calculated as 2.3 mg of CMC per ml and the energy of activation of the enzyme as 7.92 k cal per mole.     

Glucose isomerase activity of streptomyces kanamyceticus

Summary Streptomyces kanamyceticus produces a significant level of intracellular glucose isomerase when grown in submerged culture. The optimum temperature for enzyme activity is 90°C, but the optimum pH is changed by the kinds of buffer solution used. The activity is higher at pH 7.0–9.5. Treatment of cells with cetyl trimethyl ammonium bromide extracts almost the same amount of the enzyme as ultrasonic treatment. The selection of the method of treatment for enzyme extraction depends, however, on the nature of cell growth in synthetic or complex medium.     

Bioemulsifier production by an oleaginous yeastRhodotorula glutinis IIP-30

Summary A locally isolated oleaginous strain ofRhodotorula glutinis strain IIP-30 produced a growth associated extracellular emulsifying agent while utilizing glucose during fed batch fermentation under nitrogen limitation at 30°C and pH 4. 0. Similar optimum conditions were also noted for intracellular lipid accumulation.     

Removal of NH3-N from domestic waste water by fungi

Summary Nine species of fungi viz.,Aspergillus niger,A. flavus,A. terreus,Fusarium solani,Mucor sp.,Neurospora crassa,Penicillium janthinellum,Trichoderma harzianum andTrichothecium roseum were evaluated for their potential to remove NH₃–N from domestic waste water. Of the fungi tested,A. flavus was found to be the most effective in the removal of NH₃–N. Maximum reduction (92%) of NH₃–N by this organism was observed at pH 8.0 at 20°C.     

Immobilization of glucoamylase on naphthyl cotton cloth

Summary Aspergillus niger glucoamylase was adsorbed to -naphthyl cotton cloth by hydrophobic interaction. The adsorbed enzyme was cross-linked with glutaraldehyde. The immobilized glucoamylase exhibited greater pH dependence though the optimal pH did not change. The immobilized glucoamylase in a packed bed column completely hydrolysed 5% soluble starch at a specific velocity of about 4. Used naphthyl cloth could be regenerated by heating in 2 N NaOH at 100°C for 1 hour.     

Mitochondrial K + transport: effect of N-ethyl maleimide on 42 K flux

The energy-linked flux of K⁺ into rat liver mitochondria is found to be stimulated by the sulfhydryl reagent, N-ethyl maleimide. The stimulation of K⁺ influx by N-ethyl maleimide is observed only at alkaline external pH. N-ethyl maleimide also stimulates efflux of K⁺ from the mitochondria. The stimulation by N-ethyl maleimide of K⁺ influx, but not K⁺ efflux, is dependent on the availability of metabolic energy. It is suggested that the effect of N-ethyl maleimide on K⁺ influx may be secondarily the result of an inhibition of phosphate-hydroxyl exchange. The dependence of energy-linked K⁺ influx on the external pH may be interpreted as evidence for a role of OH^? as a counterion accompanying K⁺ through the mitochondrial pump mechanism.     

Study of a bacterial hydantoinase (dihydropyrimidinase) activity using alginate beads and a cell recycle system

Summary This report describes the production of N-carbamyl--alanine, by resting cells ofPseudomonas putida, in two types of continuous fermentation processes: alginate-immobilized cells in a continuous stirred tank reactor and a free cell recycle system using microporous membranes. At pH 9,0 both systems resulted in a more efficient substrate conversion and a higher yield than at pH 8,0 although they had a similar performance.     

Development of a fermentation procedure to produce a tempe-related food using common beans as substrate

Summary A basic procedure was developed to produce a tempe-like product using the mouldRhizopus oligosporus and black common beans (Phaseolus vulgaris) as substrate. The initial pH of the substrate was 5.8, and fermentation was conducted at 37°C with a relative humidity of 70% for 72 hrs. Levels of soluble solids and soluble protein increased dramatically as a result of fermentation. Some changes were as well observed in fatty acid contents of fermented samples. It was concluded that the common bean used was an acceptable substrate for preparing this product.