Journal of Fermentation Technology最新文献

The following results were obtained in the separation of yeast from yeast suspension or fermentation borth by crossflow filtration with or without backwashing, using a microporous ceramic membrane: 1) backwashing by the filtrate, which was supplied to the membrane by compressed air or by a suction pump, gave higher filtration flux, 2) there existed an appropriate filtrate volume for backwashing when the backwashing interval was fixed, 3) the initial filtration process with or without backwashing is described by the standard blocking filtration model, 4) the filtration flux at an arbitrary backwashing interval was roughly estimated using the values of the initial filtration rate and the filtration constant of the standard blocking filtration model, and memrbane whose filtration flux had been lowered were able to be regenerated by heating.

The stabilization of a pile of ground urban refuse was monitored during five months. Carbon dioxide evolution, temperature, moisture level, organic matter, and pH were measured regularly. The humification index (HI) of organic matter extracted by 0.1 M Na₄P₂O₇ plus 0.1 M NaOH was found to decrease linearly with time during the thermophilic phase from about 1.4 to 0.4. Turning of the pile caused a drop in the HI values, but the index increased again every time the temperature of the static pile reached 65°C. The value of the humification index in water extracts (HIw) reached a maximum after 4 d in the superficial layers and after 11 d at a depth of 30 cm. HIw values were found to decrease hyperbolically with time during the thermophilic phase.

Copper binding reducing activities of cell wall materials (CWM) prepared from cells of the yeast Debaryomyces hamsenii were examined. When CWM was treated with copper sulfate (0.1 mM CuSO₄), the copper was partially reduced from Cu (II) to Cu (I) and bound to CWM (below 10 nmol per mg dry wt.). The bound copper was mostly in the fraction of mannan-protein. Both copper-binding ability and protein content decreased with protease treatments. Mannan-protein prepared from CWM bound more copper than mannan did. This suggests that Cu (II) bound to the protein portion in CWM and was reduced to Cu (I). The optimum pH of copper reduction by CWM was about 5.0. The amount of copper bound to CWM increased with reducing agents and decreased with oxidizing agents. On the other hand, the copper uptake by yeast whole cells and spheroplasts was also stimulated by reducing agents, but inhibited by oxidizing agents. Furthermore, copper uptake by spheroplasts was stimulated in the presence of CWM. The optimum pH of copper uptake coincided with that of copper reducing activity. These results suggest that yeast cell wall not only supplies copper binding but also reduces copper, and the reduced copper is transported into yeast cells. The yeast cells may have copper-reducing proteins in the cell wall.

Production of l-iditol (iditol) from l-sorbose (sorbose) with d-sorbitol dehydrogenase coupled with NADH regeneration under methanol oxidation was studied with the resting cell system of a methanol yeast, Candida boidinii (Kloeckera sp.) no. 2201.

Maximum activities of iditol production and enzymes concerned with the production were found in cells grown on a medium containing methanol and d-xylose (xylose). The highest amount of iditol, 142–148 g/l (94–98% conversion rate), was obtained from 150 g/l of sorbose in the presence of 0.5 M methanol at pH 6.5. Intermittent control of the pH during the cell reaction gave a significantly higher amount of iditol than that obtained without such control. Freeze-thawing cells showed rather higher productivity than resting cells. The product was identified as iditol without contamination of its C-2 epimer, d-sorbitol, by high performance liquid chromatography.

The kinetics of enzymatic interesterification of oils and fats, using acetone-dried cells of Rhizopus chinensis immobilized on biomass support particles as a lipase catalyst, were investigated in batch operations at several constant water concentrations.

Even under microaqueous (i.e., low-water-content) conditions, not only interesterification but also hydrolysis occured, and the water content in the reaction system decreased. The reaction rates of interesterification and hydrolysis at constant water concentrations were determined.

For the reactions between olive oil and methyl stearate at several water concentrations, the parameters involved in the reaction model were determined by a trial-and-error method so as to make the calculated results correlate with the experimental data. The relationship between the parameters obtained and water concentration were examined.

The rate constants involved in the reaction model of both interesterification and hydrolysis increased or decreased monotonically with the increasing water content, while the apparent activity of the lipase catalyst for interesterification had a maximum value at a water concentration of about 50 ppm. This suggests that when the water content is excessive the hydrolysis activity of lipase is accelerated more than its interesterification activity, and that when the water content is too little lipase activity can not be activated for either hydrolysis or interesterification.

Enzymatic degradation of dehydrodivanillin (DDV) was studied using high performance liquid chromatography (HPLC) with an anaerobic DDV-degrading recombinant FE7 under both aerobic and anaerobic conditions. When 200 mg of FE7 cells were mixed with 40 μg DDV in 1 ml phosphate buffer (0.01 M, pH 7.0) and 10 mM mercaptoethanol and incubated at 37°C for 24 h under an O₂-free CO₂ atmosphere, about 20 μg of DDV was decomposed. Only 12 μg DDV could be degraded when the same reaction was done under aerobic conditions, suggesting that the reaction occurs more easily under anaerobic than aerobic conditions. Enzymatic degradation of DDV was performed using a cell-free extract as a crude enzyme solution under aerobic conditions in a similar way. A reaction product detected and analysed by thin layer, high performance liquid and gas chromatographies and mass spectrometry was found to be vanillin from enzymatic reaction mixture. This enzymatic activity was not detected in either the culture supernatant or the heat-inactivated control. These results suggest that there may be an intracellular enzyme system which is involved in the conversion of DDV to vanillin. This is the first report to study the enzymatic degradation of DDV by anaerobes.

A new autoregulator designated as IM2, which induces blue pigment production in Streptomyces sp. MAFF 10-06015, was discovered. The culture conditions developed here for the production of the pigment by the strain did not require the addition of an artificial inducer such as γ-nonalactone or the autoregulator of S. virginiae MAFF 10-06014, IM, which induces the production of virginiamycin by this microorganism. The major improvements in the culture conditions for spontaneous pigment production included the inoculation conditions and the dilution of the medium. The method of IM2 assay was established and the time courses of IM2 production were followed in the cultures using flasks and a jar fermentor. It was confirmed that IM2 released once into the culture filtrate from the cells was taken up into the cells again. The concentration of IM required to induce pigment production in Streptomyces sp. MAFF 10-06015 was 50 u·ml⁻¹. However a concentration of 200 u·ml⁻¹ of IM2 was unable to induce the production of virginiamycin in S. virginiae MAFF 10-06014.

Photoproduction of hydrogen gas by the green alga Chlorella pyrenoidosa was studied in a large scale culture of 2.1. Hydrogen was produced by adding sodium hydrosulfite directly to an algal suspension after anaerobiosis in darkness for activation of hydrogenase. The hydrogen production rate showed a characteristic course of an initial burst of gas then steady production, and this course appeared most clearly at cell concentrations around 0.6–0.7 kg/m³. In the final third phase, the hydrogen production rate gradually decreased until evolution ceased. The steady hydrogen evolution was inhibited 75% by a herbicide, DCMU, which blocks electron flow through photosystem II, indicating that the electron donor for hydrogen production was mainly water. The average light intensity within the culture vessel was measured with a diffusing sphere photoprobe. The rate of hydrogen evolution increased hyperbolically with the average light intensity. The duration of hydrogen photoproduction was shorter at higher light intensity due to the inhibition of hydrogenase by concomitantly released oxygen. The duration was shorter also at higher concentrations of algal suspension. It was foudd that the optimum concentration of algae, about 0.7 kg/m³ in this system, must be selected to maximize the yield of hydrogen.

In order to improve the productivity of raw cassava starch-digestive glucoamylase of Rhizopus sp. MB46 in a liquid culture, a mutant strain, AF-1, which is resistant to 2-deoxyglucose, was derived. The mutant strain produced glucoamylase in the presence of 0.5% glucose though the parent strain did not. With a rice bran liquid medium the productivity was over 2-times that of the wild type strain. A rice bran liquid medium supplemented with β-cyclodextrin was also effective for glucoamylase production. Other maceration enzymes were also produced at a higher level with mutant strain AF-1 than with the wild type strain in a liquid culture as well as in a solid culture. The elution patterns of these enzymes on CM-cellulose column chromatography were principally the same with both strains except for glucoamylase. When 10% of raw cassava starch and cassava waste were digested with the culture filtrate of mutant strain AF-1, glucose was produced in 7% after 60-h incubation and 3.2% after 48-h incubation, respectively.