Journal of Fermentation Technology最新文献

Acetone-dried cells of Rhizopus chinensis (with a 1,3-positional specificity lipase) were investigated for the interestierification reaction of olive oil and methyl stearate. First, the culture conditions for intracellular lipase production were examined, and then the activities of dried cells obtained from immobilization in Biomass Support Particles (BSPs) were compared with those of freely suspended cells.

It was clear from cultivation of freely suspended cells that intracellular lipase activity for the interesterification reaction was enhanced sifnificantly by the presence of oleic acid, oil, and tea oil, but that the presence of glucose reduced the activity.

The specific activity of dried cells within BSPs increased 7-fold compared with that obrained from freely suspended cells.

The process presented here, using immobilization within BSPs, can provide cells directly as a catalyst with high activity, where cells become immobilized simply during batch operation, and no special preparation of cells is necessary. Therefore, the reaction system using dried cells immobilized within BSPs is a promising interesterifcation process for industrial applications.

In order to produce l-arginine efficiently, continuous culture was attempted using an l-arginine producing strain of Corynebacterium acetoacidophilum, MC-13. l-Arginine production by strain MC-13 decreased after shifting from fed-batch culture to continuous culture because various strains with reduced or no l-arginine productivity, including l-arginine auxotrophs, appeared in addition to the original l-arginine producer. Strain SC-190, isolated from the continuous culture broth of strain MC-13, produced l-arginine on cultivation in a stable fashion for more than 250 h. It is suggested that strain SC-190 acquired a lower susceptibility to the inhibition of growth and l-arginine production by l-arginine than the parental strain MC-13 due to this stabilization.

Bacillus macerans enzyme (BME)-derived high molecular weight dextrins, which are by-products in the course of the industrial production of cylodextrins, were isolated and their chemical structures were characterized.

Dextrin I was obtained in a yield of about 24% from BME-hydrolyzate (a mixture of dextrin and cylodextrins, 50% each) of potato starch by fractionation with an ultrafiltrator having a membrane of cut-off molecular weight 2.0 × 10⁴. Dextrin II was obtained in a yield of about 15% from BME-hydrolyzate (a mixture of dextrins and cyclodextrins, 70 : 30) of Dextrin I by the same method.

Dextrin I and II consisted of dextrin having molecular weights over 20 × 10⁶ and dextrins having molecular weights 4 × 10³−1 × 10⁵ in the ratio of 80 : 12 and 66: 15, respectively.

The results of hydrolysis by β-amylase and methylation analysis indicated that the average, exterior and interior chain lenghts of the dextrins having molecular weights over 20 × 10⁶ and 4 × 10³−1 × 10⁵ from Dextrin I were 16.5, 8.2 and 7.3, and 11.5, 6.9 and 3.6, respectively, than those from Dextrin II were 13.6, 4.7 and 9.9, and 10.4, 5.1 and 4.3, respectively.

Because of less glutaminase activity, soy sauce made with a preparation of proteases from yellow-green Aspergilli contains less glutamic acid than soy sauce made by the traditional shoyu koji method. Thus, an acid treatment was developed to increase this amino acid in enzyme-made shoyu. Amide bonds of glutamine and asparagine in protein molecules were hydrolyzed at 100°C for 30 min with 1.3 N HCl (acid treatment). Using this method, glutamic acid per total nitrogen freed from various proteins by the concerted action of proteinases and peptidases of yellow-green Aspergillus increased to 1.0 to 3.8 times that of control (no acid treatment). An increase of about 31% of glutamic acid per total nitrogen resulted from the acid treatment method in soy sauce made with an enzyme preparation of proteases.

Escherichia coli harboring the gene encoding human interleukin-2 (IL-2) produces a mixture of two recombinant IL-2 species: one with the amino-terminal alanine (rIL-2) and the other having an additional methionine residue at the amino terminus (Met-rIL-2). Ways to increase the amount of rIL-2 and its proportion to the total IL-2 were tried. Among E. coli K-12 derivatives, N4830 was an effective producer of recombinant IL-2. The production of the mixture was greatly increased by optimizing the medium ingredients or culture conditions. However, the percentage of rIL-2 in the product decreased almost linearly with an increase of the total production of recombinant IL-2 and was less than 10% under optimal culture conditions. By adding 4.1 × 10⁻⁵ M maganese and 7.4 × 10⁻⁵ M ferric ions to the medium, we succeeded in raising the percentage of rIL-2 to 50% without any decrease of the total production.

Extraction of acrid and flavor compounds from horseradish and Wasabi with liquid- and supercritical carbon dioxide (SC-CO₂) is described. It was possible to form acrid and flavor compounds by enzymatic reaction in liquid- and SC-CO₂ as well as to extract them with liquid- and SC-CO₂. A typical acrid component, allyl-isothiocyanate (AITC), formed enzymatically from a corresponding precursor was found to be separated from freeze-pulverized horseradish with CO₂ at 20 MPa and 20°C without decreasing its peroxidase activity. Therefore, the residue after the extraction would be able to be used as a commercial source of peroxidase. The extracted AITC could be collected by forming the inclusion complex with β-cyclodextrin. The included AITC was very stable and is expected to be utilized as an additive to spices and foods.

The use of an anaerobic digester slurry of cattle waste for the reclamation of acid mine water was examined. When the digester slurry was mixed with acid mine water, anaerobic digestion, including sulfate reduction and methanogenesis, was enhanced. In the mixture of acid mine water and the digester slurry, sulfate reduction proceeded without diminishing methanogenesis. The digester slurry and its supernatant (SDF-sup) showed a significant capacity to act as a strong alkaline reagent, and the pH of the acid mine water was markedly elevated by the addition of the digester slurry of SDF-sup even at the low ratio of 1% (v/v). Precipitation of heavy metals in the acid mine water occurred as the pH was elevated by the addition of SDF-sup. When the digester slurry was added at the ratio of 5% (v/v) to acid mine water which had been pretreated with SDF-sup, the rate of sulfate reduction increased with increasing the concentration of sulfate in the mixture up to about 1,400 mg·l⁻¹. In acid mine water pretreated with SDF-sup and supplemented with the digester slurry at the ratio of 5% (v/v), the maximum amount of sulfate reduced within 20 d of incubation was about 1,000 mg·l⁻¹, and the maximum rate of sulfate reduction was about 120 mg SO₄²⁻·l⁻¹·d⁻¹.