Journal of Fermentation Technology最新文献

A mold, Chrysosporium pannorum AHU 9700, isolated from soil, was found to produce a very active inulin-hydrolyzing enzyme. The inulinase activity of this strain was induced by inulin, but not by sucrose, glucose, or fructose. The highest inulinase activity, 115 units/ml, was obtained under the optimum conditions. A crude enzyme preparation was active against inulin, levan, sucrose, and raffinose, but not melezitose. An inulin suspension of 10% was hydrolyzed completely at pH 5.6, 50°C, in 8 h, and inulo-oligosaccharides were detected in the initial stage of enzymatic reaction. Jerusalem artichoke extract was also rapidly hydrolyzed into fructose and small amounts of glucose. These results indicate that the C. pannorum crude enzyme contained exo- and endo-inulinases. The inulinase of C. pannorum AHU 9700 might be used industrially to prepare high fructose syrup from inulin-containing agricultural crops.

The overall effect of agitation on xanthan gum production by Xanthomonas campestris ATCC13951 in a stirred vessel was mechanistically analyzed considering local variation of the specific production rate due to variation of shear stress in the vessel. The whole liquid volume in a fermentor was roughly divided into three regions; the micromixing region around the impeller with high shear stress, the macromixing region dominated by a circulating flow and the stagnant region. The value of the shear rate was first ascertained by experiments in order to obtain a picture of shear rate variation in a radial direction from the impeller, and the equivalence between the volumes of the high shear stress region and micromixing region was confirmed. The shear stress obtained using a correlation between the shear rate at the impeller tip and Reynolds number of Wichterle et al. was used as a representative of the shear stress in the micromixing region, and the shear stress estimated by use of an empirical correlation between the average shear rate in a fermentor and agitation speed derived by Metzner et al. was adopted as a representative of the shear stress in the macromixing region. The information about the circulation time distribution was also used to take into account oxygen deficiency during circulation of liquid elements in the macromixing region, considering that oxygen from the gas phase was supplied mainly in the high shear region. The calculated values of xanthan gum concentrations which were obtained by the proposed simulation method agreed well with the experimental data in the time course of xanthan gum production at various agitation speeds. Experimental results of the relationship between the overall specific production rate and ND (N, agitation speed, and D, impeller diameter) was also verified by the proposed method.

The production of inosine by microbial conversion of 5′-inosinic acid (IMP) was investigated. Among the various strains of Streptomyces and Bacillus tested, Streptomyces aureus NCIB 9803 was selected for the microbial conversion process due to its high IMP-degrading activity. A maximum conversion yield of 0.43 (86% of the theoretical value) was obtained when IMP was added to the culture medium at 24 h. Kinetic studies with [8-¹⁴C] IMP showed that the difference from the theoretical values mainly attributable to the uptake of inosine by S. aureus.

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.

The effects of magnesium on excess uptake of phosphate in an aerobic-anaerobic activated sludge process were examined by the fill and draw procedure. The alternation of anaerobic and aerobic conditions in one cycle of fill and draw process was varied many ways.

The presence of sufficient magnesium was necessary for uptake of excess phosphate. When sludge contained more phosphorus than the upper limit of phosphorus content in the usual aerobic activated sludge, 2.5% by weight, magnesium was also contained in more than an ordinary amount (0.5%). Their contents in the sludge at the end of each cycle of the process were correlated with each other by a linear equation with the correlation coefficient of 0.99. When magnesium concentration was insufficient for the uptake of excess phosphate, its concentration in the treated water was of the order of 0.1 mg/l.

In the first anaerobic period both phosphate and magnesium were released, and in a successive aerobic period they were taken up again. The weight ratio of differential amounts of phosphorus and magnesium released or taken up changed with time in one cycle.

Dynamic behaviors of phosphate and magnesium removal against the step change of feed magnesium concentration also showed a stoichiometric relationship supporting the correlation equation above mentioned.

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.

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.