Journal of Fermentation and Bioengineering最新文献

The pot ales of malt whisky (MW) and grain spirit (GS) were subjected to batchwise methane fermentation. The pot ale of GS could be more easily treated than the pot ale of MW. The substantial difference in performance seemed to be due to the amount of dextrin. Therefore, the pot ale of MW was first hydrolyzed enzymatically and treated using the same method. As a result, the treatment time necessary for methane fermentation was shortened from 15 d to 11–12 d. Koji mould was cultivated aerobically in the pot ale of MW as a substitute for enzymatic hydrolysis. The dextrin content of the MW pot ale subjected to enzymatic hydrolysis was only 40% of that achieved by cultivation of koji mould. The supernatant of the culture broth was then treated continuously by methane fermentation using a novel upflow anaerobic filter process (UAFP) reactor. A maximum loading rate of 10.8 g/l/d was achieved, corresponding to a treatment time of only 18 h. The residual dextrin in the supernatant of the culture broth was completely decomposed by methane fermentation, as deduced from the elution curve after gel-permeation chromatography.

An ingenious device in the use of a multiple regression analysis model for better prediction of state variable changes in bio-processes is proposed. A correction factor was introduced in the regression equations for the estimation of specific rate parameters taking into account the data distribution resulting in the improvement of the prediction of glucose isomerase production by a Streptomyces fusant during a batch cultivation with periodical monitoring.

We examined the relationship between trehalose metabolism and the leavening ability of bakers' yeast grown in the presence of NaCl. The yeast cells were cultured at 30°C in media (5% glucose, 1% peptone, 0.5% yeast extract, 0.1% KH₂PO₄, and 0.1% MgSO₄) containing 0–3% NaCl. The cells were grown to the stationary phase for 24 h irrespective of the NaCl concentration in the medium, but the cell yield was decreased by addition of NaCl. The presence of 1% NaCl in the medium transiently enhanced the accumulation of intracellular trehalose after 24 h, however, the accumulated trehalose was hydrolyzed during further growth, and 2 or 3% NaCl decreased the intracellular trehalose content. The neutral trehalase activity in yeast cells grown for 24 h increased with increasing NaCl concentration, while the acid trehalase activity decreased. Trehalose-6-phosphate synthase (TPS) activity in cells grown for 24 h increased significantly in the presence of 1 and 2% NaCl, but decreased in the presence of 3% NaCl. When we determined the leavening ability of bakers' yeast cells grown for 24 h in the presence of 0–3% NaCl using dough without addition of NaCl, the leavening ability increased with increasing NaCl concentration in the culture medium. The cells having the highest leavening ability were those that had the lowest amounts of trehalose and the lowest TPS activity among the conditions tested. The leavening ability of bakers' yeast grown in the presence of NaCl appears not to correlate with intracellular trehalose content.

We screened oligotrophic microorganisms for those which were capable of reducing the concentration of yttrium (Y), a representative of the rate-earth elements, in culture medium. From 465 strains of oligotrophic microorganisms (grown on $\text{1}\text{100}$ diluted nutrient agar) isolated from soil and river water samples, 7 strains capable of reducing the concentration of Y in the diluted nutrient broth containing 5 ppm Y were selected. Three strains capable of reducing the concentration of Y to a great extent were identified as Variovorax paradoxus (strain Y-1) and Comamonas acidovorans (strains Y-2 and Y-3). Energy dispersive X-ray analyses revealed that V. paradoxus Y-1 incorporated Y into both the cell and excreted materials. The three strains tended to reduce the concentrations of mostly light rare-earth elements such as La, Ce, Pr and Nd, and intermediate elements such as Tb, Dy, Ho and Er to some extent, but did not reduce the concentrations of heavy elements such as Tm, Yb and Lu. Although V. paradoxus Y-1 could not reduce the concentration of trivalent metal ions such as Fe³⁺ and Cr³⁺ (5 ppm) which were added individually to the $\text{1}\text{100}$ diluted nutrient broth, when both Y and Fe³⁺ or Cr³⁺ were added to the broth, the concentration of Fe³⁺ or Cr³⁺ was reduced concomitantly with that of Y. In the case of divalent metal ions such as Mn²⁺, Cu²⁺ and Fe²⁺, such a phenomenon was not observed. Y induced the production of the extracellular materials by V. paradoxus Y-1, suggesting that Y might affect the physiological activity of this strain.

Two lysis genes, gene-t and gene-e, encoded in bacteriophage T4 were cloned in vectors pUC118 and pET26b(+), respectively. Immediately after the induction of gene-t expression, growth of Escherichia coli JM 109 cells was halted. Since the expression of gene-t was toxic to the cells, the expressed gene-t product (gp-t) could not be detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). On the other hand, expression of gene-e cloned in vector plasmid pUC118 did not give rise to any detectable change in E. coli JM 109 cells; normal cell growth was observed, and the gene-e product (gp-e) was identified by SDS-PAGE. Lysis genes cloned in vector pET26b(+) were expressed in BL21 (DE3) host cells carrying plasmid pLysS, which encodes T7 lysozyme. It is thought that the expressed protein is translocated into the periplasmic space driven by the signal peptide of the peIB outermembrane protein of E. coli fused in the frame at the N-terminal end of the lysis protein. Immediate cell disruption was observed when the gene-t cloned in pET26b(+) was expressed in the logarithmic growth phase. β-Galactosidase activity was observed in the centrifuged supernatant of the cell culture producing gp-t. Almost 100% of the activity of the β-galactosidase produced in the BL21(DE3)pLysS cells was identified in the supernatant 30 min after the start of the induction period of gene-t, indicating that complete cell disruption had occurred at that time. The production of gp-e with the N-terminal fusion of the signal peptide of pelB did not cause immediate cell lysis, but it did result in a morphological change in the BL21(DE3)pLysS cells, from rod-shaped to elliptical. Resuspension of the gp-e-producing BL21(DE3)pLysS cell nellet with pure water caused cell lysis followed by the release of β-galactosidase into the medium. Almost 100% of the β-galactosidase activity was identified in the resuspended supernatant.

A xylanase gene xynG1 was isolated and sequenced from Aspergillus oryzae KBN616 used for making shoyu koji. The structural part of the xynG1 gene was found to be 725 bp and was predicted to be interrupted by a single intron which was 62 bp in size. The mature XynG1 was predicted to be 189 amino acids in size and had high amino acid homology to other fungal xylanases classified in family 11 glycosidase. The XynG1 was detected in the culture supernatant of A. oryzae KBN616 grown in xylan medium but was not detected when A. oryzae KBN616 was grown in glucose medium. The xynG1 gene was introduced into A. nidulans and was found to be expressed even in the glucose media. This expression pattern was confirmed using a luciferase gene as a reporter in A. nidulans.