Journal of Fermentation Technology最新文献

Screening of a strain which contained a large amount of ubiquinone Q-10 and a variety of isoprenoid compounds using different culture conditions and mutations was carried out.

Protomonas extorquens TK 0045, which was found to contain carotenoid pigments, Hop-22(29)-ene, and Hopan-22-ol, was selected on the basis of cell yield and the content of ubiquinone Q-10. The contents of ubiquinone and sterols increased as the age of the culture increased, and reached a maximum level during the stationary phase.

The contents of ubiquinone, sterols and carotenoid pigments, and ubiquinone homologs produced by P. extorquens TK 0045 were varied using mutagenesis. Mutants that had increased or decreased contents of carotenoid pigments were obtained with a high frequency. Most mutants had varying contents of other isoprenoid compounds. The ubiquinone homologs obtained by mutagenesis varied with a high frequency, and mutants which possessed increased levels of ubiquinone Q-9, Q-11 or Q-12 were isolated. However, the major ubiquinone component in these mutants was Q-10 the same as that in the wild strain. The production of ubiquinone was increased considerablyby repeated mutagenesis, with the content of ubiquinone produced by the third generation mutant (strains HB-5) being approximately 3.3 mg·g dry cell⁻¹ (2.5 times that of the wild strain). The acquisition of mutants exhibiting altered synthesis of carotenoid pigments would be useful for increasing the content of ubiquinone Q-10 in bacterial cells.

The growth kinetics of Aspergillus niger on a solid support i.e. sugarcane bagasse, impregnated with a liquid glucose medium, were investigated under different culture conditions. The water activity of the medium, the amount of spore inoculum and the support particle size were shown to be critical factors for mold growth. The elevated rates of growth observed with high substrate concentration media demonstrated the feasibility of the method for culturing filamentous fungi.

Segregation of diploid strains by a haploidizing agent was used to improve citric acid producing strains of Aspergillus niger. Stable diploid strains were obtained via protoplast fusion between two citric acid-producing strains from different genealogies, one for shaking culture and the other for solid culture. Diploid strains were treated by benomyl as a haploidizing agent, and many segregants were obtained. Prototrophic segregants were selected and their haploidy was confirmed by their conidial size and DNA contents. The prototrophic segregants were very variable in their citric acid productivities, some of them better either in shaking culture or in solid culture than both the parental strains. The presence of methanol stimulated citric acid production by the parental and the diploid strains. However, all prototrophic segregants derived from one diploid strain had higher productivities in solid cultures without methanol than in those with methanol.

Starch from wheat flour was enzymatically hydrolyzed and used for ethanol production by Zymmonas mobilis. The addition of a nitrogen source like ammonium sulfate was sufficient to obtain a complete fermentation of the hdyrolyzed strach. In batch culture a glucose concentration as high as 223 g/l could be fermented (conversion 99.5%) to 105 g/l of ethanol in 70 h with an ethanol yield of 0.47 g/g (92% of theoretical). In continuous culture the use of a flocculent strain and a fermentor with an internal settler resulted (D=1,4 h⁻¹) in a high ethanol productivity of 70.7 g/l·h with: ethanol concentration 49.5 g/l, ethanol yield 0.50 g/g (98% of theoretical and substrate conversion 99%.

Lac⁺ recombinant plasmids encoding a β-galactosidase fused protein and lactose permease of Escherichia coli were introduced Zymomonas mobilis. The fused protein was expressed with 450 to 5,860 Miller units of β-galactosidase activity, and functioned as lactase. Raffinose uptake by Z. mobilis CP4 was enhanced in the plasmid-carrying strain over the plasmid-free strain, suggesting that the lactose permease was functioning in the organism. Z. mobilis carrying the plasmid could produce ethanol from lactose and whey, but could not grow on lactose as the sole carbon source. It was found that the growth of the organism was inhibited by either galactose of the galactose liberated from lactose.

The effect of Eh on the methanogenesis of methanol by Methanosarcina barkeri strain Fusaro was studied in pH-controlled anaerobic batch cultures at 37°C, in which the Eh of the culture medium was controlled by the addition of Ti(III)-citrate at values ranging from −340 to −520 mV. The changes in Eh revealed that the specific growth rate, μ, specific methane production rate, Q_CH4 and growth yield, Y_X/S were optimum under an Eh between −430 and −520 mV, while they decreased at the higher Eh of −340 mV. The maximum values of Q_CH4 and μ under the optimum Eh condition were 210 ml CH₄/g dry cell weight·h⁻¹ and 0.11 h⁻¹, respectively.

Glutaminase activity was found in a water extract of a wheat bran koji (extracellular fraction) of Aspergillus oryzae strains Lee-1, H-16 and MA-27-IM isolated from a commercial koji ssed for soy sauce fermentation, as well as in thier mycelia (intracellular fraction). Both the intracellular and the extracellular glutaminases were purified from strain MA-27-IM. Polyacrylamide gel electrophoresis of each purified preparation gave a single band with identical electrophoretic mobility. The molecular weight of the intracellular and the extracellular glutaminases were estimated to be approximately 113, 000. Both preparations hydrolyzed various γ-glutamyl compounds besides l-glutamine but did not exhibit asparaginase activity. Further investigation of these preparations inidicated that these glutaminases possessed almost the same properties, suggesting their similarity.