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.
By connecting a rhomboid unit for fermentation and an exchangeable tubular unit for extraction, a novel bioreactor was designed to produce high concentration of ethanol solution from non-peeled sugar cane chips by means of a cyclic system for exchanging old chips with new ones. The rhomboid and tubular units were packed with 1.0–1.5 mm biocatalyst entrapped yeast-cells with Al alginateand cane chips of 2.0–3.0 mm in width, respectively. The volume ratio of the two units was 1.0. At the start of the first cycle, 2 g/l of Al2(SO4)3 14–18 H2O solution was added to the bioreactor, where the ratio of the solution to the working volume was 0.85. Both sugar extraction and fermentation were anaerobically performed at pH 2.5 and a temperature of 30°C by circulating the solution through the two units. After each cycle, the tubular unit was exchanged for a new unit packed with new chips. The combined solution of free ethanol and the ethanol obtained by pressing the old chips was re-used as the circulating solution.
When the volume ratio of the biocatalyst to the total working volume was 0.1 and the amount of dried cane chips in the tubular unit was 200 g/l, 16% (w/v) ethanol was produced after 7 cycles. Each cycle was established at about 20 h. The number of free cells in the circulating solution was only 2×107/ml after 7 cycles.
Mycelia from Aspergillus terreus K 26 were flocculated with a polyelectrolyte complex consisting of potassium poly9vinyl alcohol) sulfate (KPVS) and poly(diallyldimethyl-ammonium chloride) (PDDA) by three different methods: (a) PDDA was added into the broth obtained from precultivation of the hyphal inoculum in the presence of KPVS; (b) use of KPVS and PDDA was reversed from that in method a; (c) after the precultivation in the absence of the polymer, the mycelia were harvested, dispersed in 0.1 M phosphate buffer containing PDDA, then flocculated by addition of KPVS. The three types of the flocculated mycelia were investigated concerning growth and itaconic acid production in shake flask cultures. Viscosity and sedimentation were further examined to characterize the flocculated mycelial broths. A slight inhibition caused by flocculation on growth and acid production was observed at the beginning of repeated cultivation, but this was eliminated when cultivation in the fresh medium was repeated. There was no marked difference in the specific rates of acid production between fre and flocculated cells. Viscosity of the flocculated mycelial system was close to that of the medium, even while maintaining a cell concentration of 2 g/dl. The poor sedimentation of mycelia was favorably imporved with these flocculation methods, especially with methods b and c.
The effects of the impeller diameter and width on the volumes of the micromixing and macromixing regions, and on the circulation time distribution were investigated at various agitation speeds to formulate the relationships of them in emperical equations. A fermentor was a 10-l capacity, which was equipped with a turbine impeller with six flat balades and aerated at 1 vvm. It was found that the volumes of the micromixing and macromixing regions depended on the tip speed of the impeller, ND, and the discharging performance of the impeller, ND2W, respectively, in the xabthan gum solution with concentrations of 0.9, 1.8, 2.7, and 3.9%. Empirical equations were derived to estimate the volume of each mixing region from the impeller diameter, D, impeller width, W, agitation speed, N, and consistency coefficient of the xanthan gum solution. On the other hand, the circulation time distribution could be estimated empirically from only the impeller diameter and agitation speed, regardless of variation in the impeller width and consistency coefficient of the xanthan gum solution tested.
A yeast growing at 48°C was isolated from soil and the strain was identified as Cryptococcus lactativorus. The aldose reductase which the strain produced was purified 114-fold with an overall recovery of 36%. The stability of the enzyme was higher than that of other aldose reductases. The half life of the enzyme was 800 h and 14 h at 30°C and 50°C, respectively. The enzyme showed the best activity with d-xylose. l-Sorbose and d-fructose were also reduced by the enzyme. The enzyme was active with both NADPH and NADH as a conenzyme, and the activity with NADH was 1.25 times higher than that with NADPH. The Kmapp value for d-xylose was 8.6 mM and the Vmaxapp was 20.8 units/mg NADH was used as a coenzyme. The Kmapp values for NADPH and NADH were 6μM and 170 μM, respectively, when d-glucose was used as a substrate.
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, QCH4 and growth yield, YX/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 QCH4 and μ under the optimum Eh condition were 210 ml CH4/g dry cell weight·h−1 and 0.11 h−1, respectively.
The distribution of rare actinomycetes in 237 soil samples from various locations throughout Japan was investigated using a special isolation medium, HV agar.
The populations (colony forming units) of these actinomycetes per gram of dried soil were Microtetraspora 6 × 103, Saccharomonospora 1.7 × 104, Dactylosporangium 5.4 × 104, Streptosporangium 1.2 × 105, Microbispora 1.4 × 105, Nocardioforms 1.9 × 105, and Micromonospora 6.8 × 105. Streptomycetes 2.2 × 106, and Unidentified actinomycetes 0.9 × 106 were also observed.
Their distributions seemed to be associated with environmental factors such as soil type (Land Use Classification), soil pH, humus content, and the characteristics of the humic acid. In general, the largest populations were found in soils of cultivated fields, which were rich in humus and had pH values between 6.5–7.0.
However, the distribution of some genera in cultivated field soils (154 samples) was remarkable. The numbers of Microbispora and Streptosporangium were the largest in humus-rich acidic (pH 5.0–6.05) soils with low humic acid Δ log K values (black colored humic acid). Saccharomonospora was found most frequently in relatively humus-poor alkaline (pH 7.0–7.5) soils having higher Δ log K values (brown humic acid).
Dactylosporangium and Microtetraspora, Saccharomonospora, and Micromonospora were most frequently isolated from mountainous forest soils, level-land forest or cultivated field soils, and pasture soils, respectively.
There is a possibility of developing a new kind of saké in which the refreshing sour taste of citric acid is introduced. In this study, we bred a new mutant of Aspergillus usamii mut. shiro-usamii that produced much citric acid. The koji prepared with the mutant contained about 20 mg of citric acid per gram of dry koji, twice that of the koji of the parental strain. The activities of a-amylase, glucoamylase, and acidic protease in the koji prepared with the mutant were 82%, 94%, and 95%, respectively, those of the parental strain. Using this koji with the mutant, saké was produced. The levels of citric acid and isoamyl acetate were 5.1 and 1.4 times, respectively, those of saké prepared with koji of A. oryzae. Sensory tests indicated that saké made with koji with the mutant was refreshingly sour, with a good aroma.
The cell-free extract of Brevibacterium fuscum DC33 contained three kinds of hydroxysteriod dehydrogenase (3a-, 7a-, and 12a-hydroxysteriod dehydrogenases). 7a-Hydroxysteroid dehydrogenase (EC 1.1.1.59) was purified to electrophoretical homogeneity by ion exchange chromatography, affinity chromatography, and preparative electrophoresis. Its molecular weight was 104, 000 and the enzyme was composed of four identical subunits. The enzyme had an optimum pH of 5.3 for dehydrocholic acid reduction, and around 10 for cholic acid oxidation. It was stable in a pH range of 5.7 to 10.5 at 5°C overnight. The enzyme was most active at 25° to 30°C. The activity was not affected by incubation at 30°C for 30 min, but it was lost at 40°C for 30 min. Withe the assumption of two-substrate kinetics, we calculated various kinetic constants for dehydrocholic acid, 7, 12-diketolithocholic acid, 12-ketochenodeoxycholic acid, and 3, 12-diketolithocholic acid (for the structure of bile acids, see Table 2) together with NAD+ or NADH. The enzyme was active only toward hydroxysteroids with a 7a-hydroxyl group. The production of 7-ketochenodeoxycholic acid from cholic acid and of 3, 12-diketolithocholic acid from dehydrocholic acid by the purified 7a-hydroxysteroid dehydrogenase was confirmed by thin-layer chromatography.
12a-Hydroxysteroid dehydrogenase was purified by a similar method. It was active toward hydroxysteroids with a 12a-hydroxyl group.
3a-Hydroxysteroid dehydrogenase was purified by preparative electrophoresis. It was active toward hydroxysteroids with a 3a-hydroxyl group.
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：