Journal of Fermentation Technology最新文献

We examined the productivity of mirin-making and the quality if the mirin produced using koji prepared with a new mutant (mutant CA) that originated from Aspergillus usamii mut. shiro-usamii. The koji prepared with the mutant CA contained a large amount of citric acid. Therefore, the concentration of the brewing alcohol added to prevent bacterial contamination of the mash was decreased to 6.0% from the 12.5% needed when the mash was made with koji of the conventional Aspergillus oryzae. A mash containing this low concentration of alcohol was incubated with koji of the mutant CA and enzyme preparations such as α-amylase (6,000 DU/kg mash) from Bacillus subtilis and acidic protease (1,000 PU/kg mash) from Aspergillus niger. The starch and protein in this mash was sufficiently digested. The yield of mirin obtained from this mash was high (96% based on the mash weight), and the resulting mirin contained much citric acid, malic acid, succinic acid, nitrogen compounds, isomaltose, isomaltotriose, and oligosaccarides. The taste of the mirin was refreshingly sour and flavorsome.

Among about 200 Rhizopus strains isolated in Thailand, Rhizopus sp. MB46 was selected as a producer of raw cassava starch-digestive glucoamylase. Rice bran was effective for the enzyme production in a solid culture as well as wheat bran. Addition of turpentine oil into the rice bran solid culture increased the productivity. Rhizopus sp. MB46 was found to produce glucoamylase in a liquid culture containing 1% rice bran but not in one consisting of 10% raw cassava starch of 2% glucose. The productivity per 1 g solids in the medium in liquid culture was finally improved 6-times by utilization of n-hexane-treated rice bran, supplement of 0.1% meat extract and addition of gauze as a support. The activity was superior to that in turpentine oil-supplemented solid culture.

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 K_m^app value for d-xylose was 8.6 mM and the V_max^app was 20.8 units/mg NADH was used as a coenzyme. The K_m^app values for NADPH and NADH were 6μM and 170 μM, respectively, when d-glucose was used as a substrate.

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.

A monoclonal antibody against recombinant thermostable α-amylase produced by Escherichia coli was isolated from serum-free medium and immobilized on Sepharose 4B. The adsorption equilibrium between α-amylase and the immobilized immuno-adsorbent showed a Langmuir type isotherm. The breakthrough curve calculated numerically using the averaged volumetric coefficient coincided well with the experimental data. More than 90% of the activity of bound α-amylase could be recovered by eluting with glycine-HCl buffer (pH 2.5). The elution profile at pH 2.5 became sharper with increasing temperature. By using an immuno-affinity column, the recombinant α-amylase produced by E. coli could be purified homogeneously from crude extract enzyme solution with two-step elution.

l-Methionine-enriched cells production of an ethionine-resistant mutant of Candida boidinii no. 2201 was greatly improved by the control of pH and by feeding of methanol and other medium components during cultivation in a jar fermentor. Under the optimal conditions, 38.5 g (as dry weight)_of cells abd 282 mg of pool methionine (intracellular pool of free l-methionine) per l of culture broth were obtained after 11 d of cultivation.

The culture conditions for production of l-methionine-enriched cells in continuous culture were investigated. With limited methanol in continuous cultivation, pool methionine productivity reached a maximum value of 1.14 mg·l⁻¹·h⁻¹ at a dilution rate of 0.05·h⁻¹. During methanol-limited growth in continuous cultivation, the pool methionine content of the mutant was about 20–35% higher than that in batch cultivation.

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.