Anomalous uptake ofd-ribose byRhodotorula gracilis

d-Ribose was found to enter the cells ofRhodotorula gracilis by a mechanism resembling simple diffusion (proportionality between rate and concentration, no effect of inhibitors, of temperature, of other sugars) at concentrations from 0.001 to 10mm. With a lag of about 1 hour,d-ribose was oxidized and, with a lag of about 20 hours, it could serve as a growth substrate. The transport step appears to be rate-limiting for the subsequent metabolic processes. The oxidation was stimulated byd-xylose but unaffected byd-glucose. Dedicated to Academician Ivan Málek on the occasion of his 60th birthday     

Production of laccase byCurvularia sp.

ACurvularia sp. isolated from soil was found to contain laccase activity toward guaiacol as substrate. The organism produced an extracellular laccase in a medium containing yeast extract, peptone and dextrose. Initial medium pH 4.0 and cultivation temperature 30°C were found to be most suitable for maximum enzyme production. The optimum pH and temperature for laccase activity were found to be 5.2 and 50°C, respectively. Under optimum conditions, the enzyme had aK _m (guaiacol) of 0.75 mmol/L and aV of 1.50 CU min⁻¹ ml⁻¹. Some divalent metal ions inhibited laccase activity at very low concentrations.     

Production of cellulases by Thermomonospora sp.

Glucose, cellulose, Avicel, and Solka Floc were utilized as substrates for growth of Thermomonospora sp in order to study the induction–repression characteristics of its associated cellulase system. While glucose proved to be an effective repressor of the cellulase enzymes, the other three substrates induced relatively high levels of enzyme activity as measured by the filter paper assay. On a unit cell mass basis the highest values of cellulase activity were obtained when Avicel was utilized as the carbon and energy source. The nature of the cellulosic material and its initial concentration were identified as two very important parameters of the induction process.     

黑竹冲河两种蜉蝣种群动态、生活史、生产量及营养基础研究

蜉蝣在河流生态系统中发挥着重要作用.2003年6月至2004年6月间对汉江流域二级河流--黑竹冲河蜉蝣优势种类的生产力及其营养基础进行了为期一周年的调查研究.结果表明,优势种小裳蜉(Leptophlebia sp.)和蜉蝣(Ephemera sp.)的生活史均为一年两代,两世代之间界限比较明显;小裳蜉的羽化主要发生在秋季和冬季,而蜉蝣的羽化主要发生在夏季和冬季.小裳蜉和蜉蝣种群的生物量和多度均出现两次峰值.采用体长频率法测算的周年生产量分别为:小裳蜉,38.0362g/m2·a,P/B为11.4;蜉蝣,76.0318g/m2·a,P/B为11.8.两种蜉蝣的主要食物为无形态碎屑和硅藻,其中:无形态碎屑分别占小裳蜉和蜉蝣食物组成的81.7% 和 94.6%,对其生产量的贡献率为 59.2% 和84.9%;硅藻占小裳蜉和蜉蝣食物组成的16.8%和1.5%,对其生产量的贡献率为36.4%和4.1%.     

Antibiotic Production by Cutaneous Brevibacterium sp.

Three isolates of a Brevibacterium species isolated from human skin produced an antibiotic active against Gram positive and Gram negative bacteria. The active compound is most probably a peptide with'a molecular weight in the range 1100–1400; there is chromatographic similarity to compounds such as tyrothricin. Production of such a compound in vivo could contribute to microbial interaction in, for example, tinea pedis.     

Production of valine by a Bacillus sp.

A bacterium isolated from Burdwan (India) soil was found to accumulate L-valine in the growth medium and identified to be a strain of Bacillus subtilis. The strain is able to grow and accumulate valine in a purely synthetic medium, but supplementation of the synthetic medium with either Casamino acids or yeast extract or with both, significantly improves the yield. The entire fermentation period can be divided into a growth phase and a production phase, which can be prolonged by adjustment of pH to the neutral range. Among the different carbon and nitrogen sources tested glucose at 8.5% and L-glutamic acid at 0.8%, respectively, were found most suitable. Cane sugar molasses tested as a substitute for glucose significantly stimulated growth but valine production was less. Different vitamins tested stimulated growth and valine yield and an inoculum level of 10% (v/v) of the medium was found to be optimal. The yield of valine under optimal conditions was found to be 4.53 g per litre of the medium. Valine has been isolated in crystalline form from the fermented broth by ion exchange resin chromatography and found to be a pure sample of the L-isomer.     

Production of Polyalcohol by a Corynebacterium sp.

A gluconate-utilizing strain of Corynebacterium was found to be capable of utilizing aldopentoses and producing corresponding pentitols when pentoses were added to the medium containing gluconate as a carbon source during the cultivation of the organism.

Pentitols produced from d-xylose, l-arabinose, and d-ribose were isolated from the cultured medium and identified as xylitol, l-arabitol, and ribitol, respectively.

The pentitol production was significantly influenced by the concentration of gluconate in the initial medium and that of pentose added to the medium during the cultivation.

The amount of xylitol, l-arabitol, and ribitol reached 69 mg/ml, 60 mg/ml, and 32 mg/ml, respectively, after 14 days of incubation when pentoses were added to the medium containing 9.6% potassium gluconate to give a final concentration of 150 mg/ml.     

Synthesis of L-phenylalanine analogs byRhodotorula glutinis. Bioconversion of cinnamic acids derivatives

The synthesis of L-alpha aromatic amino acids by amination of forty-one derivatives of cinnamic acid and related compounds is tested with the yeastRhodotorula glutinis.     

Accumulation of lipid byRhodotorula glutinis in continuous culture

Summary Rhodotorula glutinis accumulated 35% (w/w) lipid when grown nitrogen-limited in a chemostat at a dilution rate (D) of 0.02^–1 . At D = 0.10 h^–1, the lipid content was only 15% (w/w). Dual limitation of nitrogen and phosphate increased neither the amount of lipid produced nor the lipid yield (14g lipid per 100g glucose consumed). The fatty acid composition was unchanged by the growth rate.     

Production of trypsin inhibitor by a Cephalosporium sp.

Conditions for the production of the trypsin inhibitor from Cephalosporium sp. KM 388 were investigated. Polypeptone-meat extract-glucose medium supported excellent production of the trypsin inhibitor. In this medium, polypeptone and meat extract were utilized both as carbon and nitrogen sources and as limiting substrates for the cell growth. Glucose was consumed during the stationary growth phase and prevented the disappearance of inhibitor activity. Cephalosporium sp. KM 388 grew at a rate of a first-order reaction for the cell concentrations. Trypsin inhibitor production paralleled cell growth. At 27 degrees C the maximum specific rates of growth and inhibitor production were 0.14 h-1 and 2.1 U of inhibitor/h per mg of cell, respectively. The production rate and the maximum yield of the inhibitor were increased 1.5- and 1.2-fold, respectively, when the initial pH 6.3 was maintained throughout the fermentation.     

Production of trypsin inhibitor by a Cephalosporium sp.

Conditions for the production of the trypsin inhibitor from Cephalosporium sp. KM 388 were investigated. Polypeptone-meat extract-glucose medium supported excellent production of the trypsin inhibitor. In this medium, polypeptone and meat extract were utilized both as carbon and nitrogen sources and as limiting substrates for the cell growth. Glucose was consumed during the stationary growth phase and prevented the disappearance of inhibitor activity. Cephalosporium sp. KM 388 grew at a rate of a first-order reaction for the cell concentrations. Trypsin inhibitor production paralleled cell growth. At 27 degrees C the maximum specific rates of growth and inhibitor production were 0.14 h-1 and 2.1 U of inhibitor/h per mg of cell, respectively. The production rate and the maximum yield of the inhibitor were increased 1.5- and 1.2-fold, respectively, when the initial pH 6.3 was maintained throughout the fermentation.     

鞘胺醇杆菌肝素酶的产生

肝素类分子是一类结构异常复杂的高度硫酸化的糖胺聚糖,是临床上的一种主要的抗凝剂。除了抗凝血及其相关的抗栓活性以外,肝素还具有多种其他生物学功能,如抗平滑肌细胞及肾小球系膜细胞的增殖^[1]、抗炎症^[2]和阻止肿瘤生长及转移的作用^[3]等。因而肝素可用于防治球囊扩充血管成型术后的血管再狭窄、肾小球系膜细胞增生性肾炎、病理性炎症及肿瘤。但由于完整肝素的抗凝血活性,会引起出血及血小板减少综合症等负作用,限制了肝素在这些方面的临床应用。研究表明,肝素的抗凝血活性依赖于一种独特的肝素五糖序列,约占完整肝素链的1／3,除了五糖序列以外,还需要附近的至少13糖残基,因而不含五糖序列或含五糖序列小于18糖的肝素其抗凝活性大大降低^[4]。而六糖以上的肝素片段就具有抗平滑肌细胞增生、抗炎症及抗肿瘤的活性,并且这些活性与抗凝活性无关。因此,可利用特异性的肝素酶降解肝素长链,产生一系列不同结构及大小的肝素片段,并从中筛选出具有不同生物活性的片段。     

Production of chiral epoxides by an ethene-utilisingMicrococcus sp.

Summary An ethene-utilising bacterium was isolated in pure culture from soil and was tentatively identified as aMicrococcus sp. The organism accumulated epoxyalkanes (0.2–13 mM) from internal, terminal, cyclic and aryl-substituted olefins and exhibited a substrate specificity which was different from that expected on the basis of the chemical reactivity pattern in peracid epoxidations. Epoxyalkanes were hydrolysed at a much slower rate than the epoxidation step which allowed them to accumulate. Ethene-grown cells catalysed the stereospecific formation of R-1,2-epoxypropane (enantiomeric excess: e.e.=96%), R-1,2-epoxybutane (e.e.=94%) andtrans-(2R,3R)-epoxybutane (e.e.=84%). An ethene monooxygenase was implicated in the production of chiral epoxides in cell-free extracts of the bacterium. The (2S,3S)-enantiomer of racemictrans-2,3-epoxybutane was stereoselectively hydrolysed to completion resulting in an enrichment in the (2R,3R)-enantiomer. Further hydrolysis of 1,2-epoxyalkanes (C₃-C₄), however, occurred via complete destruction of both stereoisomers.     

Production and characterization of curdlan by Agrobacterium sp.

Agrobacterium sp. was studied for the production of curdlan by conventional one-factor-at-a-time technique and response surface methodology. Factors such as initial pH, urea concentration, sucrose concentration having the greatest influence on the curdlan production were identified. By using response surface methodology (RSM), the curdlan production by Agrobacterium sp. was increased significantly by 109%, from 2.4 g/L to 5.02 g/L when the strain was cultivated in the optimal medium developed by RSM as compared to conventional one-factor-at-a-time technique. The curdlan production rate of 0.84 g/(L h) was obtained when Agrobacterium sp. was cultivated in the optimal medium developed by RSM, which was the highest curdlan production rate reported to date. The infrared (IR) and NMR spectra, the thermogram of DSC and pattern of X-ray diffraction for the curdlan of the present study were almost identical to those of the authentic curdlan sample (from Alcaligenes faecalis; Sigma). The purified curdlan was a linear polysaccharide composed of exclusively β-(1,3)-glucosidic linkages with the molecular weight of 160,000 Da by GPC. The crystalline melting point (T_m), glass transition temperature (T_g) and X-ray diffraction of the sample indicated low crystallinity in the structure.     

Purification and characterization of the Bacillus subtilis levanase produced in Escherichia coli.

The enzyme levanase encoded by the sacC gene from Bacillus subtilis was overexpressed in Escherichia coli with the strong, inducible tac promoter. The enzyme was purified from crude E. coli cell lysates by salting out with ammonium sulfate and chromatography on DEAE-Sepharose CL-6B, S-Sepharose, and MonoQ-Sepharose. The purified protein had an apparent molecular mass of 75,000 Da in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which is in agreement with that expected from the nucleotide sequence. Levanase was active on levan, inulin, and sucrose with Km values of 1.2 microM, 6.8 mM, and 65 mM, respectively. The pH optimum of the enzyme acting on inulin was 5.5, and the temperature optimum was 55 degrees C. Levanase was rapidly inactivated at 60 degrees C, but activity could be retained for longer times by adding fructose or glycerol. The enzyme activity was completely inactivated by Ag+ and Hg2+ ions, indicating that a sulfhydryl group is involved. A ratio of sucrase to inulinase activity of 1.2 was found for the purified enzyme with substrate concentrations of 50 mg/ml. The mechanism of enzyme action was investigated. No liberation of fructo-oligomers from inulin and levan could be observed by thin-layer chromatography and size exclusion chromatography-low-angle laser light scattering-interferometric differential refractive index techniques. This indicates that levanase is an exoenzyme acting by the single-chain mode.