Enhanced expression of aconitase raises acetic acid resistance in Acetobacter aceti

Acetobacter spp. are used for industrial vinegar production because of their high ability to oxidize ethanol to acetic acid and high resistance to acetic acid. Two-dimensional gel electrophoretic analysis of a soluble fraction of Acetobacter aceti revealed the presence of several proteins whose production was enhanced, to various extents, in response to acetic acid in the medium. A protein with an apparent molecular mass of 100 kDa was significantly enhanced in amount by acetic acid and identified to be aconitase by NH2-terminal amino acid sequencing and subsequent gene cloning. Amplification of the aconitase gene by use of a multicopy plasmid in A. aceti enhanced the enzymatic activity and acetic acid resistance. These results showed that aconitase is concerned with acetic acid resistance. Enhancement of the aconitase activity turned out to be practically useful for acetic acid fermentation, because the A. aceti transformant harboring multiple copies of the aconitase gene produced a higher concentration of acetic acid with a reduced growth lag-time.     

Ethanol from lignocellulosic materials by a simultaneous saccharification and fermentation process (SFS) with Kluyveromyces marxianus CECT 10875

Simultaneous saccharification and fermentation (SSF) process for ethanol production from various lignocellulosic woody (poplar and eucalyptus) and herbaceous (Sorghum sp. bagasse, wheat straw and Brassica carinata residue) materials has been assayed using the thermotolerant yeast strain Kluyveromyces marxianus CECT 10875. Biomass samples were previously treated in a steam explosion pilot plant to provide pretreated biomass with increased cellulose content relative to untreated materials and to enhance cellulase accessibility. SSF experiments were performed in laboratory conditions at 42 °C, 10% (w/v) substrate concentration and 15 FPU/g substrate of commercial cellulase. The results indicate that it is possible to reach SSF yields in the range of 50–72% of the maximum theoretical SSF yield, based on the glucose available in pretreated materials, in 72–82 h. Maximum ethanol contents from 16 to 19 g/l were obtained in fermentation media, depending on the material tested.     

Synergistic temperature and ethanol effect on<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis> dynamic behaviour in ethanol bio-fuel production

The impact of ethanol and temperature on the dynamic behaviour of Saccharomyces cerevisiae in ethanol biofuel production was studied using an isothermal fed-batch process at five different temperatures. Fermentation parameters and kinetics were quantified. The best performances were found at 30 and 33°C around 120 g l^-1 ethanol produced in 30 h with a slight benefit for growth at 30°C and for ethanol production at 33°C. Glycerol formation, enhanced with increasing temperatures, was coupled with growth for all fermentations; whereas, a decoupling phenomenon occurred at 36 and 39°C pointing out a possible role of glycerol in yeast thermal protection.     

血栓溶解酶产生菌及其培养条件的研究

通过对根霉１２号发酵液的分析及发酵条件的研究,发现其发酵液中含有能溶解血栓的物质,但不能分解血细胞。它在麸皮胰蛋白胨培养基（ｐＨ５．１）上３０℃振荡培养４８～６０ｈ,ｐＨ值达到７．４左右时产生血栓溶解酶的活力最高。     

Oxytetracycline production by Streptomyces rimosus in solid-state fermentation of corncob

Corn-cob was used as a substrate in the production of oxytetracycline by Streptomyces rimosus TM-55 in a solidstate fermentation. Oxytetracycline was detected on day 4, and reached its maximum on day 8. Optimal conditions for oxytetracycline production were an initial pH of 5.2 to 6.3, an initial moisture content of 64% to 67%, supplementation with 20% (w/w) rice bran or 1.5% to 2.5% (w/w) (NH₄)₂SO₄ as sole N source, 1.0% (w/w) CaCO₃, 2% (w/w) MgSO₄.7H₂O, and 0.5% (w/w) KH₂PO₄, with incubation for 8 days at 25 to 30°C. Each g substrate produced 7 to 8 mg oxytetracycline.     

Encapsulation enhances protoplast fusant stability

A barrier to cost-efficient biomanufacturing is the instability of engineered genetic elements, such as plasmids. Instability can also manifest at the whole-genome level, when fungal dikaryons revert to parental species due to nuclear segregation during cell division. Here, we show that by encapsulating Saccharomyces cerevisiae-Pichia stipitis dikaryons in an alginate matrix, we can limit cell division and preserve their expanded metabolic capabilities. As a proxy to cellulosic ethanol production, we tested the capacity of such cells to carry out ethanologenic fermentation of glucose and xylose, examining substrate use, ploidy, and cell viability in relation to planktonic fusants, as well as in relation to planktonic and encapsulated cell cultures consisting of mixtures of these species. Glucose and xylose consumption and ethanol production by encapsulated dikaryons were greater than planktonic controls. Simultaneous co-fermentation did not occur; rather the order and kinetics of glucose and xylose catabolism by encapsulated dikaryons were similar to cultures where the two species were encapsulated together. Over repeated cycles of fed-batch culture, encapsulated S. cerevisiae-P. stipitis fusants exhibited a dramatic increase in genomic stability, relative to planktonic fusants. Encapsulation also increased the stability of antibiotic-resistance plasmids used to mark each species and preserved a fixed ratio of S. cerevisiae to P. stipitis cells in mixed cultures. Our data demonstrate how encapsulating cells in an extracellular matrix restricts cell division and, thereby, preserves the stability and biological activity of entities ranging from genomes to plasmids to mixed populations, each of which can be essential to cost-efficient biomanufacturing.     

限制和修饰系统LlaBIII在构建抗噬菌体菌株中的作用

限制和修饰 (ｒｅｓｔｒｉｃｔｉｏｎａｎｄｍｏｄｉｆｉｃａｔｉｏｎ ,Ｒ Ｍ)系统是指由限制性内切酶和甲基化酶组成的单亚基或多亚基复合酶系统 ,两者通常成对出现 ,具有相同的ＤＮＡ识别位点 ,其作用相反。Ｒ Ｍ系统在原核生物中普遍存在 ,在保护细胞免遭外源病毒侵害方面具有重要作用[1] 。作为发酵剂的乳酸乳球菌在乳制品发酵中具有重要作用 ,但这类菌株极易遭受噬菌体感染 ,导致菌株产酸力降低 ,甚至发酵失败 ,造成严重的经济损失。所以在乳制品发酵过程中防止噬菌体感染就成为十分重要的问题。通过自然筛选或诱变处理等手段筛选噬菌…     

前体及诱导子和发酵条件对烟曲霉TMS-26产紫杉醇发酵体系优化

紫杉醇是一种广谱的抗癌药物,因其具有独特的抗癌机制、良好的抗癌效果和供不应求的市场等特征而备受关注。紫杉醇具有重大经济效益,但产量受到制约,价格极为昂贵,通过内生真菌发酵法生产紫杉醇能在一定程度上缓解其来源困难的问题。在产紫杉醇内生真菌TMS-26发酵液中添加前体物质和诱导子,并通过对接种量、装液量、初始pH和发酵时间等条件进行优化研究。单因素及正交试验表明在PDB培养基中加入苯丙氨酸20mg/L、苯甲酸钠30mg/L、乙酸钠8g/L、甘氨酸15mg/L、CuSO₄ 0.05mg/L、H₂O₂ 6mmol/L、3,5-二硝基水杨酸15mg/L时能有效提高紫杉醇产量,比优化前增产46.64%,达到446.28µg/L,并且发现最适菌株TMS-26的发酵条件为pH7.5、接种量5%、装液量120mL/250mL、发酵时间为10d。     

尖孢镰刀菌生产蒽醌色素的液体发酵条件研究

优化了尖孢镰刀菌液体发酵生产蒽醌类红色素的发酵条件。通过单因素实验和正交优化实验,确定最佳产色素发酵培养基为：可溶性淀粉30％,(NH4)2SO4 3％,MgSO4 0.3％,KH2PO4 4％,pH 6.0。产色素最适培养条件为：初始pH6.0,装液量20％,接种量10％,吐温-80添加量1％,温度28℃,摇床转速200r/min,发酵周期120h。此条件下,色素效价即可达到8.184U/ml,比优化前提高了1.8倍。国内首次对尖孢镰刀菌所产蒽醌色素进行研究,为其进一步应用奠定基础。