非碳水化合物对木醋杆菌合成细菌纤维素影响规律的初探

该文论述了在静置培养条件下乙醇、醋酸和柠檬酸对木醋杆菌(Acetobcter xylinum)产细菌纤维素的量都有不同程度的增效作用。其中，添加1．5％的乙醇，细菌纤维素产量为2.44g/L；添加0．1％的醋酸，细菌纤维素为2．75g／L；添加0．2％的柠檬酸，细菌纤维素产量为2．15g／L。     

不同培养方式制备的细菌纤维素性质的比较

分别以静置和振荡培养方式培养木醋杆菌,对静置培养及振荡培养得到的细菌纤维素的纤维丝结构、红外光图谱、持水性、复水性以及灰分含量进行了测试,分析了在静置培养和振荡培养下得到的细菌纤维素的性质和结构差异。结果表明,静置培养所产纤维素成一薄膜,纤维结构较纤细、致密,振荡培养所产纤维素成球状,两者结构有明显差异;两者的红外光图谱基本一致;振荡培养得到的细菌纤维素的吸水性和复水性均比较好,而静置培养得到的细菌纤维素灰分含量较低。     

细菌纤维素高产菌株的诱变选育和发酵条件研究

为了选育高产细菌纤维素的木葡糖酸醋杆菌((Gluconacetobacter oboediens)突变菌株,通过硫酸二乙酯和氯化锂复合诱变,得到-株产细菌纤维素能力最高的突变菌株GO2,其细菌纤维素产量为9.91 g/L,比出发菌株提高36.5%.同时确定突变菌株GO2的静置培养条件为发酵时间为6 d,接种量为80(v/v),面积/体积比为1.58～2.08 cm-1.     

多菌种混合发酵生产细菌纤维素和饮料

在以葡萄糖和酵母粉为主要成分的培养基中,研究了假丝酵母菌(Candida Sp.Y-7)和胚乳杆菌(LactobocillusPlantarum L-1)对木醋杆菌(A.Xylinum X-2)生产细菌纤维素的影响.假丝酵母菌(Candida Sp.Y-7)能促进木醋杆菌(A.Xylinum X-2)生产细菌纤维素,产量提高了39%,而胚乳杆菌(Lactobocillus Plantarum L-1)对木醋杆菌生产纤维素无明显促进作用.以蔗糖和荼水为培养基,利用木醋杆菌(A.Xylinum X-2)、假丝酵母菌(Candida sp.Y-7)和胚乳杆菌(Lactobocillus Plantarum L-1)三株菌的互生作用,生产细菌纤维素及饮料,实现清洁生产和零废水排放.培养3d,当pH3.0时终止发酵,细菌纤维素产量0.5g/L.发酵液经调配制成饮料,保质期大于6个月.发酵液深度及气液表面积对细菌纤维素的产量有影响,发酵液深度以2～4cm为宜.采用间歇反复发酵生产工艺,可将细菌纤维素产量提高至2.0g/L.     

流加发酵生产细菌纤维素工艺初探

由于分批培养细菌纤维素的产量受到一定限制,同时葡萄糖的转化率较低,试验探讨采用流加发酵的方式生产细菌纤维素,并根据纤维素产量最终确定最佳流加方案。最佳方案:每隔1 d向三角瓶中流加20 mL新鲜液体培养基,细菌纤维素的产量最高;向培养液中流加葡萄糖时比补加其他物质的纤维素产量要高;随着流加葡萄糖量的增加,纤维素的产量也呈现增加的趋势,但葡萄糖转化率下降。     

蔗糖二步发酵法提高细菌纤维素产量的研究

研究了一株木醋杆菌(A,xylium)细菌纤维素发酵的二步发酵法的工艺条件：在气升罐恒定pH5．0,溶解氧20％,30℃培养7Oh后转移到浅盘,30℃静止培养74h,细菌纤维素产量达到15．86g/L,比静止发酵法的细菌纤维素产量明显提高。     

木醋杆菌最佳发酵条件

通过试验筛选出木醋杆菌发酵产生纤维素的最佳碳源为葡萄糖,最佳氮源为酵母膏和蛋白胨,并通过正交试验确定出木醋杆菌发酵的最佳条件是:pH 5.0,温度30 ℃,葡萄糖1.5 g/dL,酵母膏0.5 g/dL,蛋白胨1 g/dL.乙醇、醋酸、乳酸对木醋杆菌生产纤维量都有增效作用,优化后的培养基添加0.4 g/dL醋酸,细菌纤维素产量为3.40 g/L.添加体积分数1%的乙醇,细菌纤维素产量为3.65 g/L.添加0.4 g/dL乳酸,细菌纤维素产量为3.54 g/L.     

用里氏木霉(RUT-C30)流加培养生产纤维素酶

里氏木霉(RVT—C30)流加培养达半稳定状态时,相应的在菌体浓度和产酶率方面,具体的细胞维持系数为0.029g纤维素/g菌体·h,纤维素酶产率也在9.6～11.9IV/g菌体·h之间(滤纸酶活力)。当纤维素流加率为1.0g/h·L时,纤维素酶总产率为201 IU/L·h,其最高收率为57 IU/ml。     

不同培养方式对红发夫酵母产虾青素的影响

通过间歇流加培养、指数流加培养、混合碳源-番茄汁流加培养和恒速流加培养等4种培养方式的实验,说明进行流加培养有利于红发夫酵母细胞生长及虾青素的合成。与分批培养相比,所有流加模式下生物量及虾青素产量都有不同程度地提高。其中流加混合碳源-番茄汁获得了最好的实验结果,最终的生物量、虾青素含量和产量分别达到33.71g/L、1106μg/g和36.26mg/L。     

木醋杆菌发酵培养基优化及发酵方式的探讨

以木醋杆菌（Acetobacter xylinum）为出发菌株，细菌纤维素产量为指标，通过正交试验优化发酵培养基，其最优组成为葡萄糖15g/L、蛋白胨10g／L、酵母膏5g／L、玉米浆40mL/L、磷酸三钠3g／L、柠檬酸钠1g／L、硫酸镁2g／L、氯化钙0．2g／L、硫酸亚铁0．03g／L、乙醇10mL/L。适宜的发酵方式为先130r／min振荡培养10h，后静置培养10d。经验证试验，细菌纤维素产量可达3．81g／L。     

Effects of pH and dissolved oxygen on cellulose production by Acetobacter xylinum BRC5 in agitated culture

Acetobacter xylinum BRC5 was cultivated in a jar fermentor using glucose as the sole carbon source. Strain BRC5 oxidized almost all of the glucose to gluconic acid; thereafter, it biosynthesized cellulose by utilizing gluconic acid accumulated in the broth. The optimal pH for metabolizing glucose to gluconic acid was 4.0, while a pH of 5.5 was preferred for cell growth and cellulose production from the accumulated gluconic acid in the medium. Shifting the pH from 4.0 to 5.5 during the cellulose production phase in batch cultures improved cellulose production and reduced the total fermentation time, compared to batch cultures at constant pH. In constant fed-batch culture, 10 g/l of cellulose was obtained from 40 g/l of glucose, a yield which was approximately 2-fold higher than in batch culture with the same initial glucose concentration, even without control of the level of dissolved oxygen. The highest cellulose yield was obtained in fed-batch cultures in which the dissolved oxygen concentration was controlled at 10% saturation. Control of pH and dissolved oxygen to optimal levels was effective for improving the production rate and yield of cellulose, to achieve a high cellulose productivity of 0.3 g cellulose/l x h. Approximately 15 g/l of cellulose was considered to be the highest yield obtainable using conventional fermentors because the culture broth then became too viscous to allow satisfactory aeration.     

产朊假丝酵母核酸高产株的选育及其发酵性能研究

为了获得一株发酵性能优良的高核酸酵母,以产朊假丝酵母(Candida utilis)CL1501为出发菌株,采用紫外-亚硝基胍复合诱变,筛选获得一株高核酸含量的突变株CL15013,经测定其核酸含量占菌体干质量的16.8%,高于出发菌47.8%。对比研究其流加及分批培养工艺,流加培养细胞收获量为16.9 g/L,比分批培养提高94.3%;正交试验设计优化流加培养条件后,CL15013的收获量达21.3 g/L,比分批培养提高144.8%,具有良好的生产应用潜力。     

pH-stat控制流加培养红发夫酵母产虾青素

通过酸碱流加培养、混合碳源-氨水流加培养、混合碳源-尿素流加培养等pH-stat控制流加培养红发夫酵母产虾青素。pH-stat控制流加培养与分批培养相比较,生物量及虾青素产量都有不同程度地提高。从提高虾青素产量和降低生产成本综合考虑,混合碳源-氨水流加培养是最理想的方法,培养96 h虾青素产量最高达到19.94 mg/L。     

固定化红曲葡萄糖母液流加发酵红曲色素的研究

对固定化红曲(Monascus purpureus)，在生物反应器中流加葡萄糖母液发酵生产红曲色素进行了研究，建立了简单的数学模型控制流加。结果表明：当总葡萄糖母液浓度为150g/L时，以90g/L初始葡萄糖母液开始发酵，当流加因子K=0．0013时，变速流加发酵组的色素浓度比非流加发酵组的色价提高32％。     

碳酸氢铵为氮源对螺旋藻培养的影响

以碳酸氢铵作为氮源,研究在分批培养及流加培养条件下其对螺旋藻生长的影响。结果表明：当培养液中碳酸氢铵浓度小于5mmol/L时,螺旋藻生长正常;碳酸氢铵浓度超过5mmol/L时,螺旋藻生长受到抑制,解体死亡。采用生物量反馈补料的流加策略可以使培养液中螺旋藻生物量达到3.08g/L,产率达到0.26g/(L ·d),藻体中蛋白质及叶绿素含量分别达到65.06%和13.37mg/g,结果证实了碳酸氢铵为氮源高密度培养螺旋藻的可行性。     

Enhancement of retinal production by supplementing the surfactant Span 80 using metabolically engineered Escherichia coli

The optimal temperature and pH for retinal production using metabolically engineered Escherichia coli in a 7-l fermentor were found to be 30°C and 7.0, respectively. The agitation speed was a critical factor for retinal production. The optimal agitation speed was 400 rpm (oxygen transfer coefficient, k(L)a, = 92 1/h) in batch culture and 600 rpm (k(L)a=148 1/h) in a fed-batch culture of glycerol. Span 80 was selected as a surfactant for retinal production in metabolically engineered E. coli because Span 80 had proven the most effective for increased retinal production among the tested surfactants. Under the optimal conditions in the fed-batch culture with 5 g/l Span 80, the cell mass and the concentration, content, and productivity of retinal were 24.7 g/l, 600 mg/l, 24.3mg/g-cells, and 18 mg l(-1)h(-1) after 33 h, respectively. They were 1.2-, 2.7-, 2.3-, and 2.7-fold higher than those in the fed-batch culture without Span 80, respectively. The concentration and productivity of retinal in this study were the highest ever reported. The hydrophilic portion of Span 80 (sorbitan) did not affect cell growth and retinal production, but the hydrophobic portion (oleic acid) stimulated cell growth. However, oleic acid plus sorbitan did not stimulate retinal production. Thus, Span 80, as a linked compound of oleic acid and sorbitan produced by esterification, proved to be an effective surfactant for the enhancement of retinal production.     

Fed-batch coculture of Lactobacillus kefiranofaciens with Saccharomyces cerevisiae for effective production of kefiran

In a batch coculture of kefiran-producing lactic acid bacteria Lactobacillus kefiranofaciens and lactate-assimilating yeast Saccharomyces cerevisiae, lactate accumulation in the medium was observed, which inhibited kefiran production. To enhance kefiran productivity by preventing lactate accumulation, we conducted lactose-feeding batch operation with feedforward/feedback control during the coculture, so that the lactate production rate of L. kefiranofaciens was balanced with the lactate consumption rate of S. cerevisiae. The lactate concentration was maintained at less than 6 g l(-1) throughout the fed-batch coculture using a 5 l jar fermentor, although the concentration reached 33 g l(-1) in the batch coculture. Kefiran production was increased to 6.3 g in 102 h in the fed-batch coculture, whereas 4.5 g kefiran was produced in 97 h in the batch coculture. The kefiran yield on lactose basis was increased up to 0.033 g g(-1) in the fed-batch coculture, whereas that in the batch coculture was 0.027 g g(-1).     

木醋杆菌在转盘式反应器中的发酵动力学研究

对细菌纤维素生产菌株QAX993的发酵动力学特性进行了研究,基于Logistic方程,提出了菌体生长动力学、基质消耗动力学、纤维素合成动力学模型,得到了使用转盘式反应器分批发酵合成细菌纤维素的动力学模型参数,同时对实验数据与模型进行了比较,模型与实验数据能够较好地拟合,模型基本上反映了该菌株在转盘式反应器中分批发酵过程的动力学特征.     

Using a fed-batch culture strategy to enhance rAAV production in the baculovirus/insect cell system

Recombinant adeno-associated virus (rAAV) is one of the most promising vectors for human gene therapy. However, the production systems that are currently available have a limited capacity and cannot provide sufficient quantities of rAAV for preclinical or clinical trials. Many novel methods for improving rAAV production have been developed, but few researchers have focused on the culture process. In this study, we use a fed-batch culture system to enhance rAAV yield in the baculovirus/insect cell system. When the insect cells were co-infected with MOI = 5 of Bac-GFP at a ratio of 1:9:9 (Bac-GFP: Bac-Rep: Bac-VP), the fed-batch culture achieved optimal rAAV yields. In batch culture, the optimal cell density for producing rAAV was found to be 1 × 10⁶ cells/ml, and the highest rAAV yield (1.22 × 10⁸ IVP/ml, 122 IVP/cell) occurred at day 5 post-infection. In the fed-batch culture, rAAV yield reached 2.13 × 10⁸ IVP/ml at day 4 post-infection, and the highest rAAV yield was 2.40 × 10⁸ IVP/ml (240 IVP/cell) at day 5 post-infection. The cost of the batch and fed-batch cultures is similar; however, the rAAV yield was 2.6-fold higher in the fed-batch culture system compared with that in the batch culture system. Therefore, here we demonstrated an economical and efficient strategy for rAAV production.     

Production of an Alcoholic Beverage by Fermentation of Whey Permeate with Kluyveromyces fragilis I: Primary Metabolism

Whey permeate from the ultrafiltration processing of cheese manufacturing was used for alcoholic fermentation with Kluyveromyces fragilis, the objective being the production of an alcoholic beverage of low alcoholic grade. The effect of temperature, initial pH, agitation and initial biomass on yeast growth and ethanol production were assayed in batch cultures. In addition, continuous culture behaviour was studied due to interest in a continuous industrial process for a new product. An unstructured kinetic model (a Riccati kinetic equation) is proposed; batch data being employed to obtain the kinetic parameters. This model fits the continuous culture results well except for ethanol production, where calculated values were lower than experimental data. When the fermentation temperature was changed from 18 to 37°C, a maximum of Y_P/S close to 30°C was observed, which gives an efficiency in the conversion of lactose to ethanol of 88%. The initial pH of the whey did not affect yeast growth significantly. Experiments carried out at different initial biomass concentrations showed that an initial dry weight close to 0.5 g/litre was sufficient to carry out the fermentation. An increase in ethanol concentrations was found at higher rates of agitation. In continuous culture, a maximum productivity for biomass and ethanol was attained at a dilution rate of 0.11 h^?1. Higher efficiencies (96%) were achieved in continuous culture rather than in batch cultivation mode.