苏云金杆菌7216菌株的摇瓶发酵试验

用苏云金杆菌发酵生产的杀虫剂是一种不污染环境,对人畜无毒,能有效防治鳞翅目农林害虫的细菌农药,目前已有14个血清型、19个以上的变种,其产毒部分主要是δ-内毒素即伴孢晶体和芽孢。作为蔬菜无公害生产的技术措施,我国应用杀虫菌剂综合防治蔬菜害虫取得了较大进展,其中细菌农药的发酵即应用苏云金杆菌7216、HD-1等优良菌株,为使其工艺控制符合发酵生产的要求,达到菌数多、毒力高、周期短、成本低等综合指标,我们对7216进行了摇瓶发酵试验,研究不同培养条件下的呼吸作用、生长繁殖、营养利用及伴孢晶体和芽孢的形成,为工业发酵生产提供科学依据。     

赖氨酸发酵过程溶氧控制研究

L-赖氨酸是当前国内外全价配合饲料的主要添加剂,具有提高饲料利用率,促进动物生长和改进肉质的功效。近年来,随着养殖业、饲料业等行业的迅猛发展,国内市场对赖氨酸的需求量大大增加。当前,赖氨酸的生产主要以发酵法为主,本文重点对目前赖氨酸发酵过程中溶氧的控制进行分析,综述了工业改善溶氧的措施。     

苏云金芽孢杆菌培养基优化及间歇发酵

对苏云金芽孢杆菌的培养基配方进行室内摇瓶优化筛选,首先用摇瓶培养筛选到Ⅱ号培养基,在此配方的基础上,将培养基组分划分为氮源、碳源及无机盐三因素,采用三因素二水平正交旋转组合设计的方法进行培养基优化组合研究,建立其芽孢产量依氮源、碳源、无机盐的响应面方程。借助此方程获得响应面最佳点即培养基各组分的最佳配比。实验结果表明,该方法是苏云金芽孢杆菌培养基优化中十分简便、实用、快速的途径。此外,对其间歇发酵过程也进行了初步考察。     

苏云金杆菌在味精废水中的培养与发酵特性

该文讨论了苏云金杆菌HM－1菌株在以味精废水为原料的培养基上的生长,经多次摇瓶培养,确定了最适培养基成份,在此基础上,进行了30L通风搅拌罐的深层培养,研究了苏云金杆菌HM－1菌株在30升通风发酵罐深层培养的发酵特性。     

苏云金芽孢杆菌BtR05菌株发酵培养基的优化

为提高苏云金芽胞杆菌BtR05菌株的发酵水平,本研究通过正交试验并将优选出的培养基组合进行综合优选,最终筛选出的培养基为:玉米粉2%,豆粕粉3%,蔗糖1%,硫酸铵0.1%,三水磷酸氢二钾0.3%,磷酸二氢钾0.2%,七水硫酸镁0.04%,酵母提取物0.3%和碳酸钙0.3%.该培养基配方在接种量为3%,200 r/min.30℃摇瓶振荡培养至44 h时,芽孢率达90%,活菌数达37.33×108cfu/ml.     

苏云金杆菌33菌株最佳培养基和发酵条件研究

应用正交试验L27(313)对鳞翅目昆虫高毒效的苏云金杆菌33菌株的发酵培养基进行研究,得到了适合其发酵培养的优化复合培养基配方—0.5％玉米粉 2．00％黄豆粉 0．15％酵母粉 0．25％鱼粉 0．075％蛋白胨 0．25％磷酸二氢钾 0．05％碳酸钙 0．035％硫酸镁。另外实验还证实适当增加通气量、发酵初始酸碱度控制在pH7．5、发酵温度30℃、转速180r／min、培养40h更适合该菌株液体深层发酵。     

苏云金杆菌Bt0601菌株发酵培养基的优化

运用正交试验L18(37)设计对携带杀虫基因cry1Ac和虎纹捕鸟蛛毒素基因hwtx-Ⅰ的苏云金杆菌工程菌Bt0601的发酵培养基进行了优化研究.试验获得的最佳优化复合培养基配方为(%)玉米粉1.0,黄豆饼粉0.50,酵母膏0.15,蛋白胨0.05,磷酸二氢钾0.75,碳酸钙0.05,硫酸镁0.035.Bt0601在该优化培养基下发酵,48 h每mL发酵液产芽孢11.4×109个,伴孢晶体23.0×107个,对3龄小菜蛾(Plutella xylostella)48 h的致死率达96.7%.普通发酵培养基下相应的芽孢产量为9.33×109个,伴孢晶体9.57×107个,毒力为68.5%.     

苏云金杆菌“79007”菌株发酵工艺的研究

对苏云金杆菌79007菌进行了生长条件的研究,获得了该菌最佳发酵培养基配方和最优发酵工艺。最佳培养基配方(g/100 mL):豆饼粉2.5,淀粉2.0,酵母粉2.0,玉米浆2.0,添加剂Ⅰ号0.1,葡萄糖1.0,KH2PO40.3,CaCO30.1,CaCl20.05,MgCl20.01,CuCl20.005,ZnSO40.002,CoCO30.005;15 m3发酵罐最优工艺:通气量1∶0.5~1.1,培养温度28~33℃,搅拌转速0~200 r/min。40 m3发酵罐连续4批试验表明,平均发酵效价6 053.5 IU/μL、平均晶体蛋白含量达0.5%,产品质量达到原粉优质品。     

产耐热蛋白酶苏云金芽胞杆菌的发酵动力学

对苏云金芽胞杆菌FZ62耐热蛋白酶的代谢过程进行初步研究,酶生成与菌体生长为耦联过程。以Logistic方程和Luedeking—Piret方程为基础,建立该菌发酵过程中菌体生长、产物生成和基质消耗的动力学模型,求得模型参数,该动力学模型与试验结果拟和程度较好。     

Effect of oxygen on steady-state product distribution in Bacillus polymyxa fermentations

Bacillus polymyxa ferments glucose to 1-2,3 butanediol, acetoin, ethanol, acetic acid, lactic acid, and formic acid. This research investigates product formation as a function of oxygen availability. A predictive model that simulates product distribution at known oxygen transfer rates is developed on the hypothesis that, in an energy-limited environment, B. polymyxa utilizes glucose and oxygen in the most efficient manner. The efficiency of utilization of glucose and oxygen is measured in terms of the ATP yields of each oxidative pathway. The identity of the products constituting the profile at the given oxygen transfer rate is determined by comparing the ATP production and consumption rates. While the ATP generated is calculated from a knowledge of the oxygen transfer rate and ATP yields of the oxidative pathways, the ATP consumption is estimated by the Pirt expression in terms of growth- and nongrowth-associated components. The product formation rates are obtained by solving ATP and NAD balance equations. They equate the production and consumption rates of these intermediates and are derived from the pseudo-steady-state hypothesis. The model is applied to continuous culture systems that are both open and closed with respect to biomass. At a given oxygen transfer rate, dilution rate, and inlet glucose concentration, the model predicts steady-state concentrations of two dominant fermentation endproducts with the help of four parameters that can be determined from independent experiments. In contrast with earlier approaches, the experimental studies are carried out in continuous culture. Product profiles are obtained at various oxygen transfer rates, fer rates, inlet glucose concentrations, and dilution rates. The effect of pH on the relative distribution of products is also demonstrated. Results indicate that the model is fairly successful in predicting product profiles as a function of oxygen availability. (c) 1992 John Wiley & Sons, Inc.     

High cell density induces spontaneous bifurcations of dissolved oxygen controllers during CHO cell fermentations

High cell density cultures of CHO cells growing in a bioreactor under dissolved oxygen control were found to undergo spontaneous bifurcations and a subsequent loss of stability some time into the fermentation. This loss of stability was manifested by sustained and amplified oscillations in the bioreactor dissolved oxygen concentration and in the oxygen gas flow rate to the reactor. To identify potential biological and operational causes for the phenomenon, linear stability analysis was applied in a neighborhood of the experimentally observed bifurcation point. The analysis revealed that two steady state process gains, K(P1) and K(P2), regulated k(l)a and gas phase oxygen concentration inputs, respectively, and the magnitude of K(P1) was found to determine system stability about the bifurcation point. The magnitude of K(P1), and hence the corresponding open-loop steady state gain K(OL1), scaled linearly with the bioreactor cell density, increasing with increasing cell density. These results allowed the generation of a fermentation stability diagram, which partitioned K(C)-N operating space into stable and unstable regions separated by the loci of predicted critically stable controller constants, K(C,critical), as a function of bioreactor cell density. This consistency of this operating diagram with experimentally observed changes in system stability was demonstrated. We conclude that time-dependent increases in cell density are the cause of the observed instabilities and that cell density is the critical bifurcation parameter. The results of this study should be readily applicable to the design of a more robust controller.     

溶氧对L-缬氨酸发酵过程的影响

目的:以黄色短杆菌XV0505为供试菌,探索溶氧对L-缬氨酸发酵过程的影响及其控制策略。方法:利用5L发酵罐,考察了不同溶氧浓度对L-缬氨酸发酵的影响,并采用代谢流分析对其结果进行阐述,提出分阶段溶氧控制策略。结果:采用分阶段溶氧控制策略,即在0～24h溶氧浓度为20%,24～60h溶氧浓度为5%,发酵60h,L-缬氨酸可达到58.36g/L,比5%和20%溶氧浓度下分别提高了18.95%和13.56%。结论:溶氧浓度对L-缬氨酸发酵有重要影响。     

Identity of hemolysins produced by Bacillus thuringiensis and Bacillus cereus

A hemolysin (Bt-hemolysin) produced by Bacillus thuringiensis var. kurstaki HD-1 producing crystalline toxin(s) was purified by successive treatments of ammonium sulfate (45-65%) and column chromatography using DEAE-cellulose, Sephadex G-75 and KB-002 (a hydroxyapatite column for fast protein liquid chromatography). A hemolysin (Bc-hemolysin) produced by B. cereus HG-6A was also purified by the same procedure. The purified Bt-hemolysin and Bc-hemolysin, both of which are thiol-activated hemolysins, were biologically, physicochemically and immunologically identical. These findings provide further evidence of the similarity of B. thuringiensis, which is being used as a biological insecticide, to B. cereus, a toxigenic organism of food poisoning.     

Effects of Carbon dioxide on the Rheological behavior and oxygen transfer in submerged penicillin fermentations

Fermentations of Penicillium chrysogenum have been made with different CO(2) contents in the influent gas streams. The rheological behavior of the culture broth was found to be significantly changed by exposure to high levels of CO(2). This is attributed to the wide variation in the morphology of P. chrysogenum, from normal mycelia with long hyphae to roughly spherical pellets when subjected to high levels of CO(2). A correlation has been developed relating volumetric O(2) transfer coefficients, k(L)a, with the effective O(2) diffusion coefficients, D(e), and the apparent viscosities, mu(app), based on the results obtained in this study. The use of CO(2) as a potent means for altering the rheological properties of culture broths and consequently improving the O(2) transfer capabilities in penicillin fermentations was clearly demonstrated.     

Dissolved oxygen concentration and diversity of benthic macroinvertebrates in an artificially destratified lake

Changes in species composition and diversity of benthic macroinvertebrates during summer and fall were compared in an area of a lake artificially destratified and in an arm not destratified. Numbers of species, diversity, and density were significantly correlated with the concentration of dissolved oxygen, while none of the biotic variables were correlated with temperature.Research supported with funds from the Oklahoma Water Resources Research Institute     

Enzyme induction by oxygen in the accumulation of cytochrome P-450 during batch fermentations in 20% d-glucose with Saccharomyces cerevisiae

Production of cytochrome P-450 [RH, reduced-flavoprotein:oxygen oxidoreductase (RH-hydroxylating), EC 1.14.14.1] by Saccharomyces cerevisiae NCYC 754, grown in batch culture on 20% d-glucose medium, was markedly affected by the speed of the orbital shaker. Oxygenation rather than agitation was confirmed as the likely cause of this effect using an optimized system in a microprocessor-controlled 4 litre batch fermenter. Oxygen may be acting as a substrate inducer of the cytochrome P-450 in this yeast.