Effect of aeration and pH on gramicidin S production by Bacillus brevis

Although the biosynthesis of the antibiotic gramicidin S (GS) by Bacillus brevis ATCC 9999 has been studied extensively, almost no attention has been given to environmental control of its fermentation process. In this respect, GS fermentations conducted in a 7.5 dm³ fermentor in complex (YP) medium revealed that a high aeration rate resulted in a high biomass yield (12 g DCW dm^?3) with very low GS levels (170 mg GS dm^?3). Lowering the aeration rate (5 dm³ air min^?1 at 300 rev min^?1) caused a dramatic increase in GS formation (2100 mg GS dm^?3) and comparable but slower biomass formation. In chemically-defined (F3/6) medium fermentations, an aeration rate of 5 dm³ air min^?1 at 300 rev min^?1 was apparently too high as only 0.104 mg GS mg^?1 DCW was produced. A much lower aeration rate (2 dm³ air min^?1 at 250 rev min^?1) was needed to arrive at a higher specific antibiotic level: 0.130 mg GS mg^?1 DCW. These data seem compatible with the finding that oxygen is known to inactivate the GS-synthetases. Furthermore, keeping the pH constant at 7.3 under low aeration conditions increased specific GS production up to 0.220 mg GS mg^?1 DCW in YP, as well as in F3/6 fermentations. Both environmental pH and dissolved oxygen tension clearly affect growth pattern, growth extent and GS production in these high yielding media. These data stress the importance of controlling pH and aeration rate during GS fermentations.     

Production of Protocatechuic Acid in Bacillus Thuringiensis ATCC33679

Protocatechuic acid, or 3,4-dihydroxybenzoic acid, is produced by both soil and marine bacteria in the free form and as the iron binding component of the siderophore petrobactin. The soil bacterium, Bacillus thuringiensis kurstaki ATCC 33679, contains the asb operon, but does not produce petrobactin. Iron restriction resulted in diminished B. thuringiensis kurstaki ATCC 33679 growth and the production of catechol(s). The gene product responsible for protocatechuic acid (asbF) and its receptor (fatB) were expressed during stationary phase growth. Gene expression varied with growth temperature, with optimum levels occurring well below the Bacillus anthracis virulence temperature of 37 °C. Regulation of protocatechuic acid suggests a possible role for this compound during soil growth cycles.     

Functional studies of synthetic gramicidin hybrid ion channels in CHO cells

The function of a gramicidin hybrid ion channel in living Chinese hamster ovary (CHO) cells was investigated by the patch clamp method. The synthetic ion channel 1 consists of two cyclohexyl ether amino acids that link two mini-gramicidin strands. With 1 at a concentration of 1.0 microM, an increase in the whole-cell membrane conductance was observed after 1.37 min. The conductance showed larger currents when Cs(+) was used as charge carrier than when Na(+) and K(+) were used. In single-channel recordings with Cs(+) as charge carrier, the substance showed comparable single-channel amplitudes in the membrane of living cells and artificial black lipid bilayers. In addition to functioning as a cation channel, compound 1 appeared to be a water channel. Exposure of the CHO cells to an extracellular hypoosmotic solution did not substantially change the cell volume. Extracellular hypoosmotic conditions in the presence of 1 increased the cell size to 146.5 % that of the control. Thus, the synthetic hybrid channel 1 can function as a cation channel with some Cs(+) specificity, and as a water channel in CHO cells.     

Fermentation and oxygen transfer characteristics in serine alkaline protease production by recombinant Bacillus subtilis in molasses‐based complex medium

Serine alkaline protease (SAP) production in a complex medium based on physically pretreated molasses by recombinant Bacillus subtilis carrying pHV1431::subC gene is described. The effects of oxygen transfer were investigated in 3.5 dm³ bioreactor systems with controls for agitation rate, dissolved oxygen, pH, temperature, and foam formation under two different agitation rates, ie N = 500 and 750 min^?1, and four different air flow rates, ie Q/V_R = 0.2, 0.5, 0.7, and 1.0 vvm, at a molasses concentration equivalent to initial sucrose concentration (C_So) of 20 kg m^?3. The yield values (Y_X/S, Y_X/O, Y_S/O) and maintenance coefficient of oxygen (m_O), were calculated. m_O decreased with the increase in the air‐inlet rate. Increase in oxygen transfer rate increased the rate of growth and SAP activity, and affected the cultivation time to achieve maximum expression of SAP activity. At Q/V_R = 0.5 vvm and N = 750 min^?1, SAP activity reached 2250 U cm^?3 at t = 36 h. The oxygen transfer coefficient (K_La) and oxygen uptake rate (?r_O) were measured throughout the fermentations and their variation with the oxygen transfer conditions determined. New correlations for the calculation of K_La and ?r_O are proposed. Copyright © 2004 Society of Chemical Industry     

枯草芽孢杆菌产烟酰胺酶的发酵工艺条件优化

对已筛选出的菌株枯草芽孢杆菌N-17进行发酵条件优化,利用单因素实验方法,对烟酰胺酶的发酵培养基的组分及发酵条件进行优化,确定了各因素的最适值.结果表明:该菌株在温度28℃,起始pH值7.0,己内酰胺浓度为0.2％,葡萄糖1.2％,酵母粉0.6％,Mg2+0.02％时,产烟酰胺酶活性最大,酶活比之前提升了213.8％.     

氨基甲酸乙酯水解酶在枯草芽孢杆菌中的表达及发酵优化

将来源于赖氨酸芽孢杆菌SC02的氨基甲酸乙酯水解酶(UH)基因在枯草芽孢杆菌Bacillus subtilis WB600中进行克隆和表达,在枯草芽孢杆菌中实现了UH活性表达,在摇瓶水平通过单因素考察和响应面分析实验对氨基甲酸乙酯水解酶发酵进行优化. 结表明,酶活最高可达到14.20 U/mL,产酶最佳培养基成分为：淀粉10 g/L、磷酸氢二钾9 g/L、麦芽浸膏25 g/L、硫酸镁1 g/L、胰蛋白胨55 g/L,最适发酵温度为37℃,最佳接种量4%. 在3 L发酵罐中采用最优发酵条件,酶活在16 h达到18.03 U/mL.     

木聚糖酶产生菌XY1432液体发酵的响应面法优化

用响应面法对短小芽孢杆菌XY1432液体发酵生产木聚糖酶的培养条件进行了优化,首先用单因素试验,选出最佳的碳源为玉米芯 麸皮,氮源为碳酸铵,pH为8;然后用Plakett-Birman法对12个相关影响因素进行了评价,选出3个主要的影响因素碳源,硫酸镁和磷酸二氢钾做最陡爬坡试验,逼近最大产酶区域;最后用响应面法分析确定了主要影响因素的最佳条件,使酶活性由638IU提高到1882IU.     

胶质芽孢杆菌培养条件及发酵工艺的研究进展

对胶质芽孢杆菌在微生物肥料、矿物分解和生物絮凝领域中培养条件及发酵工艺的研究进展进行了综述. 在微生物肥料方面综述了以高产量芽孢为目的的培养工艺及生物反应器发酵的研究;在矿物分解方面综述了以分解矿物和浸出矿物元素为目的的土壤矿物分解和矿石分解条件的研究;在生物絮凝方面综述了以提高絮凝率为目的的培养工艺和絮凝环境条件的研究. 在对现有研究总结的基础上,指出通过发酵模型的建立、流变学特性的研究指导发酵过程调控及将胶质芽孢杆菌应用于土壤改良是进一步研究和探索的方向.     

枯草杆菌溶栓酶恒溶氧发酵动力学参数估计

用10 L自控搅拌式反应器对枯草杆菌(Bacillus subtilis HL-986)发酵生产溶栓酶的动力学进行了研究，建立了恒溶氧分批培养条件下细胞生长、还原糖消耗及溶栓酶积累的动力学模型.     

Free radicals formation induced by the ozonation of humic substances in aqueous medium

This laboratory study was designed to investigate the mechanism of the formation of the OH radicals during the ozonation of humic substances solutions. The evaluation of the formation of these radical species was performed by using 1,1,2-trichloro ethane (TCA) as a probe. The apparent removal of TCA observed during the ozonation treatment implies the production of secondary species that catalyze the generation of OH radicals from ozone. These species are formed by a reaction between H₂O₂, formed in-situ, and O₂ and by a radical mechanism involving reactive humic substances sites.     

Production of cyclodextrin glycosyltransferase by batch and chemostat culture of Bacillus macerans in chemically defined medium

A chemically defined medium for cultivation of Bacillus macerans is reported. Growth rates and cyclodextrin glycosyltransferase (CGT) titres obtained were similar to those obtained using media containing potato extract. The proteins in supernatant fluids from a batch culture were separated by disc electrophoresis and results obtained showed that CGT was produced after growth ceased, in agreement with results of activity measurements. The maximum growth rate in the chemostat considerably exceeded that in batch culture; this anomalous effect is unexplained. High CGT titres were produced at low dilution rates (0.03 to 0.05 h^?1) but residual starch was present at higher dilution rates and CGT synthesis was repressed. Enzyme titres obtained in chemostat cultures at D = 0.03 h^?1 using defined medium containing 13 g starch/1 were 2.75 times greater than the maximum obtainable by batch cultivation and about 20 times greater than those reported by other workers using medium containing diced potato and CaCO₃. A two-stage chemostat cultivation was performed using dilution rates of 0.1 h^?1 and 0.033 h^?1 in the first and second stages, respectively. The CGT activity in the second stage increased by 57 per cent when a maintenance feed of starch was supplied at 0.08 g g^?1 dry biomass h^?1. Only negligible CGT titres were obtained when a dilution rate of 0.5 h^?1 was used in the first stage. For reasons not understood, DM medium would not support biomass yields greater than 5 g 1^?1. This limitation was not due to production of an inhibitor, or to deficiency of N, Fe, Zn, Mn, thiamine or biotin.     

The Effect of pH Control on Acetone-Butanol-Ethanol Fermentation by Clostridium acetobutylicum ATCC 824 with Xylose and D-Glucose and D-Xylose Mixture

D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with ea...     

解淀粉芽孢杆菌ZM9液体发酵伊枯草菌素A培养基优化

运用单因子实验法和正交实验法,得到解淀粉芽孢杆菌ZM9液体发酵伊枯草菌素A的优化培养基为:豆粕80 g/L,玉米淀粉30 g/L(液化处理),KH2PO41 g/L,Mg SO40.5 g/L,Fe SO40.15 g/L,Mn SO40.05 g/L,伊枯草菌素A的产量为3.37 g/L,较出发培养基产量2.19 g/L提高了53.88%。     

核黄素基因工程菌的构建及其发酵的初步研究

构建整合型核黄素质粒pRB63,该质粒含有解调的B.subtilis核黄素操纵子,将其转化入B.subtilisRH13并在染色体上进行适当的扩增后得到RH13::[pRB63]n系列工程菌,其核黄素合成能力随着pRB63扩增程度的增加而增强,最终达到RH13的6～7倍.随后以RH13::[pRB63]n系列工程菌和B.subtilis YB1为亲株进行原生质体融合,筛得重组菌B.subtilis RH33.该菌在含10%葡萄糖或蔗糖的分批发酵中培养64h可产核黄素量4.2 g·L-1.采用以葡萄糖为碳源的流加发酵工艺,24 h可积累核黄素7～8 g·L-1,48 h达11～12 g·L-1,核黄素对葡萄糖的得率为0.056 g·g-1.     

解淀粉芽孢杆菌ZM9液体发酵伊枯草菌素A培养基优化

运用单因子实验法和正交实验法,得到解淀粉芽孢杆菌ZM9液体发酵伊枯草菌素A的优化培养基为:豆粕80 g/L,玉米淀粉30 g/L(液化处理),KH2PO41 g/L,Mg SO40.5 g/L,Fe SO40.15 g/L,Mn SO40.05 g/L,伊枯草菌素A的产量为3.37 g/L,较出发培养基产量2.19 g/L提高了53.88%。     

VC发酵大菌不同组分对小菌生长及产酸的影响

在VC的二步混菌发酵中,作为伴生菌,巨大芽孢杆菌(大菌)对酮古龙酸杆菌(小菌)的生长和产酸有促进作用.通过比较大菌培养液不同分子量的组分对小菌的促进作用,发现分子量小于1 000的组分对小菌的促进作用最明显.     

Optimization of pullulan production from synthetic medium by Aureobasidium pullulans in a stirred tank reactor by response surface methodology

The production of pullulan from synthetic medium by Aureobasidium pullulans P56 in a stirred tank fermenter was investigated. The kinetics of polysaccharide, pullulan and biomass production was determined. Response surface methodology was used to investigate the effects of three factors (initial sugar concentration, aeration rate and agitation speed) on the concentration of pullulan in batch cultures of A pullulans. In the experiments, the range of values used for the three variables described were; 30–70 g dm^?3 initial sugar concentration, 200–600 rpm agitation speed and 1.0–3.0 vvm aeration rate. No previous work has used statistical analysis in determining the interactions among these variables in pullulan production. Results of the statistical analysis showed that the fit of the model was good in all cases. Aeration rate, agitation speed and sugar concentration had a strong linear effect on pullulan concentration. Moreover, pullulan concentration was significantly influenced by the negative quadratic effects of the given variables and by their positive or negative interactions with the exception that the interaction between agitation speed and aeration rate was insignificant (P > 0.05). Maximum pullulan concentration of 17.2 g dm^?3 was obtained at the optimum levels of process variables (initial sugar concentration 51.4 g dm^?3, aeration rate 2.36 vvm, agitation speed 345.3 rpm). These values were obtained by fitting of the experimental data to the model equation. Scanning electron microscope (SEM) photographs of polysaccharide particles containing different concentrations of pullulan were also taken to observe the morphological differences of the samples. Copyright © 2005 Society of Chemical Industry