翼形轴流桨在红霉素发酵中的应用研究

在20t工业发酵罐中,研究了翼形轴流桨搅拌对红霉素发酵过程的影响。重点考察了粘度,溶氧,效价等过程参数变化,以及搅拌功耗与发酵产量之间的关系。研究结果表明：（1）与传统的涡轮搅拌桨相比,翼形轴流桨搅拌其发酵过程参数（粘度,溶氧,效价等）随时间的变化曲线有明显的差异;（2）在相同的生产条件下,用翼形轴流桨代表涡轮桨可有效提高生产效率。     

高粘发酵体系不同搅拌桨的CFD模拟及发酵验证

搅拌桨是高好氧高黏度微生物发酵实现高效反应必不可少的因素之一,不同搅拌桨组合对发酵过程的影响十分重要。威兰胶是由产碱杆菌在高耗氧高粘度发酵体系下合成的胞外微生物多糖,广泛应用于水泥、石油、油墨、食品等行业中。本研究借助于计算流体力学(Computational fluid dynamics,CFD)的方法,以威兰胶发酵液体系为研究体系,研究了6种不同搅拌桨组合在反应器内流体速率分布、剪切速率、和气含率等参数。将模拟效果较好的3种组合用于威兰胶发酵过程。研究表明MB-4-6搅拌桨组合对改善发酵罐内部的溶氧及流场分布效果最明显,威兰胶产量水平提高了13%。同时在该组合下威兰胶的产品粘度得到有效提高。     

影响酵母细胞麦角固醇的发酵控制参数的分析

研究了麦角固醇发酵过程中的参数。比较了溶氧、OUR、Ph和残糖浓度与酿酒酵母的生物量和麦角固醇含量的关系 ,并研究了这些参数之间的内在联系。研究表明 ,溶氧能比较准确地反映酵母的生长状况 ,是发酵过程中的一个较好的控制参数。将溶氧控制在 12 %左右能有效提高单位体积发酵液中的麦角固醇的产量。     

发酵法生产葡萄糖酸钠过程中参数检测

主要研究了发酵法生产葡萄糖酸钠过程中的各参数的变化规律,通过在线监测和离线分析检测,得出各参数的变化规律:各参数的变化均与黑曲霉的生长周期有关;发酵初期(0~5 h)各参数维持恒定;发酵期(5~16 h)溶氧、残糖质量浓度分别快速降低至30%、15 g/L;酶活、葡萄糖酸钠含量快速上涨至500 U/mL、18 g/L;发酵中后期(16~20 h)维持阶段,各参数缓慢变化;发酵结束后溶氧回升。各参数的变化规律与黑曲霉生长周期的关系研究为工厂进一步优化发酵工艺、缩短发酵周期提供原始的理论依据。     

发酵过程中溶氧浓度对D-核糖发酵的影响

通过固定不同溶氧浓度(DOT)对短小芽孢杆菌(Bacillus pumlus)进行分批发酵的过程参数变化的比较,发现发酵前期与后期对氧的需求不尽相同,探讨了氧代谢途径及溶氧浓度对核糖发酵的影响机理,并提出分阶段供氧模式。结果表明,发酵时间44h后,整个发酵过程保持了较高的核糖产率和葡萄糖消耗率,最终核糖产量和细胞生成量分别提高了5.0％和18.8％。     

木聚糖酶发酵工艺在50L罐中的放大

自制的酵母水解液成功替代有机N源酵母浸膏被应用于木聚糖酶发酵,大大降低了原料成本。在此基础上,于50 L罐中进行发酵工艺放大,得到最佳发酵条件:搅拌转速220 r/min、空气流量23 L/min、初始pH 5.5、温度30℃、罐压0.04 MPa,最终发现产酶水平可达到2 864 U/mL,用箭叶圆盘涡轮搅拌桨代替上层平叶圆盘涡轮搅拌桨,产酶水平无显著变化,搅拌功率节约11%。     

溶氧控制策略对结冷胶发酵过程的影响

结冷胶作为一种吸水水性极强的胶体,其广泛应用于食品,饮料,医药,化妆品等行业。发酵法生产结冷胶的过程中,由于发酵液的黏度很高,溶解氧(DO)的控制极为困难。大规模工业化生产结冷胶的过程中,通常可以通过增加通气量或提高搅拌转速这两种策略来提高发酵过程中的溶氧水平。本文通过对比这两种控制策略对60吨发酵罐生产结冷胶产量、能耗的影响,得出通过提高搅拌转速的溶氧控制策略更加高效和节能。提高搅拌转速的发酵批次与增加通气量的发酵批次相比,结冷胶平均产量提高了9%,能耗降低了10%。     

用于红霉素生产的500m3生物反应器的理性设计

红霉素(erythromycin)是由绛红色糖多胞菌(Saccharopolyspora erythraea)发酵生产的次级代谢产物,其生产水平不仅受发酵工艺的影响,也受反应器结构影响。为解决红霉素发酵过程放大问题,本研究采用时间常数法和计算流体力学(computational fluid dynamics,CFD)数值模拟验证相结合的方法设计了500m³超大规模红霉素耗氧发酵生物反应器。首先,通过对50L反应器红霉素发酵过程研究,发现溶氧是关键性限制因素,通过氧消耗速率(oxygen uptake rate,OUR)等参数分析计算得到设备的氧供应时间常数t_mt需小于6.25s。然后,基于时间常数法和经验关联式理性设计500m³反应器搅拌桨叶组合方式,即底层BDT8桨叶+两层MSX4桨叶的搅拌桨组合,并通过经验公式及CFD方法对设计结果进行了模拟验证。两种验证方法结果均表明500m³反应器采取底层BDT8桨叶+两层MSX4桨叶的组合方式时设备的氧供应时间常数小于6.25s,且反应器内流场特性(如持气率、剪切率和速度矢量等)均能满足红霉素大规模发酵的需要。经实际发酵验证,设计的生物反应器能够满足红霉素的工业规模发酵应用。     

出芽短梗霉发酵过程溶氧控制的研究

在搅拌罐式生物反应器中,通过控制DO（溶氧浓度）的变化,对出芽短梗霉（Aureobasidium pullulans）发酵过程的控制进行了研究。以100g/L玉米粉水解液做碳源,比较了不同溶氧控制条件下发酵参数的变化及其对出芽短梗霉发酵结果的影响。结果表明,过低的DO对菌体生长和多糖生产都不利,过高的DO使培养液中糖大部分消耗在菌体的生长上,也不利于多糖的生产,通过控制搅拌速度和通气量能将DO维持在较合适的水平。     

通过参数相关性分析对发酵控制策略在植酸酶高密度发酵中的作用探讨

为了优化植酸酶高密度发酵条件,有必要获取在发酵过程中由于控制策略引起有关参数的实时变化及其关联性.本研究利用传感器对植酸酶工程菌高密度发酵过程进行数据在线采集,通过改变转速、接种量与补料甘油,探讨三方面控制因素对高密度发酵产酶过程参数具体影响及各参数变化之间的相关性,建立起与转速-细胞密度-溶氧-乳酸相关的发酵罐内外环...     

Gas-liquid dispersion with dual Rushton turbine impellers

Aerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height-to-diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding-loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed-filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller-impeller flow pattern interactions occur.     

Effects of agitator configuration and rotational speed on the production of extracellular polysaccharide by Xanthomonas cucurbitae PCSIR B-52

A strain of Xanthomonas cucurbitae PCSIR B-52, efficiently produced extracellular polysaccharide using partially deproteinized low-acid cheese whey without hydrolysis. The effects of the agitator configuration and rotational speed on the viscosity of the fermented broth and the productivity of extracellular polysaccharide based on bacterial growth were evaluated in a batch process. Agitation was performed by a six-bladed disc turbine impeller and by a similar agitator, equipped with six vertically attached stabilizing fins. Comparatively, the magnitude of the decrease in the DO tension resulting from increased viscosity of the broth was less with the stabilizing-fin agitator due to increased system damping. A drastic increase in the mechanical agitation speed after 30-h fermentation, however, increased the broth viscosity and the accumulation of polysaccharide. Moreover, the volume of the macromixing region decreased with increasing rotational speed of agitator.     

Effect of hydromechanical forces on the production of filamentous haemagglutinin and pertussis toxin ofBordetella pertussis

Summary The production ofBordetella pertussis extracytoplasmic filamentous haemagglutinin (FHA) and pertussis toxin (PT) in a bioreactor under stirring conditions was studied in order to investigate the effect of hydromechanical forces on yields of both antigens. It was shown that FHA loses its haemagglutinin activity when the power transmitted by the agitator and the aerator per unit volume increases, whereas PT production is not affected. The loss of FHA activity can be explained by the action of shear forces on the filamentous structure of this antigen.Nomenclature C^* dissolved oxygen saturation concentration - C₁ dissolved oxygen concentration - D impeller diameter - power transmitted by the agitator and the aerator per unit of liquid volume - E_m maximum local energy dissipation rate per unit of liquid volume - K_La volumetric oxygen transfer coefficient - N impeller speed - Pg power input in aerated system - qO₂m maximum specific oxygen consumption rate - R_e Reynold number (D²N /) - VVM volume of air per volume of fermentation broth per minute - Xm maximum of biomass concentration - o Kolmogorov-microscale - fermentation broth viscosity - fermentation broth kinematic viscosity - fermentation broth density - expt experiment     

Oxygen transfer efficiency in the biosynthesis of antibiotics in bioreactors with a modified RUSHTON turbine agitator

In this work, the oxygen mass transfer efficiency and power consumption in a non-biological system and an antibiotic biosynthesis process, using a modified RUSHTON turbine agitator, were investigated. It was demonstrated that a simple modification of the blades through the increase of the blade height, simultaneously with the discontinuation of the blade surface, could improve the oxygen transfer efficiency by about 30%. Experiments performed in stirred tank bioreactors with an overall volume of 20 m³, equipped with the modified RUSHTON turbine agitator, showed that the power consumption diminished by a factor of 1.18 to 1.6 during the fermentation processes of Streptomyces erithreus, Streptomyces griseus, Streptomyces noursei, and Nocardia mediaterranei, compared to the witness bioreactor. The use of the modified RUSHTON turbine for the antibiotic biosynthesis process may contribute to the decrease of the overall costs and the obtainment of better productivity, allowing an intensive utilization of power inputs for aeration and agitation.     

不同搅拌器类型对齿毛菌发酵产漆酶的影响

【目的】白腐菌Cerrena unicolor Y-G07是一种不产孢子的丝状真菌,其漆酶合成与生长相偶联。应用于单细胞微生物发酵的搅拌器并不适用于白腐真菌。在此,综合考虑溶氧效果和剪切力作用,研究不同搅拌器类型对白腐菌Cerrena unicolor Y-G07发酵生产漆酶产量的影响。【方法】针对Y-G07菌株生长过程需氧量大,且对剪切力敏感的特性,订制5种不同类型的搅拌器(径向流、轴向流等),在通气已控制在设备最大量程及转速优化的前提下,研究Y-G07在发酵生产过程中使用不同类型搅拌器对菌丝生长形态、生长速度、溶氧情况、糖代谢和漆酶合成的影响。【结果】Cerrena unicolor Y-G07菌株对不同类型搅拌器产生的发酵液流态性质和剪切力敏感,表现在菌丝体的生长形态、细胞浓度差异较大,且生长周期改变,从而影响漆酶的合成。采用六折叶DT602搅拌器最有利于该菌株形成致密度合适的网状菌丝体,菌丝体细胞浓度高,断裂少、生长状况好,漆酶的单位产量可达690 U/m L,相对于普通使用的六叶平直叶搅拌器(448 U/m L)提高了54%。【结论】选择合适的搅拌器类型有利于好氧但对剪切力敏感的微生物发酵。     

Carbon monoxide mass transfer for syngas fermentation in a stirred tank reactor with dual impeller configurations

This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding.     

Power consumption of agitated gas-liquid-solid systems with particular relevance to solid substrate submerged culture fermentations

Summary The Michel and Miller (1962) equation is routinely used to estimate the effect of aeration on power consumption in submerged culture fermentation systems. However this correlation was developed for systems that do not contain solid substrates. Since many industrial fermentations use solid substrates, this study developed a modification of the Michel and Miller equation that can be used to predict power consumption when solid substrates are present. A correlation relating power to solids addition was established by adding bran and apple pomace to water, and measuring the power drawn by four separate impeller configurations.This correlation applies to solids content up to 16.7% w/w and bulk densities between 1020 to 1210 kg/m³. It was found that when aerated the power consumption decreased upon addition of solid substrate. The most likely explanation of this behaviour is that initially the gas hold up increased, decreasing power consumption. At high solid loadings, the power decrease was up to 30% (compared to 66% decrease in power caused by high aeration rates).     

Submerged culture production of chitinase by Trichoderma harzianum in stirred tank bioreactors – the influence of agitator speed

The chitinase fermentation process utilizing chitin as the sole carbon source was investigated in a stirred tank bioreactor. Agitator speed of 224 rpm was found to be most suitable for cell growth as well as for chitinase production. Chitinase yield decreased rapidly at higher agitator speed, while decrease in cell yield at higher agitator speed was not rapid. Probably, mass transfer limitation was predominant in the fermentation process at lower agitator speed. Higher agitator speed appears to reduce chitinase production.