Growth rate dependence of enzyme synthesis in chemostat cultures: α-amylase, β-galactosidase,acid phosphatase and β-fructosidase

Specific rate of enzyme synthesis in microbial cells was correlated to specific growth rate in chemostat culture using three strains of microorganism. α-Amylase production by Bacillus subtilis was linearly associated with growth rate in a glucose-limited chemostat culture. β-Galactosidase production by Saccharomyces fragilis was rather invariable with growth rate in a galactose medium. β-Fructosidase production by Saccharomyces carlsbergensis in a phosphate-poor glucose medium was independent on growth rate, except at low dilution rates where it increased with growth rate. Production of acid phosphatase by the same microbe showed a maximum at a particular intermediate dilution rate. These relationships were summarised with an equation of induction—repression model. Comparison of the chemostat results with those of batch fermentation provided some enhancement factors of a continuous fermentation: 1.23–9.82 regarding enzyme productivity and 0.53–2.88 regarding enzyme concentration. The production of β-fructosidase was much improved among the enzymes tested when continuous culture methods were used.     

Mathematical modelling and its use for design of feeding strategies for L‐Sorbose fermentation

Batch sorbitol to sorbose bioconversion by Acetobacter suboxydans using initial sorbitol concentration (S₀ = 100 g/L) yielded a productivity of 10.11 g/L‐h and 98.6% conversion in 10 h time. The batch kinetics was then used to develop an unstructured mathematical model. Model parameters were identified using a nonlinear regression technique assisted by a computer program which minimized the deviation between the model predictions and actual batch experimental data. F test indicated 99% confidence on the prediction of model using optimized parameters. The batch model was eventually extrapolated to identify nutrient feeding strategies to maintain constant noninhibitory sorbitol supply and eliminate substrate limitation for fed‐batch fermentation in order to improve the sorbose productivity. The adequacy of the fed‐batch model was established by excellent agreement between experimental data and model simulation (except towards the end of fermentation).     

Computer simulation of the biomass production rate of cyclic fed batch continuous culture

The biomass productivity of cyclically operated variable volume fermenters has been investigated as a function of the initial volume and the feed flow rate. The results of computer simulations show that the productivity-dilution rate curves are similar to those for a constant volume chemostat, which represents a limiting case for the cyclic operation. Both cyclic fed batch and fed batch plus batch operation have been studied for Monod and substrate inhibition kinetics. The results obtained for variable volume operation can be used to estimate the loss in productivity when a chemostat inadvertently undergoes volume fluctuations.     

发酵罐中剪切环境与菌体形态和代谢

结合青霉素发酵过程,考察了产黄青霉形态与剪切环境的关系;在搅拌槽内流场研究的基础上,分析了现有各种表征发酵罐内总体剪切环境的参数的合理性,提出了菌体对高强度剪切呈现出“印象衰减”效应这一新观点.据此而得的特征剪切强度,可用于发酵罐中轴向、径向叶轮组合搅拌的设计.     

地衣芽孢杆菌P-104发酵生产g-聚谷氨酸条件优化

对地衣芽孢杆菌P-104发酵合成g-PGA的条件(接种时间、接种量和培养基组成等)进行了优化,并在发酵罐中进行了批式发酵实验. 结果表明,该菌可利用合成培养基生产较高浓度超高分子量(大于2500 kDa)的g-PGA,最佳培养基组分为(g/L)：葡萄糖 80,谷氨酸钠 70,柠檬酸钠 10, (NH4)2SO4 10, MnSO4 0.15, MgSO4 0.8, K2HPO4 0.6, NaNO3 4. 接种时间与量分别为8 h和3%(j)、初始pH 7.5条件下,37℃下180 r/min摇瓶培养24 h,发酵液中g-PGA浓度可达44.7 g/L,比生产速率为1.49 g/(L×h),是已报道的同类比生产速率的2倍. 采用优化培养基在6.6 L发酵罐中批式发酵培养33 h, g-PGA浓度为32 g/L,比生产速率为0.97 g/(L×h).     

山梨醇连续发酵生产山梨糖过程的研究

在工作容积１０立升的发酵罐内进行了山梨醇的连续发酵试验，探讨了工业生产的可能性。通过实验，求得了满足工业生产要求的工艺操作条件，并与分批发酵作比较，连续发酵具有较高的生产能力。实验结果表明，山梨醇连续发酵生产山梨糖具有工业化的前景。     

Evaluation of Optimization Metrics for Continuous Fermentation of Plasmid DNA

An evaluation of cumulative productivity metrics for optimizing the continuous fermentation of plasmid DNA (pDNA) is carried out in this work. DNA plasmids provide a good illustrative example for comparison because of the plasmid instability issues associated with their production. However, the analysis presented in this work can also be applied to other intracellular bioproduct continuous fermentation systems. The productivity metrics considered are cumulative product mass per time, profit, and cost objective functions. These metrics are used to determine the optimal continuous fermentation run time at a given dilution rate, during the dynamic period associated with switching from batch to continuous fermentation. The results of this study indicate that different optimum continuous fermentation run times are predicted based upon the choice of the continuous fermentation operating conditions and optimization metric. In particular, the dilution rate must be larger than the inverse of a characteristic time, that is a function of the initial batch operating and plasmid stability times before continuous operation becomes optimal. Provided that this condition is met, different optimal continuous operation run times are obtained depending on the cumulative productivity metric, or operating objective, that is employed.     

汽爆秸秆膜循环酶解耦合丙酮丁醇发酵

利用新型的汽爆玉米秸秆膜循环酶解耦合发酵系统进行了丙酮丁醇发酵的研究,并对使用该系统所导致的丙酮丁醇梭菌(Clostridium acetobutylicum AS1.132)代谢的变化进行了讨论. 在稀释率为0.075 h-1的条件下,丁醇的产量为0.14 g/g (纤维素+半纤维素),最大丁醇产率达到0.31 g/(L×h),溶剂组成为丁醇:丙酮:乙醇65.3:24.3:10.4(体积比),纤维素和半纤维素的转化率分别为72%和80%,使用单位纤维素酶所产生的丁醇量为3.9 mg/IU,是分步水解批次发酵的1.5倍. 利用该系统使酶解和发酵分别在各自最适的条件下同时连续进行,减少了纤维素酶的用量,有效地解除了酶解产物对纤维素酶的抑制作用,并减轻了溶剂产物尤其是丁醇对微生物活性的影响,延长了发酵周期.     

Optimisation of a fermentation process for butanol production by particle swarm optimisation (PSO)

BACKGROUND: The performance of three particle swarm optimisation (PSO) algorithms was assessed in relation to their capability to optimise an alternative fermentation process for the production of biobutanol. The process consists of three interconnected units: fermentor, cell retention system and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The dynamic behaviour of the process was described by a non‐linear mathematical model. Four constrained optimisation problems were formulated concerning the operation and design of flash fermentation: (1) maximisation of butanol productivity; (2) maximisation of substrate conversion; (3) and (4) adjustment of operating conditions in the face of problems of fluctuations in the quality of the agricultural raw material and changes in the kinetics of the microorganisms. RESULTS: The design and operation of the flash fermentation process based on the optimisation of productivity, instead of substrate conversion, resulted in a smaller fermentor and provided satisfactory values of operating conditions able to overcome problems of variations in the glucose concentration in the raw material and changes in kinetics. CONCLUSIONS: The differences among the PSO algorithms, i.e. the velocity equation and parameters values, had significant effects on the optimisation, the best results being obtained with the original velocity equation with the inertia weight decreasing linearly with each iteration. The PSO algorithms obtained solutions that obeyed constraints, demonstrating that a constraint handling method originally developed for genetic algorithms can be applied successfully to PSO algorithms. Copyright © 2010 Society of Chemical Industry     

Analysis of fed-batch fermentation processes by graphical methods

Graphical methods are used for many types of engineering calculations. Their appeal is often related to calculational simplicity, but probably the increased understanding that accompanies a graphical calculation method is chiefly responsible for their popularity. In the present work existing graphical concepts which have been used in chemical reaction engineering and fermentation technology have been extended to allow the calculation of biomass and product formation for a variety of fermentation processes. Comparisons in productivity are made among chemostat, batch, fed batch with variable and constant feed rate, and cyclic fed-batch operations.     

利用甘蔗糖蜜半连续发酵生产琥珀酸

为获得较高的琥珀酸发酵产量和生产强度,对Actinobacillus succinogenes CGMCC1593两级双流半连续发酵甘蔗糖蜜生产琥珀酸的工艺过程进行了研究。通过对一级罐初始总糖浓度、补加培养基体积分数和批次发酵时间等发酵条件的优化,琥珀酸产量较分批发酵36 h提高12.9％,与补料分批发酵结果接近;生产强度较分批发酵和补料分批发酵分别提高111％和114%。     

大孔离子交换树脂在重组大肠杆菌生产hEGF中的原位分离作用

引　言乙酸是重组大肠杆菌培养过程中的主要代谢副产物[1,2 ] ,乙酸的产生和积累对重组菌的生长和外源蛋白表达都有严重的抑制作用[3,4 ] .许多研究者对此开展了多方面的研究 ,如通过代谢工程手段构建乙酸酶缺陷菌株作为宿主菌来减少乙酸的产生[5] 、采用发酵 /分离耦合技术除去或降低乙酸量[6～ 8] 、透析培养技术[9,10 ] 、控制菌体的比生长速率及限制基质葡萄糖浓度等方法 .　　　本实验室开展了重组大肠杆菌分泌性高效表达人表皮生长因子 (humanepidermalgrowthfactor ,hEGF)的研究 ,发现在重组菌培养过程中乙酸的积累对重组菌生长和hEGF表达有严重抑制作用 .本文开展了高效吸附乙酸的离子交换树脂筛选 ,并在摇瓶和发酵罐规模两个水平上研究离子交换树脂在重组大肠杆菌发酵生产hEGF过程中对乙酸的原位分离作用 .1　材料与方法1 1　菌株与质粒E coliJM10 1/pSP10 3,本研究所保存的高效分泌型hEGF的重组大肠杆菌 .1 2　培养基及培养方法种子培养基和发酵培养基 ,种子培养、摇瓶培养及 2 5LB Braun发酵罐培养的条件参照文献[11],其中发酵培养基中...     

新型优化策略在青霉素间歇发酵过程中的应用研究

基于全面关注间歇发酵过程中间状态的思想,提出由求解一系列端点时间不固定最优控制子问题形成的新型优化控制策略,并在优化目标函数中加入了菌体平均生长速率和流加时间间隔对发酵产量的影响因素.在此基础上提出基于遗传算法的最优控制策略实现算法,同时获得了最优流加时间间隔及相应的最优流加速率.将该方法在青霉素发酵过程进行仿真,将仿...     

赖氨酸发酵动力学研究——流加方式优化

在４０Ｌ中试发酵罐上用优选菌株进行了Ｌ—赖氨酸分批流加发酵,用实验数据对文献报道的分批发酵动力学模型进行了验证。结果发现所有模型都不能很好的描述赖氨酸分批发酵过程动力学。最后,探讨了赖氨酸分批发酵的动力学机理,给出了流加优化方案。     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

桔青霉产美伐他汀发酵条件优化和小罐放大

首先研究了不同碳、氮源,无机盐,初始pH值和接种量等因素对桔青霉HD-32-2产美伐他汀生产能力的影响,然后着重对4种发酵培养基组分(葡萄糖,麦牙糖,黄豆饼粉和磷酸氢二钾)进行正交试验,形成了最优的发酵培养基。与最初的发酵培养基相比,在最优发酵培养基上发酵水平提高了3倍,达到了986 mg/L,并在15 L小型发酵罐上进行了放大比较研究,进一步说明了优化后培养基具有明显的提高美伐他汀发酵水平的能力。     

SELF-FORCING OF A CHEMOSTAT WITH SELF-SUSTAINED OSCILLATIONS FOR PRODUCTIVITY ENHANCEMENT

The effects of self-forcing simple limit-cycle type self-sustained oscillations (SSO) on a single chemostat with the aim to enhance its productivity was investigated using four different microbial systems with increasing complexities. It was demonstrated via simulation that for a chemostat with monod-type growth and with substrate-and-product-inhibited growth and product formation, it is possible to increase its productivity several fold by self-forcing the chemostat with SSO without incurring extra costs normally associated with external periodic forcing. Despite significant difference in the models used to simulate the chemostats, all four systems show a similar pattern of behavior in their productivity-vs.-mean residence time plots.     

基于核Fisher包络分析的间歇过程故障诊断

随着间歇过程越来越受重视,其过程监控和故障诊断技术也成为研究热点。以核Fisher判别分析为基础,提出了基于核Fisher的正常工况与故障包络面模型,给出了基于该模型的在线故障诊断流程。此方法利用了Fisher判别分析对类别的划分特点,分别针对正常工况数据和各故障类型数据建立包络曲面模型。与多向Fisher判别分析相比,该方法按批次方向将数据展开,能够解决生产周期不一致问题,在线故障诊断时也不需要预报完整的生产轨迹,并且加入核函数来处理复杂的非线性。最后在青霉素发酵过程的仿真平台上对该方法进行测试,与改进多向Fisher判别分析方法进行对比,该方法获得了满意的诊断效果：能够及早诊断出故障的发生,并在有效识别已有故障的同时还具有对新故障的自学习能力。     

Lovastatin production by Aspergillus terreus in a two‐staged feeding operation

BACKGROUND: Lovastatin is known to inhibit its own synthesis in the fungus Aspergillus terreus. Therefore, the use of a fermentation strategy that continuously removes some of the lovastatin produced from the bioreactor can enhance its productivity. This paper reports on the effects of dilution rate and the composition of the feed medium on lovastatin production by A. terreus. RESULTS: The feeding strategy consisted of an initial batch/fed‐batch phase and a semi‐continuous culture phase in which the pelleted biomass was retained inside a slurry bubble column. A nitrogen‐free medium was fed at various fixed dilution rates in the semi‐continuous phase. In experiments that were designed to assess the effects of the composition of the medium, the dilution rate was held at 0.42 d^?1, but different feed media were used in separate runs. The best two‐staged production strategy was shown to consist of a 96 h batch/fed‐batch phase that used a nutritionally complete medium. This was followed by a semi‐continuous operation using a medium that was free of both nitrogen and carbon sources. CONCLUSION: Semi‐continuous operation enhanced productivity of lovastatin by 315% compared with a conventional batch operation. The optimal dilution rate in semi‐continuous operation was about 0.42 d^?1. Copyright © 2008 Society of Chemical Industry     

Self-forcing of a chemostat with self-sustained oscillations for productivity enhancement

The effects of self-forcing simple limit-cycle type self-sustained oscillations (SSO) on a single chemostat with the aim to enhance its productivity was investigated using four different microbial systems with increasing complexities. It was demonstrated via simulation that for a chemostat with monod-type growth and with substrate-and-product-inhibited growth and product formation, it is possible to increase its productivity several fold by self-forcing the chemostat with SSO without incurring extra costs normally associated with external periodic forcing. Despite significant difference in the models used to simulate the chemostats, all four systems show a similar pattern of behavior in their productivity-vs.-mean residence time plots.