“现代工业发酵调控学”课程的研究性教学探索

传统现代发酵调控学课程教学已不能满足创新人才培养的要求,课题组结合江西农业大学一流本科建设课程改革要求在现代工业发酵调控学教学中引入研究性教学方法。从教学的设计、实施和学习评价改革入手,就研究性教学方法在现代工业发酵调控学课程教学中的应用进行有效的探索,取得较好的教学效果。

我校《发酵乳制品学》精品课程立项两年来建设与改革情况浅谈

吉林农业科技学院《发酵乳制品学》精品课程立项两年来,从课程建设实际出发,在课程设计、教学方法与手段、实践教学等多方面进行了建设与改革,取得明显的成效,提升了教学效果。

在线检测用发酵液透析分离器的研究

设计了一种膜透析分离器,以期用于发酵液中葡萄糖浓度的在线检测。对两种膜材料进行了比较,研究了压差、流速、温度和载流液种类对透析分离的影响。在给定的条件下,葡萄糖浓度在10—70mmol/L范围内透过率约为12%。透过率随操作压差、温度而变化,重现性好,CV<4%,对酵母发酵液进行透析分离,葡萄糖透过率至少稳定48h。用于发酵过程在线检测,结果与离线检测相吻合,相关系数r=0.985。

以摇瓶所得摄氧率为基准进行发酵放大

通过设计特殊摇瓶,用亚硫酸盐法测出摇瓶口纱布层氧通透率的基础上,在实际发酵情况下通过测定瓶内气、液相氧的变化得出其发酵过程中的摄氧率(OUR)及氧传递系数(K_La)。以特制摇瓶取得的菌体OUR为基准进行发酵过程和发酵罐的放大。通过质谱仪在线检测及采样分析,研究了3种不同供气流量及搅拌转速下的放大结果。摇瓶与发酵罐在菌体OUR、菌体产量方面吻合很好,而在整个放大过程中,发现摇瓶与发酵罐内的氧传递系数(K_La)、溶解氧(c_L)差异较大。

2-酮-L-古洛酸的补料分批发酵的研究

通过对２－酮－Ｌ－古洛酸的一般发酵与补料分批发酵过程比较研究，发现了补糖分批发酵的一些表观特征，为其发酵控制提供了依据。

发酵液中添加物对气含率的影响

气含率是决定气液接触面积和传质系数的重要因素。也是表示气液两相流体力学特征的重要参数。发酵液中添加物对气含率的影响,过去虽有一些研究,但范围非常狭窄,仅局限于部分无机或有机小分子添加物,与实际发酵过程存在着一定的差异,特别对天然营养物质的影响尚未有研究。同时由于气含率对物性的高度敏感性,使现有的气含率关联式已不能适用于发酵液中的所有添加物。Shah则建议,鉴于气含率容易测量,根据某一特定体系进行的小试结果将比任何已知关联式所预测的要好。本文研究发酵过程中常用添加物对气含率的影响,并从理论上推导得出气含率的关联式,对研究发酵液中不同组分与氧传递速率的关系以及前文中氧传质系数的计算均有重要意义。

海洋真菌岩藻多糖酶的固态发酵条件研究

本文对海洋真菌Dendryphiella arenaria(TM94)岩藻多糖酶的固态发酵条件进行了研究,主要内容包括碳源、氮源、添加物、起始pH、接种量及温度等。固态发酵最佳培养基组成:麸皮7.5g,葡萄糖0.5g,海带粉0.6g,NaNO3为4g/L;最佳培养条件为培养温度28℃,起始pH6,接种量3ml (孢子浓度为106个/ml)。在28℃培养24h,酶活力可达35.5 IU/g干培养基,比活力为1.39 IU/mg蛋白质。对岩藻多糖酶酶学性质也进行了研究。

微生物连续培养过程中动态行为研究

研究了具有底物和产物抑制以及代谢过量特征的微生物连续培养过程的数学模型.在模型中引入连续时滞,通过计算得出系统在一定的操作条件下存在Hopf分叉以及分支值随操作参数变化的规律,并对系统的周期性进行了研究.同时,利用数值解法绘制了周期解的图形和相图.该模型定性地描述了实验中的振荡和过渡现象.

基于酶电极系统的葡萄糖浓度在线控制

补料分批技术在发酵工业中被广泛应用,其物料流加方式有3类,其中恒流速和指数补料属无反馈控制操作,靠经验或预设的数学模型决定补料速度,但由于发酵过程的复杂性,实际过程往往偏离预设的模型;恒底物浓度流加属反馈控制,通过对特定参数的检测,根据参数的变化情况反馈控制物料的流加,可控制菌生长在最佳条件下,从而获得高浓度的目的产物。反馈控制分直接控制和间接控制。

Isolation and Identification of a Taxol-producing Endophytic Fungus Identified from Taxus media

[Objective] The aim was to isolate and identify a taxol-producing endophytic fungus from Taxus media. [Method] 32 strains of endophytic fungi were identified form the inner bark of T. media,and their fermentation products were detected by high performance liquid chromatography (HPLC). [Result] Through the screening,a strain of taxol-producing endophytic fungi M57 was obtained,which could produce 45-50 μg/L of taxol,and M57 was defined as Rhizopus sp. through morphological observation and 18S rDNA sequence analysis. [Conclusion] The finding of Rhizopus sp. M57 provided a promising strain for producing taxol with taxol-producing fungi fermentation process.

Run-to-run Optimization for Fed-batch Fermentation Process with Swarm Energy Conservation Particle Swarm Optimization Algorithm

An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter identification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.

A new improved Alopex-based evolutionary algorithm and its application to parameter estimation

In this work, focusing on the demerit of AEA (Alopex-based evolutionary algorithm) algorithm, an improved AEA algorithm (AEA-C) which was fused AEA with clonal selection algorithm was proposed. Considering the irrationality of the method that generated candidate solutions at each iteration of AEA, clonal selection algorithm could be applied to improve the method. The performance of the proposed new algorithm was studied by using 22 benchmark functions and was compared with original AEA given the same conditions. The experimental results show that the AEA-C clearly outperforms the original AEA for almost all the 22 benchmark functions with 10, 30, 50 dimensions in success rates, solution quality and stability. Furthermore, AEA-C was applied to estimate 6 kinetics parameters of the fermentation dynamics models. The standard deviation of the objective function calculated by the AEA-C is 41.46 and is far less than that of other literatures' results, and the fitting curves obtained by AEA-C are more in line with the actual fermentation process curves.

Improved elastase production by Bacillus sp. EL31410—further optimization and kinetics studies of culture medium for batch fermentation

An efficient culture medium producing a bacterial elastase with high yields was developed further following preliminary studies by means of response surface method. Central composite design (CCD) and response surface method-ology were applied to optimize the medium constituents. A central composite design was used to explain the combined effect of three medium constituents, viz, glucose, K2HPO4, MgSO47H2O. The strain produced more elastase in the completely optimized medium, as compared with the partially optimized medium. The fitted model of the second model, as per RSM, showed that glucose was 7.4 g/100 ml, casein 1.13 g/100 ml, corn steep flour 0.616 g/100 ml, K2HPO4 0.206 g/100 ml and MgSO47H2O 0.034 g/100 ml. The fermentation kinetics of these two culture media in the flask experiments were analyzed. It was found that the highest elastase productivity occurred at 54 hours. Higher glucose concentration had inhibitory effect on elastase production. At the same time, we observed that the glucose consumption rate was slow in the completely optimized medium, which can explain the lag period of the highest elastase production. Some metal ions and surfactant additives also affected elastase production and cell growth.

Efficient Separation of Butyric Acid by an Aqueous Two-phase System with Calcium Chloride

One of the bottlenecks for bioproduction of butyric acid as bulk chemical is the difficulty in separating butyric acid from the fermentation broth,compared with the petroleum-based chemical synthesis method.In the present work,a novel separation methodology was developed based on an aqueous two-phase system with inor-ganic salts.Calcium chloride was screened out for effective separation of butyric acid from butyric acid-water-salt systems.Within appropriate concentration range of butyric acid and salt,butyric acid was enriched in the upper phase and most of calcium ions remained in the lower phase.This"salting out"effect is very efficient to separate butyric acid from the simulated butyrate fermentation broth,which consists of butyric acid and acetic acid with concentration ratio of 4︰1,so that the final ratio of butyric acid/acetic acid in the upper phase is improved to 9.87. The aqueous two-phase system was used to separate butyric acid from the actual fermentation broth with satisfac-tory result.

Kinetics of High Cell Density Fed-batch Culture of Recombinant Escherichia coli Producing Human-like Collagen

The kinetics of batch and fed-batch cultures of recombinant Escherichia coli producing human-like collagen was investigated. In the batch culture, a kinetic model of a simple growth-association system was concluded without consideration of cell endogeneous metabolism. The cell lag time, the maximum specific growth rate and Yx/s were determined as 1.75h, 0.65h^-1 and 0.51g·g^-1, respectively. In the fed-batch culture, different specific growth rates were set at （0.15, 0.2, 0.25h^-1） by the method of pseudo-exponential feeding, and the expressions for the specific rate of substrate consumption, the growth kinetics and the product formation kinetics of each phase were obtained. The result shows that the concentrations of cell and product can reach 77.5g·L^-1 and 10.2g·L^-1 respectively. The modal predictions are in good agreement with the experimental data.

A Mathematical Model for Simultaneous Saccharification and Co-fermentation （SSCF） of C6 and C5 Sugars

Reliable production of biofuels and specifically bioethanol has attracted a significant amount of re-search recently.Within this context,this study deals with dynamic simulation of bioethanol production processes and in particular aims at developing a mathematical model for describing simultaneous saccharification and co-fermentation （SSCF） of C6 and C5 sugars.The model is constructed by combining existing mathematical mod-els for enzymatic hydrolysis and co-fermentation.An inhibition of ethanol on cellulose conversion is introduced in order to increase the reliability.The mathematical model for the SSCF is verified by comparing the model predic-tions with experimental data obtained from the ethanol production based on kraft paper mill sludge.When fitting the model to the data,only the yield coefficients for glucose and xylose metabolism were fine-tuned,which were found to be 0.43 g·g-1 （ethanol/glucose） and 0.35 g·g-1 （ethanol/xylose） respectively.These promising validation results encourage further model application to evaluate different process configurations for lignocellulosic bioetha-nol technology.

Three-stage fermentation and kinetic modeling of bioflocculant by Corynebacterium glutamicum

Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.

Learning control of fermentation process with an improved DHP algorithm

Control of the fed-batch ethanol fermentation processes to produce maximum product ethanol is one of the key issues in the bioreactor system.However,ethanol fermentation processes exhibit complex behavior and nonlinear dynamics with respect to the cell mass,substrate,feed-rate,etc.An improved dual heuristic programming algorithm based on the least squares temporal difference with gradient correction(LSTDC) algorithm(LSTDC-DHP) is proposed to solve the learning control problem of a fed-batch ethanol fermentation process.As a new algorithm of adaptive critic designs,LSTDC-DHP is used to realize online learning control of chemical dynamical plants,where LSTDC is commonly employed to approximate the value functions.Application of the LSTDC-DHP algorithm to ethanol fermentation process can realize efficient online learning control in continuous spaces.Simulation results demonstrate the effectiveness of LSTDC-DHP,and show that LSTDC-DHP can obtain the near-optimal feed rate trajectory faster than other-based algorithms.