碳源对土曲霉中洛伐他汀生物合成的影响

通过摇瓶培养考察碳源种类及其初始水平对土曲霉次级代谢物洛伐他汀生物合成的影响。蔗糖和葡萄糖等快速利用碳源产洛伐他汀量较低,且易积累其直接前体monacolin J;淀粉和甘油等缓慢利用碳源有利于细胞生长和产物合成,其monacolin J积累相对较少,甘油为碳源时,可获得最高产物量(937.5±12.3)mg/L,乳糖不利于细胞生长导致较低的产物量。以淀粉为碳源时,其初始水平的增加可促进洛伐他汀的合成,碳质量分数为2%时对底物利用率较高,4%时最高产物量可达(875.4±23.1)mg/L,monacolin J则在2%—3%时积累较多,同时产生较多的2-甲基丁酸。     

Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two‐stage feeding strategy

A two‐stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed‐batch phase and a semi‐continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi‐continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two‐stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry     

Optimized reuse and bioconversion from retentate of pre‐filtered palm oil mill effluent (POME) into microbial protease by Aspergillus terreus using response surface methodology

BACKGROUND: The membrane filtration process enables the treatment of wastewater, producing permeate which is less polluted. However, disposal is usually required for the retentate, which is produced as a concentrated constituent along with the permeate. In this study, the authors explored the possibility of reusing, rather than disposing of, the retentate of pre‐filtered palm oil mill effluent (POME) as a fermentation substrate in protease production by a wild type strain of Aspergillus terreus IMI 282743. In addition, the quantitative and interactive effects of the concentration factor for retentate, temperature, inoculum concentration, and fermentation time on the optimization of protease production were investigated using response surface methodology (RSM). RESULTS: Using RSM, the optimum conditions were found to be a concentration factor of 7.27, temperature of 37.95 °C, inoculum concentration of 1.30% (v/v) and fermentation time of 3.83 days. The protease production was increased 4.37‐fold in comparison with the results obtained under non‐optimized conditions. CONCLUSION: To a certain extent, protease production could be enhanced with an increase in concentration factor and temperature, and a decrease of inoculum concentration and fermentation time. Also, POME retentate was found to be a good substrate for protease production with high product activity and without nutrient supplementation. Copyright © 2009 Society of Chemical Industry     

响应面法优化以重组大肠杆菌发酵生产类人胶原蛋白过程

In order to improve the production of human-like collagen Ⅲ (HLC Ⅲ) by fed-batch culture of recom-binant Escherichia coli BL21, the Plackett-Burman and Box-Behnken design were applied to optimize the fermen-tation process parameters.Three variables (induction time, inoculum age and pH), which have significant effects on HLC Ⅲ production, were selected from eight variables by Plackett-Burman design.With the regression coefficient analysis in the Box-Behnken design, a relationship between HLC Ⅲ production and three significant factors was obtained, and the optimum levels of the three variables were as follows: induction time 3.2h, inoculum age 12.6 h and pH 6.7.The 3D response surface plots and 2D contour plots created by the Box-Behnken design showed that the interaction between induction time and pH and that between innoculum age and pH were significant.An aver-age 9.68 g·L~(-1)HLC Ⅲ production was attained in the validation experiment under optimized condition, which was 80% higher than the yield of 5.36 g·L~(-1) before optimization.     

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     

Effects of ultrasound on culture of Aspergillus terreus

BACKGROUND: Fermentations of Aspergillus terreus are commercially used to produce lovastatin. How ultrasound might influence this fermentation is unknown. While high‐intensity ultrasound is effective in disrupting microbial cells, ultrasound of low intensity is known to improve productivity of some fermentation processes without damaging cells. Mechanisms behind productivity improvements have not been clearly identified in earlier studies. This work reports on the effects of ultrasound on A. terreus fermentation for low (957 W m^?3), medium (2870 W m^?3) and high (4783 W m^?3) values of sonication power input in a slurry bubble column sonobioreactor. RESULTS: Sonication at any power level did not affect biomass growth profiles in comparison with negative controls. In contrast, medium‐ and high‐intensity sonication greatly reduced production of lovastatin and substantially altered the growth morphology. At medium and high intensity, ultrasound disrupted fungal pellets and caused the biomass to grow mainly as dispersed hyphae. Sonication affected broth rheology because rheology depends on the morphology of the suspended biomass. CONCLUSION: Sonication can be used to modify growth morphology and broth rheology without affecting growth of filamentous fungi. Sonication appears to influence the primary growth metabolism and secondary metabolism differently in different situations. Copyright © 2008 Society of Chemical Industry     

Statistical optimization of process parameters for the production of vanillic acid by solid‐state fermentation of groundnut shell waste using response surface methodology

BACKGROUND: Vanillic acid is a flavoring agent and also serves as precursor for vanillin production. Culture medium and fermentation condition for the single step production of vanillic acid from Phanerochaete chrysosporium using lignocellulosic waste as a substrate under solid state fermentation (SSF) were optimized using response surface methodology. RESULTS: The process parameters were chosen by borrowing methodology, and L‐asparagine, pH and moisture content of the solid medium during SSF were identified as the most significant variables. The optimum value of selected variable and their mutual interactions were determined by response surface methodology. The result demonstrated that a yield of 73.58 mg vanillic acid g^?1 substate was predicted under optimum conditions (L‐asparagine 5.98 mmol L^?1 (2.37 mg g^?1 groundnut shell), pH of solid medium 4.51 and moisture content 74.83%). The predicted response was experimentally validated and resulted in a maximum vanillic acid yield of 73.69 mg g^?1 after 8 days of SSF. CONCLUSION: The optimization of fermentation variables resulted in a maximum 10‐fold increase in vanillic acid yield compared with that observed under sub‐optimal conditions (from 7.2 mg g^?1 to 73.69 mg g^?1). Copyright © 2011 Society of Chemical Industry     

响应面法优化壳聚糖酶产生菌Mitsuaria sp.K1的产酶发酵条件

壳聚糖（chitosan）及其降解产物因具有优良的物理特性和生物活性而被广泛关注。通过平板透明圈初筛、摇瓶复筛方法,从青岛海岸土壤中分离筛选到1株产壳聚糖酶活性较高的细菌Mitsuaria sp.K1,并对其产酶发酵条件进行了单因素试验和响应面优化分析试验。结果表明：在最适培养基组成（1%粉末壳聚糖、0.5%硝酸钾、0.22%KH2PO4、0.1%Na2HPO4、0.15%KCl、0.05%MgSO4?7H2O）和最佳培养条件（培养温度25.2 ℃,培养时间25.4 h,起始pH值6.5,接种量3%,装液量100 mL/500 mL摇瓶,160 r/min）下,Mitsuaria sp.K1的发酵粗酶液最高酶活平均达11.56 U/mL,比优化前的2.17 U/mL提高了4.32倍。与前人研究结果相比,该菌发酵产酶温度降低了5～10 ℃,产酶周期缩短了23～47 h,因此具有工业发酵应用价值。     

Formulation and optimization of sucrose polyester physical properties by mixture response surface methodology

The physical properties of sucrose polyester (SPE), prepared from different composite blends of fatty acid methyl esters (FAME) of safflower oil, palm oil, and peanut oil, were evaluated by mixture response surface methodology. Optimum combinations of fatty, acids to achieve specific physical properties of SPE were determined. The SPE most similar in physical properties to peanut oil was obtained with a 55:45 molar ratio of mixed FAME from safflower oil and peanut oil. The physical properties of SPE were significantly affected by the degree of saturation and the average chainlength of their composite fatty acids.     

响应面法优化达托霉素发酵培养基

采用响应面法对玫瑰孢链霉菌发酵产达托霉素的培养基进行了优化。首先通过Placket-Burman设计法筛选出影响达托霉素产量的4个重要因素:初始pH值、葡萄糖、L-天冬氨酸(L-Asp)、硫酸钾。其中初始pH值的影响极为显著(p<0.01),因此,对初始pH值进行了单因素试验,得到最优初始pH值为8.6。在此基础上对其余3个因素用最陡爬坡路径逼近最大响应区域后,利用响应面中心组合设计对显著因素进行优化,得到最适培养基组成为:葡萄糖13.0 g/L、L-Asp 2.6 g/L、硫酸钾4.1 g/L。在此优化条件下,达托霉素产量达373.98 mg/L,与预测值(365.76 mg/L)非常接近,比优化前产量提高了2.25倍。     

响应面法优化月桂酸单甘油酯的酶催化合成工艺

以月桂酸三甘油酯和甘油为原料,脂肪酶催化甘油解反应合成月桂酸单甘油酯。在单因素试验的基础上,采用响应面分析法进行合成工艺优化。结果表明,含水量(相对于甘油的质量)对月桂酸单甘油酯产率的影响最为显著,且较优合成条件为:恒温振荡器转速100 r/min,酶添加质量分数(相对于底物)5%,n(甘油)∶n(月桂酸三甘油酯)=6∶1,底物质量分数(相对于整个反应体系)51.9%,温度65℃,含水量4.23%,反应时间5 h。在此条件下,月桂酸单甘油酯产率的预测值和实验值分别为81.68%和81.32%,说明二次多项回归模型具有良好的预测性。     

Optimization of 1,3‐propanediol production by novel recombinant Escherichia coli using response surface methodology

Response surface methodology was used to optimize 1,3-propanediol production by a novel recombinant Escherichia coli JM109 (pHsh-dhaB-yqhD). The optimal fermentation parameters for enhanced 1,3-propanediol yield were found to be: glycerol 61.8 g L⁻¹, yeast extract 6.2 g L⁻¹, Vitamin B₁₂ 0.049 g L⁻¹ and fermentation time 30 h. Subsequent experimental trials confirmed the validity of the model. These optimal fermentation conditions in the cultivation flask culture led to a 1,3-propanediol concentration of 43.1 g L⁻¹ and a conversion rate of 69.7% (g g⁻¹). A maximum 1,3-propanediol concentration of 41.1 g L⁻¹ was achieved in a 5 L fermenter using the optimized parameters. Copyright © 2006 Society of Chemical Industry     

基于响应面法的折流板除雾器分离性能优化

用响应面分析法分析不同排液结构对新式异型折流板除雾器气液分离性能的影响,并对排液结构参数进行优化设计. 通过单因素实验对比筛选对除雾器性能具有显著影响的关键参数,用中心复合设计实验建立响应面多元回归模型,分析影响除雾器性能系数的参数间交互作用,得出最优参数. 结果表明,影响除雾器性能参数的最优取值为分离气速2.6 m/s、排液钩高度7.3 mm、前置排液槽和后置排液槽宽度分别为3.1和2.3 mm. 优化的折流板除雾器性能系数计算值为2.073,实验值为1.875,优化结果较可靠.     

中心组合设计响应面法优化烟梗提取工艺

为了提高造纸法再造烟叶原料烟梗的提取率,以水为溶剂,以提取时间、提取温度、液料比进行3因素5水平的中心组合设计,采用响应面法优化烟梗提取参数,建立数学模型并进行验证。结果表明,最优工艺条件为：提取温度59℃,提取时间45min,液料比9．1：1,对最佳工艺条件提取率的预测值为38．33％,实测值为38．03％,相对误差仅为0．78％。     

基于响应面法光热-光电膜蒸馏系统优化研究

设计并搭建了太阳能光热-光电方腔型膜蒸馏系统,为研究该系统机理与优化问题,首先以料液进口温度、流量、太阳辐照度为影响因子,膜通量、能耗为响应值,采用响应面法分析各影响因子与响应值间的关系;其次结合中心复合设计法设计实验工况,建立响应值与影响因子的二次多项式回归模型,通过方差分析、实验验证对所建立的模型进行可靠性分析;最后对响应值进行响应面分析与系统优化,获得了系统最佳运行工况和最优膜通量、能耗值,并进行了实验验证。结果表明,系统最佳工况为：料液进口温度为63℃,料液进口流量为232 L/h,太阳辐照度为700 W/m²,在此工况下实际膜通量达到7.28 L/(m²·h),高于预测值6.39 L/(m²·h),两者误差为12.23%,对应的能耗值为10.40 L/(kW·h)。     

响应曲面法多目标优化铜冶炼渣氧压选择性浸出工艺

采用响应曲面法的中心组合设计原理,建立浸出温度、硫酸浓度及液固比及三者之间交互作用对选择性浸出率与矿浆过滤速率的多元二次回归方程,并使用自适应权重粒子群算法对铜冶炼渣氧压硫酸选择性浸出工艺进行多目标优化。结果表明：浸出温度、硫酸浓度和液固比均是影响浸出率和过滤速率的主要因素,各响应因素间存在交互效应,且选择性浸出率与矿浆过滤速率在最佳条件上存在差异。优化后的选择性浸出率和矿浆过滤速率最佳的工艺条件为：温度为204.1℃、硫酸浓度为0.46mol/L、液固比为6.9mL/g,此条件下选择性浸出率为96.95%,过滤速率为399.42L/(m²?h),与验证实验中平均选择性浸出率、平均过滤速率分别为96.57%,398L/(m²?h)相比,偏差较小,预测值与验证实际值吻合好,表明模型选择准确,优化方案可信。     

Optimization of the production of chitosan from beet molasses by response surface methodology

Chitosan was produced by Rhizopus oryzae 00.4367 in shake flask culture and a stirred tank fermenter. Synthetic medium, treated and untreated beet molasses were used as cultivation media in shake flask cultures. In the stirred tank fermenter, the cultivation media were synthetic medium and untreated beet molasses. Shake flask culture containing untreated molasses with a sugar concentration of 40 g dm^?3 produced the maximum chitosan yield (961 mg dm^?3). Chitosan concentration reached its maximum value at the late exponential growth phase of R oryzae. In all experiments almost 8–10% of biomass and 32–38% of alkali‐insoluble material was extracted as chitosan. A central composite design was employed to determine the optimum values of process variables (aeration rate, agitation speed and initial sugar concentration) leading to maximum chitosan concentration in the stirred tank fermenter. In all cases, the fit of the model was found to be good. Aeration rate, agitation speed and initial sugar concentration had a strong linear effect on chitosan concentration. Moreover, the concentration of chitosan was significantly influenced by the negative quadratic effects of the given variables and by their positive or negative interactions. A maximum chitosan concentration of 1109.32 mg dm^?3 was obtained in untreated molasses medium containing an initial sugar concentration of 45.37 g dm^?3 with an aeration rate and agitation speed of 2.10 vvm and 338.93 rpm, respectively. Copyright © 2004 Society of Chemical Industry     

Lactic acid production from dining‐hall food waste by Lactobacillus plantarum using response surface methodology

BACKGROUND: Food waste generally has a high starch content and is rich in nutritional compounds, including lipids and proteins. It therefore represents a potential renewable resource. In this study, dining‐hall food waste was used as a substrate for lactic acid production, and response surface methodology was employed to optimise the fermentation conditions. RESULTS: Lactic acid biosynthesis was significantly affected by the interaction of protease and temperature. Protease, temperature and CaCO₃ had significant linear effects on lactic acid production, while α‐amylase and yeast extract had insignificant effects. The optimal conditions were found to be an α‐amylase activity of 13.86 U g^?1 dried food waste, a protease activity of 2.12 U g^?1 dried food waste, a temperature of 29.31 °C and a CaCO₃ concentration of 62.67 g L^?1, which resulted in a maximum lactic acid concentration of 98.51 g L^?1 (88.75% yield). An increase in inoculum size would be appropriate for accelerating the depletion of initial soluble carbohydrate to enhance the efficiency of α‐amylase in dining‐hall food waste fermentation. CONCLUSION: A suitable regression model for lactic acid production was developed based on the experimental results. Dining‐hall food waste was found to be a good substrate for lactic acid fermentation with high product yield and without nutrient supplementation. Copyright © 2008 Society of Chemical Industry     

Improved xylitol production in media containing phenolic aldehydes: application of response surface methodology for optimization and modeling of bioprocess

BACKGROUND: The combined effects of vanillin and syringaldehyde on xylitol production by Candida guilliermondii using response surface methodology (RSM) have been studied. A 2² full‐factorial central composite design was employed for experimental design and analysis of the results. RESULTS: Maximum xylitol productivities (Q_P = 0.74 g L^?1h^?1) and yields (Y_P/S = 0.81 g g^?1) can be attained by adding only vanillin at 2.0 g L^?1 to the fermentation medium. These data were closely correlated with the experimental results obtained (0.69 ± 0.04 g L^?1 h^?1 and 0.77 ± 0.01 g g^?1) indicating a good agreement with the predicted value. C. guilliermondii was able to convert vanillin completely after 24 h of fermentation with 94% yield of vanillyl alcohol. CONCLUSIONS: The bioconversion of xylose into xylitol by C. guilliermondii is strongly dependent on the combination of aldehydes and phenolics in the fermentation medium. Vanillin is a source of phenolic compound able to improve xylitol production by yeast. The conversion of vanillin to alcohol vanilyl reveals the potential of this yeast for medium detoxification. Copyright © 2009 Society of Chemical Industry     

Process optimization for foam separation of yak whey protein by response surface methodology

In order to recovery whey protein from yak whey wastewater effectively, a facile method of foam separation to be suitable for the local nomadic herdsmen in Qinghai-Tibet Plateau has been established in this research. The effects of the four factors, protein concentration, gas velocity, temperature and pH, on the performance of foam separation were investigated. Based on the single factor experiments, the response surface software was adopted to optimize and to investigate conditions of foam separation for whey protein, and the optimal conditions were found to be protein concentration of 120 μg/mL, gas velocity of 310 mL/min, temperature of 41°C and pH of 3.8, respectively. The as-obtained results of verification experiments, recovery percentage 88.3% and enrichment ratio 9.25 showed that foam separation technique was a simple equipment and environmental compatibility method to separate whey protein from yak whey wastewater.