Kinetics of continuous whey fermentation by Kluyveromyces fragilis

Continuous whey fermentation by Kluyveromyces fragilis was studied in a 30-dm³ stirred fermenter as a function of the dilution rate (D) and feed concentration of lactose (S_o). By using the concept of material and energy balances, it was possible not only to check the consistency of the experimental steady-state responses, but also to develop an unstructured model based on a Monod-type kinetic equation for cell growth and two independent linear equations for the consumption rates of lactose and oxygen. Moreover, a typical Lineweaver—Burk plot enabled the yeast specific growth rate to be described as that of an enzyme-catalysed reaction in the presence of an unknown noncompetitive inhibitor (that was identified with a reference intermediate compound produced by the microorganism itself under partially anaerobic conditions and expressed in terms of ethanol equivalent). In this way, the experimental cell concentrations were reconstructed with a mean standard error of about 10%, thus confirming the capability of this model to provide a reliable basis for further scale-up of this fermentation process.     

菊芋预处理方法对多糖质量分数影响的研究

通过对新鲜菊芋的几种干燥及贮存方式的探讨研究,从中确定了适于产业化的干燥、贮存及提取纯化菊芋多糖的最佳工艺条件,为进一步工业化奠定了基础.     

菊芋资源开发利用研究进展

综述了菊芋在国内沙漠化土地以及盐碱地的种植现状,介绍了利用菊芋制备菊粉、果糖、高果糖浆、低聚果糖等产品的国内外研究进展以及菊芋作为食物和发酵原料的应用情况,指出了菊芋可在生产功能糖、发酵基料中替代玉米淀粉的可行性和应用前景。     

稀酸水解菊芋制乙醇技术研究

考察了固液质量比、酸浓度、反应温度和反应时间4个条件对菊芋粉稀酸水解的总糖浓度和总糖转化率的影响。结果表明,菊芋稀酸水解的最优化条件为:固液比0.3,硫酸浓度3%,反应温度80℃,反应时间90 min。在此条件下水解菊芋,水解液中的总糖浓度为24.1%,总糖转化率为80.3%;水解液经过中和后,接入酵母菌发酵产乙醇,最终乙醇浓度可达到10.4%,乙醇得率为86.4%。     

泵注入方式进料催化菊芋根茎溶液制备多元醇

以硝酸镍和偏钨酸铵为前驱体,活性炭(AC)为载体,通过等体积浸渍氢气还原法分别制备Ni-W2C/AC和Ni/AC催化剂,利用N2吸附仪、XRD、TEM、TG和XRF等对催化剂及原料进行表征。釜式反应器中,对催化剂催化果糖或果糖基能源植物菊芋根茎制备多元醇高附加值化合物进行评价。结果表明,相同反应温度下,与间歇进料方式相比,泵注入方式能进一步提高1,2-丙二醇和乙二醇收率。以果糖为底物,泵速0.5 m L·min-1条件下,氢气起始压力4.0 MPa、温度245℃时,1,2-丙二醇和乙二醇收率分别为41.4%和18.7%,二者总收率较间歇进料增加17.9个百分点;以菊芋根茎为底物,氢气起始压力3.5 MPa、温度255℃时,1,2-丙二醇和乙二醇收率分别为37.7%和27.4%,二者总收率较间歇进料增加10.7个百分点。结合果糖、葡萄糖分子在氢气气氛下进行的逆羟醛缩合和加氢过程,分析泵注入进料提高1,2-丙二醇和乙二醇收率的主要原因。     

A study on the factors for improving the ethanol production from Jerusalem artichoke by Kluyveromyces fragilis

This study is to investigate the factors influencing the alcohol production byKluyveromyces fragilis using the juice of Jerusalem Artichoke tubers. The cell growth rate and ethanol production rate were stimulated by aeration and by the addition of unsaturated fatty acids and the cell mass production and the ethanol production were substantially improved. It was found that oxygen and unsaturated fatty acids added played a decisive role on the increase of alcohol tolerance of yeast.     

酵母细胞连续发酵过程振荡现象的研究进展

振荡现象在连续发酵过程中普遍存在,本文综述了酿酒酵母连续发酵中不同类型振荡现象的研究进展。一类以乙醇连续发酵过程中参数振荡为代表的特殊振荡现象,普遍存在于工业发酵过程,对发酵系统的稳定运行造成不利影响。本文论述了这类振荡现象产生的机理、调控策略的研究进展及其潜在的应用价值。     

Optimal continuous fermentation reactor design

Many optimum reactor combination schemes have been proposed for fermentation (autocatalytic) reaction systems. Usually these consist of series of stirred tanks or plug flow vessels. The basis for choosing an optimal scheme is here presented and it is found that for many cases of interest the combination of stirred tank - plug flow is the best.     

A strategy to regulate continuous fermentation processes with unknown reaction rates

Identification and control of continuous fermentation processes are dif-ficult tasks due to the complexity and high coupling of dynamic behaviour of this kind of system. In this work is implemented an on-line estimation technique of the main uncertainties of a fermentation processes (e.g. specific growth rate, biomass concentration and yield coefficient) based on a mass balance, to generate a linearising feedback control law that provides a robust stabilisation against uncertainties. By numerical simulations the performance of the closed-loop system and the controller design procedure is illustrated.     

Optimisation of a continuous flash fermentation for butanol production using the response surface methodology

Factorial design and response surface techniques were used in combination with mathematical modelling and computational simulation to optimise an innovative industrial bioprocess, the production of biobutanol employing the flash fermentation technology. A parametric analysis performed by means of a full factorial design at two levels determined the influence of operating variables on butanol yield and productivity. A second set of simulations were carried out based on the central composite rotatable design. This procedure generated simplified statistical models that describe butanol yield and productivity as functions of the significant operating variables. From these models, response surfaces were obtained and used to optimise the process. For a range of substrate concentration from 130 to 180 g/l, the optimum operating ranges ensure butanol productivity between 7.0 and 8.0 g/l h, butanol yield between 19 and 22%, substrate conversion above 90% and final butanol concentration around 25 g/l.     

乳酸连续化发酵进展

对一些新型的乳酸连续化发酵装置,包括恒浊器、两级恒化器、两级固定床、两级膜细胞循环反应器、三相流化床-电渗析、塑料支持生物膜反应器及相应的发酵条件进行了综述;讨论了连续化发酵的控制(无反馈控制、反馈控制)、数学模型、最优化方法;并分析了不同连续化发酵装置的优缺点及前景.     

林可霉素发酵液组合连续絮凝

用组合连续絮凝法及容器实验絮凝法对林可霉素发酵液进行絮凝分离研究.容器实验絮凝法结果显示：阳离子型聚丙烯酰胺絮凝分离效果优于壳聚糖和草酸,其最佳浓度为70 mg•L^-1,此时絮体沉降速率比用草酸时高24%,过滤速率高31%.组合连续絮凝法是对容器实验絮凝法的改进,其实验路线为：泵和管道输送发酵液→絮凝剂和发酵液在混合器中混合→絮凝柱连续流动絮凝→分离器固液分离.絮凝柱流量1 L•min^-1,平均停留时间10 min,pH为3,温度20℃,阳离子型聚丙烯酰胺浓度70 mg•L^-1.结果显示：组合连续絮凝法比容器实验絮凝法的沉降速率提高46%,过滤速率提高67%.该结果为工业发酵液高效过滤分离及高效离心分离提供了重要依据.     

PDMS膜在ABE连续发酵中的渗透汽化性能研究

构建了膜生物反应器封闭循环ABE连续发酵系统,研究了系统中PDMS膜的渗透汽化性能.实验共进行2轮,第一轮进行274 h,采用发酵-渗透汽化间歇耦合的方式;第二轮进行312 h,前196 h采用发酵-渗透汽化连续耦合,之后实行间歇耦合.间歇耦合操作模式下,2轮的丁醇分离因子分别为11.00和12.94,总通量分别为711.07和579.98 g/(m2·h);连续耦合操作模式下,第二轮丁醇分离因子为5.54,总通量为555.80g/(m2·h).实验中膜性能稳定,分离性能良好,未出现膜堵塞和膜破损现象.     

Optimization of fermentation medium composition in substrate-controlled continuous stirred tank reactors

A ‘carbon source controlled shift technique’ was developed for fermentation medium optimization in continuous culture with the objective to maximize growth rate and growth-linked product formation of a biological system. An automatic culture medium preparation system was operated together with 2 parallel stirred tank reactors and a HPLC system for on-line analysis of the carbon source concentration in the reactors. A genetic algorithm was applied for experimental design. The concentrations of 7 medium components (mineral salts and vitamins) were optimized automatically within 40 continuous experiments to result in a maximum growth rate of the methylotrophic yeast Candida boidinii and growth-linked production of the formate dehydrogenase enzyme (FDH). The specific growth rate of Candida boidinii and the specific activity of the FDH enzyme at a set-point of 420 mM methanol in the reactor were, thus, improved by 19% to 0.16 h^?1 and 26% to 164 U g^?1, respectively, compared to the previously used medium, which has already been previously optimized in shake flask experiments. The results of the continuous medium optimization were evaluated with a full second order seven-dimensional polynomial model (regression coefficient 96.8%).     

Liquid-liquid and vapour-liquid behaviour of oleyl alcohol applied to extractive fermentation processing

Investigations into the product recovery step of the extractive ethanol fermentation through partition experiments for ethanol-water-Adol^r? 85 NF ternary systems were undertaken. Experimental liquid-liquid equilibrium data for this ternary system were compared with numerical predictions based on the UNIFAC method. The influence of salts on distribution coefficients for ethanol extraction was also examined. An improvement in extraction characteristics was observed for ternary systems with salts. Flash vaporisation was used to subsequently examine the effect of liquid-liquid ternary compositions on vapour-liquid partitioning. The UNIFAC model was found to be very useful for semi-quantitative analysis of such liquid extraction systems.     

Production of ethanol by continuous fermentation and liquid–liquid extraction

A continuous pilot plant was constructed for fermentation production of ethanol, using liquid–liquid extraction to remove the product and with recycle of the fermented broth raffinate. The plant was operated for up to 18 days with feed glucose concentrations in the range 10·0–45·8% (w/w). The solvent was n-dodecanol and immobilised yeast was used to overcome the problem of emulsification. The concentration of by-products in the fermented broth had no adverse effect on the rate of ethanol production. A mathematical model to predict the time required for achievement of 99% of the steady-state by-products concentrations was shown to be in good agreement with the experimentally determined concentration of the main by-product, glycerol. At a feed glucose concentration of 45·8% (w/w), the aqueous purge was equivalent to 2·8 m³ of effluent per m³ of ethanol produced and represented a 78% reduction in the volume of the aqueous purge compared with using a feed containing 10% (w/w) glucose.     

Use of long-chain alcohol in extraction and purification of lincomycin from fermentation broth

Low selectivity for lincomycin in butanol extraction process leads to relatively higher content of impurities. A novel process for extraction of lincomycin from fermentation broth was studied in this work. Mixture of n-octanol and n-decanol is used as extradant to replace n-butanol in extraction of lincomycin. Optimal operation conditions for the process have been studied. Due to higher extraction selectivity for lincomycin A by long-chain alcohol, content of impurity (lincomycin B) in the final product is much lower than that in product by butanol process. Furthermore, the practicability for combination of long-chain alcohol and butanol in purification of lincomycin was investigated.     

木薯酒精渣的预处理及补料同步糖化发酵制取乙醇

木薯酒精渣的处置是制约木薯燃料乙醇大规模产业化的问题之一。本文立足于探索木薯酒精渣利用途径,分析了木薯酒精渣的主要成分,对比了氨水、氢氧化钠、氨水组合稀硫酸3种预处理方式对于木薯酒精渣纤维素和木素含量及纤维素酶水解效率的影响,分析了处理前后木薯酒精渣的表面结构及纤维素结晶度,并以氨水处理后的木薯酒精渣为底物,进行了同步糖化发酵。结果表明,3种预处理方法中组合预处理能更好地增加纤维素含量和提高纤维素酶水解效率,与未处理原料相比,组合预处理后纤维素含量增加了111.26%,木素下降了35.05%,酶水解72h纤维素转化率从42.10%增加到61.71%。氨水预处理后,原料的木素含量降低,处理后木薯酒精渣的表面变得更加粗糙,纤维素结晶度有所增加,以氨水处理后的木薯酒精渣为底物进行分批补料同步糖化发酵,当初始底物浓度为100.0g/L,分别在20h、40h、60h进行补料至最终底物浓度为400.0g/L时,发酵120h乙醇浓度达到51.0g/L。     

A comparative study of effects of soy and corn flours on the evolution of alcohol fermentation in successive batches

The evolution of alcohol fermentation in ten successive batches was analysed using three distinct media, all containing commercial sucrose as substrate. The first medium contained mineral salts and yeast extract, the second contained only soy flour as the nutrient source and the third only corn flour. The alcohol contents and yeast viabilities were determined during ten successive batches with each medium. There was no significant differentiation in ethanol yield during the total period of tests (60 h with each medium). However, the medium containing soy flour showed the best evolution of yeast viability. The best specific productivity of ethanol was obtained with the medium containing corn flour, which justifies the traditional and empirical use of the component in the fermentation step by the small producers of sugar cane spirits in Brazil.     

乙醇连续发酵与膜超滤耦合过程研究

采用ＣＡ－Ｔｉ复合管式膜组件与发酵耦合操作，用啤酒酵母从葡萄糖连续发酵乙醇是一个从不稳态到稳态的过程。其稳态的最佳操作参数为：初始葡萄糖浓度１４０ｇ／Ｌ，稀释率０．３ｈ~（－１），轴出比０．６３８，相应的细胞浓度２×１０~９ｃｅｌｌ／ｍＬ，葡萄糖利用率９２％，生产率２２ｇ／（Ｌ·ｈ）。当细胞浓度增加到一定程度时，乙醇生产率和酵母比生长速率的增长减缓。反应器中细胞的浓度由稀释率和轴出比决定。