稀释速率对高浓度酒精连续发酵过程振荡行为的影响

在一搅拌罐和三段管式反应器组成的组合反应器系统中,使用葡萄糖浓度为280g/L,添加5g/L酵母膏和3g/L蛋白胨的底物,在总稀释速率分别为0.032h^-1,0.024h^-1,0.017h^-1,0.012h^-1和0.006h^-1的条件下,考察了稀释速率对高浓度酒精发酵系统振荡行为的影响。结果表明,振荡行为在特定的稀释速率条件下呈现,进而基于数学上的分岔理论,分析了振荡行为发生的可能性及对应的稀释速率范围,并与实验结果进行了比较,在此基础上,讨论了振荡行为对酒精发酵过程的影响。     

自絮凝酵母SPSC01在组合反应器系统中酒精连续发酵的研究

建立了一套由四级磁力搅拌发酵罐串联组成、总有效容积4000mL的小型组合生物反应器系统 ,其中一级罐作为种子培养罐。以脱胚脱皮玉米粉双酶法制备的糖化液为种子培养基和发酵底物 ,进行了自絮凝颗粒酵母酒精连续发酵的研究。种子罐培养基还原糖浓度为100g L ,添加 (NH₄)₂HPO₄ 和KH₂PO₄ 各 20g L ,以0.017h^-1 的恒定稀释速率流加 ,并溢流至后续酒精发酵系统。发酵底物初始还原糖浓度 220g/L ,添加 (NH₄)₂HPO₄ 15g/L和KH₂PO₄2 5g/L ,流加至第一级发酵罐 ,稀释速率分别为 0.017、0.025、0.033、0.040和0.05 0h^-1。实验数据表明 ,自絮凝颗粒酵母在各发酵罐中呈部分固定化状态 ,在稀释速率0.040h^-1 条件下 ,发酵系统呈一定的振荡行为 ,其他四个稀释速率实验组均能够达拟稳态。当稀释速率不超过 0 0 33h^-1 ,流出末级发酵罐的发酵液中酒精浓度可以达到 12 % (V/V)以上 ,残还原糖和残总糖分别在 0 11%和 0 35 % h^-1,流出末级发酵罐的发酵液中酒精浓度可以达到12%（V/V）以上,残还原糖和残总糖分别在0.11%和0.35%（W/V）以下。在稀释速率为0.033h^-1时,计算发酵系统酒精的设备生产强度指标为3.32（g·L^-1·h^-1）,与游离酵母细胞传统酒精发酵工艺相比,增加约1倍。     

能源上的应用

891021最大限度提高固定化细胞反应器的产量〔会,英〕/Vega,J.L.…了Aoll.N.Y .Aead.Sei一1957,506一208~228〔译自DBA,1988,7(16),88一08088〕 固定化细胞反应器的乙醇产量已提高到最大限度。利用由戊二醛交联在明胶载体上的酿酒酵母(Saccharom夕cesc“re”i“ae)的立式固定化细胞反应器,对于达到高的稀释率和细胞浓度是有效的。反应器长时间很稳定,在这段时期内细胞浓度不断增加而不达到稳定态。为了从空隙中除去多余的生物量,必须定期进行气体清洗。在葡萄糖浓度为15一20%时,”%的葡萄糖转化为乙醇。底物浓度高和流速快促进了质量传…     

甲醇抑制时重组毕赤酵母发酵的特性研究

本文对毕赤酵母进行了恒化培养研究。以甲醇为唯一碳源时,在稀释率较低时(D<0.048 h^-1),连续培养系统操作很稳定。但在稀释率高时(D>0.048h^-1),连续培养系统的定态点不止一个,实验不能维持,故采用比生长速率恒定的分批流加培养进行研究。结果表明,毕赤酵母的生长符合Andrew普遍化底物抑制模型。综合考虑水蛭素的生成、底物的消耗,在生产中维持甲醇浓度为限制性浓度(0.5 g/L),且维持比生长速率为0.02 h^-1时,水蛭素Hir65的比生成速率达到最大值0.2 mg/(g·h)且甲醇的比消耗速率为0.04 g/(g·h)。     

自絮凝颗粒酵母乙醇连续发酵耦合酵母回用工艺的研究

模拟现有酒精发酵行业普遍采用的多级发酵罐串联系统,建立了一套由三级串联操作的搅拌式发酵罐和两个沉降罐组成的反应器系统,以脱胚脱皮玉米粉双酶法制备的糖化液为发酵底物,培养基初始还原糖浓度为220g/L,添加(NH4)2HPO41.5g/L和KH2PO42.5g/L,以0.057h-1的恒定稀释速率流加,将自沉降浓缩后的酵母乳先后经活化和不活化两种方式处理并循环至第一级发酵罐,系统在两种操作条件下分别达到了拟稳态。实验结果表明活化处理对改善发酵工艺技术指标方面发挥了显著的作用,发酵终点乙醇浓度达到101g/L,还原糖和残总糖分别在3.2和7.7g/L左右,发酵系统的设备生产强度指标为5.77g/(L.h),与无酵母回用的搅拌式反应器系统中自絮凝颗粒酵母乙醇发酵工艺相比,提高了70%。     

一种用于微藻培养的新型板式光生物反应器

微藻的闪光效应可以大幅提高微藻的光效率,提高微藻产量。通过在传统的板式光生物反应器中加入斜挡板以增强微藻的闪光效应。以小球藻为模型藻种,考察了新型板式光生物反应器内不同光强和不同进口流速对小球藻生长速率和光效率的影响。结果表明,当进口流速为0.16 m/s时,随着光强的提高,小球藻的细胞浓度逐渐增加,光效率逐渐降低;在500μmol/(m2·s)的光强条件下,小球藻细胞浓度和光效率均随着进口流速的提高而增加。新型板式光生物反应器内小球藻的细胞浓度比传统板式光生物反应器提高了39.23%,表明在传统板式光生物反应器内加入斜挡板可有效增强微藻的闪光效应。     

螺旋藻连续培养与动力学模型

在内循环气升式光生物反应器中 ,研究了钝顶螺旋藻 (SpirulinaplatensisGeitler)细胞的连续生长及其对碳源底物的利用特性。结果表明 :随着稀释率的增大 ,反应器中碳源浓度和细胞浓度分别呈上升和下降趋势 ,它们之间的关系可用Monod类型的方程很好地加以关联。细胞产率和碳消耗速率与稀释率的关系存在峰值现象 :在本实验条件下 ,最大细胞产率为 0 .36 2g/(L·d) ,最大碳消耗速率为 0 .177g/(L·d) ,此时稀释率为 0 .45 /d ,细胞浓度为OD560 =1.2 82 ,细胞对碳的得率系数为 2 .0 5 0g/g。所提出的连续培养动力学模型与实验数据拟合较好     

初始条件对高浓度乙醇连续发酵过程的影响及振荡行为提高发酵效率的机理分析

前期实验在稀释速率为0.027h-1的高浓度乙醇连续发酵过程中,发现了一种长周期、宽振幅的参数振荡现象。本实验进一步考察了不同稀释速率下的连续发酵过程,发现在稀释速率为0.04h-1条件下,也能出现类似的振荡现象;在稀释速率为0.027h-1或0.04h-1的条件下,改变系统的初始状态可以得到振荡和稳态两种不同的发酵过程。比较振荡和稳态过程的实验数据后,发现在稀释速率为0.04h-1的条件下,与稳态过程相比,振荡过程的平均残糖浓度降低了14.8%,平均乙醇浓度提高了12.6%,平均设备生产强度提高了12.3%。进一步分析表明:与稳态过程相比,振荡过程动力学行为不仅存在滞后,而且在相同残糖和乙醇浓度条件下,所对应的平均比生长速率提高了53.8%。     

固定化酵母酒精生成动力学及其数学模型

本文采用解析法对海藻酸钙为载体,以葡萄糖为底物进行酒精连续发酵的管式反应器内所呈现的固定化K字酵母酒精发酵动力学进行了较为系统的研究,建立了由6个方程组成的酒精生成动力学数学模型,并对此模型进行了应用方面的研究。结果表明：此动力学呈现葡萄糖的反竞争性和酒精非竞争性联合抑制的不可逆特征,其数学模型在所涉及的参数拟合及分别在不同反应器和浓度扩展时的发酵过程所进行的实际校验中,最大的算术平均百分误差为13．8l％,在薯干糖化液的发酵动力学应用中,具有平均差为8．28％之良好预测精度,同时,通过模型中参数式计算得葡萄糖抑制的浓度范围为130—450g／L,而酒精抑制的浓度范围是3．07—16．45％(v／v)。     

城市生活污水浇灌对金盏菊生长的影响

用三种稀释倍数的城市生活污水[污水:清水(v/v)为1:0、1:0.5、1:1]处理金盏菊种子及盆花,结果表明,污灌处理不仅显著地降低种子的萌发率,还增加萌发后幼苗病害的发生率;未经稀释的原生污水显著抑制金盏菊幼苗的生长,而稀释后抑制作用降低,当稀释至适当浓度时,则对幼苗生长起促进作用;对于金盏菊成年植株,污灌处理(不论稀释与否)显著地增加其茎、叶和根的鲜重,分别较对照增加161.63%~215.12%、86.77%~109.23%和23.89%~34.13%。综合分析表明,原生污水经过适当稀释后用于草花污灌,可以使污水中的营养盐得到回用,提高草花的观赏性。     

Comparative study of ethanol production by an immobilized yeast in a tubular reactor and in a multistage reactor

Summary The productivity of continuous ethanol fermentation has been increased using fixed bed reactors where a high density of yeast cells was maintained on a packing of wood chips. Two different systems have been used: 1. A tubular reactor which produced alcohol solutions containing up to 13.5% (V/V) ethanol. High CO₂ retention and a poor mass transfer between bulk medium and immobilized biomass prevented production rates higher than 2.2 g/l·h. 2. A multistage reactor where a better utilisation of the reactor volume led to improved performances. Solutions containing 132 g/l of ethanol (16.5% V/V) were produced with a productivity increased up to 4.8 g/l·h. A better distribution of the active biomass and a lower gradient of alcohol concentration between support and bulk medium are possible reasons for this improvement.     

Production of ethanol in repeated-batch fermentation with membrane-type bioreactor

The average ethanol content in sake is 14 wt%; continuous production of such a high ethanol content was found not to be stably maintained in a packed-bed bioreactor with immobilized yeast cells, used normally for production of an ethanol content of up to 10 wt%. However, use of repeated-batch ethanol fermentation incorporating a membrane filter for product separation enabled a high ethanol content and improved productivity to be achieved. In this bioreactor, the yeast cells were retained within the bioreactor and a high yeast concentration was possible. A filtrate containing 14 wt% ethanol was obtained steadily after each batchwise operation. At a yeast concentration of 110 g/l, an ethanol productivity of 3.5 g/l/h was attained, which is 9 times higher than that in conventional batch fermentation. A mathematical model is proposed for assessment of the repeated-batch fermentation process. The estimated results agreed well with the observed ones. With a view to the application of this system to sake production, the aroma components of the filtrate were assayed and compared with those of a commercial-grade sake.     

The production of ethanol from lactose in a tubular reactor by immobilized cells of Kluyveromyces fragilis

Summary An immobilized-cell tubular reactor for the continuous fermentation of lactose by Kluyveromyces fragilis was developed. Two types of supporting media were successfully tested; beechwood cubes and activated charcoal pellets. Ethanol productivity of 17.2 g/l/h was achieved from a 15% whey-lactose solution using K. fragilis immobilized on charcoal pellets, with a final ethanol concentration of 18 g/l. The use of two reactors in series demonstrated that it is possible to obtain up to 50 g/l of ethanol in the final product. No decrease in biological activity of the immobilized yeast cells occurred over a period of up to 31 days of continuous operation.     

Parameter oscillations in a very high gravity medium continuous ethanol fermentation and their attenuation on a multistage packed column bioreactor system

The quasi-steady-states, marked by small fluctuations of residual glucose, ethanol, and biomass concentrations, and sustainable oscillations marked by big fluctuations of these monitored fermentation parameters were observed during the continuous ethanol fermentation of Saccharomyces cerevisiae when very high gravity media were fed and correspondingly high ethanol concentrations reached. A high ethanol concentration was shown to be one of the main factors that incited these oscillations, although the residual glucose level affected the patterns of these oscillations to some extent. The lag response of S. cerevisiae to high ethanol stress that causes the shifts of morphology, viability loss, and death of yeast cells is assumed to be one of the probable mechanisms behind these oscillations. It was predicted that the longer the delay of this response was, the longer the oscillation periods would be, which was validated by the experimental data and the comparison with the oscillatory behaviors reported for the ethanologen bacterium, Zymomonas mobilis. Furthermore, three tubular bioreactors in series were arranged to follow a stirred tank bioreactor to attenuate these oscillations. However, exaggerated oscillations were observed for the residual glucose, ethanol, and biomass concentrations measured in the broth from these tubular bioreactors. After the tubular reactors were packed with Intalox ceramic saddle packing, these oscillations were effectively attenuated and quasi-steady-states were observed during which there were very small fluctuations of residual glucose, ethanol, and biomass within the entire experimental run.     

An immobilized cell reactor with simultaneous product separation. II. Experimental reactor performance

The simultaneous separation of volatile fermentation products from product-inhibited fermentations can greatly increase the productivity of a bioreactor by reducing the product concentration in the bioreactor, as well as concentrating the product in an output stream free of cells, substrate, or other feed impurities. The Immobilized Cell Reactor-Separator (ICRS) consists of two column reactors: a cocurrent gas-liquid "enricher" followed by a countercurrent "stripper" The columns are four-phase tubular reactors consisting of (1) an inert gas phase, (2) the liquid fermentation broth, (3) the solid column internal packing, and (4) the immobilized biological catalyst or cells. The application of the ICRS to the ethanol-from-whey-lactose fermentation system has been investigated. Operation in the liquid continuous or bubble flow regime allows a high liquid holdup in the reactor and consequent long and controllable liquid residence time but results in a high gas phase pressure drop over the length of the reactor and low gas flow rates. Operation in the gas continuous regime gives high gas flow rates and low pressure drop but also results in short liquid residence time and incomplete column wetting at low liquid loading rates using conventional gas-liquid column packings. Using cells absorbed to conventional ceramic column packing (0.25-in. Intalox saddles), it was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation. Using cells sorbed to an absorbant matrix allowed operation in the gas continuous regime with a liquid holdup of up to 30% of the total reactor volume. Good reaction rates and product separation were obtained using this matrix. High reaction rates were obtained due to high density cell loading in the reactor. A dry cell density of up to 92 g/L reactor was obtained in the enricher. The enricher ethanol productivity ranged from 50 to 160 g/L h while the stripper productivity varied from 0 to 32 g/L h at different feed rates and concentrations. A separation efficiency of as high as 98% was obtained from the system.     

Continuous SSCF of AFEX™ pretreated corn stover for enhanced ethanol productivity using commercial enzymes and Saccharomyces cerevisiae 424A (LNH‐ST)

High productivity processes are critical for commercial production of cellulosic ethanol. One high productivity process—continuous hydrolysis and fermentation—has been applied in corn ethanol industry. However, little research related to this process has been conducted on cellulosic ethanol production. Here, we report and compare the kinetics of both batch SHF (separate hydrolysis and co‐fermentation) and SSCF (simultaneous saccharification and co‐fermentation) of AFEX? (Ammonia Fiber Expansion) pretreated corn stover (AFEX?‐CS). Subsequently, we designed a SSCF process to evaluate continuous hydrolysis and fermentation performance on AFEX?‐CS in a series of continuous stirred tank reactors (CSTRs). Based on similar sugar to ethanol conversions (around 80% glucose‐to‐ethanol conversion and 47% xylose‐to‐ethanol conversion), the overall process ethanol productivity for continuous SSCF was 2.3‐ and 1.8‐fold higher than batch SHF and SSCF, respectively. Slow xylose fermentation and high concentrations of xylose oligomers were the major factors limiting further enhancement of productivity. Biotechnol. Bioeng. 2013; 110: 1302–1311. © 2012 Wiley Periodicals, Inc.     

Rapid ethanol fermentation with immobilized Zymomonas mobilis in a three stage reactor system

Summary Using the Zymomonas mobilis NRRL B 14023 strain for ethanol fermentation with immobilized cells the combination of two external loop reactors followed by a plug flow reactor was the most effective reactor configuration. A maximal productivity of 92 and 108 g/l·h at practically complete sugar consumption was obtained with Carrageenan and Alginate catalysts respectively. Due to the high dilution rate nonsterile operation for extended periods of weeks was possible.     

Optimization of batch alcoholic fermentation of glucose syrup substrate

The quantitative effects of substrate concentration, yeast concentration, and nutrient supplementation on ethanol content, fermentation time, and ethanol productivity were investigated in a Box–Wilson central composite design experiment, consisting of five levels of each variable, High substrate concentration, up to 30° Brix, resulted in higher ethanol content (i.e., up to 15.7% w/v or 19.6% v/v) but longer fermentation time and hence lower ethanol productivity. Increasing yeast concentration, on the other hand, resulted in shorter fermentation time and higher productivity. The highest ethanol productivity of about 21 g EiOH/L h was obtained at low substrate concentration (i.e., 12° Brix), low alcohol content (i.e., 6% by weight), high yeast concentration (i.e., 4.4%), and high supplementation of yeast extract (i.e., 2.8). Productivity of this magnitude is substantially higher that that of the traditional batch fermentation of fed-batch fermentation. It is comparable to the results of continuous fermentation but lower than those of vacuum fermentation but lower than those of vacuum fermentation. Optimal conditions for maximal ethanol productivity can be established by a multiple regression analysis technique and by plotting the contours of constant response to conform to the constraints of individual operations.     

Ethanol fermentation in a magnetically fluidized bed reactor with immobilized Saccharomyces cerevisiae in magnetic particles

Ethanol fermentation by immobilized Saccharomyces cerevisiae cells in magnetic particles was successfully carried out in a magnetically stabilized fluidized bed reactor (MSFBR). These immobilized magnetic particles solidified in a 2 % CaCl(2) solution were stable and had high ethanol fermentation activity. The performance of ethanol fermentation of glucose in the MSFBR was affected by initial particle loading rate, feed sugar concentration and dilution rate. The ethanol theoretical yield, productivity and concentration reached 95.3%, 26.7 g/L h and 66 g/L, respectively, at a particle loading rate of 41% and a feed dilution rate of 0.4 h(-1) with a glucose concentration of 150 g/L when the magnetic field intensity was kept in the range of 85-120 Oe. In order to use this developed MSFBR system for ethanol production from cheap raw materials, cane molasses was used as the main fermentation substrate for continuous ethanol fermentation with the immobilized S. cerevisiae cells in the reactor system. Molasses gave comparative ethanol productivity in comparison with glucose in the MSFBR, and the higher ethanol production was observed in the MSFBR than in a fluidized bed reactor (FBR) without a magnetic field.     

Overexpression of the OLE1 gene enhances ethanol fermentation by Saccharomyces cerevisiae

 The fermentation characteristics of Saccharomyces cerevisiae strains which overexpress a constitutive OLE1 gene were studied to clarify the relationship between the fatty acid composition of this yeast and its ethanol productivity. The growth yield and ethanol productivity of these strains in the medium containing 15% dextrose at 10 °C were greater than those of the control strains under both aerobic and anaerobic conditions but this difference was not observed under other culture conditions. During repeated-batch fermentation, moreover, the growth yield and ethanol productivity of the wild-type S. cerevisiae increased gradually and then were similar to those of the OLE1-overexpressing transformant in the last batch fermentation. However, the unsaturated fatty acid content (77.6%) of the wild-type cells was lower than that (86.2%) of the OLE1-recombinant cells. These results suggested that other phenomena caused by the overexpression of the OLE1 gene, rather than high unsaturated fatty acid content, are essential to ethanol fermentation by this yeast. Received: 11 June 1999 / Received last revision: 12 November 1999 / Accepted: 28 November 1999