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%。     

产琥珀酸放线杆菌固定CO_2制备丁二酸

在富含CO2的厌氧环境下,产琥珀酸放线杆菌NJ113固定CO2合成丁二酸作为主要代谢终产物。在5 L发酵罐探讨了培养条件对产琥珀酸放线杆菌NJ113固定CO2制备丁二酸的影响。考察了CO2供体形式、通气量、搅拌转速、培养温度和pH值对产琥珀酸放线杆菌NJ113厌氧发酵过程中CO2固定速率以及丁二酸产率的影响。结果表明,选择CO2气体作为CO2供体,CO2通气量为0.75 L/min,搅拌转速达到200 r/min,培养温度为37℃,NaOH调节pH值为6.6,可增加细胞内可利用的CO2。在此优化条件下培养,CO2固定速率达到0.6 g/(L.h),丁二酸产率达到1.61 g/(L.h)。     

氧化还原电位调控对Actinobacillus succinogenes 厌氧发酵产丁二酸的影响

对氧化还原电位调控在产琥珀酸放线杆菌厌氧发酵产丁二酸过程中的代谢产物分布的作用进行了研究。在血清瓶发酵培养过程中,筛选出对发酵过程无抑制作用的氧化剂铁氰化钾和还原剂二硫苏糖醇作为发酵体系的氧化还原电位调节剂。在3L发酵罐上利用铁氰化钾和二硫苏糖醇调节发酵体系氧化还原电位值在-100～-450mV,结果表明-350mV为菌体生长和产丁二酸的最佳电位,丁二酸生产速率由0.75g/(L·h)提高到1.18g/(L·h),产物丁二酸与副产物乙酸的质量浓度比由2.5提高到3.9。     

放线杆菌生产琥珀酸的研究进展

总结了利用放线杆菌生产琥珀酸时,提高琥珀酸产量的主要途径,并介绍了琥珀酸的回收方法。     

利用甘蔗糖蜜与乳清粉厌氧发酵制备丁二酸

考察了甘蔗糖蜜替代昂贵葡萄糖作为碳源、乳清粉替代大部分酵母粉作为氮源时,对Actinobacillus succinogenes NJ113发酵制备丁二酸的影响。血清瓶厌氧发酵结果证明：对照组（葡萄糖40 g/L）的丁二酸产量仅为26.04 g/L,而以糖蜜为碳源（以总还原糖计算为40 g/L）时,丁二酸产量达到28.27 g/L,比对照组提高了8.57%。在此基础上,以糖蜜为碳源、不同比例的乳清粉和酵母粉为混合氮源发酵制备丁二酸,确定了糖蜜、乳清粉和酵母粉混合使用的最佳浓度分别为40 g/L、8 g/L和2 g/L。此外,在3 L发酵罐体系中添加40 g/L糖蜜、8 g/L乳清粉、2 g/L酵母粉进行发酵试验,实验结果证明：丁二酸终产量达到32.54 g/L,收率达到81.13%。     

Continuous bioremediation of phenol‐polluted air in an external loop airlift bioreactor with a packed bed

An external loop airlift bioreactor with a small amount (99% porosity) of stainless steel mesh packing inserted in the riser section was used for bioremediation of a phenol‐polluted air stream. The packing enhanced volatile organic chemical and oxygen mass transfer rates and provided a large surface area for cell immobilization. Using a pure strain of Pseudomonas putida, fed‐batch and continuous runs at three different dilution rates were completed with phenol in the polluted air as the only source of growth substrate. 100% phenol removal was achieved at phenol loading rates up to 33 120 mg h^?1 m^?3 using only one‐third of the column, superior to any previously reported biodegradation rates of phenol‐polluted air with 100% efficiency. A mathematical model has been developed and is shown to accurately predict the transient and steady‐state data. Copyright © 2006 Society of Chemical Industry     

Fermentation of cheese whey powder solution to ethanol in a packed‐column bioreactor: effects of feed sugar concentration

BACKGROUND: Cheese whey powder (CWP) is a concentrated source of lactose and other essential nutrients for ethanol fermentation. CWP solution containing different concentrations of total sugar was fermented to ethanol in an up‐flow packed‐column bioreactor (PCBR) at a constant hydraulic residence time (HRT) of 50 h. Total sugar concentration in the feed was varied between 50 and 200 g L^?1 and a pure culture of Kluyveromyces marxianus was used for ethanol fermentation of lactose. Variations of ethanol and sugar concentrations with the height of the column and with the feed sugar concentration were determined. RESULTS: Ethanol concentration increased and total sugar decreased with the column height for all feed sugar contents. The highest effluent ethanol concentration (22.5 g L^?1) and ethanol formation rate were obtained with feed sugar content of 100 g L^?1. Percentage sugar utilization decreased with increasing feed sugar content above 100 g L^?1 yielding lower ethanol contents in the effluent. The highest ethanol yield coefficient (0.52 gE g^?1S) was obtained with a feed sugar content of 50 g L^?1. Biomass concentration also decreased with column height, yielding low ethanol formation in the upper section of the column. CONCLUSION: The packed column bioreactor was found to be effective for ethanol fermentation from CWP solution. The optimum feed sugar content maximizing the effluent ethanol and the specific rate of ethanol formation was found to be 100 g L^?1. High sugar content above 100 g L^?1 resulted in low ethanol productivities due to high maintenance requirements. Copyright © 2008 Society of Chemical Industry     

响应面优化木糖母液发酵产丁二酸

对产琥珀酸放线杆菌（Actinobacillus succinogenes）GXAS137发酵木糖母液产丁二酸的条件进行优化,探索利用废弃木糖母液合成高附加值丁二酸的可行性。首先通过Plackett-Burman实验设计确定影响丁二酸发酵的显著因子,然后采用最陡爬坡实验逼近各显著因子的最优区域,最后通过Box-Behnken实验设计确定各因子的最优水平。影响木糖母液发酵产丁二酸的显著因子及最优浓度分别为：木糖母液64.75g/L,玉米浆15.71g/L,碱式碳酸镁46.39g/L。在最优发酵培养条件下,丁二酸产量达到38.01g/L,比优化前提高了20.7%,与模型预测值（38.41g/L）基本一致。进一步利用2L发酵罐进行了放大试验,发酵72h丁二酸产量最高可达48.99g/L,较厌氧瓶发酵提高了28.9%,丁二酸得率为0.80g/g总糖。结果表明,采用低价的木糖母液作为底物,可为未来低成本、高效产业化生产丁二酸奠定坚实的基础。     

Optimization of inulinase production by solid‐state fermentation in a packed‐bed bioreactor

BACKGROUND: This work is focused on inulinase production by solid‐sate fermentation (SSF) using sugarcane bagasse, corn steep liquor (CSL), pre‐treated cane molasses, and soybean bran as substrates in a 3‐kg (dry basis) packed‐bed bioreactor. SSF was carried out by the yeast Kluyveromyces marxianus NRRL Y‐7571 and response surface methodology was used to optimize the temperature, air flow rate and initial mass of cells. RESULTS: The optimum inulinase activity (436.7 ± 36.3 U g^?1 dry substrate) was obtained at 24 h at an inlet air temperature of 30 °C, air flow rate 2.2 m³ h^?1 and 22 g of cells for fermentation. Inulinase productivity at these conditions was 18.2 U gds^?1 h^?1. Kinetic evaluation at the optimized conditions showed that the maximum inulinase production was verified at 24 h of fermentation. The carbon dioxide and the metabolic heat generation are directly associated with the consumption of total reducing sugars present in the medium. CONCLUSION: The high productivity achieved in this work shows the technical viability of inulinase production by SSF in a packed‐bed bioreactor. Copyright © 2009 Society of Chemical Industry     

The use of CO2 for reversible pH shifting,and the removal of succinic acid in a polymer‐based two‐phase partitioning bioreactor

BACKGROUND: Succinic acid (SA) is an intermediate in the production of commodity chemicals, but SA bioproduction has not yet been commercialized due to end product inhibition and high product separation costs. Two‐phase partitioning bioreactors (TPPBs) can increase volumetric productivity through in situ product removal, although SA uptake by polymers requires a pH below the pK_A2 of SA (4.2). It was proposed to reversibly reduce the pH with CO₂ sparging for absorption of SA, followed by nitrogen stripping to allow continued bioproduction after returning to metabolic pH levels. RESULTS: At 1 atm CO₂ sparging lowered the pH of RO water to 3.8 but only to 4.75 in medium, requiring acid/base pH adjustment in subsequent experiments. Actinobacillus succinogenes was temporarily exposed to pH 4.2 for between 5 min and 4 h to observe the effect on subsequent growth; cells could grow after up to 4 h of low pH exposure, sufficient time for SA uptake. Because atmospheric CO₂ could not adequately lower the pH of medium, a TPPB was operated with the pH being shifted using strong acid/base; SA was recovered in situ, however, the accumulation of salts hindered further cell growth. CONCLUSION: Several key elements of this novel processing strategy were successfully demonstrated, and work is continuing with high pressure CO₂ to achieve the desired pH adjustment levels. Copyright © 2011 Society of Chemical Industry     

Residence time distribution in a packed bed bioreactor containing porous glass particles: Influence of the presence of immobilized cells

An experimental investigation of the liquid phase residence time distribution (RTD) in a packed bed bioreactor containing porous glass particles is presented. For Re < 1, intraparticle forced convection is negligible and only diffusion, characterized by an effective diffusion coefficient, must be considered to describe the mass transfer process between the extraparticle and the intraparticle fluid phase. For Re > 1, the mass transfer rate becomes dependent on the liquid flow rate, indicating the existence of intraparticle convection. A model including axially dispersed flow for the external fluid phase and an ‘apparent’ effective diffusivity that combines diffusion and convection, predicts experimental RTD data satisfactorily. Yeast cells immobilized inside the porous glass beads did not affect the mass transfer rate at low biomass loading. At high biomass loading (0·02 g yeast cells g^?1 carrier), the mass transfer rate between the extraparticle and intraparticle fluid phase was significantly decreased. Comparison of the RTD data from experimets performed in the presence and absence of cells in the external fluid phase revealed that the mass transfer rate is influenced by the cells immobilized inside the porous particles and not by the cells present in the external fluid phase.     

Process intensification with a hybrid system: A tubular packed bed bioreactor with immobilized activated sludge culture coupled with membrane filtration

Performance of a hybrid system consisting of a tubular bioreactor and a membrane filter was studied for removing carbohydrate and protein. Microporous polyurethane (sponge) was used as the packing medium for immobilization activated sludge culture. The bioreactor was operated in series with a cross flow ultrafiltration system to study the effect of influent flow rate and chemical oxygen demand (COD) concentration on the overall system performance. The removal efficiency in the bioreactor decreased linearly with increase in loading. The decline of removal efficiency at higher loadings was more significant for protein than carbohydrate. Coupling the bioreactor with a membrane separation process increased the overall removal rates and provided a consistent effluent quality. The flux through ultrafiltration membrane did not change significantly even when the bioreactor effluent had high levels of protein. Morphological examination of the packing medium both visually and by SEM showed significant accumulation of organisms on the surface which indicates that biofilm thickness was controlled by diffusion limitations. Advantages of the hybrid system include small footprint, economical packing medium, and space savings by coupling the bioreactor with a membrane filtration process.     

Kinetics of growth and lactic acid production from whey permeate by Lactobacillus helveticus

Batch fermentation kinetics of Lactobacillus helveticus were examined in detail. The nature of the culture medium had a significant effect on the product synthesis mechanism. In a glucose synthetic medium, lactic acid produced by the non-growth-associated mechanism was less than that by the growth-associated mechanism. In a lactose synthetic medium, the contribution of both mechanisms was approximately equal at the end of fermentation. In the whey-yeast extract permeate medium, the contribution by the non-growth-associated mechanism was superior to that of the growth-associated mechanism. Temperature and pH also influenced the relative contribution of the two mechanisms on the total production of lactic acid in whey-yeast extract permeate medium. Under optimal conditions for temperature and pH, the contribution of non-growth-associated product formation was the highest among all temperatures, and the lowest among all pH's. The ATP concentration-biomass concentration relationship in the batch fermentation process could be roughly approximated by a Luedeking-Piret-like equation.     

固定床生物反应器模拟溶浸采铀吸附尾液中Fe2+的氧化试验

以活性炭作载体固定嗜酸氧化亚铁硫杆菌,构建固定床生物反应器,模拟溶浸采铀矿山吸附尾液全Fe浓度和溶液pH条件,对生物反应器氧化Fe²⁺工艺参数进行了试验研究。结果表明:活性炭作载体比无载体时生物反应器氧化Fe²⁺速率增加了1.4倍,由0.5 g·L^-1·h^-1增大至1.2 g·L^-1·h^-1;生物反应器运行过程中溶液中全Fe因生成铁钒而不断消耗,需要定期清理反应器中的铁矾和补充FeSO₄以保持溶液中全Fe浓度;生物反应器最优的操作条件是:底部通气,Fe²⁺浓度为5 g·L^-1时,溶液流量为1.2~1.4 L·h^-1;Fe²⁺浓度为1 g·L^-1时,溶液流量为5.4 L·h^-1。     

Strategies of pH control and glucose‐fed batch fermentation for production of succinic acid by Actinobacillus succinogenes CGMCC1593

BACKGROUND: Succinic acid is an important precursor of numerous products, including pharmaceuticals, feed additives, green solvents, and biodegradable polymers. In this work, strategies of pH control and glucose‐fed batch fermentation for producing succinic acid using Actinobacillus succinogenes CGMCC1593 were carefully optimized. RESULTS: The production of succinic acid was stable within the pH range 6.0–7.2. Both cell growth and succinic acid production were inhibited by high concentrations of sodium and calcium ions, while there was no significant inhibition by magnesium ions. With an initial glucose concentration of 25 g L^?1, and glucose concentration was maintained between 10 and 15 g L^?1 during the course of fed batch fermentation, succinic acid concentration, productivity and yield were 60.2 g L^?1, 1.3 g L^?1 h^?1 and 75.1%, respectively. CONCLUSION: Of all the neutralization reagents used for pH control of A. succinogenes CGMCC1593, solid MgCO₃ was the most satisfactory. With increase of initial glucose concentration, the time course showed a longer growth lag period and the maximum biomass declined, while more carbon was diverted to succinate synthesis. The results obtained in this study should be helpful for the design of a highly efficient succinic acid production process. Copyright © 2008 Society of Chemical Industry