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%。     

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。     

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)。     

Clarification of succinic acid fermentation broth by ultrafiltration in succinic acid bio–refinery

BACKGROUND: Succinic acid is an important precursor chemical for the synthesis of high value‐added products. In this work, ultrafiltration was first investigated to clarify succinic acid fermentation broth by integrating fermentation and separation and removal processes of the product in situ. Four different ultrafiltration membranes (PES 100 kDa, PES 30 kDa, PES 10 kDa and RC 10 kDa) were used in this work. RESULTS: Results indicate that ultrafiltration is feasible for clarifying succinic acid fermentation broth. Almost all the microorganism cells (99.6%) were removed from the fermentation broth. Proteins were also removed effectively by all the membranes studied. The removal rate was 79.86% for PES 100 kDa, 86.43% for PES 30 kDa, 86.83% for PES 10 kDa, and 80.06% for the RC 10 kDa. After ultrafiltration, a clearer permeate was obtained compared with that from centrifugation. CONCLUSION: Membranes operating at high flux are always susceptible to rapid fouling. Compared with molecular weight cut‐offs (MWCO), membrane material has a significant influence on the flux. Membrane flux measured in this study shows industrial potential of this technology in treatment of succinic acid fermentation broth. © 2012 Society of Chemical Industry     

Fed‐batch fermentation of olive mill wastewaters for lipase production

In the Mediterranean basin countries, huge amounts of olive mill wastewaters (OMW) are produced by the olive oil industry. It constitutes a serious environmental problem, nevertheless its composition turns OMW into a potential growth medium to lipolytic microorganisms. The aim of this work was to study lipase production as well as OMW degradation in fed‐batch cultures of Candida cylindracea CBS 7869, Candida rugosa CBS 2275 and Yarrowia lipolytica W29 (ATCC 20460). Besides the improvement of lipase production, the fed‐batch approach enhanced the effluent degradation, since it led to good COD and lipids reduction, both higher than 50%. C. rugosa achieved the highest value of lipase productivity (130 U L^?1 h^?1), in parallel with highest lipids reduction (77%). This study demonstrates that OMW are becoming a competitive and valuable growth medium in fermentation processes with lipolytic microorganisms. The fed‐batch strategy used proved to be an efficient approach to enhance lipase production from OMW and to reduce significantly the final organic load of the medium. Copyright © 2012 Society of Chemical Industry     

基于高密度培养的反复分批发酵法生产丁二酸

引言丁二酸俗称琥珀酸,是三羧酸循环的中间代谢产物和厌氧代谢的终端还原产物,广泛存在于动物、植物及微生物体内。作为重要的C4平台化合物,丁二酸可用于多种大宗化学品以及生物可降解材料的制备。利用微生物发酵生产丁二酸,由于     

Effect of sucrose on nisin production in batch and fed‐batch culture by Lactococcus lactis

The effects of sucrose on cell growth and nisin production by Lactococcus lactis were investigated in batch and pH feed‐back controlled fed‐batch cultures. In batch cultures, nisin titer reached its maximum, 2658 IU cm^?3, at the initial sucrose concentration of 30 g dm^?3. With sucrose concentrations higher than 30 g dm^?3, nisin production decreased while the biomass was not influenced significantly. By using the pH feed‐back controlled method, residual sucrose concentration could be controlled well in fed‐batch cultures and three conditions (sucrose maintained at 2, 16, 20 g dm^?3, respectively) were evaluated. Maintaining a low sucrose concentration at 2 g dm^?3 during feeding favored nisin biosynthesis, and the maximum nisin titer obtained was 4961 IU cm^?3 compared with 3370 IU cm^?3 (16 g sucrose dm^?3)and 3498 IU cm^?3 (20 g sucrose dm^?3), respectively. Copyright © 2005 Society of Chemical Industry     

代谢控制发酵产琥珀酸研究进展

琥珀酸作为一种重要的化工原料被广泛应用于现代工业的各个领域,具有庞大的市场需求。利用生物法发酵生产琥珀酸因具有资源可再生利用、绿色清洁节能等方面不可替代的优势而成为当今研究的热点。本文从代谢调控的角度出发分析总结了一些产琥珀酸菌株,尤其是重组大肠杆菌在发酵生产琥珀酸中所应用到的方法和策略,如对代谢途径中关键酶的调控以及发酵生产中的关键因素(如氧化还原回复力调控、CO₂调节、代谢途径改造等),着重突出了代谢控制发酵生产方面的研究进展,并对今后的发展方向提出了一些设想。     

氧化还原电位调控对产琥珀酸放线杆菌代谢通量分布的影响

利用代谢通量分析方法分析了氧化还原电位调控对产琥珀酸放线杆菌NJ113厌氧发酵产丁二酸过程的影响。结果表明,氧化还原电位调控可以改变HMP与EMP途径的代谢通量,从而影响胞内NADH/NAD⁺。在菌体最适氧化还原电位（-350 mV）条件下, HMP途径与EMP途径的通量比由43.6∶56.2提高至63.2∶36.5,间接合成更多的NADH,解决了丁二酸合成过程中还原力不足的矛盾,整个发酵过程中胞内NADH/NAD⁺比值有明显提高,发酵初期NADH/NAD⁺比值由2.19提高至8.73。最终丁二酸代谢通量从114.5 mmol.(g DCW)^-1.h^-1增至129.3 mmol.(g DCW)^-1.h^-1,副产物乙酸、甲酸的代谢通量分别降低30.6%、30.2%;丁二酸收率由75.46%提高至89.34%,生产强度达到1.18 g.L^-1.h^-1。     

Alcaligenes sp. CGMCC2428产威兰胶的分批发酵动力学模型

利用分批发酵研究Alcaligenes sp. CGMCC2428产微生物多糖威兰胶的合成特性,结果表明威兰胶的合成和菌体生长模型为部分偶联型.菌体和威兰胶质量浓度分别达到3.30和26.50 g/L,威兰胶对细胞干质量得率系数（YP/X）为8.20.根据分批发酵实验结果采用Logistic方程、Luedeking-Piret方程和Luedeking-Piret相似方程,得到了描述Alcaligenes sp. CGMCC2428生长、威兰胶以及葡萄糖底物消耗分批发酵动力学模型.同时改变初始葡萄糖质量浓度,实验数据与模型预测值进行了比较拟合,平均相对误差小于10%,表现出很好的适用性.     

High cell density fermentation via a metabolically engineered Escherichia coli for the enhanced production of succinic acid

BACKGROUND: Succinic acid is a valuable four‐carbon organic chemical with applications in many fields. It was found that cell mass was an important factor in succinic acid production by metabolically engineered Escherichia coli strains. In this work, high cell density fermentation was investigated for succinic acid production by a metabolically engineered strain SD121 with ldhA, pflB, ptsG mutation and heterogenous cyanobacterial ppc overexpression. RESULTS: Under two‐stage cultivation, the controlled DO feeding strategy during the aerobic growth phase facilitated biomass up to a dry cell weight of 19.6 g L^?1, and enhanced succinic acid production in the following anaerobic fermentation phase to a concentration of 116.2 g L^?1. A near theoretical maximum succinic acid yield of 1.73 mol mol^?1 glucose was achieved with an average productivity of 1.55 g L^?1 h^?1. CONCLUSION: The results indicated the potential advantage of high cell density fermentation for improvement of succinic acid production by E. coli. Copyright © 2010 Society of Chemical Industry     

Simultaneous saccharification and fermentation of sludge‐containing cassava mash for batch and repeated batch production of bioethanol by Saccharomyces cerevisiae CHFY0321

BACKGROUND: The aim of this study was to examine the repeated batch production of bioethanol from sludge‐containing cassava mash as starchy substrate by flocculating yeast to improve volumetric bioethanol productivity and to simplify the process of a pre‐culture system. RESULTS: For the repeated batch production of bioethanol using cassava mash, the optimal recycling volume ratio was found to be 5%. The repeated batch fermentation was completed within 36 h, while the batch fermentation was completed after 42 h. Volumetric productivity, final ethanol concentration, and ethanol yield were attained to 2.15 g L^?1 h^?1, 83.64 g L^?1, and 85.15%, respectively. Although cell accumulation in the repeated batch process is difficult due to the cassava mash, the repeated batch process using Saccharomyces cerevisiae CHFY0321 could exhibited 10‐fold higher initial viable cell number (1.7 × 10⁷ CFU mL^?1) than that of the batch process. CONCLUSION: The liquefied cassava powder was directly used for the repeated batch process without removal of sludge. Repeated batch bioethanol production by simultaneous saccharification and fermentation using self‐flocculating yeast could reduce process costs and accelerate commercial applications. This result was probably due in part to the effect of the initial viable cell density. Copyright © 2008 Society of Chemical Industry     

Maximum volumetric production of β‐galactosidase by Kluyveromyces fragilis in fed‐batch culture with automatic control

The production of β‐galactosidase by Kluyveromyces fragilis was studied in different culture systems, with dissolved oxygen concentration control and using defined media. An operating strategy of fed‐batch culture with automatic control of substrate addition regulated by dissolved oxygen concentration, consisting of the replacement of variable volumes of broth by fresh medium (once the fed‐batch culture has finished), was designed. The volumetric enzyme productivity (Q_p, 13 600 UI dm^?3 h^?1) obtained was 38% higher than that reached in continuous culture of K fragilis with dissolved oxygen concentration control and far higher than that obtained by batch culture of K fragilis under the same aeration conditions. © 2002 Society of Chemical Industry