γ－亚麻酸发酵条件研究

本文对γ－亚麻酸发酵的碳源、氮源、ｐＨ值、菌体得率、油脂含量、γ－亚麻酸含量等进行了考察,并通过均匀设计,得到了该菌株发酵生产γ－亚麻酸的优化配方,用优化配方发酵结果表明,菌体得率、γ－亚麻酸含量均有显著的提高。     

枯草芽孢杆菌C1-B941的D-核糖发酵中间试验

使用转酮醇酶变异株—枯草芽孢杆菌C1－B941进行了D－核糖发酵中间试验。3000L发酵罐试验结果表明,发酵培养基中的葡萄糖浓度为18％时,发酵周期约为64h,发酵转化率达36．84％。发酵液经离子交换树脂纯化后,可以直接用于生产VBZ合成的中间体—N－D－核糖醇基－3,4－二甲苯胶。     

维生素C二步发酵过程动力学模型的研究

本文系统地分析了L－山梨糖到2－酮基L－古龙酸的生物转化过程,提出了生长因子的假定,对发酵机理进行了新的探讨,对发酵过程做了必要与合理的简化。首次建立了维生素c第二步发酵过程的动力学模型。运用多面体最优化法和Runge-Kutta积分法等数学方法处理模型,获得最佳模型参数。结果表明,模型计算值与实验值得到良好的吻合,从而证明动力学模型是正确的和有效的。     

r——亚麻酸发酵条件研究

本文对ｒ－亚麻酸发酵的碳源、氮源、ｐＨ值、菌体得率、油脂含量、ｒ－亚麻酸含量等进行了考察,并通过均匀设计,得到了该菌株发酵生产ｒ－亚麻酸的优化配方,用优化配方发酵结果表明,菌体得率、ｒ－亚麻酸含量均有显著的提高。     

枯草芽孢杆菌C1—B941的D—核糖发酵中间试验

使用转酮醇酶变异株－枯草芽孢杆菌Ｃ１－Ｂ９４１进行了Ｄ－核糖发酵中间试验。３０００Ｌ发酵罐试验结果表明,发酵培养基中的葡萄糖浓度为１８％时,发酵周期约为６４ｈ,发酵转化率达３６．８４％,发酵液经离子交换树脂纯化后,可以直接用于生产ＶＢ２合成的中间体－Ｎ－Ｄ－核糖醇基－３,４－二甲苯胺。     

几种添加物对D—核糖产量的影响

研究了几种物质对D－核糖产量的影响,研究表明,当发酵培养基中玉米浆的含量为25g/L,D－核糖产量达到最高,为65g/L。发酵培养基中添加适量的粉及山梨醇亦有利于D－核糖的积累,当粉与山梨醇的添加量分别为10g/L及40g/L时,D－核糖产率分别增加7.8%、4.7%,而在发酵培养基中加入丙二酸可抑制D－核的分泌,在40ml发酵培养基中添加1ml丙二酸后,D－核糖的产率下降73.8％。甲醇也可抑制D－核糖的积累,当发酵培养基中的甲醇添加量为16g/L时,D－核糖产率下降66.2%。     

β-胡萝卜素的生物合成与发酵促进剂

本文论述了β－胡萝卜素的生物合成途径及某些发酵助剂对微生物产β－胡萝卜素的影响。据对甘些植物和真菌产生β－胡萝卜素的研究,认为β－胡萝卜素及相关类胡萝卜素是一类自己酰ＣＯＡ开始的次生代谢产物。通过大量的研究实例表明,添加合适的发酵促进剂是提高β－胡萝卜素产量和降低生产成本非常有效的工艺学途径。     

L－赖氨酸快速发酵新菌种及工艺研究

以我室选育的赖氨酸生产菌Ｓ－２１－２４为出发菌株,经硫酸二乙酯（ＤＥＳ）和紫外线（Ｕ．Ｖ．）的复合处理,选育到一株代谢速率高,发酵周期短的新菌株ＦＴＳ－１。对该菌的发酵条件作了研究,选择了最佳培养条件,该菌在５Ｌ发酵罐中发酵４８小时产酸８０ｇ／Ｌ以上,７２小时产酸可达１１０ｇ／Ｌ。     

L－赖氨酸快速发酵新菌种及工艺研究

以我室选育的赖氨酸生产菌Ｓ－２１－２４为出发菌株,经硫酸二乙酯（ＤＥＳ）和紫外线（Ｕ．Ｖ．）的复合处理,选育到一株代谢速率高,发酵周期短的新菌株ＦＴＳ－１。对该菌的发酵条件作了研究,选择了最佳培养条件,该菌在５Ｌ发酵罐中发酵４８小时产酸８０ｇ／Ｌ以上,７２小时产酸可达１１０ｇ／Ｌ。     

氧载体对L-天冬酰胺酶发酵过程影响的研究

以抗癌药物L－天冬酰胺酶生产为应用背景,针对发酵过程中存在严重耗氧问题,研究了氧载体对发酵过程的影响。通过对几种氧载体的筛选,认为正十二烷最适合于该发酵过程。随后以产物L－天冬酰胺酶活性、菌体浓度以及溶氧水平为主要指标,考察了氧载体在发酵过程中的作用．实验表明,发酵基质中5％正十二烷的添加量为最佳浓度,这种氧载体的加入,明显地提高了发酵介质中的溶氧水平,改善了供氧条件,增加了菌体浓度,提高了L－天冬酰胺酶发酵水平,在优化条件下,可使发酵液最终酶活提高21％左右。     

Biosensor online control of citric acid production from glucose by Yarrowia lipolytica using semicontinuous fermentation

Our study aimed at the development of an effective method for citric acid production from glucose by use of the yeast Yarrowia lipolytica. The new method included an automated bioprocess control using a glucose biosensor. Several fermentation methodologies including batch, fed‐batch, repeated batch and repeated fed‐batch cultivation were tested. The best results were achieved during repeated fed‐batch cultivation: Within 3 days of cycle duration, approximately 100 g/L citric acid were produced. The yields reached values between 0.51 and 0.65 g/g and the selectivity of the bioprocess for citric acid was as high as 94%. Due to the elongation of the production phase of the bioprocess with growth‐decoupled citric acid production, and by operating the fermentation in cycles, an increase in citric acid production of 32% was achieved compared with simple batch fermentation.     

Simultaneous saccharification and co‐fermentation of paper sludge to ethanol by Saccharomyces cerevisiae RWB222. Part II: Investigation of discrepancies between predicted and observed performance at high solids concentration

The simultaneous saccharification and co‐fermentation (SSCF) kinetic model described in the companion paper can predict batch and fed batch fermentations well at solids concentrations up to 62.4 g/L cellulose paper sludge but not in batch fermentation at 82.0 g/L cellulose paper sludge. Four hypotheses for the discrepancy between observation and model prediction at high solids concentration were examined: ethanol inhibition, enzyme deactivation, inhibition by non‐metabolizable compounds present in paper sludge, and mass transfer limitation. The results show that mass transfer limitation was responsible for the discrepancy between model and experimental data. The model can predict the value of high paper sludge SSCF in the fermentation period with no mass transfer limitation. The model predicted that maximum ethanol production of fed‐batch fermentation was achieved when it was run as close to batch mode as possible with the initial solids loading below the mass transfer limitation threshold. A method for measuring final enzyme activity at the end of fermentation was also developed in this study. Biotechnol. Bioeng. 2009; 104: 932–938. © 2009 Wiley Periodicals, Inc.     

Increased lovastatin formation by Aspergillus terreus using repeated fed-batch process

Lovastatin biosynthesis with Aspergillus terreus in batch fermentation reached 160 U/l in 161 h at pH 6.8 and a dissolved O tension maintained at 70%. At the end of repeated fed batch fermentations, the yield of lovastatin was increased by 37% though this took over twice as long as in the batch fermentation.     

Nisin production of Lactococcus lactis N8 with hemin‐stimulated cell respiration in fed‐batch fermentation system

In this study, nisin production of Lactococcus lactis N8 was optimized by independent variables of glucose, hemin and oxygen concentrations in fed‐batch fermentation in which respiration of cells was stimulated with hemin. Response surface model was able to explain the changes of the nisin production of L. lactis N8 in fed‐batch fermentation system with high fidelity (R² 98%) and insignificant lack of fit. Accordingly, the equation developed indicated the optimum parameters for glucose, hemin, and dissolved oxygen were 8 g L^?1 h^?1, 3 μg mL^?1 and 40%, respectively. While 1711 IU mL^?1 nisin was produced by L. lactis N8 in control fed‐batch fermentation, 5410 IU mL^?1 nisin production was achieved within the relevant optimum parameters where the respiration of cell was stimulated with hemin. Accordingly, nisin production was enhanced 3.1 fold in fed‐batch fermentation using hemin. In conclusion the nisin production of L. lactis N8 was enhanced extensively as a result of increasing the biomass by stimulating the cell respiration with adding the hemin in the fed‐batch fermentation. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:678–685, 2015     

Establishing a Fed‐Batch Process for Protease Expression with Bacillus licheniformis in Polymer‐Based Controlled‐Release Microtiter Plates

Introducing fed‐batch mode in early stages of development projects is crucial for establishing comparable conditions to industrial fed‐batch fermentation processes. Therefore, cost efficient and easy to use small‐scale fed‐batch systems that can be integrated into existing laboratory equipment and workflows are required. Recently, a novel polymer‐based controlled‐release fed‐batch microtiter plate is described. In this work, the polymer‐based controlled‐release fed‐batch microtiter plate is used to investigate fed‐batch cultivations of a protease producing Bacillus licheniformis culture. Therefore, the oxygen transfer rate (OTR) is online‐monitored within each well of the polymer‐based controlled‐release fed‐batch microtiter plate using a µRAMOS device. Cultivations in five individual polymer‐based controlled‐release fed‐batch microtiter plates of two production lots show good reproducibility with a mean coefficient of variation of 9.2%. Decreasing initial biomass concentrations prolongs batch phase while simultaneously postponing the fed‐batch phase. The initial liquid filling volume affects the volumetric release rate, which is directly translated in different OTR levels of the fed‐batch phase. An increasing initial osmotic pressure within the mineral medium decreases both glucose release and protease yield. With the volumetric glucose release rate as scale‐up criterion, microtiter plate‐ and shake flask‐based fed‐batch cultivations are highly comparable. On basis of the small‐scale fed‐batch cultivations, a mechanistic model is established and validated. Model‐based simulations coincide well with the experimentally acquired data.     

Assessing viability and cell-associated product of recombinant protein producing Pichia pastoris with flow cytometry

This paper describes the establishment of flow cytometric methods for recombinant Pichia pastoris strains, and their application to a lab scale fed batch fermentation. Using a strain which secretes human trypsinogen, the viability and the product which remained associated to the cell were measured with propidium iodide and immunofluorescent staining, respectively. Viability decreases significantly below 70% during the methanol fed batch phase, indicating a stress situation triggered by the fermentation conditions. Cell associated product is accumulated earlier after methanol induction than secreted product. These data demonstrate that flow cytometry is a powerful tool for the analysis and optimization of recombinant protein production processes, and they indicate the need to further improve a widely used fermentation protocol for P. pastoris.     

Defining an optimal carbon source/methionine feed strategy for growth and cephalosporin C formation by Cephalosporium acremonium.

The effect of the method of methionine addition, growth-limiting carbon source (glucose vs sucrose), and culture growth rate on cephalosporin C production was investigated in a Cephalosporium acremonium defined medium fed batch fermentation. Batch addition of methionine, at a concentration of 3 g/L, prior to the start of a fed sucrose fermentation was found to interfere with the ability of the culture to utilize this sugar, thus limiting growth and decreasing cephalosporin C production. Batch methionine addition had no effect on glucose-limited cultures. Concurrent exponential feeding of methionine with sucrose improved both culture growth and productivity. Under the control of identical carbon source limiting feed profiles, sucrose was observed to support greater cephalosporin C production than glucose. Optimal cephalosporin C production in a C. acremonium defined medium fed batch fermentation was obtained through controlling culture growth during the rapid growth phase at a relatively low level with respect to mumax (mu approximately 0.036 h-1) until achieving a desired cell mass with a concurrent sucrose and methionine feed, followed by maintaining relatively vigorous growth (mu approximately 0.01 h-1) with sucrose for the duration of the fermentation.     

毕赤酵母高密度发酵工艺的研究

高密度发酵是毕赤酵母提高蛋白表达量的一种重要策略,发酵工艺是高密度发酵的一个重要因素。采用下列措施均可以有效地提高表达水平：调节基础培养基,采用变pH和变温发酵,提高DO,选择最适的诱导前菌体密度和比生长速率并降低甘油初始浓度和采用分段式指数流加进行调控。选择合适的甲醇补料策略：甲醇限制补料（MLFB）、氧气限制补料（OLFB）、甲醇不限制补料（MNLFB）和温度限制补料（TLFB）。采用两种方式调控补料：诱导阶段菌体生长时,甲醇比消耗速率(qMeOH)为0.02-0.03gg-1h-1,而菌体不生长时,qMeOH采用较高值。     

Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by Ralstonia eutropha in high cell density palm oil fermentations

Improved production costs will accelerate commercialization of polyhydroxyalkanoate (PHA) polymer and PHA-based products. Plant oils are considered favorable feedstocks, due to their high carbon content and relatively low price compared to sugars and other refined carbon feedstocks. Different PHA production strategies were compared using a recombinant strain of Ralstonia eutropha that produces high amounts of P(HB-co-HHx) when grown on plant oils. This R. eutropha strain was grown to high cell densities using batch, extended batch, and fed batch fermentation strategies, in which PHA accumulation was triggered by nitrogen limitation. While extended batch culture produced more biomass and PHA than batch culture, fed batch cultivation was shown to produce the highest levels of biomass and PHA. The highest titer achieved was over 139 g/L cell dry weight (CDW) of biomass with 74% of CDW as PHA containing 19 mol% HHx. Our data suggest that the fermentation process is scalable with a space time yield (STY) better than 1 g PHA/L/h. The achieved biomass concentration and PHA yield are among the highest reported for the fermentation of recombinant R. eutropha strains producing P(HB-co-HHx).     

丙酸絮凝发酵新工艺研究

报道了丙酸发酵的一种新工艺:絮凝发酵工艺。采用谢氏丙酸杆菌(Propionibacterium shermanii)W125在批次发酵产酸达到29g/L的基础上,选择氢氧化钙作为中和剂兼絮凝剂,建立了絮凝半连续发酵工艺,连续运行250h,产酸量达到了35.4g/L,产酸率提高了22%,糖酸转化率达到了51.56%,体积效率达到了0.37g/(L/h)。