Influence of Salt Concentration and Nitrogen Source on Growth and Productivity of Anaerobiosprillum succiniciproducens

The influence of salts and organic nitrogen sources on the growth and acid production of Anaerobiosprillum succiniciproducens was studied. In shake flask experiments, maximum specific growth rate and acid production increased by reducing the salt concentration. Additionally, growth and acid production were affected by the type of organic nitrogen source and by the pH value. Through the optimization, optical density could be increased from 1.9 ± 0.1 to 3.0 ± 0.1 and succinic acid concentration from 4.0 ± 0.2 to 6.5 ± 0.1 g L^–1. In fed‐batch experiments with the optimized medium, the final succinic acid concentration was 25.6 % higher compared to the reference. Also, the succinic acid/acetic acid ratio was affected by the optimization. The experimental results indicated that A. succiniciproducens consumed only organic nitrogen sources because growth and productivity were not influenced by the addition of ammonium sulfate.     

Batch and Fed‐Batch Degradation of Enrofloxacin by the Fenton Process

Enrofloxacin is a synthetic second‐generation fluoroquinolone used as an antimicrobial agent exclusively in veterinary medicine. To simulate the treatment of wastewater contaminated by enrofloxacin, four‐day long fed‐batch runs were carried out according to the Fenton process with an enrofloxacin solution as model, to which hydrogen peroxide and ferrous ion were added twice a day. The residual enrofloxacin concentration was practically coincident to that detected at the end of the batch tests. Hydrogen peroxide was almost completely consumed after each feeding period, while the total organic carbon (TOC) concentration decreased gradually within three days, corresponding to a reduction > 58 %. From the third day on, the TOC falling rate was quite low. A yellow sludge settled due to the precipitation of both Fe(OH)₃ and a complex formed by ferric ion with adsorbed enrofloxacin and/or its oxidation products.     

反复分批发酵法生产甘油研究

研究了反复分批发酵法在耐高渗酵母生产甘油中的应用 ,通过对比可知 ,游离耐高渗酵母的反复分批发酵性能优于固定化耐高渗酵母的反复分批发酵 ,且在反复分批发酵 1 2个批次后 ,其发酵性能依然稳定。由对游离细胞反复分批发酵的动力学参数分析可知 ,反复分批发酵法之所以具有良好的发酵性能 ,主要是由发酵液中高的菌体密度决定的。     

Neural and Hybrid Neural Modeling and Control of Fed‐Batch Fermentation for Streptokinase: Comparative Evaluation under Nonideal Conditions

Fermentations involving competition between two or more kinds of cells under nonideal conditions show complex profiles that are sensitive to the extra‐cellular environment. These fermentations therefore require accurate and rapid on‐line data acquisition and control. However, both on‐line measurements and modelling are difficult and expensive for large bioreactors, thus limiting the usefulness of model‐based control. While neural networks offer an alternative, they require extensive training and can be difficult to optimize for large arrays. Hybrid networks combining a few neural networks with some mathematical equations offer a good compromise. The possibility of using a hybrid model for simulation‐cum‐control has been examined here for the fed‐batch production of streptokinase. Under noideal conditions, hybrid neural models outperformed both mathematical models and arrays of neural networks, thus suggesting their viability for large‐scale fermentation monitoring and control.     

From Microbial Succinic Acid Production to Polybutylene Bio-Succinate Synthesis

A simplified and scalable one-pot process for the anaerobic production of succinic acid using a metabolically engineered Corynebacterium glutamicum strain is demonstrated. With targeted bioprocess optimization, succinic acid titer of 78 g L⁻¹ and yield of 1.41 mol_SAmol_GLC⁻¹ were achieved. Succinic acid was recovered from the neutral fermentation broth by electrochemically induced crystallization and applied for polybutylene bio-succinate synthesis using a biocompatible zinc catalyst. Except for a slight color change, the final biopolymer was comparable to the polymer from commercial precursors.     

Prediction of the Profit Function for Industrial 2‐Keto‐L‐Gulonic Acid Cultivation

The profit function is the generic criterion to describe the cost effect of a batch process. To focus on the prediction of the profit function for 2‐keto‐L‐gulonic acid (2‐KGA) cultivation, which is potentially applicable for process monitoring and optimal scheduling, rolling learning‐prediction (RLP) based on a support vector machine (SVM) is applied. The RLP implies that the SVM training database is rolling updated as the batch of current interest proceeds, and the SVM learning is then repeated for the prediction. The database is further updated after termination of a batch. The updating procedures are investigated in detail. Pseudo‐online prediction is carried out using the data from industrial‐scale 2‐KGA cultivation under actual and hypothetical inoculation sequences. The results indicate that the average relative prediction error is less than 5 % in the later phase of fermentation in all inoculation sequences.     

Neural Optimization of Fed‐batch Streptokinase Fermentation in a Non‐ideal Bioreactor

Microbial fermentations involving two or more kinds of competing cells and operating under realistic conditions are difficult to monitor, model and optimize by model‐based methods. They deviate from ideal behavior in two significant aspects: incomplete dispersion in the broth and the influx of disturbances. The approach here has been to optimize the filtered noise and dispersion on‐line through neural networks. This method has been applied to the fed‐batch production of streptokinase (SK). The culture has two kinds of cells — active (or productive) and inactive — and their growth is inhibited by the substrate and the primary metabolite (lactic acid). Using simulated data, the fermentation was optimized by a system of three neural networks, updated continually during successive time intervals. Such sequential optimization with dynamic filtering of inflow noise generated better cell growth and SK activity than static optimization and even an ideal fermentation.     

Combined Effect of Agitation/Aeration and Fed‐Batch Strategy on Ubiquin‐ one‐10 Production by Pseudomonas diminuta

The effects of aeration rate and agitation speed on ubiquinone‐10 (CoQ10) submerged fermentation in a stirred‐tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (k_La) were affected by both aeration and agitation. An agitation speed of 400 rpm and aeration rate of 0.5 vvm supported the maximum production (38.56 mg L^–1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an k_La of 27.07 h^–1 with the highest specific productivity and CoQ10 yield of 0.064 mg g^–1h^–1 and 0.96 mg g^–1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth‐associated constant (a = 5.067 mg g^–1) to be higher than the nongrowth‐associated constant (β = 0.0242 mg g^–1h^–1). These results were successfully utilized for the development of fed‐batch fermentation, which increased the CoQ10 production from 38.56 mg L^–1 to 42.85 mg L^–1.     

Enhanced Production of Podophyllotoxin by Fed‐batch Cultivation of Podophyllum hexandrum

Podophyllum hexandrum (Indian May Apple) was successfully cultivated in a 3 L stirred tank bioreactor under low shear conditions in batch and fed‐batch modes of operation. A statistically optimized culture medium was used for the batch cultivation of Podophyllum hexandrum. Under optimum culture conditions of P. hexandrum, the batch culture showed a growth‐associated product formation with a maximum biomass of 21.4 g/L dry cell weight (DCW) basis and a podophyllotoxin production of 13.8 mg/L in 26 d. A mathematical model was developed to design the nutrient feeding strategies for a fed‐batch cultivation to prolong the productive log phase of cultivation. The fed‐batch cultivation was able to enhance the biomass and podophyllotoxin accumulation to 48 g/L (DCW basis) and 43.2 mg/L, respectively, in 60 d. The volumetric productivity of podophyllotoxin in fed‐batch cultivation was found to be 0.72 mg/(L. d) as opposed to 0.53 mg/(L. d) in batch cultivation under optimized culture conditions.     

Batch and Continuous Production of Lactic Acid from Beet Molasses by Lactobacillus delbrueckii IFO 3202

Process variables were optimized for the production of lactic acid from pretreated beet molasses by Lactobacillus delbrueckii IFO 3202 for batch and continuous fermentations. In the batch fermentation, maximum yields (95·4% conversion, 77·1% effective) and maximum lactic acid volumetric productivity (4·83 g dm⁻³ h⁻¹) was achieved at 45°C, pH 6·0, 78·2 g dm⁻³ sugar concentration with 10 g dm⁻³ yeast extract. Various cheaper nitrogen sources were replaced with yeast extract on equal nitrogen bases in batch fermentation. Of all the nitrogen sources tested, yeast extract yielded the highest and malt sprouts yielded the second highest level of lactic acid. In the continuous fermentation, maximum lactic acid (4·15%) was obtained at a dilution rate of 0·1 h⁻¹. Maximum volumetric lactic acid productivity (11·20 g dm⁻³ h⁻¹) occurred at D = 0·5 h⁻¹ dilution rate. © 1997 SCI.     

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     

豆粕水解液为氮源细菌厌氧流加发酵生产L-乳酸

采用细菌厌氧发酵法生产L-乳酸,由实验确定了最佳接种量、发酵温度和pH调节剂,考察了初始葡萄糖浓度对L-乳酸生产的影响,确定初始糖浓度为70~90 g/L时得率、产率、最终生物量分别达到92.68 g/g, 3.17 g/(L×h)和8.5′107 mL-1. 为进一步降低L-乳酸生产成本,以豆粕水解液为氮源代替酵母粉,同时应用流加发酵技术,L-乳酸产量、得率、产率及转化率分别达到155 g/L, 95.5 g/g, 1.64 g/(L×h)和96.9%. 在保证L-乳酸最终浓度的同时可降低生产成本,为进一步工业化奠定了基础.     

Fed‐batch culture of hybridoma cells in serum‐free medium using an optimized feeding strategy

The achievement of high cell density and monoclonal antibody concentration depends on understanding cell metabolism and the control of cell culture. A model of cell metabolism and monoclonal antibody production in hybridoma cell culture is presented. Fed‐batch culture in serum‐free medium was conducted in a bioreactor with an optimized feeding strategy according to the model. In the process, nutrient concentrations, especially glucose and glutamine, were maintained at relatively constant and low levels. The formation of toxic byproducts, such as ammonia and lactate, was greatly reduced in comparison with that in non‐optimized batch culture. The concentration of monoclonal antibody reached 350 mg dm^?3, which was seven times greater than in non‐optimized batch culture. Copyright © 2003 Society of Chemical Industry     

Glutaminase Production using Zygosaccharomyces rouxii NRRL‐Y 2547: Effect of Aeration,Agitation Regimes and Feeding Strategies

Systematic investigations on the effect of varying dissolved oxygen (DO) concentrations and agitation profiles on glutaminase yield from Zygosaccharomyces rouxii NRRL Y‐2547 were conducted in a batch stirred tank reactor. The agitation rate was varied in the range of 100–400 rpm, while the DO values studied were 20, 40 and 60 %, respectively. Furthermore, a stepwise reduction in DO was investigated wherein the DO concentration was decreased from 40 % for the first 12 h to 20 % for the following 24 h, and finally decreased to 5 % DO up to 54 h (end of batch period). The maximum enzyme yield in all cases was observed after 48 h at 37 °C. An agitation rate of 200 rpm and a three‐stage DO maintenance strategy (40‐20‐5 % DO) gave maximum glutaminase productivity. Yeast extract and glucose feeding increased the enzyme production from 370.75 ± 4.97 units/L to 437.14 ± 4.44 and 417.99 ± 5.82 units/L, respectively.     

Production of Alternansucrase by Leuconostoc mesenteroidesNRRL B-1355 in Batch Fermentation with Controlled pH and Dissolved Oxygen

The effect of controlled pH and dissolved oxygen (DO) tension on the production of total glucosyltransferase activity (GTF), extracellular GTF and alternansucrase was studied in controlled batch fermentations of Leuconostoc mesenteroides NRRL B-1355. Controlled aeration had a positive effect on the production of extracellular GTF in pH-uncontrolled fermentations. An aerated batch fermentation controlled at 90% DO at controlled pH 6·7 resulted in complete utilisation of the carbon source. At controlled pH 5·5, maximal extracellular GTF (0·6 U cm⁻³), total GTF (3·4 U cm⁻³) and alternansucrase activities (1·2 U cm⁻³) were higher in a controlled aerated (75% DO) batch fermentation than in a non-aerated batch fermentation. Acetic acid production was lowest in the non-aerated fermentation process. Controlled DO batch fermentations carried out at pH 5·5, 6·0 and 6·5 resulted in an increasing energy efficiency. While highest alternansucrase activity (1·5 U cm⁻³) occurred in pH 6·5 controlled batch cultures, the highest total GTF activity (3·4 U cm⁻³) was found in the pH 5·5 controlled fermentation. © 1997 SCI.     

Oxidation Kinetics of Carbon Deposited on Cerium‐Doped FePO4 during Dehydration of Glycerol to Acrolein

A cerium‐doped FePO₄ catalyst dehydrates glycerol to acrolein in the gas phase but carbon accumulation reduces the reaction rate with time. Reaction rates may be maintained for longer times by co‐feeding low concentrations of oxygen together with the glycerol, but the acrolein yield drops proportionally to the oxygen concentration. The catalyst is easily regenerated by air and the reaction rate is proportional to both the oxygen concentration and quantity of carbon. The carbonaceous deposits may be due to both glycerol and acrolein: when either is fed to the catalyst, the CO₂/CO ratio is close to 1; during the regeneration step, the CO₂/CO ratio is near 4. A kinetic model of first order in both oxygen concentration and adsorbed sites characterizes the transient data very well.     

Batch production of L(+) lactic acid from whey by Lactobacillus casei (NRRL B‐441)

The effects of temperature, pH, and medium composition on lactic acid production by Lactobacillus casei were investigated. The highest lactic acid productivity values were obtained at 37 °C and pH 5.5. The productivity was 1.87 g dm^?3 h^?1 at 37 °C in shake flasks. In the fermenter, a productivity of 3.97 g dm^?3 h^?1 was obtained at pH 5.5. The most appropriate yeast extract concentration was 5.0 g dm^?3. Whey yielded a higher productivity value than the analytical lactose and glucose. Initial whey lactose concentration did not affect lactic acid productivity. MnSO₄ ·H₂O was necessary for lactic acid production by L casei from whey. Product yields were approximately 0.93 g lactic acid g lactose^?1. Copyright © 2004 Society of Chemical Industry     

玉米芯稀酸预处理和分步糖化与发酵工艺生产燃料乙醇的中试研究

利用正交试验在中试水平考察了玉米芯的稀硫酸预处理和分步糖化与水解生产乙醇的工艺。结果:最佳预处理工艺为稀硫酸浓度1.1%,温度120℃,固液比1∶8,时间3 h;酶解糖化最佳工艺为:起始底物浓度180 g/L,滤纸酶活:纤维二糖酶活=20 IU/g底物:7 IU/g底物,pH=5.0,48 h;利用运动发酵单胞菌发酵酶解液,35℃,48 h,发酵液中乙醇浓度最高67.8 g/L。     

Biodiesel Production Using a Carbon Solid Acid Catalyst Derived from β‐Cyclodextrin

A novel carbon solid acid catalyst was prepared by incomplete hydrothermal carbonization of β‐cyclodextrin into small polycyclic aromatic carbon sheets, followed by the introduction of –SO₃H groups via sulfonation with sulfuric acid. The physical and chemical properties of the catalyst were characterized in detail. The catalyst simultaneously catalyzed esterification and transesterification reactions to produce biodiesel from high free fatty acid (FFA) containing oils (55.2 %). For the as‐prepared catalyst, 90.82 % of the oleic acid was esterified after 8 h, while the total transesterification yield of high FFA containing oils reached 79.98 % after 12 h. By contrast, the obtained catalyst showed comparable activity to biomass (such as sugar, starch, etc.)‐based carbon solid acid catalyst while Amberlyst‐15 resulted in significantly lower levels of conversion, demonstrating its relatively high catalytic activity for simultaneous esterification and transesterification. Moreover, as the catalyst can be regenerated, it has the potential for use in biodiesel production from oils with a high FFA content.