Acetic Acid Production by an Electrodialysis Fermentation Method with a Computerized Control System

In acetic acid fermentation by Acetobacter aceti, the acetic acid produced inhibits the production of acetic acid by this microorganism. To alleviate this inhibitory effect, we developed an electrodialysis fermentation method such that acetic acid is continuously removed from the broth. The fermentation unit has a computerized system for the control of the pH and the concentration of ethanol in the fermentation broth. The electrodialysis fermentation system resulted in improved cell growth and higher productivity over an extended period; the productivity exceeded that from non-pH-controlled fermentation. During electrodialysis fermentation in our system, 97.6 g of acetic acid was produced from 86.0 g of ethanol; the amount of acetic acid was about 2.4 times greater than that produced by non-pH-controlled fermentation (40.1 g of acetic acid produced from 33.8 g of ethanol). Maximum productivity of electrodialysis fermentation in our system was 2.13 g/h, a rate which was 1.35 times higher than that of non-pH-controlled fermentation (1.58 g/h).     

Lactate production in an integrated process configuration: reducing cell adsorption by shielding of adsorbent

The problem of binding of microbial cells to an adsorbent matrix during in situ recovery of bioproducts from a fermentation broth has been addressed by shielding the adsorbent with a thin layer of a non-ionic polymer. Extractive bioconversion of lactic acid by integrating ion-exchange adsorption with the fermentation stage was studied. The effect of coating of the ion-exchanger with agarose on product recovery and cell adsorption was evaluated. Extractive fermentation with both uncoated and coated resin resulted in an increase in reactor productivity as compared to the normal fermentation. The free cell density in the system with agarose-coated beads was similar to that in control fermentation, but was significantly lower in the system with the uncoated ion-exchanger. Electron microscopic scanning of the bead surface after passage of the fermentation broth showed cells attached to the native adsorbent but not to the coated one.     

In situ separation of lactic acid from fermentation broth using ion exchange resins

Lactic acid fermentation is an end product inhibited reaction. In situ separation of lactic acid from fermentation broth using ion exchange resins was investigated and compared with conventional fermentation system. Amberlite resin (IRA-400, Cl⁻) was used to separate lactic acid from fermentation broth and pH was controlled online with an automatic pH controller. The effect of process variables on lactic acid production by Lactobacillus casei in whey permeate was studied. The maximum productivity was obtained at pH = 6.1, T = 37 °C and impeller speed = 200 rpm. The maximum concentration of lactic acid at optimum condition was found to be 37.4 g/L after 38 h of fermentation using in situ separation system. The productivity of in situ separation system was five times increased in comparison with conventional system.     

红茶菌群中菌株相互作用影响菌体生长和代谢

[背景]红茶菌是一种由细菌和酵母菌共生发酵而成的传统茶饮料.该饮料中含有多种有益人体健康的营养物质,具有促进消化、消炎、抗菌、抗糖尿病等生理作用.这些有益的代谢物是以醋酸菌和酵母菌为主的微生物相互作用而产生的.因此,红茶菌是一个优良的研究微生物相互作用的体系.[目的]分析不同菌株单独培养和混合培养对菌体生长和代谢产物的...     

基于pH的反馈补料方法在谷氨酸发酵中的应用

为简化谷氨酸发酵补料工艺,提出了一种新型的基于pH的补料方式。考察谷氨酸发酵过程中氨消耗量 (x) 和糖消耗量 (y) 发现,两者之间存在较好的线性关系 (y=7.4744x,R2=0.9989),以此为pH反馈补料工艺中补料液中葡萄糖与氨的混合比例,能较好地将谷氨酸发酵过程中葡萄糖浓度稳定在12~21 g/L。比较恒定葡萄糖浓度补料工艺与pH反馈补料工艺发现,采用pH反馈补料工艺进行发酵,葡萄糖转化率、谷氨酸产酸速率分别提高了9.06％和17.5％左右,同时发酵周期缩短2 h以上。     

Computer modeling of antibiotic fermentation with on-line product removal

The fermentation of Streptomyces griseus for the production of cycloheximide is similar to other antibiotic fermentations in that product synthesis is subject to feedback regulation and the desired product is degraded in the fermentation broth. The productivity of this fermentation can thus be dramatically increased by removing the antibiotic from the whole broth as it is produced. One means for effecting this on-line product removal is to contact the whole fermentation broth with neutral polymeric resin immobilized in hydrogel beads. The antibiotic adsorbs to the immobilized resin via hydrophobic interactions. In this work, the adsorption of the antibiotic onto the immobilized resin was characterized. A biochemical model of the fermentation was then used to describe the time profiles of biomass, substrate, and antibiotic in a fermentation system in which whole broth is circulated from the fermentor through a continuously stirred extractor containing the adsorbent beads. Various operating conditions were examined to optimize the productivity of the fermentation.     

Ethanol fermentation of raw cassava starch with Rhizopus koji in a gas circulation type fermentor

Studies have been conducted in a gas circulation type fermentor in order to characterize the ethanol fermentation of uncooked cassava starch with Rhizopus koji. Results showed that ethanol concentration reached 13-14% (v/v) in 4-day broth, and the maximum productivity of ethanol was 2.3 g ethanol/L broth h. This productivity was about 50% compared to the productivity of a glucose-yeast system. Ethanol yield reached 83.5-72.3% of the theoretical yield for the cassava starch used. The fermentor used in the present work has been proven by experiment to be suitable for ethanol fermentation of the broth with solid substrate.     

Rice straw fermentation using lactic acid bacteria

To efficiently utilize rice straw and lessen its disposal problem on the environment, a lactic acid bacteria community, SFC-2 was developed from natural fermentation products of rice straw by continuous enrichment with the MRS-S broth (MRS broth with sucrose), and used to accelerate the fermentation of air-dried straws. The SFC-2 could rapidly lower the pH of the broth and produce high levels of lactic acid. Using a combination of plate isolation, denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequencing, the microbial composition of the SFC-2 was classified into Lactobacillus, mainly comprised of L. fermentum, L. plantarum and L. paracacei. An evaluation of the fermentation effect of SFC-2 on rice straw showed that it lowered the pH and significantly (P<0.05) increased lactic acid concentration in the straw. Further analysis with DGGE indicated that L. plantarum, L. fermentum and L. paracasei were the dominant species during fermentation.     

Extractive fermentation for butyric acid production from glucose by Clostridium tyrobutyricum

A novel extractive fermentation for butyric acid production from glucose, using immobilized cells of Clostridium tyrobutyricum in a fibrous bed bioreactor, was developed by using 10% (v/v) Alamine 336 in oleyl alcohol as the extractant contained in a hollow-fiber membrane extractor for selective removal of butyric acid from the fermentation broth. The extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor. The fermentation pH was self-regulated by a balance between acid production and removal by extraction, and was kept at approximately pH 5.5 throughout the study. Compared with conventional fermentation, extractive fermentation resulted in a much higher product concentration (>300 g/L) and product purity (91%). It also resulted in higher reactor productivity (7.37 g/L. h) and butyric acid yield (0.45 g/g). Without on-line extraction to remove the acid products, at the optimal pH of 6.0, the final butyric acid concentration was only approximately 43.4 g/L, butyric acid yield was 0.423 g/g, and reactor productivity was 6.77 g/L. h. These values were much lower at pH 5.5: 20.4 g/L, 0.38 g/g, and 5.11 g/L. h, respectively. The improved performance for extractive fermentation can be attributed to the reduced product inhibition by selective removal of butyric acid from the fermentation broth. The solvent was found to be toxic to free cells in suspension, but not harmful to cells immobilized in the fibrous bed. The process was stable and provided consistent long-term performance for the entire 2-week period of study.     

Extractive lactic acid fermentation in poly (ethyleneimine)-based aqueous two-phase system

The potential of an aqueous two-phase system composed of a polycation, poly(ethyleneimine) (PEI), and an uncharged polymer, (hydroxyethyl) cellulose (HEC), for extractive lactic acid fermentation was tested. Batch fermentation with 20 g/L glucose in two-phase medium using Lactococcus lactis without external pH control resulted in 3-4 times higher amount of lactate and biomass produced as compared to that in a conventional one-phase medium. Lactic acid was preferentially partitioned to the PEI-rich bottom phase. However, the cells which favored the HEC-rich top phase in a fresh two-phase medium were partitioned to a significant extent to the bottom phase after fermentation. Addition of phosphate buffer or pH adjustment to 6.5 after fermentation caused fewer cells to move to the bottom phase. With external pH control, fermentation in normal and two-phase medium showed no marked differences in glucose consumption and lactic acid yield, except that about 1.3 times higher cell density was obtained in the two-phase broth, especially at initial glucose concentrations of 50-100 g/L. Use of higher concentration of phosphate during batch fermentation in the two-phase medium with 50 g/L sugar provided a 15% higher yield of lactic acid, but the growth rate of cells was nearly half of the normal, thus affecting the productivity. Continuous fermentation with twice the normal phosphate concentration resulted in higher cell density, product yield, and productivity in two-phase medium than in monophasic medium. (c) 1996 John Wiley & Sons, Inc.     

In situ extractive fermentation of acetone and butanol

The productivity of the acetone-butanol fermentation was increased by continuously removing acetone and butanol from the fermentation broth during fed-batch culture. Whole broth containing viable cells of Clostridium acetobutylicum was cycled to a Karr reciprocating plate extraction column in which acetone and butanol were extracted into oleyl alcohol flowing counter-currently through the column. By continuously removing these toxic metabolites from the broth, end product inhibition was reduced, and a concentrated feed solution containing 300 g/L glucose was fermented at an overall butanol productivity of 1.0 g/L h, 70% higher than the productivity of normal batch fermentation. The continuous extraction process provides flexible operation and lends itself to process scale-up.     

Effect of pH and nonionic surfactant on profile of intracellular and extracellular Monascus pigments

The uptake of nutrients and export of intracellular products are essential issues of microbial fermentation. Two-stage of Monascus fermentation using monosodium glutamate (MSG) as the sole nitrogen source, i.e., the first stage microbial fermentation in an aqueous solution and the second stage perstractive fermentation in a nonionic surfactant micelle aqueous solution, was carried out under different initial pH conditions. The results revealed that extracellular pH influences on the uptake of MSG and the export of water-soluble red pigment derivates into its extracellular broth. On the other hand, the export of intracellular hydrophobic pigments is affected by perstractive fermentation in nonionic surfactant micelle aqueous solution. All of those factors exhibit strong effect on the profile of Monascus pigments. This information is key to controlling profile of extracellular Monascus pigments by perstractive fermentation in nonionic surfactant micelle aqueous solution.     

A novel membrane-integrated fermentation reactor system: application to pyruvic acid production in continuous culture by Torulopsis glabrata

This paper describes the performance of a novel bio-reactor system, the membrane-integrated fermentation reactor (MFR), for efficient continuous fermentation. The MFR, equipped with an autoclavable polyvinylidene difluoride membrane, has normally been used for biological wastewater treatment. The productivity of the MFR system, applied to the continuous production of pyruvic acid by the yeast Torulopsis glabrata, was remarkably high. The volumetric productivity of pyruvic acid increased up to 4.2 g/l/h, about four times higher than that of batch fermentation. Moreover, the membrane was able to filter fermentation broth for more than 300 h without fouling even though the cell density of the fermentation broth reached 600 as OD₆₆₀. Transmembrane pressure, used as an indicator of membrane fouling, remained below 5 kPa throughout the continuous fermentation. These results clearly indicate that the MFR system is a simple and highly efficient system that is applicable to the fermentative production of a range of biochemicals.     

Production and rheological characteristics of the microbial polysaccharide gellan

B. MANNA, A. GAMBHIR AND P. GHOSH. 1996. Sphingomonas paucimobilis was used for the synthesis of the microbial polysaccharide gellan. In a 60 h fermentation, polysaccharide yield and productivity obtained were 0.45 g gellan per g glucose consumed and 0.21 g I⁻¹ h⁻¹ respectively. The broth showed pseudoplastic behaviour with yield stress. The requirement of the solvent propanol to precipitate gellan from the broth depended on the volume of the broth rather than on gellan concentration. The addition of salt to the broth reduced the propanol requirement. Attempts to separate cells from the highly viscous broth by microfiltration were not successful. Ultrafiltration reduced the propanol requirement but appreciable membrane fouling and loss of gellan was observed.     

Ethanol extraction by supported liquid membrane during fermentation

A supported liquid membrane system was developed for the extraction of ethanol during semicontinuous fermentation of Saccharomyces bayanus. it consisted of a porous Teflon sheet as support, soaked with isotridecanol. This assembly permitted combining biocompatibility, permeation efficiency, and stability. The removal of ethanol from the cultures led to decreased inhibition and, thus, to a gain in conversion of 452 g/L glucose versus 293 g/L glucose without extraction. At the same time, the ethanol volumetric productivity was enhanced 2.5 times, due to an improvement of yeast viability, while the substrate conversion yield was maintained above 95% of its theoretical value. Besides these improvements in fermentation performances, the process resulted in ethanol purification, since the separation was selective towards microbial cells and carbon substrate, and likely selective to mineral ions present in the fermentation broth. For pervaporation, a concentration of ethanol four times greater was obtained in the collected permeate.     

High cell density fed-batch fermentations for lipase production: feeding strategies and oxygen transfer

This review is focused on the production of microbial lipases by high cell density fermentation. Lipases are among the most widely used of the enzyme catalysts. Although lipases are produced by animals and plants, industrial lipases are sourced almost exclusively from microorganisms. Many of the commercial lipases are produced using recombinant species. Microbial lipases are mostly produced by batch and fed-batch fermentation. Lipases are generally secreted by the cell into the extracellular environment. Thus, a crude preparation of lipases can be obtained by removing the microbial cells from the fermentation broth. This crude cell-free broth may be further concentrated and used as is, or lipases may be purified from it to various levels. For many large volume applications, lipases must be produced at extremely low cost. High cell density fermentation is a promising method for low-cost production: it allows a high concentration of the biomass and the enzyme to be attained rapidly and this eases the downstream recovery of the enzyme. High density fermentation enhances enzyme productivity compared with the traditional submerged culture batch fermentation. In production of enzymes, a high cell density is generally achieved through fed-batch operation, not through perfusion culture which is cumbersome. The feeding strategies used in fed-batch fermentations for producing lipases and the implications of these strategies are discussed. Most lipase-producing microbial fermentations require oxygen. Oxygen transfer in such fermentations is discussed.     

Stirred tank bioreactor with a recirculation loop for improved L-lysine production

Summary A bioreactor equipped with a recirculation loop was used to investigate the fermentation for L-lysine production. The broth was pumped from the bottom of the fermenter and fed back to the top. With the recirculation stream, antifoam was not required as the fermentation proceeded and the proposed system significantly improved the productivity for L-lysine fermentation.     

Production of emulsan in a fermentation process using soybean oil (SBO) in a carbon-nitrogen coordinated feed

A fermentation process for the microbial production of an amphipatic lipopolysaccharide, emulsan, has been established using a triglyceride carbon source in a coordinated carbon-nitrogen feed strategy. The polysaccharide was produced by the Acinetobacter strain at a productivity of about 0.5 g emulsan/L h while utilizing only the fatty acids (FA) portion of the triglycerides or free fatty acids that were fed into the medium.A useful correlation between the utilization of the fatty acids and the consumption of the nitrogen was found and employed for the practical feed strategy using an appropriate C--N ratio (7.7 g C/g N) of the soybeanoil (SBO) (carbon source) to the ammonium hydroxide base (nitrogen source). Either the pH control or the supervising computer system could accomplish the adequate balanced feed in to the fermentor. Lipolysis slowdown was overcome by switching from a triglyceride carbon source to a free fatty acids one. A yield of about 0.2 g emulsan/g fatty acids was obtained and a final concentration of over 20 g/L was reached. The polymeric product was found to be partially associated with the cell-oil complexes in the fermentation broth unless the oily carbon source was efficiently exhausted. A fedbatch fermentation that employed a shift of the carbon source feed from triglycerides to free fatty acids appeared to be an appropriate and feasible way of producing the polymer.     

Prozeßtechnische Untersuchungen zur Ausschöpfung mikrobieller Leistungsgrenzen

The knowledge of the upper limits of growth rate and cell density is necessary to define the maximum possible productivity of a growth process. After a brief survey of the theoretical basis of microbial growth in dependence of mass transfer of oxygen and rheological properties of fermentation medium recent experimental results on the influence of higher pressure in the fermenter, of different substrate and dissolved oxygen concentrations on growth rate and yield coefficients of methanol utilizing bacteria are presented. Also some correlations between cell concentration and viscosity of fermentation broth are considered.     

Simultaneous Production and Recovery of Fumaric Acid from Immobilized Rhizopus oryzae with a Rotary Biofilm Contactor and an Adsorption Column

An integrated system of simultaneous fermentation-adsorption for the production and recovery of fumaric acid from glucose by Rhizopus oryzae was investigated. The system was constructed such that growing Rhizopus mycelia were self-immobilized on the plastic discs of a rotary biofilm contactor during the nitrogen-rich growth phase. During the nongrowth, production phase, the biofilm was alternately exposed to liquid medium and air upon rotation of the discs in the horizontal fermentation vessel. The product of fermentation, fumaric acid, was removed simultaneously and continuously by a coupled adsorption column, thereby moderating inhibition, enhancing the fermentation rate, and sustaining cell viability. Another beneficial effect of the removal of fumaric acid is release of hydroxyl ions from a polyvinyl pyridine adsorbent into the circulating fermentation broth. This moderates the decrease in pH that would otherwise occur. Polyvinyl pyridine and IRA-900 gave the highest loading for this type of fermentation. This fermentation system is capable of producing fumaric acid with an average yield of 85 g/liter from 100 g of glucose per liter within 20 h under repetitive fed-batch cycles. On a weight yield basis, 91% of the theoretical maximum was obtained with a productivity of 4.25 g/liter/h. This is in contrast to stirred-tank fermentation supplemented with calcium carbonate, whose average weight yield was 65% after 72 h with a productivity of 0.9 g/liter/h. The immobilized reactor was operated repetitively for 2 weeks without loss of biological activity.