Pilot-scale production of bacterial cellulose by a spherical type bubble column bioreactor using saccharified food wastes

Bacterial cellulose (BC) was produced by Acetobacter xylinum KJ1 in a modified airlift-type bubble column bioreactor, which had a low shear stress and high oxygen transfer rate (k _L a). Saccharified food wastes (SFW) were used as the BC production medium due to its low cost. An aeration rate of 1.2 vvm (6 L/min) was tentatively determined as the optimal aeration condition in a 10 L spherical type bubble column bioreactor, by analysis of the oxygen transfer coefficient. When 0.4% agar was added, the BC production reached 5.8 g/L, compared with 5.0 g/L in the culture without the addition of agar. The BC productivity was improved by 10% in the addition of 0.4% agar into the SFW medium. Then, by conversion of a linear velocity of 0.93 cm/sec, from the relationship between the linear velocity and oxygen transfer rate, 1.0 vvm (30 L/min) was determined as an optimal aeration condition in a 50 L spherical type bubble column reactor. Using SFW medium, with the addition of 0.4% agar, and air supplied of 1.0 vvm, 5.6 g/L BC was produced in the 50 L spherical type bubble column bioreactor after 3 days of cultivation, which was similar to that produced in the 10 L bioreactor. In conclusion, the addition of agar, a viscous polysaccharide, into SFW medium is effective for the production of BC, and this scale-up method is very useful for the mass production in a 50 L spherical type bubble column bioreactor by decreasing the shear stress and increasing the k _L a.     

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     

Citronensäure-Fermentation — biotechnologische Probleme und Möglichkeiten der Rechnersteuerung

Citric acid fermentation – biotechnological problems and possibilities of computer control . Citric acid today is produced almost exclusively by fermentation with the mold Aspergillus niger according to the surface or submerged process. The application of complex raw materials, like molasses, gives rise to considerable waste water burdens as well as to problems with microbiological process control. In order to gain qualitative and quantitative ideas about the metabolic activities of the mold during citric acid fermentation according to the submerged process production fermentors were equipped with several measuring points for the acquisition of physico-chemical changes in the medium and with devices for waste air analysis. The measured values were requested in rotation by an on-line computer and converted to characteristic derivative data. Together with additional analytical laboratory values these data were appropriate for getting a deeper insight into the biochemical events during fermentation. In this way mathematical models could be prepared which supported a better control and optimization of the fermentation course. The knowledge derived from these investigations permitted the extension of the data acquisition and computer system for monitoring and control of all production fermentors.     

Novel two‐in‐one bioreactor greatly improves lactic acid production from xylose by Lactobacillus pentosus

BACKGROUND: Simultaneous xylose isomerization and fermentation was investigated to improve the lactic acid production from xylose by Lactobacillus pentosus in a novel two‐in‐one bioreactor constructed by packing the immobilized xylose isomerase (65 g) in a fixed bed reactor (diameter 56 mm × 66 mm, packing volume 154 mL) with a permeable wall, which was installed inside a conventional fermenter (2 L) and rotated along the axis together with the mechanical stirrer of the fermenter. RESULTS: Xylose (20 g L^?1) was completely consumed within 24 h in the novel bioreactor, compared with 72 h needed for the control without packed enzyme. The maximum cell density (17.5 g L^?1) in the novel bioreactor was twice that in the control and the lactic acid productivity (0.58 g L^?1 h^?1) was 3.8 times higher. Repeated use of the immobilized enzyme showed that the lactic acid productivity and yield obviously dropped after the first batch fermentation but maintained almost unchanged afterwards. CONCLUSION: Simultaneous xylose isomerization and fermentation significantly improved lactic acid production from xylose by Lactobacillus pentosus. The novel bioreactor made it easier to recycle and reuse the immobilized enzyme. © 2012 Society of Chemical Industry     

Comparative Study of Sterol Ester Synthesis using <Emphasis Type="Italic">Thermomyces Lanuginosus</Emphasis> Lipase in Stirred Tank and Packed-Bed Bioreactors

A comparative study was done on the production of different sterol esters using a stirred tank batch reactor (STBR) and packed bed reactor (PBR) using Thermomyces lanuginosus (Lipozyme TLIM) enzyme, a commercially immobilized lipase. Different oils were used as the sources of particular fatty acids, e.g., fish oil for n-3 polyunsaturated fatty acids (n-3 PUFA), linseed oil for alpha linolenic acid (ALnA) and mustard oil for erucic acid. Reaction parameters, such as substrate molar ratio, reaction temperature and enzyme concentration, were standardized in the STBR and maintained in the PBR. To provide equal time of residence between the substrate and enzyme in both the reactors for the same amount of substrates, the substrate flow rate in the PBR was maintained at 0.27 ml/min. Thin layer chromatography was used to monitor the reaction, and column chromatography was used to determine the product yields. Fatty acid compositions of the esters were determined by gas chromatography. The study showed that the packed bed bioreactor was more efficient than the batch reactor in sterol-ester synthesis with less migration of acyl groups.     

In‐line mixing for production of citric acid by Candida lipolytica grown on n‐paraffins

This study reports on the effects of internal fermenter and external in‐line agitation and fed‐batch mode of operation on citric acid production from Candida lipolytica using n‐paraffin as the carbon source. An optimum range of fermenter agitation speeds in the range 800–1000 rpm corresponding to Reynolds numbers of 50433–62947 (based on initial batch conditions) seemed to give the best balance between substrate utilization for biomass growth and citric acid production. Proof of concept evidence is presented that indicates that an external in‐line agitator could be used in place of high speed internal agitation to increase citric acid production. However, more work is required to optimize the external agitator concept. Application of multiple fed‐batch feedings can be used to extend the batch fermentation and increase final citric acid concentrations and product yield. Experiments were conducted implementing a three‐cycle fed‐batch process which increased overall citric acid yields to 0.8–1.0 g citric acid g^?1 n‐paraffin, approximately 200% improvement from those found in the normal batch process. The three‐cycle fed‐batch mode of operation also increased the final citric acid concentration to 42 g dm^?3 from about 6 g dm^?3 for normal batch operation. Increased citric acid concentrations in three‐cycle fed‐batch mode was achieved at longer fermentation times. Copyright © 2004 Society of Chemical Industry     

Interaction of transport resistances with biochemical reaction in packed bed solid state fermenters: The effect of gaseous concentration gradients

Mass transfer plays an important role in solid state fermentation (SSF) systems. Earlier work on SSF in tray bioreactors⁷ indicated that steep gaseous concentration gradients developed within the substrate bed, owing to mass transfer resistances, which may adversely affect the bioreactor performance. For all practical purposes these gradients have been eliminated using a packed bed column bioreactor with forced aeration. Gaseous concentrations (oxygen and carbon dioxide) and enzyme activities were measured at various bed heights for various air flow rates during the course of fermentation. The results indicated that concentration gradients were decreased effectively by increasing air flow rate. For example, the actual oxygen and carbon dioxide concentration gradients reduced from 0.07% (v/v) cm^?1 and 0.023% (v/v) cm^?1 to 0.007% (v/v) cm^?1 and 0.0032% (v/v) cm^?1 respectively when the air flow rate was increased from 5 dm³ min^?1 to 25 dm³ min^?1. This resulted in an overall improvement in the performance of the bioreactor in terms of enzyme production.     

Immobilization of trophic anaerobic acetogen for semi-continuous syngas fermentation

The massive consumption of fossil energy forces people to find new sources of energy. Syngas fermentation has become a hot research field as its high potential in renewable energy production and sustainable development. In this study, trophic anaerobic acetogen Morella thermoacetica was successfully immobilized by calcium alginate embedding method. The ability of the immobilized cells on production of acetic acid through syngas fermentation was compared in both airlift and bubble column bioreactors. The bubble column bioreactor was selected as the better type of bioreactor. The production of acetic acid reached 32.3 g·L^-1 in bubble column bioreactor with a space-time yield of 2.13 g·L^-1·d^-1. The immobilized acetogen could be efficiently reused without significant lag period, even if exposed to air for a short time. A semi-continuous syngas fermentation was performed using immobilized cells, with an average space-time acetic acid yield of 3.20 g·L^-1·d^-1. After 30 days of fermentation, no significant decrease of the acetic acid production rate was observed.     

Xylitol production by Candida tropicalis from corn cob hemicellulose hydrolysate in a two‐stage fed‐batch fermentation process

BACKGROUND: Xylitol, a sugar alcohol widely used in food and pharmaceutical industries, can be produced through biological reduction of xylose present in hemicellulose hydrolysates by Candida tropicalis. However, the aeration rate and by‐products originating from hemicellulose hydrolysis strongly inhibit the production of xylitol in a fermentation process. A two‐stage fed‐batch fermentation system was developed to reduce these inhibitory effects and to improve xylitol production from corn cob hemicellulose hydrolysates by C. tropicalis. RESULTS: Results of batch fermentations indicated that high xylitol production could be obtained from C. tropicalis at an initial xylose concentration of 80 g L^?1 in corn cob hydrolysate medium at an aeration rate of 0.4 vvm at the micro‐aeration stage. In the two‐stage fed‐batch fermentation process, 96.5 g L^?1 xylitol was obtained after 120 h, giving a yield of 0.83 g g^?1 and a productivity of 1.01 g L^?1 h^?1, which were 12.16% and 65.57% higher than those in a batch fermentation. CONCLUSION: High xylitol production can be achieved in a two‐stage fed‐batch fermentation process, in which the negative effects of aeration rate and inhibitory compounds on xylitol formation can be considerably reduced. Copyright © 2011 Society of Chemical Industry     

A continuous ultrasound‐assisted packed‐bed bioreactor for the lipase‐catalyzed synthesis of caffeic acid phenethyl ester

BACKGROUND: The focus of this paper is the ultrasound‐assisted synthesis of caffeic acid phenethyl ester (CAPE) from caffeic acid and phenyl ethanol in a continuous packed‐bed bioreactor. Immobilized Novozym^® 435 (from Candida antarctica) is used as the catalyst. A three‐level–three‐factor Box–Behnken design and a response surface methodology (RSM) are employed to evaluate the effects of temperature, flow rate, and ultrasonic power on the percentage molar conversion of CAPE. RESULTS: Based on ridge max analysis, it is concluded that the optimum condition for synthesis is reaction temperature 72.66 °C, flow rate 0.046 mL min^?1, and ultrasonic power 1.64 W cm^?2. The expected molar conversion value is 97.84%. An experiment performed under these optimal conditions resulted in a molar conversion of 92.11 ± 0.75%. The enzyme in the bioreactor was found to be stable for at least 6 days. CONCLUSIONS: The lipase‐catalyzed synthesis of CAPE by an ultrasound‐assisted packed‐bed bioreactor uses mild reaction conditions. Enzymatic synthesis of CAPE is suitable for use in the nutraceutical and food production industries. Copyright © 2011 Society of Chemical Industry     

Biochemistry of Citric Acid Production from Rapeseed Oil by <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> Yeast

The growth of wild type strain Yarrowia lipolytica VKM Y-2373 and its mutant Y. lipolytica NG40/UV7 as well as the biosynthesis of citric and isocitric acid on rapeseed oil were studied. It was indicated that the initial step of assimilation of rapeseed oil in the yeast Y. lipolytica is its hydrolysis by extracellular lipases with the formation of glycerol and fatty acids, which appear in the medium in the phase of active growth. The concentrations of these metabolites were changed insignificantly upon further cultivation. Lipase and the key enzymes of glycerol metabolism (glycerol kinase) and the glyoxylate cycle responsible for the metabolism of fatty acids (isocitrate lyase and malate synthase) are induced just at the beginning of the growth phase and remain active in the course of further cultivation. These results, taken together, suggest that glycerol and fatty acids available in the medium do not suppress the metabolism of each other. Citric acid production and a ratio between citric and isocitric acids depended on the strain used. It was revealed that the wild strain produced almost equal amounts of citric and isocitric acids while the mutant produced only citric acid (175 g/L) with a yield of 1.5 g of CA per g of oil.     

正十六烷发酵产生柠檬酸的研究

通过试验筛选出产柠檬酸较高的菌种解脂复膜孢酵母１４６０菌和适宜培养基,确定了适宜的菌种起始浓度和底物浓度,证实谷氨酸对产生柠檬酸的促进作用,对分批培养发酵过程中细胞生长和产物生成速率进行了数学表达。     

Scaling up the Bioconversion of Cheese Whey Permeate into Fungal Oil by Mucor circinelloides

The bioconversion of hydrolyzed whey permeate into an oil-rich biomass by Mucor circinelloides was scaled up from 250 mL to 4 L with the use of an aerated stirred tank bioreactor. Biomass production and oil accumulation were strongly influenced by agitation speed (99–451 rpm) and aeration rate (0.29–1.70 vvm). Higher agitation and aeration rates (e.g., >400 rpm, >1 vvm), resulted in significantly higher biomass yield due to increased oxygen transfer capabilities and better mixing. Additionally, oil accumulation in the fungal biomass was related to high agitation (>400 rpm), while aeration (0.5–1.5 vvm) had no significant effect within the range evaluated. The predictive model was validated at the optimal conditions of 450 rpm and 1 vvm. Maximum biomass yield of 10.7 g L⁻¹ and lipid content of 32% dry biomass were achieved during 120 hours of fermentation. Simultaneous optimization of agitation and aeration in a bioreactor was found to not only improve fungal growth but also lipid content (24% vs. 32%), lipid yield (2.2 vs. 3.1 g L⁻¹) and γ-linoleic production (73–464 mg L⁻¹) compared to that of shake-flask. This study resulted in a scaled-up and optimized fermentation process that increased production of M. circinelloides biomass for subsequent use as raw material for food, feed, and fuel applications. This signifies a starting point for further studies aimed at assessing the development of a fully functioning fungi-to-food/fuel system on an industrial scale for several agricultural streams.     

INCREASE IN PHYTASE SYNTHESIS DURING CITRIC PULP FERMENTATION

Citric pulp bran was used for the first time as substrate for phytase synthesis under solid-state fermentation. An A. niger FS3 phytase strain was applied in optimization studies. A Plackett-Burman screening design identified significant physicochemical variables. These preselected variables were subsequently optimized using a central composite rotational design (CCRD). The maximum phytase production was achieved with the following optimum variables: 30°C temperature, 65% initial moisture content, 0.3 M Na-citrate buffer concentration, initial pH 5.0, and 1.5% urea concentration. An overall 4.3-fold improvement in phytase production was successfully achieved.     

Mathematical model of heat transfer during solid‐state fermentation in well‐mixed rotating drum bioreactors

We present a mathematical model that describes heat and mass transfer during solid‐state fermentation (SSF) of Aspergillus oryzae in a well‐mixed rotating drum bioreactor (RDB). In addition to the substrate bed and the headspace, the model recognises the bioreactor wall as a subsystem, allowing it to identify the role of this subsystem in heat removal from the bed. Model predictions agree well with previously published experimental data obtained in a rotating drum bioreactor of 0.19 m diameter and 0.85 m length, with maximum temperatures up to 15 °C greater than the incubation temperature being reached. The model offers insights into the rate limiting steps in heat removal, and how SSF performance might be improved in the experimental system. Copyright © 2003 Society of Chemical Industry     

Kinetic modelling of lactic acid production from whey by Lactobacillus casei (NRRL B‐441)

The biomass growth, lactic acid production and lactose utilisation kinetics of lactic acid production from whey by Lactobacillus casei was studied. Batch fermentation experiments were performed at controlled pH and temperature with six different initial whey lactose concentrations (9‐77 g dm^?3) in a 3 dm³ working volume bioreactor. Biomass growth was well described by the logistic equation with a product inhibition term. In addition, biomass and product inhibition effects were defined with corresponding power terms, which enabled adjustment of the model for low‐ and high‐substrate conditions. The Luedeking‐Piret equation defined the product formation kinetics. Substrate consumption was explained by production rate and maintenance requirements. A maximum productivity of 2.5 g dm^?3 h^?1 was attained with an initial lactose concentration of 35.5 g dm^?3. Copyright © 2006 Society of Chemical Industry     

黑曲霉生产柠檬酸的控制论模型

黑曲霉发酵是工业生产柠檬酸的主要途径,研究该过程的动力学模型对更好地理解这一工业微生物的代谢机理有重要意义。基于黑曲霉(Aspergillus niger)柠檬酸发酵过程主要代谢途径的分析,构建了简化的碳代谢网络,建立了胞内物质和酶浓度的平衡模型。引入一阶闭环调节器模型描述发酵初期微生物酶系的建立过程。结合生物反应器模型,给出了重要宏观状态变量(如细胞物质浓度、基质浓度、产物浓度)和胞内酶浓度的动态仿真结果与实验值的对比。     

固定床反应器培养固定化大肠杆菌生产β-葡聚糖酶

以多孔陶瓷为载体吸附法固定重组大肠杆菌E. coli JM 109-pLF3表达胞外β-葡聚糖酶。考察了固定床间歇培养时循环流速和曝气量对发酵液酶活力的影响。当循环流速达到44.19 mL/min,曝气量达到0.6 mL/min时,培养48 h后,发酵液的酶活力达100.3 U/mL。固定化细胞具有良好的重复使用能力,在连续5批次实验中,培养48 h后的酶活力均在100 U/mL左右。固定床连续培养时,固定化细胞能够保持恒定的产酶效率,当稀释率为0.05 h－1时,发酵液中得到的酶活力为39.1 U/mL。     

Assessment of Relevant Factors Influencing Lipolytic Enzyme Production by Thermus thermophilus HB27 in Laboratory‐Scale Bioreactors

Nowadays, there is not much information on the large‐scale production of thermostable lipolytic enzymes by thermophilic organisms. Therefore, in this study the lipolytic enzyme production by Thermus thermophilus HB27 in laboratory‐scale bioreactors was undertaken. In order to determine the most suitable bioreactor, two configurations were investigated: stirred‐tank and airlift bioreactor. It was demonstrated that the stirred‐tank configuration led to the highest lipolytic extracellular activities, about 2.3‐fold higher than those found in the corresponding cultivation in the airlift bioreactor. On the other hand, the influence of several factors such as culture nutrients concentration, aeration, and agitation rate on the production of thermophilic lipolytic enzymes in a 5‐L stirred‐tank bioreactor was assayed. At reduced nutrients concentration (50 % with respect to the basal medium), a higher product/biomass yield was attained, without any operational problems. From the relationship between mass transfer coefficient (K_La), aeration, and agitation rates it was concluded that there is a lesser dependence on the aeration than the agitation rate. In addition, the mechanical stirring of the bioreactor could tear the membranes that contain the rotund bodies often found in cultures of thermophilic microorganisms, thus increasing the extracellular enzyme production.     

Cichoric acid production from hairy root cultures of Echinacea purpurea grown in a modified airlift bioreactor

BACKGROUND: Hairy root cultures of Echinacea offer great potential for the production of valuable cichoric acid, but scale‐up of the culture in the bioreactor represents a big challenge. Therefore, there is great interest in developing a suitable bioreactor for hairy root culture of Echinacea and novel bioprocessing strategies for intensifying cichoric acid production. RESULTS: Homogenous distribution of inoculum roots and high cichoric acid production were observed in a bioreactor modified by installing a mesh draught tube with an average pore size 700 µm, slightly larger than the hairy root, about 500 µm. Improved root growth and cichoric acid production were improved by increasing the aeration rate from 0.002 m³ h^?1 to 0.012 m³ h^?1. The hairy root cultures in the modified bioreactor exposed once to 6 min of ultrasound treatment at day 20 gave the highest biomass accumulation of 12.8 ± 0.3 g L^?1, which resulted in the maximum cichoric acid production of 178.2 ± 4.9 mg L^?1 at day 30. CONCLUSION: The present work demonstrated the effectiveness of hairy root culture in a modified airlift bioreactor. The biomass distribution remained homogenous in the modified airlift bioreactor, and the cichoric acid production was improved owing to the even root growth at optimal air flow rate. An interesting finding of this investigation was that ultrasound stimulated root growth and cichoric acid production considerably in the modified airlift bioreactor. Copyright © 2009 Society of Chemical Industry