Enhancement of pyruvate production by Torulopsis glabrata using a two-stage oxygen supply control strategy

The effect of agitation speeds on the performance of producing pyruvate by a multi-vitamin auxotrophic yeast, Torulopsis glabrata, was investigated in batch fermentation. High pyruvate yield on glucose (0.797 g g(-1)) was achieved under high agitation speed (700 rpm), but the glucose consumption rate was rather low (1.14 g l(-1) h(-1)). Glucose consumption was enhanced under low agitation speed (500 rpm), but the pyruvate yield on glucose decreased to 0.483 g g(-1). Glycerol production was observed under low agitation speed and decreased with increasing agitation speed. Based on process analysis and carbon flux distribution calculation, a two-stage oxygen supply control strategy was proposed, in which the agitation speed was controlled at 700 rpm in the first 16 h and then switched to 500 rpm. This was experimentally proven to be successful. Relatively high concentration of pyruvate (69.4 g l(-1)), high pyruvate yield on glucose (0.636 g g(-1)), and high glucose consumption rate (1.95 g l(-1)h(-1)) were achieved by applying this strategy. The productivity (1.24 g l(-1) h(-1)) was improved by 36%, 23% and 31%, respectively, compared with fermentations in which agitation speeds were kept constant at 700 rpm, 600 rpm, and 500 rpm. Experimental results indicate that the difference between the performances for producing pyruvate under a favorable state of oxygen supply (dissolved oxygen concentration >50%) was caused by the different regeneration pathways of NADH generated from glycolysis.     

Effects of agitation intensity on mycelial morphology and protein production in chemostat cultures of recombinant Aspergillus oryzae

The effects of agitation on fragmentation of a recombinant strain of Aspergillus oryzae and its consequential effects on protein production have been investigated. Constant mass, 5.3-L chemostat cultures at a dilution rate of 0.05 h-1 and a dissolved oxygen level of 75% air saturation, have been conducted at 550, 700, and 1000 rpm. These agitation speeds were chosen to cover a range of specific power inputs (2.2 to 12 kW m-3) from realistic industrial levels to much higher values. The use of a constant mass chemostat linked to a gas blender allowed variation of agitation speed and hence gas hold-up without affecting the dilution rate or the concentration of dissolved oxygen. The morphology of both the freely dispersed mycelia and clumps was characterized using image analysis. Statistical analysis showed that it was possible to obtain steady states with respect to morphology. The mean projected area at each steady state under growing conditions correlated well with the 'energy dissipation/circulation" function, [P/(kD3tc)], where P is the power input, D the impeller diameter, tc the mean circulation time, and k is a geometric constant for a given impeller. Rapid transients of morphological parameters in response to a speed change from 1000 to 550 rpm probably resulted from aggregation. Protein production (alpha-amylase and amyloglucosidase) was found to be independent of agitation speed in the range 550 to 1000 rpm (P/V = 2.2 and 12.6 kW m-3, respectively), although significant changes in mycelial morphology could be measured for similar changes in agitation conditions. This suggests that mycelial morphology does not directly affect protein production (at a constant dilution rate and, therefore, specific growth rate). An understanding of how agitation affects mycelial morphology and productivity would be valuable in optimizing the design and operation of large-scale fungal fermentations for the production of recombinant proteins. Copyright 1999 John Wiley & Sons, Inc.     

Enhanced riboflavin production by recombinant Bacillus subtilis RF1 through the optimization of agitation speed

Dissolved oxygen is one of the most important bioprocess parameters that could affect cell growth and product formation, and it is easy to control by changing agitation speed. In this work, the effects of agitation speed on the performance of riboflavin production by recombinant Bacillus subtilis RF1 was investigated in fed-batch fermentation. The lower agitation speed (600 rpm) was beneficial for cell growth and riboflavin biosynthesis in the initial phase of fermentation process. While, during the later phase, higher agitation speed (900 rpm) was favor for cell growth and riboflavin biosynthesis. Thus, a two-stage agitation speed control strategy was proposed based on kinetic analysis, in which the agitation speed was controlled at 600 rpm in the first 26 h and then switched to 900 rpm to maintain high μ for cell growth and high q _p for riboflavin production during the entire fermentation process. However, it was observed that a sharp increase of agitation speed resulted in an adverse effect on cell growth and riboflavin synthesis within a short time. To avoid this phenomenon, a multi-stage agitation speed control strategy was set up based on the two-stage control strategy, the maximum concentration of riboflavin reached 9.4 g l^?1 in 48 h with the yield of 0.051 g g^?1 by applying this strategy, which were 20.5 and 21.4 % over the best results controlled by constant agitation speeds.     

Hydrodynamic and kinetic study of cellulase production by Trichoderma reesei with pellet morphology

Numerical simulations and experimental validation were performed to understand the effects of hydrodynamics on pellet formation and cellulase production by filamentous T. reesei. The constructed model combined a steady-state multiple reference frame (MRF) approach describing mechanical mixing, oxygen mass transfer, and non-Newtonian flow field with a transient sliding mesh approach and kinetics of oxygen consumption, pellet formation, and enzyme production. The model was experimentally validated at various agitation speeds in a two-impeller Rushton turbine fermentor. Results from simulation and experimentation showed that higher agitation speeds led to increases in the pellet diameter and the proportion of pelletized (vs. filamentous) forms of the biomass. It also led to increase in dissolved oxygen mass transfer rate in shear-thinning fluid and cellulase productivity. The extent of these increases varied considerably among agitation speeds. Pellet formation and morphology were presumably affected within a viscosity-dependent shear-rate range. Cellulase activity and cell viability were shown to be sensitive to impeller shear. A maximum cellulase activity of 3.5 IU/mL was obtained at 400 rpm, representing a twofold increase over that at 100 rpm.     

Agitator speed and dissolved oxygen effects in xanthan fermentations

Agitation speed affects both the extent of motion in Xanthan fermentation broths because of their rheological complexity and the rate of oxygen transfer. The combination of these two effects causes the dissolved oxygen concentration and its spatial uniformity also to change with agitator speed. Separating these complex interactions has been achieved in this study in the following way. First, the influence of agitation speeds of 500 and 1000 rpm has been investigated at a constant nonlimiting dissolved oxygen concentration of 20% of air saturation using gas blending. Under these controlled dissolved oxygen conditions, the results demonstrate that the biological performance of the culture was independent of agitation speed as long as broth homogeneity could be ensured. With the development of increasing rheological complexity lending to stagnant regions at Xanthan concentrations >20 g/L, it is shown that the superior bulk mixing achieved at 1000 rpm, compared with 500 rpm, leading to an increased proportion of the cells in the fermentor to be metabolically active and hence higher microbial oxygen uptake rates, was responsible for the enhanced performance. Second, the effects of varying dissolved oxygen are compared with a control in each case with an agitator speed of 1000 rpm to ensure full motion, but with a fixed, nonlimiting dissolved oxygen of 20% air saturation. The specific oxygen uptake rate of the culture in the exponential phase, determined using steady-state gas analysis data, was found to be independent of dissolved oxygen above 6% air saturation, whereas the specific growth rate of the culture was not influenced by dissolved oxygen, even at levels as low as 3%, although a decrease in Xanthan production rate could be measured. In the production phase, the critical oxygen level was determined to be 6% to 10%, so that, below this value, both specific Xanthan production rate as well as specific oxygen uptake rate decreased significantly. In addition, it is shown that the dynamic method of oxygen uptake determination is unsuitable even for moderately viscous Xanthan broths. Copyright 1998 John Wiley & Sons, Inc.     

Enhanced welan gum production using a two-stage agitation speed control strategy in Alcaligenes sp. CGMCC2428

Batch fermentative production of welan gum by Alcaligenes sp. CGMCC2428 was investigated under various oxygen supply conditions using regulating agitation speed. Based on a three kinetic parameters analysis that includes specific cell growth rate (μ), specific glucose consumption rate (q _s), and specific welan formation rate (q _p), a two-stage agitation speed control strategy was proposed to achieve high concentration, high yield, and high viscosity of welan. During the first 22 h, the agitation speed in 7.5 L fermenter was controlled at 800 rpm to maintain high μ for cell growth. The agitation was then reduced step-wise to 600 rpm to maintain a changing profile with stable dissolved oxygen levels and obtain high qp for high welan accumulation. Finally, the maximum concentration of welan was reached at 26.3 ± 0.89 g L⁻¹ with a yield of 0.53 ± 0.003 g g⁻¹ and the welan gum viscosity of 3.05 ± 0.10 Pa s, which increased by an average of 15.4, 15.2, and 20.1% over the best results controlled by constant agitation speeds.     

Dynamics of mycelial aggregation in cultures of Aspergillus oryzae

Previous work has shown that in many mycelial fermentations the predominant morphological form is clumps (aggregates) which cannot be further reduced by dilution. During fermentation, the clump size and shape is affected by fragmentation, which in turn depends on agitation conditions. This paper addresses the question of whether mycelial aggregation can also occur during a fermentation. The dynamics of changes in mycelial morphology due to aggregation were investigated in 5.3-L chemostat cultures of Aspergillus oryzae by imposing a step decrease in agitation speed from 1,000 to 550 rpm under conditions of controlled non-limiting dissolved oxygen tension, with a steady-state biomass concentration of 2 g/L. The mean projected area (size) of the mycelia, measured using image analysis, increased from 5,300녘 µm² (at 1,000 rpm) to 9,400덌 µm² (at 550 rpm). This change occurred too rapidly for it to be solely caused by mycelial growth. Instead, it is proposed that the increase in size was indeed due to aggregation, probably due to physico-chemical affects such as hydrophobicity or charge interactions. Aggregation was also shown to occur in 4-L aerated batch cultures at higher biomass concentrations (5.3 and 11.2 g/L) in which the agitation speed was decreased from 1,100 to 550 rpm. Experiments were also conducted off-line in a mixing vessel in the absence of oxygen. In this case, aggregation was not observed. Thus, though the cause of aggregation at this stage is not clear, aerobic metabolism appears to be required.     

Comparative study on the influence of dissolved oxygen control approaches on the microbial hyaluronic acid production of <Emphasis Type="Italic">Streptococcus zooepidemicus</Emphasis>

Three different dissolved oxygen (DO) control approaches were proposed to improve hyaluronic acid (HA) production: a three-stage agitation speed control approach, a two-stage DO control approach, and an oxygen vector perfluorodecalin (PFC) applied approach. In the three-stage agitation speed control approach, agitation speed was 200 rpm during 0–8 h, 400 rpm during 8–12 h, and 600 rpm during 12–20 h. In the two-stage DO control strategy, DO was controlled at above 10% during 0–8 h and at 5% during 8–20 h. In the PFC applied approach, PFC (3% v/v) was added at 8 h. HA production reached 5.5 g/L in the three-stage agitation speed control culture model, and 6.3 g/L in two-stage DO control culture model, and 6.6 g/L in the PFC applied culture model. Compared with the other two DO control approaches, the PFC applied approach had a lower shear stress and thus a higher HA production was achieved.     

Production of rosmarinic acid by<Emphasis Type="Italic">Lavandula vera</Emphasis> MM cell suspension in bioreactor: effect of dissolved oxygen concentration and agitation

The relationship between dissolved oxygen (DO) concentration, agitation rate and growth of Lavandula vera MM and rosmarinic acid biosynthesis was investigated in 3 l laboratory bioreactor. Lavandula vera MM cell suspension accumulated the highest amounts of biomass (34.8 g/l) and rosmarinic acid (1870.6 mg/l) on day 12 of cultivation at 50% dissolved oxygen and agitation speed 100 rpm and at 30% dissolved oxygen and agitation speed 300 rpm, respectively.     

Vancomycin production is enhanced in chemostat culture with biomass-recycle

Production of the glycopeptide antibiotic vancomycin by Amycolatopsis orientalis ATCC 19795 was examined in phosphate-limited chemostat cultures with biomass-recycle, employing an oscillating membrane separator, at a constant dilution rate (D= 0. 14 h-1). Experiments made under low agitation conditions (600 rpm) showed that the biomass concentration could be increased 3.9-fold with vancomycin production kinetics very similar to that of chemostat culture without biomass-recycle. The specific production rate (qvancomycin) was maximal when the biomass-recycle ratio (R) was 0.13 (D= 0.087 h-1). When the dissolved oxygen tension dropped below 20% (air saturation), the biomass and vancomycin concentrations decreased and an unidentified red metabolite was released into the culture medium. Using increased agitation (850 rpm), used to maintain the dissolved oxygen tension above 20% air saturation, maximum increases in biomass concentration (7.9-fold) and vancomcyin production 1.6-fold (0.6 mg/g dry weight/h) were obtained when R was 0.44 (D= 0.056 h -1) compared to chemostat culture without biomass-recycle. Moreover, at this latter recycle ratio the volumetric vancomycin production rate was 14.7 mg/L/h (a 7-fold increase compared to chemostat culture without biomass-recycle). These observations encourage further research on biomass-recycling as a means of optimising the production of antibiotics.     

Enhanced 2,3-butanediol production by Klebsiella oxytoca using a two-stage agitation speed control strategy

Batch fermentative production of 2,3-butanediol by Klebsiella oxytoca was investigated using various oxygen supply methods though varying agitation speed. Based on the analysis of three kinetic parameters including specific cell growth rate (μ), specific glucose consumption rate (q_s) and specific 2,3-butanediol formation rate (q_p), a two-stage agitation speed control strategy, aimed at achieving high concentration, high yield and high productivity of 2,3-butanediol, was proposed. At the first 15 h, agitation speed was controlled at 300 rpm to obtain high μ for cell growth, subsequently agitation speed was controlled at 200 rpm to maintain high q_p for high 2,3-butanediol accumulation. Finally, the maximum concentration of 2,3-butanediol reached 95.5 g l⁻¹ with the yield of 0.478 g g⁻¹ and the productivity of 1.71 g l⁻¹ h⁻¹, which were 6.23%, 6.22% and 22.14% over the best results controlled by constant agitation speeds.     

Effect of aeration on denitrification byOchrobactrum anthropi SY509

Aeration was found to affect the biological denitrification byOchrobactrum anthropi SY509. Although cell growth was vigorous under 1 vvm of aeration and an agitation speed of 400 rpm in a 3-L jar fermentor, almost no nitrate was removed. Yet under low agitation speeds (100, 200, and 300 rpm), denitrification occurred when the dissolved oxygen was exhausted shortly after the inoculation of the microorganism.Ochrobactrum anthropi SY509 was found to express highly active denitrifying enzymes under anaerobic conditions. The microorganism also synthesized denitrifying enzymes under aerobic conditions (1 vvm and 400 rpm), yet their activity was only 60% of the maximum level under anaerobic conditions and the nitrate removal efficiency was merely 15%. However, although the activities of the denitrifying enzymes were inhibited in the presence of oxygen, they were fully recovered when the conditions were switched to anaerobic conditions.     

Influence of oxygen transfer on <Emphasis Type="Italic">Pseudomonas putida</Emphasis> effects on growth rate and biodesulfurization capacity

The growth rate and desulfurization capacity accumulated by the cells during the growth of Pseudomonas putida KTH2 under different oxygen transfer conditions in a stirred and sparged tank bioreactor have been studied. Hydrodynamic conditions were changed using different agitation conditions. During the culture, several magnitudes associated to growth, such as the specific growth rate, the dissolved oxygen concentration and the carbon source consumption have been measured. Experimental results indicate that cultures are influenced by the fluid dynamic conditions into the bioreactor. An increase in the stirrer speed from 400 to 700 rpm has a positive influence on the cell growth rate. Nevertheless, the increase of agitation from 700 to 2000 rpm hardly has any influence on the growth rate. The effect of fluid dynamics on the cells development of the biodesulfurization (BDS) capacity of the cells during growth is different. The activities of the intracellular enzymes involved in the 4S pathway change with dissolved oxygen concentration. The enzyme activities have been evaluated in cells at several growth time and different hydrodynamic conditions. An increase of the agitation from 100 to 300 rpm has a positive influence on the development of the overall BDS capacity of the cells during growth. This capacity shows a decrease for higher stirrer speeds and the activity of the enzymes monooxygenases DszC and DszA decreases dramatically. The highest value of the activity of DszB enzyme was obtained with cells cultured at 100 rpm, while this activity decreases when the stirrer speed was increased higher than this value.     

Enhanced acetoin production by Serratia marcescens H32 using statistical optimization and a two-stage agitation speed control strategy

Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett-Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L) and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed, and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved.     

Effect of various process parameters on morphology, rheology, and polygalacturonase production by Aspergillus sojae in a batch bioreactor

The effects of pH, agitation speed, and dissolved oxygen tension (DOT), significant in common fungal fermentations, on the production of polygalacturonase (PG) enzyme and their relation to morphology and broth rheology were investigated using Aspergillus sojae in a batch bioreactor. All three factors were effective on the response parameters under study. An uncontrolled pH increased biomass and PG activity by 27% and 38%, respectively, compared to controlled pH (pH 6) with an average pellet size of 1.69 +/- 0.48 mm. pH did not significantly affect the broth rheology but created an impact on the pellet morphology. Similarly, at constant agitation speed the maximum biomass obtained at 500 rpm and at 30 h was 3.27 and 3.67 times more than at 200 and 350 rpm, respectively, with an average pellet size of 1.08 +/- 0.42 mm. The maximum enzyme productivity of 0.149 U mL-1 h-1 was obtained at 200 rpm with an average pellet size of 0.71 +/- 0.35 mm. Non-Newtonian and pseudoplastic broth rheology was observed at 500 rpm agitation speed, broth rheology exhibited dilatant behavior at the lower agitation rate (200 rpm), and at the medium agitation speed (350 rpm) the broth was close to Newtonian. Furthermore, a DOT range of 30-50% was essential for maximum biomass formation, whereas only 10% DOT was required for maximum PG synthesis. Non-Newtonian shear thickening behavior (n > 1.0) was depicted at DOT levels of 10% and 30%, whereas non-Newtonian shear thinning behavior (n < 1.0) was dominant at 50% DOT. The overall fermentation duration (50-70 h) was considerably shorter compared to common fungal fermentations, revealing the economic feasibility of this particular process. As a result this study not only introduced a new strain with a potential of producing a highly commercially significant enzyme but also provided certain parameters significant in the design and mathematical modeling of fungal bioprocesses.     

Dependence of morphology on agitation intensity in fed-batch cultures of Aspergillus oryzae and its implications for recombinant protein production

We previously reported that, although agitation conditions strongly affected mycelial morphology, such changes did not lead to different levels of recombinant protein production in chemostat cultures of Aspergillus oryzae (Amanullah et al., 1999). To extend this finding to another set of operating conditions, fed-batch fermentations of A. oryzae were conducted at biomass concentrations up to 34 g dry cell weight/L and three agitation speeds (525, 675, and 825 rpm) to give specific power inputs between 1 and 5 kWm(-3). Gas blending was used to control the dissolved oxygen level at 50% of air saturation except at the lowest speed where it fell below 40% after 60-65 h. The effects of agitation intensity on growth, mycelial morphology, hyphal tip activity, and recombinant protein (amyloglucosidase) production in fed-batch cultures were investigated. In the batch phase of the fermentations, biomass concentration, and AMG secretion increased with increasing agitation intensity. If in a run, dissolved oxygen fell below approximately 40% because of inadequate oxygen transfer associated with enhanced viscosity, AMG production ceased. As with the chemostat cultures, even though mycelial morphology was significantly affected by changes in agitation intensity, enzyme titers (AGU/L) under conditions of substrate limited growth and controlled dissolved oxygen of >50% did not follow these changes. Although the measurement of active tips within mycelial clumps was not considered, a dependency of the specific AMG productivity (AGU/g biomass/h) on the percentage of extending tips was found, suggesting that protein secretion may be a bottle-neck in this strain during fed-batch fermentations.     

Improvement of poly(γ-glutamic acid) biosynthesis and quantitative metabolic flux analysis of a two-stage strategy for agitation speed control in the culture of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> NX-2

In this study, the production of poly(γ-glutamic acid) by Bacillus subtilis NX-2 (PGA) at different agitation speeds was investigated. Based on the analysis of specific cell growth rate (μ) and specific PGA formation rate (q _p ), a two-stage strategy for agitation speed control was proposed. During the first 24 h, an agitation speed of 600 rpm was used to maintain a high μ for better cell growth, which then reduced to 400 rpm after 24 h to maintain a high q _p to enhance PGA production. Using this method, the maximum concentration of PGA reached 40.5 ± 0.91 g/L and the PGA productivity was 0.56 ± 0.012 g/L/h, which was 17.7 and 9.8% higher, respectively, than the best results obtained when a constant agitation speed was used. The flux distributions and the related enzymes of 2-oxoglutarate could be affected by this two-stage strategy for agitation speed. The activity of isocitrate dehydrogenase and glutamate dehydrogenase at the key node of 2-oxoglutarate increased, and more flux distribution was directed to glutamate. The flux distribution from extracellular to intracellular glutamate also increased and improved PGA production as the glutamate uptake rates increased using the agitation-shift control method.     

An oxygen supply strategy for the large-scale production of tissue plasminogen activator by microcarrier cell culture

An oxygen supply strategy involving agitation speed and aeration method for the large-scale production of tissue plasminogen activator (TPA) by a microcarrier cell culture was investigated by small-scale model experiments. A preliminary calculation indicated that diffusion limitation of dissolved oxygen (DO) could be caused in a microcarrier sedimentation layer more than 0.5 mm in thickness. Within an agitation speed range above 70 rpm, which was the critical speed for all of the microcarrier beads to remain suspended and thus for avoiding a deficiency of DO, the TPA productivity was higher at a lower agitation speed, while the cell concentration was not affected by the agitation speed. The addition of soluble starch to the culture medium prevented sedimentation of the microcarrier beads, even at the low agitation speed of 20 rpm, resulting in a TPA productivity higher than that at 70 rpm, which was the optimum speed without soluble starch. Use of an air spray system with an optimized air flow rate resulted in a k_La 2.35 times higher than that with simple surface aeration. Increasing the internal pressure of the culture from 0.2 kg/cm² (1209 hPa) to 1.5 kg/cm² (2483 hPa) had no effect on the cell growth but slightly increased the TPA production rates. However, based on the glucose consumption, both the cell and TPA yields were much improved by pressurization. As an optimum mixing and oxygen supply strategy for the production of TPA on a large scale, it is recommended that soluble starch be added to the culture medium to allow the microcarrier suspension to be maintained at a low agitation speed, while keeping a high oxygen transfer rate by means of an air spray system and pressurization.     

Optimization of agitation and aeration conditions for maximum virginiamycin production

To maximize the productivity of virginiamycin, which is a commercially important antibiotic as an animal feed additive, an empirical approach was employed in the batch culture of Streptomyces virginiae. Here, the effects of dissolved oxygen (DO) concentration and agitation speed on the maximum cell concentration at the production phase, as well as on the productivity of virginiamycin, were investigated. To maintain the DO concentration in the fermentor at a certain level, either the agitation speed or the inlet oxygen concentration of the supply gas was manipulated. It was found that increasing the agitation speed had a positive effect on the antibiotic productivity independent of the DO concentration. The optimum DO concentration, agitation speed and addition of an autoregulator, virginiae butanolide C (VB-C), were determined to maximize virginiamycin productivity. The optimal strategy was to start the cultivation at 450 rpm and to continue until the DO concentration reached 80%. After reaching 80%, the DO concentration was maintained at this level by changing the agitation speed, up to a maximum of 800 rpm. The addition of an optimal amount of the autoregulator VB-C in an experiment resulted in the maximal production of virginiamycin M (399 mg/l), which was about 1.8-fold those obtained previously. Received: 13 July 1998 / Received revision: 19 August 1998 / Accepted: 13 September 1998     

溶氧对Blakeslea trispora分批发酵生产β-胡萝卜素的影响

在摇瓶和5 L发酵罐中研究了溶氧 (DO) 对Blakeslea trispora分批发酵生产β-胡萝卜素的影响,总结了5 L发酵罐中β-胡萝卜素发酵过程中溶氧的变化规律.结果表明,当500 mL摇瓶装液量为50 mL,转速为240 r/min条件下发酵生产β-胡萝卜素产量最大,达到3.416 g/L; 5 L发酵罐中,在搅拌转速为1 000 r/min,通气量为1.5 vvm的条件下,β-胡萝卜素的产量可达到3.712 g/L,略高于摇瓶,这可能是由于5 L发酵罐中的气液传递和混合状况好于摇瓶,促进了产物的合成.