A new model for relationship between irradiance and the rate of photosynthesis in <Emphasis Type="Italic">Oryza sativa</Emphasis>

The calculated maximum net photosynthetic rate (P _N) at saturation irradiance (I _m) of 1 314.13 μmol m⁻² s⁻¹ was 25.49 μmol(CO₂) m⁻² s⁻¹, and intrinsic quantum yield at zero irradiance was 0.103. The results fitted by nonrectangular hyperbolic model, rectangular hyperbolic method, binomial regression method, and the new model were compared. The maximum P _N values calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were higher than the measured values, and the I _m calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were less than measured values. Results fitted by new model showed that the response curve of P _N to I was nonlinear at low I for Oryza sativa, P _N increased nonlinearly with I below saturation value. Above this value, P _N decreased nonlinearly with I.     

Phytoplankton primary production in a mesotrophic pond in sub-tropical Bangladesh

Annual gross primary productivity in mesotrophic Shahidullah Hall pond (Dhaka, Bangladesh) was 1383.35 g C m⁻² y⁻¹ (arithmetic mean). Daily primary productivity (between 1.6 and 6.8 g C m⁻² d⁻¹ was correlated with chlorophylla, day length and dissolved silica. Chlorophylla related significantly withk, incident light, SRP, alkalinity and conductivity. A negative correlation existed between biomass and rainfall. Productivity, biomass, conductivity, alkalinity, and SRP increased after mid-winter.k, I _k andZ _eu varied according seasonally.P _max related directly with temperature. Seasonal variation of ∝ ^B was 0.0049–0.0258 mg C (mg chla mmol PAR)⁻¹ m⁻². Q₁₀ was 2.12, community respiration 1334.99 g C m⁻² y⁻¹, and the underwater light climate 186.43μE m⁻² s⁻¹.     

Effects of different irradiances on the photosynthetic process during ex-vitro acclimation of Anoectochilus plantlets

Six months old in vitro-grown Anoectochilus formosanus plantlets were transferred to ex-vitro acclimation under low irradiance, LI [60 μmol(photon) m⁻² s⁻¹], intermediate irradiance, II [180 μmol(photon) m⁻² s⁻¹], and high irradiance, HI [300 μmol(photon) m⁻² s⁻¹] for 30 d. Imposition of II led to a significant increase of chlorophyll (Chl) b content, rates of net photosynthesis (P _N) and transpiration (E), stomatal conductance (g _s), electron transfer rate (ETR), quantum yield of electron transport from water through photosystem 2 (Φ_PS2), and activity of ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBPCO, EC 4.1.1.39). This indicates that Anoectochilus was better acclimated at II compared to LI treatment. On the other hand, HI acclimation led to a significant reduction of Chl a and b, P _N, E, g _s, photochemical quenching, dark-adapted quantum efficiency of open PS2 centres (F_v/F_m), probability of an absorbed photon reaching an open PS2 reaction centre (F_v′/F_m′), ETR, Φ_PS2, and energy efficiency of CO₂ fixation (Φ_CO2/Φ_PS2). This indicates that HI treatment considerably exceeded the photo-protective capacity and Anoectochilus suffered HI induced damage to the photosynthetic apparatus. Imposition of HI significantly increased the contents of antheraxanthin and zeaxanthin (ZEA), non-photochemical quenching, and conversion of violaxanthin to ZEA. Thus Anoectochilus modifies its system to dissipate excess excitation energy and to protect the photosynthetic machinery.     

Morpho-anatomical and physiological leaf traits of two alpine herbs, Podophyllum hexandrum and Rheum emodi in the Western Himalaya under different irradiances

Morpho-anatomical leaf traits and photosynthetic activity of two alpine herbs, Podophyllum hexandrum (shade-tolerant) and Rheum emodi (light-requiring), were studied under field (PAR>2 000 μmol m⁻² s⁻¹) and greenhouse (PAR 500 μmol m⁻² s⁻¹) conditions. Mesophyll thickness, surface area of mesophyll cells facing intercellular spaces (S_mes), surface area of chloroplasts facing intercellular spaces (S_c), intercellular spaces of mesophyll cells (porosity), photon-saturated rate of photosynthesis per unit leaf area (P _Nmax), and ribulose-1,5-bisphosphate carboxylase/oxygenase activity decreased in the greenhouse with respect to the field and the decreases were significantly higher in R. emodi than in P. hexandrum. P. hexandrum had lower intercellular CO₂ concentration than R. emodi under both irradiances. The differences in acclimation of the two alpine herbs to low irradiance were due to their highly unlikely changes in leaf morphology, anatomy, and P _Nmax which indicated that the difference in radiant energy requirement related to leaf acclimation had greater impact under low than high irradiance.     

深圳市前海桂湾公园土壤蒸发及植被蒸腾模拟

蒸散发（ET）是连接水文循环和地表能量平衡的重要组成部分,准确的估算土壤蒸发（LE_s）和植被蒸腾（LE_v）对城市水资源分配和管理具有重要意义。针对城市林地蒸散发双源模型的缺失,本研究基于MOD16模型提出了应用于城市林地区域改进的MOD16双源模型。改进的MOD16双源模型更加准确的描述城市林地区域复杂下垫面的能量分配过程。结合高时空分辨率的Sentinel-2遥感卫星影像,对2020年深圳市前海桂湾公园20个无云日的LE_s和LE_v进行反演研究。用Shuttleworth-Wallace （S-W）模型和双作物系数法（FAO dual-K_c）验证模型性能,同时分析改进的MOD16模型对输入变量的敏感度,结果表明：改进的MOD16模型与S-W模型和FAO dual-K_c之间的均方根误差（RMSE）分别为21.39 W/m²和20.41 W/m²,平均绝对误差（MAE）分别为18.81 W/m²和19.05 W/m²,R²分别为0.801和0.634。改进的MOD16模型可以应用在城市林地LE_s和LE_v估算中。桂湾公园地区总蒸散月均值在85-165 W/m²之间。研究区域的LE_s和LE_v呈现出明显的季节变化,春夏季蒸散量升高,秋冬季蒸散量降低,LE_s的变化范围为0-50 W/m²,LE_v的变化范围为0-120 W/m²。LE_v高值在研究区呈现零散分布,多集中在前海桂湾沿岸,LE_s高值集中在研究区的西北、东北和东南部。敏感性分析结果表明,改进后的MOD16模型对植被覆盖、太阳辐射和湿度更敏感。其中,LE_v模拟结果受净辐射和植被覆盖影响最大,LE_s的模拟结果受湿度和植被覆盖的影响最大。因此,应用改进的MOD16模型时需要优先确保这些参数的准确输入。修正后的MOD16模型极大地提高了高分辨率、小尺度区域城市林地LE_s和LE_v模拟的准确性,为准确获取植被耗水量信息从而科学指导城市林地灌溉、解决城市水资源分配与管理提供有力工具。     

Transpiration and whole-tree conductance in ponderosa pine trees of different heights

Changes in leaf physiology with tree age and size could alter forest growth, water yield, and carbon fluxes. We measured tree water flux (Q) for 14 ponderosa pine trees in two size classes (12 m tall and ∼40 years old, and 36 m tall and ∼ 290 years old) to determine if transpiration (E) and whole-tree conductance (g _t) differed between the two sizes of trees. For both size classes, E was approximately equal to Q measured 2 m above the ground: Q was most highly correlated with current, not lagged, water vapor pressure deficit, and night Q was <12% of total daily flux. E for days 165–195 and 240–260 averaged 0.97 mmol m^–2 (leaf area, projected) s^–1 for the 12-m trees and 0.57 mmol m^–2 (leaf area) s^–1 for the 36-m trees. When photosynthetically active radiation (I _P) exceeded the light saturation for photosynthesis in ponderosa pine (900 μmol m^–2 (ground) s^–1), differences in E were more pronounced: 2.4 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 1.2 mmol m^–2 s^–1 for the 36-m trees, yielding g _t of 140 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 72 mmol m^–2 s^–1 for the 36-m trees. Extrapolated to forests with leaf area index =1, the 36-m trees would transpire 117 mm between 1 June and 31 August compared to 170 mm for the 12-m trees, a difference of 15% of average annual precipitation. Lower g _t in the taller trees also likely lowers photosynthesis during the growing season. Received: 19 April 1999 / Accepted: 23 March 2000     

盐分胁迫下杠柳叶片光合特性的光响应研究

利用CID型便携式光合作用仪测定不同NaCl浓度下杠柳叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、水分利用效率（WUE）及光能利用率(LUE)生理参数的光响应过程,阐明盐分胁迫下其对光照响应的规律,探讨有利于杠柳正常生长的盐分浓度和光照条件。结果表明:（1）各盐分浓度下杠柳叶片光补偿点（LCP）在21.89～65.05 μmol·m^-2·s^-1之间变动,介于阴性植物与阳性植物之间;杠柳随土壤盐分的不同,其光合作用参数对光照强度表现出一定的适应性和可塑性;50 mmol·L^-1盐分浓度下杠柳光合同化能力最强,最有利于其干物质的积累,表现出一定的耐盐性。（2）轻度的盐分胁迫（小于50 mmol·L^-1）可以提高杠柳叶片的P_n、G_s、WUE和LUE,而盐分胁迫对杠柳的T_r有抑制作用,并随着盐分浓度的增加其抑制作用愈强烈。（3）维持杠柳正常生长的土壤盐分浓度小于50 mmol·L^-1,最佳PAR为1 000～2 000 μmol·m^-2·s^-1;而保持杠柳最大WUE和LUE的光照强度分别为800和100 μmol·m^-2·s^-1。     

Photosystem 2 photochemistry and pigment composition of a yellow mutant of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) under different irradiances

A yellow leaf colouration mutant (named ycm) generated from rice T-DNA insertion lines was identified with less grana lamellae and low thylakoid membrane protein contents. At weak irradiance [50 μmol(photon) m⁻² s⁻¹], chlorophyll (Chl) contents of ycm were ≈20 % of those of WT and Chl a/b ratios were 3-fold that of wild type (WT). The leaf of ycm showed lower values in the actual photosystem 2 (PS2) efficiency (Φ_PS2), photochemical quenching (q_P), and the efficiency of excitation capture by open PS2 centres 1 (F_v′/F_m′) than those of WT, except no difference in the maximal efficiency of PS2 photochemistry (F_v/F_m). With progress in irradiance [100 and 200 μmol(photon) m⁻² s⁻¹], there was a change in the photosynthetic pigment stoichiometry. In ycm, the increase of total Chl contents and the decrease in Chl a/b ratio were observed. Φ_PS2, q_P, and F_v′/F_m′ of ycm increased gradually along with the increase of irradiance but still much less than in WT. The increase of xanthophyll ratio [(Z+A)/(V+A+Z)] associated with non-photochemical quenching (q_N) was found in ycm which suggested that ycm dissipated excess energy through the turnover of xanthophylls. No significant differences in pigment composition were observed in WT under various irradiances, except Chl a/b ratio that gradually decreased. Hence the ycm mutant developed much more tardily than WT, which was caused by low photon energy utilization independent of irradiance.     

Leaf Photosynthesis of the Mangrove Avicennia Germinans as Affected by NaCl

In leaves of the mangrove species Avicennia germinans (L.) L. grown in salinities from 0 to 40 ‰, fluorescence, gas exchange, and δ¹³C analyses were done. Predawn values of F_v/F_m were about 0.75 in all the treatments suggesting that leaves did not suffer chronic photoinhibition. Conversely, midday F_v/F_m values decreased to about 0.55-0.60 which indicated strong down-regulation of photosynthesis in all treatments. Maximum photosynthetic rate (P _max) was 14.58 ± 0.22 μmol m^-2 s^-1 at 0 ‰ it decreased by 21 and 37 % in plants at salinities of 10 and 40 ‰, respectively. Stomatal conductance (g _s) was profoundly responsive in comparison to P _max which resulted in a high water use efficiency. This was further confirmed by δ¹³C values, which increased with salinity. From day 3, after salt was removed from the soil solution, P _max and g _s increased up to 13 and 30 %, respectively. However, the values were still considerably lower than those measured in plants grown without salt addition. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Photosynthesis and Chlorophyll a Fluorescence in Seedlings of Kandelia Candel (L.) Druce Grown under Different Nitrogen and NaCl Controls

Kandelia candel (L.) Druce is the dominant mangrove species on the west coast of northern Taiwan. We have measured the net photosynthetic rate (P _N) and chlorophyll (Chl) a fluorescence of seedlings grown at combinations of two nitrogen (0.01 and 0.1 mM) and two NaCl (250 and 430 mM NaCl) controls. With the same nitrogen level, seedlings grown at higher salinity (HS) had a significantly lower P _N and stomatal conductance (g _s) than those at lower salinity (LS). An increase in nitrogen availability significantly elevated P _N and g _s of the LS-grown seedlings. Compared to dark adapted leaves, the maximum quantum yield of photosystem 2 (PS2) (F_v/F_m) of leaves exposed to PFDs of 1200 and 1600 μmol m^-2 s^-1 for 2 h was significantly reduced. The degree of F_v/F_m reduction differed among leaves of the four types of treated plants. Chl fluorescence quenching analysis revealed differences among the examined plants in coefficients of non-photochemical and photochemical quenching. This revised version was published online in June 2006 with corrections to the Cover Date.     

Real-time fluid dynamics investigation and physiological response for erythromycin fermentation scale-up from 50 L to 132 m<Superscript>3</Superscript> fermenter

The physiological response of erythromycin fermentation scale-up from 50 L to 132 m³ scale was investigated. A relatively high oxygen uptake rate (OUR) in early phase of fermentation was beneficial for erythromycin biosynthesis. Correspondingly, the maximal consistency coefficient (K) reflecting non-Newtonian fluid characteristics in 50 L and 132 m³ fermenter also appeared in same phase. Fluid dynamics in different scale bioreactor was further investigated by real-time computational fluid dynamics modeling. The results of simulation showed that the impeller combination in 50 L fermenter could provide more modest flow field environment compared with that in 132 m³ fermenter. The decrease of oxygen transfer rate (OTR) in 132 m³ fermenter was the main cause for impairing cell physiological metabolism and erythromycin biosynthesis. These results were helpful for understanding the relationship between hydrodynamic environment and physiological response of cells in bioreactor during the scale-up of fermentation process.     

Application of an airlift bioreactor to the nystatin biosynthesis

Pilot plant studies were performed using a concentric-tube airlift bioreactor of 2.5 m³ fermentation volume. The results have proven the relative merits of such a system in the biosynthesis of nystatin, produced by Streptomyces noursei, in submerged aerobic cultivation and batch operation mode. The results were compared to those obtained in a pilot-scale stirred tank bioreactor of 3.5 m³ fermentation volume. The fermentation processes in the two fermentation devices were similar with respect to substrate utilization, biomass production and nystatin biosynthesis. In the riser section, the dissolved oxygen concentration was higher than that in the downcomer. The volumetric oxygen mass transfer coefficient was dependent on the rheological behaviour of the biosynthesis liquids, which was not constant during the fermentation process. The total energy consumption for nystatin production in the airlift bioreactor was 56% of that in the stirred tank, while the operating costs represented 78% of those in the stirred tank bioreactor.     

Theoretical analysis of the baker's yeast production: An experimental verification at a laboratory scale

The scale-down procedure seems an adequate tool in the design, optimization and scale-up fermentation processes. The first step in this procedure is a theoretical analysis, called process analysis, which is based on characteristic times of the mechanisms which may influence the performance of the bioreactor. This analysis must give information about the behaviour of large and small scale fermentation processes. At a small scale a verification of the results of such an analysis of the fed-batch baker's yeast production is carried out.In this paper a comparison of calculated and measured characteristic times of liquid mixing and mass transfer is presented. It was concluded that the literature correlations give a rough estimation of the characteristic times and can be used in the process analysis. Depending on the kind of sparger, the medium and the scale of the reactor, more knowledge is needed about bubble coalescence in fermentation media.The volumetric oxygen transfer coefficient increased when the biomass concentration increased. Probably this is caused by the interaction between biomass and the anti-foaming agent used.List of Symbols C kg/m³ concentration - D m diameter - m²/s effective dispersion coefficient - d m holes of the sparger - g m/s² gravitational acceleration - H m height - k _L a s^–1 volumetric mass transfer coefficient based on the liquid volume - L m length - m kg/kg gas liquid distribution coefficient - OTR kg/(m³ · s) oxygen transfer rate - OUR kg/(m³ · s) oxygen uptake rate - t s time - ^s m/s superficial gas flow rate - m length - s time constant - _g m³/s gas flow rate Indices 0 value at t=0 - cal calculated - e value at t=t (end) - g gas phase - in flow going to the fermentor - l liquid phase - m mixing - mt mass transfer - O ₂ oxygen - out flow coming out the fermentor     

Improved production of erythromycin A by expression of a heterologous gene encoding S-adenosylmethionine synthetase

An S-adenosylmethionine synthetase (SAM-s) gene from Streptomyces spectabilis was integrated along with vector DNA into the chromosome of a Saccharopolyspora erythraea E2. Elevated production of SAM was observed in the recombinant strain Saccharopolyspora erythraea E1. The results from the bioassay showed that the titer of erythromycin was increased from 920 IU ml⁻¹ by E₂ to approximately 2,000 IU ml⁻¹ by E₁. High performance liquid chromatography (HPLC) analysis revealed that there was a 132% increase in erythromycin A compared with the original strain, while the erythromycin B, the main impurity component in erythromycin, was decreased by 30%. The sporulation process was inhibited, while the SAM-s gene was expressed. The addition of the exogenous SAM also inhibited sporulation and promoted an increase in erythromycin titers. An erratum to this article can be found at     

The effect of culture conditions on the production of erythromycin by Saccharopolyspora erythraea in batch culture

Summary Saccharopolyspora erythraea growth is inhibited when grown at a low constant dissolved oxygen tension (DOT) of 10% air saturation. However, the specific erythromycin production is virtually identical to that of a culture where the DOT did not fall below 65%. In addition, at constant DOT (10%) a stirrer speed of 750 rpm in a 7 litre causes mechanical damage to the mycelia in comparison with result at 500 rpm.     

Optimization of the microbial synthesis of dihydroxyacetone from glycerol with <Emphasis Type="Italic">Gluconobacter oxydans</Emphasis>

An optimized repeated-fed-batch fermentation process for the synthesis of dihydroxyacetone (DHA) from glycerol utilizing Gluconobacter oxydans is presented. Cleaning, sterilization, and inoculation procedures could be reduced significantly compared to the conventional fed-batch process. A stringent requirement was that the product concentration was kept below a critical threshold level at all times in order to avoid irreversible product inhibition of the cells. On the basis of experimentally validated model calculations, a threshold value of about 60 kg m^-3 DHA was obtained. The innovative bioreactor system consisted of a stirred tank reactor combined with a packed trickle-bed column. In the packed column, active cells could be retained by in situ immobilization on a hydrophilized Ralu-ring carrier material. Within 17 days, the productivity of the process could be increased by 75% to about 2.8 kg m^-3 h^-1. However, it was observed that the maximum achievable productivity had not been reached yet.Abbreviations K _O Monod half saturation constant of dissolved oxygen (kg m^-3) - K _S Monod half saturation constant of substrate glycerol (kg m^-3) - O Dissolved oxygen concentration (kg m^-3) - P Product concentration (kg m^-3) - P _crit Critical product concentration constant (kg m^-3) - S Substrate concentration (kg m^-3) - t Time (s) - X Biomass concentration (dry weight) (kg m^-3) - Y _P/S Yield coefficient of product from substrate - Y _X/S Yield coefficient of biomass from substrate - Growth dependent specific production rate constant (kg m^-3) - Growth independent specific production rate constant (s^-1) - Specific growth rate (s^-1) - _max Maximum specific growth rate constant (s^-1)     

In-situ recovery of butanol during fermentation

End-product inhibition in the acetone-butanol fermentation was reduced by using extractive fermentation to continuously remove acetone and butanol from the fermentation broth. In situ removal of inhibitory products from Clostridium acetobutylicum resulted in increased reactor productivity; volumetric butanol productivity increased from 0.58 kg/(m³h) in batch fermentation to 1.5 kg/(m³h) in fed-batch extractive fermentation using oleyl alcohol as the extraction solvent. The use of fed-batch operation allowed glucose solutions of up to 500 kg/m³ to be fermented, resulting in a 3.5- to 5-fold decrease in waste water volume. Butanol reached a concentration of 30–35 kg/m³ in the oleyl alcohol extractant at the end of fermentation, a concentration that is 2–3 times higher than is possible in regular batch or fed-batch fermentation. Butanol productivities and glucose conversions in fed-batch extractive fermentation compare favorable with continuous fermentation and in situ product removal fermentations.List of Symbols C _g kg/m³ concentration of glucose in the feed - C _w dm³/m³ concentration of water in the feed - F(t) cm³/h flowrate of feed to the fermentor at time t - V(t) dm³ broth volume at time t - V _i dm³ initial broth volume - V _si dm³ volume of the i-th aqueous phase sample - effective fraction of water in the feed Part 1. Bioprocess Engineering 2 (1987) 1–12     

Application of oxygen uptake rate and response surface methodology for erythromycin production by Saccharopolyspora erythraea

A process for efficient production of erythromycin by Saccharopolyspora erythraea using statistical designs and feeding strategy was developed. The critical nutrient components were selected in accordance with fractional factorial design and were further optimized via response surface methodology. Three significant components (ZnSO₄, citric acid threonine) were identified for the optimization study. The optimum levels of these significant variables were determined with Box–Behnken design, which were ZnSO₄ 0.039 g/l, citric acid 0.24 g/l and threonine 0.42 g/l, respectively. A novel feeding strategy based on oxygen uptake rate (OUR) measurement was developed successfully to increase the flux of erythromycin biosynthesis, in which the optimized nutrient components was fed in the 50 l stirred bioreactor when OUR began to decline at 46 h. The maximum erythromycin production reached 10,622 U/ml, which was 11.7% higher than the control in the same cultivation conditions. It was the first report to integrate physiological parameter OUR and statistical methods to optimize erythromycin production.     

13C-assisted metabolomics analysis reveals the positive correlation between specific erythromycin production rate and intracellular propionyl-CoA pool size in Saccharopolyspora erythraea

Metabolomics analysis is extremely essential to explore the metabolism characteristics of Saccharopolyspora erythraea. The lack of suitable methods for the determination of intracellular metabolites, however, hinders the application of metabolomics analysis for S. erythraea. Acyl-CoAs are important precursors of erythromycin; phosphorylated sugars are intermediate metabolites in EMP pathway or PPP pathway; organic acids are intermediate metabolites in TCA cycle. Reliable determination methods for intracellular acyl-CoAs, phosphorylated sugars, and organic acids of S. erythraea were designed and validated in this study. Using the optimized determination methods, the pool sizes of intracellular metabolites during an erythromycin fermentation process were precisely quantified by isotope dilution mass spectroscopy method. The quantification results showed that the specific erythromycin production rate was positively correlated with the pool sizes of propionyl-CoA as well as many other intracellular metabolites. The experiment under the condition without propanol, which is a precursor of propionyl-CoA and an important substrate in industrial erythromycin production process, also corroborated the correlation between specific erythromycin production rate and intracellular propionyl-CoA pool size. As far as we know, this is the first paper to conduct the metabolomics analysis of S. erythraea, which makes the metabolomics analysis of S. erythraea in the industrial erythromycin production process possible.

     

Improved scale-up strategies of bioreactors

Effective scale-up is essential for successful bioprocessing. While it is desirable to keep as many operating parameters constant as possible during the scale-up, the number of constant parameters realizable is limited by the degrees of freedom in designing the large-scale operation. Scale-up of aerobic fermentations is often carried out on the basis of a constant oxygen transfer coefficient, k _L a, to ensure the same oxygen supply rate to support normal growth and metabolism of the desired high cell populations. In this paper, it is proposed to replace the scale-up criterion of constant k _L by a more direct and meaningful criterion of equal oxygen transfer rate at a predetermined value of dissolved oxygen concentration. This can be achieved by using different oxygen partial pressures in the influent gas streams for different scales of operation. One more degree of freedom, i.e., gas-phase oxygen partial pressure, is thus added to the process of scale-up. Accordingly, one more operating factor can be maintained constant during scale-up. It can be used to regulate the power consumption in large-scale fermentors for economical considerations or to describe the fluid mixing more precisely. Examples are given to show that the results of optimization achieved in the bench-scale study can be translated to the production-scale fermentor more successfully with only a small change in the gas-phase oxygen partial pressure employed in the bench-scale operation.List of Symbols a m²/m³ Specific gas/liquid interfacial area - C _L mole/m³ Dissolved oxygen concentration in bulk liquid phase - C ^* mole/m³ Equilibrium oxygen concentration at gas/liquid interface - D _i m Impeller diameter - D _T m Bioreactor diameter - H _L mole/m³ · atm Henry's-law constant - k _L m/s Liquid-phase mass transfer coefficient - N 1/s Impeller agitation speed - N _i Number of impellers - OTR mole/s · m³ Oxygen transfer rate per unit volume of the medium - P _g kW Power input in aerated fermentation - P _o kW Power input in non-gassed fermentation - p _g atm Gas-phase oxygen partial pressure - Q m³/s Volumetric gas flow rate - Re _i Impeller Reynolds number - T _Q Joule Torque applied to the mixer shaft - V m³ Liquid volume - v _s m/s Superficial gas velocity - kg/m · s Liquid viscosity - kg/m³ Liquid density