Influence of ammonium chloride feeding time and light intensity on the cultivation of Spirulina (Arthrospira) platensis

This study dealt with the influence of both the feeding time and light intensity on the fed-batch culture of the cyanobacterium Spirulina (Arthrospira) platensis using ammonium chloride as a nitrogen source. For this purpose, a 2(2) plus star central composite experimental design combined with response surface methodology was employed, and the maximum cell concentration (X(m)), the cell productivity (P(X)), and the yield of biomass on nitrogen (Y(X/N)) were selected as the response variables. The optimum values of X(m) (1,833 mg L(-1)) and Y(X/N) (5.9 g g(-1)) estimated by the model at light intensity of 13 klux and feeding time of 17.2 days were very close to those obtained experimentally under these conditions (X(m) = 1,771 +/- 41 mg L(-1); Y(X/N) = 5.7 +/- 0.17 g g(-1)). The cell productivity was a decreasing function of the ammonium chloride feeding time and a quadratic function of the light intensity. The protein and lipid contents of dry biomass collected at the end of cultivations were shown to decrease with increasing light intensity.     

Calorific Content of Certain Bacteria and Fungi

Calorific contents of dried cells of several representative species of bacteria (gram-negative rods and gram-positive rods and cocci), two species of yeasts, and a filamentous fungus were determined by bomb calorimetry. The grand mean was 5,383 cal per g of ash-free dry weight. This value was then used to determine quantity of energy assimilated (E(a)) during growth. Subsequently, E(a) was employed in the equation: Y(kcal) = Y/(E(a) + E(d)), where Y(kcal) is the yield of cells per kilocalorie of energy taken from a culture medium, Y is the yield per mole of substrate utilized, E(a) is Y times caloric content of the cells, and E(d) is the energy expended by oxidative dissimilation. An estimate of E(d) was obtained for a number of experiments by multiplying the moles of oxygen consumed per mole of substrate utilized during growth by the average quantity of energy utilized to reduce a mole of oxygen with electrons from organic compounds (106 kcal). From previous studies in our laboratories, a value for Y(kcal) of 0.118 g/kcal was predicted. The mean value for data from five studies of aerobic growth of prototrophic heterotrophs was found to be 0.111.     

Kinetic analysis of the growth of Chlorella vulgaris

The energy of the total transmitted light was subtracted from that of the incident light in a culture vessel and the difference was divided by the weight of cells. The value thus obtained was defined as the amount, E(x), of light energy absorbed per unit cell weight per unit time.Batch and continuous cultures of Chlorella vulgaris were carried out at 30 degrees C in the pH range of 6.4-6.7 while restricting illumination. Next the specific growth rate, mu, in the batch culture and the fixed dilution rate, D, in the continuous culture were plotted against E(x). The results showed that the relation between D and E(x) can be expressed in a Michaelis-Menten equation, where the maximal specific growth rate is 0.24 h (-1) and the saturation constant is 6.58 kcal/g . h.Cell concentration calculated by substituting the apparent concentration, X(e), of incubated cells and the apparent maintenance constant, M(e), for this equation agreed with that observed in almost all growth phases. Furthermore, from the change of chlorophyll productivity and the relationship between D and E(x) expressed in this equation, it is assumed that E(x) involves the light energy directly utilized in photosynthesis in the cells and that which is converted into, e.g., heat. This equation also indicated that a maximum in the growth yield existed. Then the growth yield of 0.029 g/kcal obtained at the incident light of 1.46 or 2.63 cal/cm(2) . h was maximum (maximal conversion efficiency of light energy, 15.6%).These results indicate that this method of deriving the equation for the growth rate from this study is a useful procedure for obtaining bioengineering findings.     

聚球藻7002在光生物反应器中的光自养培养

通过对聚球藻7002在光生物反应器中的培养,研究了光强在聚球藻7002培养液中的衰减规律,得到了培养过程光强随藻细胞浓度和光程距离变化的关系式,即I=I₀exp［-(-0.0239+0.0777OD₇₅₀)·L］。并对培养过程特性及培养温度、外加CO₂浓度和光照强度对藻细胞生长的影响进行了较为详细的研究,得到了反应器中较为适宜的聚球藻7002的培养条件,藻细胞培养密度达到3.4g/L(干重),体积产率达到0.57g/(L·d)的较高水平。     

Kinetics of batch single cell protein production from rice polishings with Candida utilis in continuously aerated tank reactors

Single cell protein was produced from the defatted rice polishings by fermentation with Candida utilis in an aerated 14-L fermentor to optimize bioprocess variables. Maximum values of specific growth rate coefficient (mu, h(-1)), cell mass yield (Y(X/S), g/g) and cell mass productivity (g/Lh) were 0.31, 0.65, and 1.24, respectively under optimized conditions of aeration rate (1 v.v(-1) m(-1)), dissolved oxygen (50%), corn steep liquor (5%), temperature (35 degrees C), and substrate concentration (90 g rice polishings/L) in yeast salt medium (pH 6.0). The kinetic parameters for 50-L fermentor under same conditions were 0.33 h(-1), 0.66 g/g, 1.33 g/Lh, 2.25 g/Lh, 1.23 g/Lh, 0.45 g/g substrate and 0.20 g/g cell h for mu, Y(X/S), Q(X), Q(S), Q(CP), Y(TP/S), and q(CP), respectively and were significantly higher than their respective values reported on C. utilis in batch culture studies. This biomass protein contained 23.6%, 32.75%, 11.50%, 12.95%, 10.5%, and 0.275% true protein, crude protein, crude fiber, ash, cellulose and RNA content respectively. This implied that the fermentation process could be up scaled to manufacture animal feed. Gross metabolizable energy content of dried SCP was 29,711 kcal/kg and indicated that the SCP could serve both as energy as well as a protein source. Yeast can replace expensive feed ingredients currently being incorporated in poultry feed and can reduce cost of poultry ration by 0.33 US dollars-0.51 US dollars/100 kg bag and improve the economics of feed production in our country.     

Outdoor and indoor cultivation of Spirulina platensis in the extreme south of Brazil

Water supplemented with 10% or 20% (v/v) of Zarrouk medium was used to cultivate Spirulina platensis in closed and open bioreactors under controlled conditions (30 degrees C, 32.5 micromol m(-2) s(-1), 12 h light/dark photoperiod) and in a greenhouse (9.4 to 46 degrees C, up to 2800 micromol m(-2) s(-1), variable day length photoperiod) using different initial biomass concentrations (X0) in the extreme south of Brazil (32.05 degrees S, 52.11 degrees W). Under controlled conditions the maximum specific growth rate (micromax) was 0.102 d(-1), the biomass doubling time (t(d)) was 6.8 d, the maximum dry biomass concentration (Xmax) was 1.94 g L(-1) and the maximum productivity (Pmax) was 0.059 g L(-)1 d(-1), while the corresponding values in the greenhouse experiments were micromax = 0.322 d(-1), t(d) = 2.2 d, Xmax = 1.73 g L(-1) and Pmax = 0.112 g L(-1) d(-1). Under controlled conditions the highest values for these parameters occurred when X0 = 0.15 g L(-1), while in the greenhouse X0 = 0.4 g L(-1) produced the highest values. These results show that the cultivation of S. platensis in greenhouses in the extreme south of Brazil is technically viable and that the S. platensis inoculum and the concentration of Zarrouk medium can be combined in such a way as to obtain growth and productivity parameters comparable, or superior, to those occurring in bioreactors under controlled conditions of temperature, illuminance and photoperiod.     

重组巴氏毕赤酵母高密度发酵表达rHSA

对基因工程菌Pichiapastoris的摇瓶发酵条件进行了试验 ,并根据摇瓶发酵的优化结果进行了补料分批高密度发酵。在摇瓶发酵时 ,甲醇诱导基因工程菌P .pastoris表达重组人血清白蛋白的发酵周期为 96h ;甲醇的最佳诱导浓度为 1 0g L ;发酵pH范围为 5 72～ 6 5 9;在摇瓶培养时 ,随着接种量的增加 ,虽然目的蛋白表达量缓慢增加 ,但单位细胞光密度的蛋白产率却明显下降 ,符合y =1 2 941x- 0 50 59方程 (线性相关系数r=0 9789) ,其限制性因子很可能为溶氧。在分批发酵 ,接种量为 1 0 %且种子细胞光密度 (OD60 0 )为 2 0左右时 ,细胞生长的延迟期为 2 1 1h左右 ,细胞生长光密度与培养时间的关系模型为 :y =0 7841e0 .2 3 19t(线性相关系数r=0 .993 6 ) ;在补料发酵时细胞干重浓度可达到 1 1 5g L— 1 6 0g L ,在 1 2 0h重组人血清白蛋白表达量最大达到 3 6g L。     

Influence of cultivation conditions on xylose-to-xylitol bioconversion by a new isolate of Debaryomyces hansenii

About 270 yeast isolates were screened for xylitol production using xylose as the sole carbon source. The best isolate, Debaryomyces hansenii UFV-170, released 5.84 g L(-1) xylitol from 10 g L(-1) xylose after 24 h, corresponding to a yield of xylitol on consumed substrate (Y(P/S)) of 0.54 g g(-1). This strain was cultivated batch-wise at variable starting concentrations of xylose (S(o)) and biomass (X(o)) and agitation intensity, in order to improve xylitol production and to evaluate, through simple carbon balances, the influence of these conditions on xylose metabolism. Under the best microaerobic conditions (S(o) = 53 g L(-1), X(o) = 1.4 g L(-1), 200 rpm), xylitol production reached 37.0 g L(-1), corresponding to xylitol volumetric productivity of 1.0 g L(-1)h(-1), specific productivity of 0.22 g g(-1)h(-1) and Y(P/S) = 0.76 g g(-1). Almost 83% of xylose was consumed for xylitol production, the rest being consumed for growth, while respiration was negligible. The new isolate appeared to be a promising alternative for industrial xylitol bioproduction.     

Characterization of energy conversion based on metabolic flux analysis in mixotrophic liverwort cells, Marchantia polymorpha

In order to characterize the contributions of respiratory and photosynthetic actions to energy conversions, the mixotrophic cells of Marchantia polymorpha were cultivated in the medium containing 10kg/m(3) glucose as an organic carbon source. The cultures were conducted with the supply of ordinary air (0.03% CO(2)) at constant incident light intensities of 50 and 180W/m(2). From the results of metabolic analysis, it was found that the cell yield based on ATP synthesis was estimated to be 6.3x10(-3)kg-dry cells/mol-ATP in these cultures. Under the examined conditions, energy conversion efficiency through respiration was larger than that through photosynthesis, and efficiency of overall energy conversion to ATP was maximized when the sum of energies from glucose and light captured by the cells was approximately 7.2x10(5)J/(hkg-dry cells). Taking into account the efficiency of overall energy conversion, a batch culture of M. polymorpha in a bioreactor was carried out by regulating incident light intensity ranging from 9 to 58W/m(2). In the culture with light regulation, the cell yield of 6.2x10(-9)kg-dry cells/J was achieved on the basis of energy provided to the system throughout the culture, and this value was 2.3 and 9.3 times as large as those obtained in the cultures under constant incident light intensities of 50 and 180W/m(2), respectively.     

Simplified modeling of fed-batch alcoholic fermentation of sugarcane blackstrap molasses

Simplified modeling based on material balances for biomass, ethanol and substrate was used to describe the kinetics of fed-batch alcohol fermentation of sugarcane blackstrap molasses. Maintenance requirements were previously shown to be of particular significance in this system, owing to the use of massive inoculum to minimize inhibitions; therefore, they were taken into consideration for kinetic modeling. Average values of biomass and ethanol yields, productivities, and substrate consumption rates, calculated at the end of runs performed either at constant or exponentially varying flow rates, demonstrated that all of these parameters were influenced by the initial sugar-feeding rate, F(o)S(o). Under conditions of substrate shortage (F(o)S(o) 相似文献   

Continuous cultivation of the diatom Nitzschia laevis for eicosapentaenoic acid production: physiological study and process optimization

The continuous cultures of the diatom Nitzschia laevis were performed at different dilution rates (D) and feed glucose concentrations (S(0)) to investigate cellular physiological responses and its production potential of eicosapentaenoic acid (EPA). Steady-state cell dry weight, residual glucose concentration, cell growth yield, specific glucose consumption rate, and fatty acid profiles were investigated within the range of D from 0.1 to 1.0 day(-1) (S(0) fixed at 20 g/L) and the range of S(0) from 5 to 35 g/L (D fixed at 0.3 day(-1)), respectively. The highest EPA productivity of 73 mg L(-1) day(-1) was obtained at D = 0.5 day(-1) and S(0) = 20 g/L. However, when the continuous culture achieved high productivities of EPA at certain dilution rates and feed glucose concentrations, glucose in the feed could not be consumed completely. Accordingly, the continuous culture was evaluated in terms of both EPA productivity (P) and glucose assimilation efficiency (E). The parameter eta, defined as the product of P and E, was used as an overall performance index. Since eta is a function of the two independent variables D and S(0), we employed a central composite design to optimize D and S(0) for the highest eta value. Based on the experimental results of the design, a second-order polynomial equation was established to represent the relationship between eta and D and S(0). The optimal values of D and S(0) were subsequently determined as 0.481 day(-1) and 15.56 g/L, respectively by the empirical model. The verification experiment confirmed the validity of the model. Under the optimal conditions, eta value reached 46.5 mg L(-1) day(-1), suggesting a considerably high efficiency of the continuous culture of N. laevis in terms of EPA production and glucose utilization.     

Continuous bioconversion of n-octane to octanoic acid by recombinant Escherichia coli (alk(+)) growing in a two-liquid-phase Chemostat

Escherichia coli is able to grow on sugars in the presence of a bulk n-alkane phase. When E. coli is equipped with the alk genes from Pseudomonas oleovorans, the resulting recombinant strain converts n-alkanes into the corresponding alkanoic acids. To study the effects of growth rate and exposure to a bulk apolar phase on the physiology and the productivity of E. coli, we have grown this microorganism in two-liquid-phase continuous cultures containing 5% (v/v) n-octane.In contrast to batch cultures of wild-tape E. coli grown in the presence of n-octane, cells remained viable during the entire continuous culture, which lasted 200 h. Bioconversion of n-octane to n-octanoic acid by a recombinant E. coli (alk(+)) in a two-liquid-phase continuous culture was made possible by optimizing both the recombinant host strain and the conditions of culturing the organism. Continuous production in such two-phase systems has been maintained for the least 125 h without any changes in the product concentration in the fermentation medium. The volumetric productivity was determined as a function of growth rate and showed a maximum at a dilution rate D = 0.32 h(-1), reaching a continuous production rate of 0.5 g octanoate/L . h (4 tons/m(3) . year). (c) 1993 John Wiley & Sons, Inc.     

多次补氮和增强蓝光促进三角褐指藻积累岩藻黄素

本研究旨在优化多次补氮和增强蓝光模式，以促进光发酵三角褐指藻(Phaeodactylum tricornutum)积累岩藻黄素。结果表明，在摇瓶中将含有胰蛋白胨和尿素的混合氮源(1:1,Nmol/Nmol；总氮浓度为0.02 mol/L)分6次加入培养系统是最佳的多次补氮模式；在5 L发酵罐中实施两阶段调光模式培养，在第二阶段增强蓝光(R:G:B=67.1:16.7:16.3)后，细胞密度、生物量生产率以及岩藻黄素的含量、产量和生产率分别达到1.12×108cells/mL、330mg/(d·L)、19.62mg/g、69.71mg/L和6.97mg/(d·L)。与红蓝光(R:G:B=70.9:18.3:10.9)下分6次补氮的一阶段培养相比，岩藻黄素含量显著提高了7.68%(P<0.05)，但生产率无显著差异(P>0.05)；与红蓝光(R:G:B=70.9:18.3:10.9)下一次性加入氮源的一阶段培养相比，岩藻黄素含量和生产率显著提高了45.98%和48.30%(P<0.05)。因此，本研究开发的多次补氮和增强蓝光的两阶段培养模式，有效促进了岩藻黄素积累、提高了...     

Microbial degradation of quinoline: Kinetic studies with Comamonas acidovorans DSM 6426

The microbial degradation of quinoline by Comamonas acidovorans was studied in a laboratory scale stirred tank reactor. In continuous culture experiments using quinoline as a sole source of carbon and nitrogen, it was shown by means of mass balances that quinoline was converted completely to biomass, carbon dioxide, and ammonia. Degradation rates up to 0.7 g/L h were obtained. Measured yield coefficients Y(x/s) for quinoline were about 0.7 g/g, which is in agreement with the theoretical value for complete mineralization. Kinetic constants based on Haldane substrate inhibition were evaluated. The values were mu(max) = 0.48 h(-1), K(i) = 69 mg/L, and K(s) < 1.45 mg/L. (c) 1993 John Wiley & Sons, Inc.     

Kinetic and growth parameters of Arthrospira (Spirulina) platensis cultivated in tubular photobioreactor under different cell circulation systems

Arthrospira platensis was cultivated in tubular photobioreactor in order to evaluate growth and biomass production at variable photosynthetic photon flux density (PPFD = 60, 120, and 240 μmol photons m(-2)s(-1)) and employing three different systems for cell circulation, specifically an airlift, a motor-driven pumping and a pressurized system. The influence of these two independents variables on the maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion factor (Y(X/N) ), photosynthetic efficiency (PE), and biomass composition (total lipids and proteins), taken as responses, was evaluated by analysis of variance. The statistical analysis revealed that the best combination of responses' mean values (X(m) = 4,055 mg L(-1), P(x) = 406 mg L(-1)day(-1), Y(X/N) = 5.07 mg mg(-1), total lipids = 8.94%, total proteins = 30.3%, PE = 2.04%) was obtained at PPFD = 120 μmol photons m(-2)s(-1); therefore, this light intensity should be considered as the most well-suited for A. platensis cultivation in this photobioreactor configuration. The airlift system did not exert any significant positive statistical influence on the responses, which suggests that this traditional cell circulation system could successfully be substituted by the others tested in this work.     

Cushion size, surface roughness, and the control of water balance and carbon flux in the cushion moss Leucobryum glaucum (Leucobryaceae)

We explored the size dependence of water balance and carbon flux in the cushion moss Leucobryum glaucum (Leucobryaceae). Conductance to water vapor (g(a)) was modeled empirically using 4-24 cm diameter cushions (N = 14) evaluated across wind speeds from 0.7 to 4.3 m/s in a wind tunnel. Model parameters included wind speed (u), kinematic viscosity (v), cushion diameter (L(d)), and surface roughness (L(r)). The model g(a) = -9.62(u/v)(1.21) · L(d)(-0.35) · L(r-in)(-1.85) (where L(r-in) represents a dimensionless form of L(r); R(2) = 0.88) indicates negative relationships between g(a) and both L(d) and L(r). These predictions were evaluated during a 5-d field experiment where water loss and net carbon exchange (estimated by ΔF/F(m)') were monitored. In the field (N = 18, 4-34 cm diameter cushions), L(r), but not L(d), controlled rates of evaporation due to additional turbulence that reduced size dependence of cushions along the forest floor. However, the duration of positive net carbon gain varied from 1.4 to 4.4 d and was significantly longer in larger diameter cushions. Thus, under field conditions, size-dependent changes in surface-area-to-volume relationships influence the duration of net carbon gain more than differences in water flux and lead to a strong size dependence of water balance and carbon flux.     

Optimization of medium formulation and seed conditions for expression of mature PsaA (pneumococcal surface adhesin A) in Escherichia coli using a sequential experimental design strategy and response surface methodology

PsaA, a candidate antigen for a vaccine against pneumonia, is well-conserved in all Streptococcus pneumoniae serotypes. A sequence of two-level experimental designs was used to evaluate medium composition and seed conditions to optimize the expression of soluble mature PsaA in E. coli. A face-centered central composite design was first used to evaluate the effects of yeast extract (5 and 23.6?g/L), tryptone (0 and 10?g/L), and glucose (1 and 10?g/L), with replicate experiments at the central point (14.3?g/L yeast extract, 5?g/L tryptone, 5.5?g/L glucose). Next, a central composite design was used to analyze the influence of NaCl concentration (0, 5, and 10?g/L) compared with potassium salts (9.4?g/L K(2)HPO(4)/2.2?g/L KH(2)PO(4)), and seed growth (7 and 16?h). Tryptone had no significant effect and was removed from the medium. Yeast extract and glucose were optimized at their intermediate concentrations, resulting in an animal-derived material-free culture medium containing 15?g/L yeast extract, 8?g/L glucose, 50?μg/mL kanamycin, and 0.4% glycerol, yielding 1?g/L rPsaA after 16?h induction at 25°C in shake flasks at 200?rpm. All the seed age and salt conditions produced similar yields, indicating that no variation had a statistically significant effect on expression. Instead of growing the seed culture for 16?h (until saturation), the process can be conducted with 7?h seed growth until the exponential phase. These results enhanced the process productivity and reduced costs, with 5?g/L NaCl being used rather than potassium salts.     

Variables that affect xylitol production from sugarcane bagasse hydrolysate in a zeolite fluidized bed reactor

The operational conditions for xylitol production by fermentation of sugarcane bagasse hydrolysate in a fluidized bed reactor with cells immobilized on zeolite were evaluated. Fermentations were carried out under different conditions of air flowrate (0.0125-0.0375 vvm), zeolite mass (100-200 g), initial pH (4-6), and xylose concentration (40-60 g/L), according to a 2(4) full factorial design. The air flowrate increase resulted in a metabolic deviation from product to biomass formation. On the other hand, the pH increase favored both the xylitol yield (Y(P/S)) and volumetric productivity (Q(P)), and the xylose concentration increase positively influenced the xylitol concentration. The best operational conditions evaluated were based on the use of an air flowrate of 0.0125 vvm, 100 g of zeolite, pH 6, and xylose concentration of 60 g/L. Under these conditions, 38.5 g/L of xylitol were obtained, with a Y(P/S) of 0.72 g/g, Q(P) of 0.32 g/L.h, and cell retention of 25.9%.     

Optimal temperature and photoperiod for the cultivation of Agardhiella subulata microplantlets in a bubble-column photobioreactor

The optimal temperature and illumination photoperiod requirements for the phototrophic growth of a novel microplantlet suspension culture derived from the macrophytic marine red alga Agardhiella subulata were determined. The optimal growth temperature was 24 degrees C. The effects of illumination light-dark (LD) photoperiod (hour of light:hours of darkness within a 24 h cycle) on biomass production was studied within a bubble-column photobioreactor. The 4.5 cm diameter photobioreactor was maintained at near-saturation conditions with respect to light flux (38 mciromol photons m(-2) s(-1)), nutrient medium delivery (20% nutrient replacement per day), and CO(2) delivery (0.35 mmol CO(2) L(-1) h(-1)) so that the cumulative effects of photodamage on the cell density versus time curve at photoperiods approaching continuous light could be observed. Biomass production was maximized at 16:8 LD, where biomass densities exceeding 3.6 g dry cell mass L(-1) were achieved after 60 days in culture. Biomass production was proportional to photoperiod at low fractional photoperiods (< or =10:14 LD), but high fractional photoperiods approaching continuous light (> or = 20:4 LD) shut down biomass production. Biomass production versus time profiles under resource-saturated cultivation conditions were adequately described by a cumulative photodamage growth model, which coupled reversible photodamage processes to the specific growth rate. Under light-saturated growth conditions, the rate constant for photodamage was kd = 1.17 +/- 0.28 day(-1) (+/-1.0 SE), and the rate constant for photodamage repair was kr = 5.12 +/- 0.95 day(-1) (+/-1.0 SE) at 24 degrees C.     

Effect of light irradiation on anthocyanin production by suspended culture of Perilla frutescens

After a series of experiments on photoperiodicity and light intensity under daylight supplied by an ordinary fluorescent lamp in cultivations using a flask and a roux bottle, it was found that irradiation at 27.2 W/m(2) for the whole period was effective for anthocyanin production by a suspended culture of Perilla frutescens (shiso). A high amount of anthocyanin pigments, 3.0 g/L, was obtained in a bubble column bioreactor after 10 days of cultivation at an aeration rate of 0.1 vvm with light irradiation at 27.2 W/m(2), while 2 g/L was obtained at 13.6 W/m(2) and very little at 54.4 W/m(2). A high amount of anthocyanin pigments, 2.9 g/L, was also produced using an aerated and agitated bioreactor at an agitation speed of 130 rpm, an aeration rate of 0.1 vvm and light irradiation intensity of 27.2 W/m(2). The amount of anthocyanin produced was more than twice that without light irradiation, Keeping the other cultivation conditions the same. The results obtained also showed that the amount of anthocyanin pigment accumulated in a shake flask could be rather well reproduced in bioreactors for both aerated culture, and aerated and agitated culture, by improving the conditions of light irradiation, which conspicuously affects metabolite formation.