Large-scale production of saikosaponins through root culturing of Bupleurum falcatum L. using modified airlift reactors

Modification of internal configuration of a bubble column, airlift and stirred tank reactor (10-200 L) was made for root cultures of Bupleurum falcatum L. Agitation with an impeller covered with partition mesh was ineffective for a 10-L modified reactor, because it caused intensive foaming and subsequent overflow of the culture medium even at a low rotation speed of 50 rpm and a low aeration rate of 0.1 vvm (volume per volume of medium). In contrast, efficient aeration through a ceramic sparger placed at the bottom of a 20-L bubble column reactor yielded approximately 25 g/L of dry roots and 500 mg/L of saikosaponin-a and saikosaponin-d over 42 days. On a 200-L scale, however, the roots became flocculated under the upper perforated plate initially positioned near the middle of the reactor, forming a firm disk of roots and a large empty space between the disk and the medium. Thus, the roots had poor contact with the medium, which severely suppressed their growth. To avoid this flocculation, a bottom perforated plate and draft tube were installed as a partitioning device separating the culturing area (outside the draft tube) from the aeration area (inside the draft tube). The draft tube was made of a stainless steel mesh rather than a solid material, and the tube greatly increased the root yield in the 20-L reactor. This configuration was successfully applied at the 200-L scale, yielding 500-600 mg/L of saikosaponin-a and saikosaponin-d over 56 days.     

High efficiency production of astaxanthin in an airlift photobioreactor

In photobioreactors, photosynthetic microorganisms are exposed to certain light/dark cycles caused by light intensity distribution and mixing inside the photobioreactor. In this study, Haematococcus pluvialis was cultivated in an airlift and a bubble column photobioreactor, and the cell growth and astaxanthin production were compared to clarify the effects of liquid circulation.     

Kojic acid production in an airlift bioreactor using partially hydrolyzed raw corn starch

In a culture of Aspergillus oryzae MK-107-39 in a 3-l airlift bioreactor, kojic acid was not produced when glucose/wheat germ medium (GM1) was used. However, when a jar fermentor was used, the kojic acid yield was high. A suitable medium for culture in an airlift bioreactor consisting of partially hydrolyzed corn starch and a small amount of corn steep liquor (CSL) (SM1) was selected. In the cultivation in the airlift bioreactor using SM1, nearly 40 g/l of kojic acid was produced, which was the same as the amount produced in the jar fermentor containing GM1. The optimum aeration rate for the airlift bioreactor was 2.0 vvm (0.66 cm/s of superficial linear velocity (Vs)). The cost of SM1 using the airlift bioreactor was reduced to 40% that of GM1 using the jar fermentor. Furthermore, the energy cost of kojic acid production using SM1 in the airlift bioreactor was less than one-fourth of that for the jar fermentor using GM1.     

Optimization and scale-up of L-lactic acid fermentation by mutant strain Rhizopus sp. MK-96-1196 in airlift bioreactors

We determined the optimum culture conditions such as inoculum size, initial starch concentration, pH during the fermentation and aeration rate for L-lactic acid production by Rhizopus sp. MK-96-1196 in a 3-l airlift bioreactor. More than 90 g/l of L-lactic acid was produced from only partially enzymatically hydrolyzed corn starch with a production rate of 2.6 g/l/h and a product yield of 87% based on the starch consumed under the optimum conditions in the 3-l airlift bioreactor. Scale-up from the 3-l to a 100-l airlift bioreactor for L-lactic acid fermentation was carried out using V(s)(cm/s) as a scale-up criterion. The production rates and yields of L-lactic acid in both bioreactors appeared to be fairly well correlated with k(L)a (1/h).     

Carbon dioxide stimulates the production of amylovorin L by Lactobacillus amylovorus DCE 471, while enhanced aeration causes biphasic kinetics of growth and bacteriocin production

The effects of both oxygen and carbon dioxide on growth of and product formation by Lactobacillus amylovorus DCE 471, a promising new sourdough starter culture, were assessed through controlled, in vitro fermentation experiments, using a temperature of 37 degrees C and a constant pH of 5.4. It was seen that aeration affected both cell growth and amylovorin L production. At aeration rates of 1 l min(-1) and more, the bacterial population was subjected to oxidative stress as reflected by biphasic growth patterns. During the first growth phase, the maximum specific growth rate increased with increasing aeration rates stabilizing at the highest oxygen concentrations. The maximum obtainable cell yields decreased. During the second growth phase, the amylovorin L production was stimulated at the highest aeration. However, amylovorin titers were never higher in the presence of oxygen compared with the anaerobic fermentations. Carbon dioxide did not influence cell growth of L. amylovorus DCE 471. The maximum specific growth rate and the biomass concentrations were merely affected. On the other hand, the maximum soluble bacteriocin titers coincided with the highest carbon dioxide flow rates. These results indicate that mild aeration of type II sourdoughs might enhance both cell yield and amylovorin L production by L. amylovorus DCE 471, thereby contributing to the competitiveness of the strain. Growth in an ecosystem together with yeasts producing carbon dioxide might exert a positive effect on the production of amylovorin L as well.     

Designing hypolimnetic aeration and oxygenation systems--a review

When properly designed, hypolimnetic aeration and oxygenation systems can replenish dissolved oxygen in water bodies while preserving stratification. The three primary devices are the airlift aerator, Speece Cone, and bubble-plume diffuser. In each device, gas bubbles in contact with water facilitate interfacial transfer of oxygen, nitrogen, and other soluble gases. However, early design procedures for airlift aerators were empirical, while most bubble-plume models did not account for stratification or gas transfer. Using fundamental principles, a discrete-bubble model was first developed to predict plume dynamics and gas transfer for a circular bubble-plume diffuser. The discrete-bubble approach has subsequently been validated using oxygen transfer tests in a large vertical tank and applied successfully at full-scale to an airlift aerator as well as to both circular and linear bubble-plume diffusers. The performance of each of the four completely different full-scale systems (on a scale of 10 m or more) was predicted based on the behavior of individual bubbles (on a scale of about 1 mm). The combined results suggest thatthe models can be used with some confidence to predict system performance based on applied air or oxygen flow rate, initial bubble size, and, in the case of bubble plume diffusers, near-field boundary conditions. The discrete-bubble approach has also been extended to the Speece Cone, but the model has not yet been validated due to a lack of suitable data. The unified suite of models, all based on simple discrete-bubble dynamics, represents the current state-of-the-art for designing systems to add oxygen to stratified lakes and reservoirs.     

Development of rectangular airlift bubble column installed with support material for enhancement of nitrogen removal

To enhance nitrogen removal during wastewater treatment using activated sludge, a rectangular airlift bubble column installed with support material is proposed. The flow characteristics and nitrogen removal performance were examined and compared with those of a column without support material. In the two columns, the riser was aerobic and the lower part of downcomer was anaerobic. The effects of operational conditions on the liquid circulation flow rate and liquid-phase volumetric mass transfer coefficient were examined. Using these flow characteristics, the distribution of dissolved oxygen (DO) concentration in the column was calculated. From the DO distribution, the anaerobic volume fraction in the column was estimated. The optimal anaerobic volume fraction for nitrogen removal was found to be approximately 50%. The column installed with support material showed higher nitrogen removal than the column without it.     

共生食用菌松茸菌丝体液体发酵的研究

目的研究松茸菌丝体液体发酵方法和最佳条件。方法经RAPD-PCR分析确认松茸菌丝体菌种,研究松茸液体深层发酵过程中菌丝体的生物量、残糖浓度和pH随时间变化的过程;比较不同种龄对菌丝体积累的影响,确立最佳接种种龄;比较不同初始糖浓度发酵过程的结果,运用中间补糖的方法,确定最优的补糖时间。结果最佳接种种龄为6d;初始糖浓度较低有利于缩短松茸种子液生长的延迟期,较高则可使菌丝体在较长时间保持生长并获得较高的生物量产出。d12为最优补糖时间,在摇瓶体系中培养24d最终得到12.77g/L的菌丝体生物量。结论最佳培养条件下,采用中间补糖法适合液体发酵过程中松茸菌丝体的积累。     

影响纤细角毛藻生长的因素及其脂肪酸组成的研究

对影响纤细角毛藻生长的温度、pH、通气率、光强等培养条件进行了研究,获得了纤细角毛藻培养的优化条件为温度23℃,光照强度8mW/cm2,通气速率06vvm;考察了培养条件对纤细角毛藻脂肪酸的组成含量的影响,结果显示光照强度、通气量及培养时间对二十碳五烯酸和花生四烯酸的含量有一定的影响,纤细角毛藻中EPA和AA的总量可占藻体干重的667%,高通气量及高的光照强度有利于花生四烯酸的积累,而低光照有利于二十碳五烯酸的积累。     

Comparative study of the design of continuous aeration equipment for the production of food foams

The performances of two designs of mixing heads dedicated to food aeration are compared in terms of overrun, bubble size and energy consumption in laminar flow conditions. The first design (RS) is a standard rotor-stator combination, while the second is a multi-impeller stirred column (CF) equipped with flat-blade radial turbine impellers. Experimental data demonstrate that higher overrun can be achieved at lower rotation speed, residence time and energy consumption with RS for Newtonian media, but at the expense of larger bubble sizes than with CF. Conversely, CF is more efficient for achieving high overrun and smaller bubbles when highly shear-thinning media are involved, although energy consumption remains higher. However, for both designs, the average bubble size has been related to an invariant dimensionless parameter, the laminar Weber number. Finally, the key role of the local distribution of shear has been highlighted, even at identical average shear rate in both devices.     

裂褶菌液态深层培养条件的研究

研究了裂褶菌液态深层培养过程中通风量以及控制溶氧浓度(DO)对裂褶菌丝体生长和胞外多糖产量的影响。通过在发酵过程中的不同时期改变通风量和将溶氧浓度维持在20%以上,均能有效地控制罐内氧传递速率,增加菌体对碳源的利用率,且还原糖消耗速率和菌体得率明显提高。当在发酵过程中的不同时期改变通风量时,菌丝体得率和胞外多糖产量分别为14.83g/L和2.12g/L。当溶氧浓度维持在20%以上时,菌体得率为15.56g/L,但是多糖产量仅有1.00g/L,说明高溶氧不利于多糖的生产。     

Effect of aeration and agitation on growth rate of Thermus thermophilus in batch mode

The growth kinetics of Thermus thermophilus HB27 was investigated in rich medium (Thermus medium) under batch cultivation at 65 degrees C in 3-l fermentors. The growth and oxygen consumption rates were highly dependent on the aeration and agitation rates. Volumetric mass transfer coefficient (K(L)a, h(-1)) and hence oxygen transfer rate (OTR, mol m (-3) h(-1)) into the fermentation broth increased with increased aeration and/or agitation rates. A K(L)a and OTR of 175.4 h(-1) and 31.7 mol m(-3)h(-1) respectively, corresponding to 500 rpm agitation and 2 vvm aeration with a mixture of air and oxygen, were required to avoid oxygen limitation. The maximum growth rate (mu(max), h(-1)), doubling time (t(D), h), and dry cell weight determined for T. thermophilus HB27 growing under these conditions were 0.27 h(-1), 2.67 h, and 3g/l respectively. This cell yield is higher than any previously published reports for growth of Thermus cultures, including studies that employed pressurized bioreactors.     

Continuous production of wine vinegar in bubble column reactors of up to 60-litre capacity

This paper describes the development of a continuous acetic acid fermentation process for the production of wine vinegar in bubble column reactors of up to 60 l capacity. To determine appropriate fermentation conditions a study of the influence of residual ethanol concentration, inlet flow rate and aeration was carried out using a 6-l laboratory reactor, white table wine as fermentation medium, a temperature of 30 °C and an air flow rate of 0.125 min^-1 (vvm). The concentration of acetic acid obtained in the continuous wine vinegar production ranged from 91 g/l at 28.6 ml/h to 28 g/l at 154.1 ml/h by increasing the inlet flow rate. As expected, the biomass decreased as well, from 208 mg/l to 106 mg/l. The maximum acetification rate was observed in the range 85-110 ml/h, corresponding to a value of about 1.1 g/l/h. A further increase in the flow rate produced a slight decrease in the acetification rate. Best yields, between 94.5 and 94.7%, were obtained in the flow rate range of 60-75 ml/h. The acetification rate was improved only by about 10% by increasing the aeration from 0.125 to 0.250 min^-1. The continuous wine vinegar production was scaled up from the laboratory fermentor to a 60-l pilot acetator. During the steady state (residential time >6), with an inlet flow rate of 950 ml/h, temperature of 30 °C and aeration of 0.250 min^-1, the following parameters were obtained: acetic acid concentration 72 g/l, overall productivity 1.41 g/l/h and yield 94.2%.     

Continuous Primary Beer Fermentation with Brewing Yeast Immobilized on Spent Grains

This work demonstrated the technological feasibility of the three‐phase airlift bioreactor (ALR) with brewing yeast immobilized on spent grains (a brewing by‐product) for continuous beer production. The optimum fermentation performance of the one stage immobilized cell bioreactor was achieved at residence times between 18–25 h (dilution rate 0.04–0.055 h^?1) and was characterized by an apparent degree of attenuation in the range of 70–80%. The productivity of the system in terms of ethanol concentration in green beer (ca. 4.2%) was satisfactory. Although the diacetyl concentration in the young beer was high (0.32 mg L^?1 at D = 0.04 h^?1) it is speculated that the level could be reduced by cell growth control, aeration and temperature optimisation. The immobilized yeast fermentation in the ALR was shown to be robust in recovery after process upsets.     

超声波辅助复合酶法提取松茸多糖的工艺研究

以松茸多糖得率为评价指标,采用单因素试验和正交试验,确定最佳提取工艺参数。结果表明,超声波提取优化工艺条件为超声温度90 ℃,料液比1∶15（g∶mL）,超声时间10 min。在此最佳超声提取条件下松茸多糖得率为11.18%。在超声波优化结果的基础上,进行复合酶处理,最佳酶解工艺参数为酶解温度50 ℃,酶解时间60 min,复合酶（木瓜蛋白酶∶纤维素酶∶果胶酶为1∶1∶1）添加量4.0%,酶解pH值6.0,此优化条件下松茸多糖得率为19.56%。复合酶超声辅助法比超声波法提取松茸多糖提高了8.38%。结果表明,复合酶超声辅助提取法提取松茸多糖是一种科学有效的方法,可显著提高松茸多糖得率。     

CO2气体进入聚合物熔体中的形态变化过程

在聚合物发泡中,CO2气体的浓度分散和扩散速率与初始气泡形态有关。用可视化方法,对挤出条件下CO2气体注入静、动态流场以及气体在高压和低压注入时的气泡形态和破碎问题的研究。研究表明气体小流量时,静态熔体中球形气泡形成、直径长大定型、长度不断伸长的3个阶段与动态熔体中的初始球形膨胀,头部变尖、中间涨大,尾部颈缩及断裂3个阶段有所不同;新型螺杆对气泡破碎和分离作用比收敛流道更有效。高压下,符合实际生产的气体大流量以射流注入螺槽,形成气熔混合的蜂窝状泡沫,促进了气泡的破裂和分散,加强了气体浓度分散和扩散,有助于聚合物/CO2均相溶液的形成。     

Necessity of a two-stage process for the production of azadirachtin-related limonoids in suspension cultures of Azadirachta indica

The effect of major nutrients on growth and azadirachtin-related limonoids (AZRL) production in plant cell culture of Azadirachta indica (neem) was studied with the objective to increase the yield of AZRL, one of the major group of pesticidal compounds found in intact neem trees. We report the novel online monitoring of plant cell respiration activities in a new parallel shake flask measuring device. Results obtained using three standard plant cell culture media showed non-growth-associated production characteristics for AZRL. These findings were supported by the oxygen uptake rate data. Further investigations on AZRL production in a modified MS medium with different concentrations of nitrogen and phosphorus sources resulted in 0.25 mg.g(-1) dry weight of AZRL, compared to no detectable AZRL production in standard MS media. These characteristics suggest the necessity of a two-stage process for the production of AZRL in plant cell culture. Compared to the single-stage process, an almost twofold increase in the volumetric productivity of AZRL was achieved using the two-stage process.     

松口蘑菌丝体蛋白质诱导细胞凋亡

采用深层发酵技术培养菌丝体并提取分离出的蛋白质,进行体外抗人子宫颈癌HeLa细胞增殖及诱导细胞凋亡机理的研究.试验发现松口蘑菌丝体水提液中活性蛋白质TMP在体外具有抑制肿瘤细胞增殖的作用,扫描电镜观察到TMP处理细胞产生明显的凋亡小体,TMP对细胞周期的影响是通过抑制细胞从S到G2M期的转化来抑制HeLa细胞增殖,诱导细胞发生凋亡的.DNA电泳出现以200bp左右为单位的DNA碎片.结果表明采用液体培养方法生产的松口蘑菌丝体蛋白质,具有显著的抑制细胞增殖和诱导细胞凋亡作用.     

Inactivation of ccpA and aeration affect growth, metabolite production and stress tolerance in Lactobacillus plantarum WCFS1

The growth of Lactobacillus plantarum WCFS1 and of its ΔccpA ery mutant, WCFS1-2, was compared in batch fermentations in a complex medium at controlled pH (6.5) and temperature (30°C) with or without aeration, in order to evaluate the effect of ccpA inactivation and aeration on growth, metabolism and stress resistance. Inactivation of ccpA and, to a lesser extent, aeration, significantly affected growth, expression of proteins related to pyruvate metabolism and stress, and tolerance to heat, oxidative and cold/starvation stresses. The specific growth rate of the mutant was ca. 60% of that of the wild type strain. Inactivation of ccpA and aerobic growth significantly affected yield and production of lactic and acetic acid. Stationary phase cells were more stress tolerant than exponential phase cells with little or no effect of inactivation of ccpA or aeration. On the other hand, for exponential phase cells inactivation of ccpA impaired both heat stress and cold/starvation stress, but increased oxidative stress tolerance. For both strains, aerobically grown cells were more tolerant of stresses. Evidence for entry in a viable but non-culturable status upon prolonged exposure to cold and starvation was found. Preliminary results of a differential proteomic study further confirmed the role of ccpA in the regulation of carbohydrate catabolism and class I stress response genes and allow to gain further insight on the role of this pleiotropic regulator in metabolism and stress. This is the first study in which the impact of aerobic growth on stress tolerance of L. plantarum is evaluated. Although aerobic cultivation in batch fermentations does not improve growth it does improve stress tolerance, and may have significant technological relevance for the preservation of starter and probiotic cultures.     

微藻的平板式光生物反应器高密度培养

在平板式光生物反应器中对微藻Parietochlorisincisa进行了放大培养。结果表明 ,通气速率和培养密度对藻体细胞的生长速度有直接的影响 ;并且其最适培养密度和细胞生物量产率随着通气率的增加而增加。当通气率从 70 0mL/L增加到 3 0 0 0mL/L时 ,该微藻的最适培养密度从 0 85 g/L提高到了 2 5lg/L ,其培养密度、单位体积和单位面积的细胞生物量产率也分别达到了 4 65 g/L、0 3 g/ (L·d)和 3 4 7g/ (m2 ·d)。在相对稳态的半连续培养模式下 ,通气率与采收率对藻体细胞的生长也有很大的影响 ;其细胞生物量的产量和产率随着采收率的增加而增加 ,当采收率为 2 0 %时达到最大值。在通气率为 190 0mL/L、采收率为 2 0 %的条件下 ,微藻细胞的培养密度达到了 5 15 g/L ;其单位体积和面积的细胞生物量产率分别提高到了 0 73 g/ (L·d)和 70 1g/ (m2 ·d)。