Physical and chemical mutagens improved Sporotrichum thermophile,strain ST20 for enhanced Phytase activity

ObjectivePhosphorous is an essential micronutrient of plants and involved in critical biological functions. In nature, phosphorous is mostly present in immobilized inorganic mineral and in the fixed organic form including phytic acid and phosphoesteric compounds. However, the bioavailability of bound phosphorous could be enhanced by the use of phosphate solubilizing microorganisms such as bacteria and fungi. The phytases are widespread in an environment and have been isolated from different sources comprising bacteria and fungi.MethodologyIn current studies, we show the successful use of gamma rays and EMS (Ethyl Methane Sulphonate) mutagenesis for enhanced activity of phytases in a fungal strain Sporotrichum thermophile.ResultsWe report an improved strain ST2 that could produce a clear halo zone around the colony, up to 24 mm. The maximum enzymatic activity was found of 382 U/mL on pH 5.5. However, the phytase activity was improved to 387 U/ml at 45 °C. We also report that the mutants produced through EMS showed the greater potential for phytase production.ConclusionThe current study highlights the potential of EMS mutagenesis for strain improvement over physical mutagens.     

Beta-glucan production by Botryosphaeria rhodina in different bench-top bioreactors

AIMS: Evaluation of the technical feasibility of transferring beta-glucan production by Botryosphaeria rhodina DABAC-P82 from shaken flasks to bench-top bioreactors. METHODS AND RESULTS: Three different bioreactors were used: 3 l stirred tank reactor (STR-1) equipped with two different six-blade turbines; STR as above but equipped with a three-blade marine propeller plus draft-tube (STR-2); 2 l air-lift column reactor (ALR) equipped with an external loop. STR-1, tested at three different stirrer speeds (300, 500 and 700 rev min(-1)) appeared to be less suitable for beta-glucan production by the fungus, being maximum production (19.4 g l(-1)), productivity (0.42 g l(-1) h(-1)) and yield (0.48 g g(-1) of glucose consumed) markedly lower than those obtained in shaken culture (29.7 g l(-1), 1.23 g l(-1) h(-1) and 0.61 g g(-1), respectively). Better performances were obtained with both STR-2 and ALR. With the latter, in particular, the increase of production was accompanied by reduced fermentation time (25.7 g l(-1) after only 22 h); productivity and yield were highest (1.17 g l(-1) h(-1) and 0.62 g g(-1) of glucose consumed, respectively). CONCLUSION: Using an air-lift reactor with external loop, the scaling up from shaken flasks to bench-top bioreactor of the beta-glucan production by B. rhodina DABAC-P82 is technically feasible. SIGNIFICANCE AND IMPACT OF THE STUDY: Although culture conditions are still to be optimized, the results obtained using the ARL are highly promising.     

Influence of aeration–homogenization system in stirred tank bioreactors,dissolved oxygen concentration and pH control mode on BHK-21 cell growth and metabolism

This work focused on determining the effect of dissolved oxygen concentration (DO) on growth and metabolism of BHK-21 cell line (host cell for recombinant proteins manufacturing and viral vaccines) cultured in two stirred tank bioreactors with different aeration-homogenization systems, as well as pH control mode. BHK-21 cell line adapted to single-cell suspension was cultured in Celligen without aeration cage (rotating gas-sparger) and Bioflo 110, at 10, 30 and 50 % air saturation (impeller for gas dispersion from sparger-ring). The pH was controlled at 7.2 as far as it was possible with gas mixtures. In other runs, at 30 and 50 % (DO) in Bioflo 110, the cells grew at pH controlled with CO₂ and NaHCO₃ solution. Glucose, lactate, glutamine, and ammonium were quantified by enzymatic methods. Cell concentration, size and specific oxygen consumption were also determined. When NaHCO₃ solution was not used, the optimal DOs were 10 and 50 % air saturation for Celligen and Bioflo 110, respectively. In this condition maximum cell concentrations were higher than 4 × 10⁶ cell/mL. An increase in maximum cell concentration of 36 % was observed in batch carried out at 30 % air saturation in a classical stirred tank bioreactor (Bioflo 110) with base solution addition. The optimal parameters defined in this work allow for bioprocess developing of viral vaccines, transient protein expression and viral vector for gene therapy based on BHK-21 cell line in two stirred tank bioreactors with different agitation–aeration systems.     

Production of xylanase by the thermophilic fungusThielavia terrestris

Summary The effect of varying fermentation pH and temperature on extracellular xylanase production by the thermophilic fungus,Thielavia terrestris (ATCC 26917), was studied using a stirred tank bioreactor. Maximum xylanase activity (18.8 I.U/mL) was obtained when the temperature was controlled at 48°C and the initial pH set at 4.0. Under these conditions, the volumetric productivity of xylanase was 1044 l. U./L. h. which is superior to that achieved by many mesophilic xylanolytic micro-organisms.     

A simple eccentric stirred tank mini‐bioreactor: Mixing characterization and mammalian cell culture experiments

In industrial practice, stirred tank bioreactors are the most common mammalian cell culture platform. However, research and screening protocols at the laboratory scale (i.e., 5–100 mL) rely primarily on Petri dishes, culture bottles, or Erlenmeyer flasks. There is a clear need for simple—easy to assemble, easy to use, easy to clean—cell culture mini‐bioreactors for lab‐scale and/or screening applications. Here, we study the mixing performance and culture adequacy of a 30 mL eccentric stirred tank mini‐bioreactor. A detailed mixing characterization of the proposed bioreactor is presented. Laser induced fluorescence (LIF) experiments and computational fluid dynamics (CFD) computations are used to identify the operational conditions required for adequate mixing. Mammalian cell culture experiments were conducted with two different cell models. The specific growth rate and the maximum cell density of Chinese hamster ovary (CHO) cell cultures grown in the mini‐bioreactor were comparable to those observed for 6‐well culture plates, Erlenmeyer flasks, and 1 L fully instrumented bioreactors. Human hematopoietic stem cells were successfully expanded tenfold in suspension conditions using the eccentric mini‐bioreactor system. Our results demonstrate good mixing performance and suggest the practicality and adequacy of the proposed mini‐bioreactor. Biotechnol. Bioeng. 2013; 110: 1106–1118. © 2012 Wiley Periodicals, Inc.     

Effect of bioreactor configuration on the growth and maturation of Picea sitchensis somatic embryo cultures

Somatic embryo suspension cultures of Picea sitchensis (Sitka spruce) derived from two cell lines, SS03 and SS10, were grown in shake flasks, air-lift, bubble, stirred tank and hanging stirrer bar bioreactors. Cell line SS03 yielded freely suspended and individual stage 1 embryos, while the embryos of SS10 were present in large aggregates. Compared to shake flasks, proliferation in bioreactors resulted in increased biomass; however, cell line morphology influenced the effect of different bioreactor configurations on growth and maturation of embryo cultures. Somatic embryos grown in shake flasks and bioreactors were matured on gelled solid medium and in submerged culture where gelled solid medium was covered with a layer of liquid medium. The number of stage 3 (mature) embryos produced from SS03 in the bubble bioreactor was significantly higher than those from stirred tank and hanging stirrer bar bioreactors with both solid medium and submerged culture. Submerged culture was unsuitable for SS10 embryo maturation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investigation of acid proteinase biosynthesis by the fungus Humicola lutea 120-5 in an airlift bioreactor

Acid proteinase production using filamentous fungus Humicola lutea 120-5 was studied under batch and continuous fermentation conditions in an airlift bioreactor. A comparison with proteinase production by fungal cells, cultivated in stirred tank bioreactor was made. The process performance in both fermentation devices was similar with respect to substrate utilization, biomass, and enzyme concentration. Continuous acid proteinase production was achieved for 14 days at an optimal dilution rate of 0.05/h with maximum specific activity of 90 U/mg DW of mycelia and yield of 38 U/mg glucose. The volumetric productivity (50 U/ml. h) was approximately 3 times higher than this of the batch system. All continuous experiments were carried out without any bacterial contamination, due to the low pH (3.0-3.5) during the process. The "pellet" type growth of the fungus in the airlift reactor prevented the system from plugging with filaments.     

Production of swainsonine from Metarhizium anisopliaein stirred-tank and air-lift reactors

Growth of Metarhizium anisopliaein modified starch-casein medium produced 61, 50, and 58 mg swainsonine/l when cultured in shaken flasks, stirred-tank and air-lift reactors respectively. Over approximately 45 h, the maximum swain-sonine specific productivity was 0.47 mg/g.h in a stirred tank reactor and 0.32 mg/g.h in an air-lift reactor. After 120 h, increasing broth viscosity was encountered in the latter fermenter.     

Phytase production by Sporotrichum thermophile in a cost‐effective cane molasses medium in submerged fermentation and its application in bread

Aims: Phytase production by Sporotrichum thermophile in a cost‐effective cane molasses medium in submerged fermentation and its application in bread. Methods and Results: The production of phytase by a thermophilic mould S. thermophile was investigated using free and immobilized conidiospores in cane molasses medium in shake flasks, and stirred tank and air‐lift fermenters. Among surfactants tested, Tweens (Tween‐20, 40 and 80) and sodium oleate increased phytase accumulation, whereas SDS and Triton X‐100 inhibited the enzyme production. The mould produced phytase optimally at a_w 0·95, and it declined sharply below this a_w value. The enzyme production was comparable in air‐lift and stirred tank reactors with a marked reduction in fermentation time. Among the matrices tried, Ca‐alginate was the best for conidiospore immobilization, and fungus secreted sustained levels of enzyme titres over five cycles. The phytic acid in the dough was efficiently hydrolysed by the enzyme accompanied by the liberation of soluble phosphate in the bread. Conclusions: The phytase production by S. thermophile was enhanced in the presence of Tween‐80 in cane molasses medium. A peak in enzyme production was attained in 48 h in the fermenter when compared with that of 96 h in shake flasks. Ca‐alginate immobilized conidiospores germinated to produce fungal growth that secreted sustained levels of phytase over five cycles. The bread made with phytase contained reduced level of phytic acid and a high‐soluble phosphate. Significance and Impact of the Study: The phytase accumulation by S. thermophile was increased by the surfactants. The sustainability of enzyme production in stirred tank and air‐lift fermenters suggested the possibility for scaling up of phytase. The bread made with phytase contained low level of antinutrient, i.e. phytic acid.     

Effect of growth conditions on the production of manganese peroxidase by three strains of Bjerkandera adusta

We were looking for a strain of Bjerkandera adusta that produces high titres of manganese peroxidase under optimal conditions for large-scale enzyme purification. We have chosen two strains from the University of Alberta Microfungus Collection and Herbarium, UAMH 7308 and 8258, and compared the effects of growth conditions and medium composition on enzyme production with the well-characterized strain BOS55 (ATCC 90940). Of four types of cereal bran examined, rice bran at 3% (w/v) in 60 mM phosphate buffer pH 6 supported the highest levels of enzyme production. Using 100 mL medium in 500-mL Erlenmeyer flasks, maximum enzyme levels in the culture supernatant occurred after about 10 days of growth; 5.5 U x mL(-1) for UAMH 7308, 4.4 U x mL(-1) for UAMH 8258, and 1.7 U x mL(-1) for BOS55, where units are expressed as micromoles of Mn-malonate formed per minute. Growth as submerged cultures in 10-L stirred tank reactors produced 3.5 U x mL(-1) of manganese peroxidase (MnP) by UAMH 8258 and 2.5 U x mL(-1) of MnP by 7308, while enzyme production by BOS55 was not successful in stirred tank reactors but could be scaled up in 2-L shake flasks containing 400 mL rice bran or glucose-malt-yeast extract (GMY)-Mn-glycolate medium to produce MnP levels of 1.7 U x mL(-1). These results show that the two strains of B. adusta, UAMH 7308 and 8258, can produce between two and three times the manganese peroxidase level of B. adusta BOS55, that they are good candidates for scale up of enzyme production, and that the rice bran medium supports higher levels of enzyme production than most previously described media.     

New milliliter‐scale stirred tank bioreactors for the cultivation of mycelium forming microorganisms

A novel milliliter‐scale stirred tank bioreactor was developed for the cultivation of mycelium forming microorganisms on a 10 milliliter‐scale. A newly designed one‐sided paddle impeller is driven magnetically and rotates freely on an axis in an unbaffled reaction vessel made of polystyrene. A rotating lamella is formed which spreads out along the reactor wall. Thus an enhanced surface‐to‐volume ratio of the liquid phase is generated where oxygen is introduced via surface aeration. Volumetric oxygen transfer coefficients (k_La) > 0.15 s^?1 were measured. The fast moving liquid lamella efficiently prevents wall growth and foaming. Mean power consumption and maximum local energy dissipation were measured as function of operating conditions in the milliliter‐scale stirred tank bioreactor (V = 10 mL) and compared to a standard laboratory‐scale stirred tank bioreactor with six‐bladed Rushton turbines (V = 2,000 mL). Mean power consumption increases with increasing impeller speed and shows the same characteristics and values on both scales. The maximum local energy dissipation of the milliliter‐scale stirred tank bioreactor was reduced compared to the laboratory‐scale at the same mean volumetric power input. Hence the milliliter impeller distributes power more uniformly in the reaction medium. Based on these data a reliable and robust scale‐up of fermentation processes is possible. This was demonstrated with the cultivation of the actinomycete Streptomyces tendae on both scales. It was shown that the process performances were equivalent with regard to biomass concentration, mannitol consumption and production of the pharmaceutical relevant fungicide nikkomycin Z up to a process time of 120 h. A high parallel reproducibility was observed on the milliliter‐scale (standard deviation < 8%) with up to 48 stirred tank bioreactors operated in a magnetic inductive drive. Rheological behavior of the culture broth was measured and showed a highly viscous shear‐thinning non‐Newtonian behavior. The newly developed one‐sided paddle impellers operated in unbaffled reactors on a 10 milliliter‐scale with a magnetic inductive drive for up to 48 parallel bioreactors allows for the first time the parallel bioprocess development with mycelium forming microorganisms. This is especially important since these kinds of cultivations normally exhibit process times of 100 h and more. Thus the operation of parallel stirred tank reactors will have the potential to reduce process development times drastically. Biotechnol. Bioeng. 2010; 106: 443–451. © 2010 Wiley Periodicals, Inc.     

Reaction engineering studies for the production of 2-hydroxyisobutyric acid with recombinant Cupriavidus necator H 16

Recombinant Cupriavidus necator H 16 with a novel metabolic pathway using a cobalamin-dependent mutase was exploited to produce 2-hydroxyisobutyric acid (2-HIBA) from renewable resources through microbial fermentation. 2-HIBA production capacities of different strains of C. necator H 16 deficient in the PHB synthase gene and genetically engineered to enable the production of 2-HIBA from the intracellular PHB precursor (R)-3-hydroxybutyryl-CoA were evaluated in 48 parallel milliliter-scale stirred tank bioreactors (V = 11 mL). The effects of media composition, limitations, pH, and feed rate were studied with respect to the overall process performances of the different recombinant strains. 2-HIBA production was at a maximum at nitrogen limiting conditions and if the pH was controlled between 6.8 and 7.2 under fed-batch operating conditions (intermittent fructose addition). The final concentration of 2-HIBA was 7.4 g L⁻¹ on a milliliter scale. Best reaction conditions identified on the milliliter scale were transferred to a laboratory-scale fed-batch process in a stirred tank bioreactor (V = 2 L). Two different process modes for the production of 2-HIBA, a single-phase and a dual-phase fermentation procedure, were evaluated and compared on a liter scale. The final concentration of 2-HIBA was 6.4 g L⁻¹ on a liter scale after 2 days of cultivation.     

Phytate degradation by immobilized<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> phytase in soybean-curd whey

Saccharomyces cerevisiae CY phytase-producing cells were immobilized in calcium alginate beads and used for the degradation of phylate. The maximum activity and immobilization yield of the immobilized phytase reached 280 mU/g-bead and 43%, respectively. The optimal pH of the immobilized cell phytase was not different from that of the free cells. However, the optimum temperature for the immobilized phytase was 50°C, which was 10°C higher than that of the free cells; pH and thermal stability were enhanced as a consequence of immobilization. Using the immobilized phytase, phytate was degraded in a stirred tank bioreactor. Phytate degradation, both in a buffer solution and in soybean-curd whey mixture, showed very similar trends. At an enzyme dosage of 93.9 mU/g-phytate, half of the phytate was degraded after 1 h of hydrolysis. The operational stability of the immobilized beads was examined with repeated batchwise operations. Based on 50% conversion of the phytate and five times of reuse of the immobilized beads, the specific degradation (g phytate/g dry cell weight) for the immobilized phytase increased 170% compared to that of the free phytase.     

Production,characteristics and applications of the cell-bound phytase of <Emphasis Type="Italic">Pichia anomala</Emphasis>

Among several yeasts isolated from dried flowers of Woodfordia fruticosa, Pichia anomala produced a high titre of cell-bound phytase. The optimization of fermentation variables led to formulation of media and selection of cultural variables that supported enhanced phytase production. The enzyme productivity was very high in fed batch fermentation in air-lift fermentor as compared to that in stirred tank fermentor. Amelioration in the cell-bound phytase activity was observed when yeast cells were permeabilized with Triton-X-100. The enzyme is thermostable and acid stable with broad substrate specificity, the characteristics that are desirable for enzymes to be used in the animal feed industry. The phytase-encoding gene was cloned and sequenced. The 3D structure of the enzyme was proposed by comparative modeling using phytase of Debaryomyces occidentalis (50% sequence identity) as template. When broiler chicks, and fresh water and marine fishes were fed with the feed supplemented with yeast biomass containing phytase, improvement in growth and phosphorus retention, and decrease in the excretion of phosphorus in the faeces were recorded. The cell-bound phytase of P. anomala could effectively dephytinize wheat flour and soymilk.     

Itaconic acid production from xylose in repeated-batch and continuous bioreactors

Summary Itaconic acid production from xylose by immobilized Aspergillus terreus TKK 200-5-2 mycelia was optimized both in repeated shake-flask fermentations and in continuous column bioreactors using statistical experimental design and empirical modelling. Using continuous 9-1 scale air-lift bioreactors, a pH of 2.5, aeration rate of 0.6 v/v per minute and residence time of 160 h gave the highest itaconic acid concentration. In air-lift bioreactors a cubic carrier size of 0.5 cm gave a 3.3-fold higher product concentration than 1-cm cubes. Packed-bed column reactors had a higher production rate than air-lift reactors. Offprint requests to: H. Kautola     

Is an organic nitrogen source needed for cellulase production by Trichoderma reesei Rut-C30?

The effect of organic and inorganic nitrogen sources on Trichoderma reesei Rut-C30 cellulase production was investigated in submerged cultivations. Stirred tank bioreactors and shake flasks, with and without pH control, respectively, were employed. The experimental design involved the addition of individual organic nitrogen sources (soy peptone, glutamate, glycine and alanine) within a basal medium containing Avicel (i.e. micro crystalline cellulose) and ammonium sulphate. It was found that in the shake flask experiments, the highest cellulase activities (~0.1 ± 0.02 FPU ml^?1) were obtained with media containing soy peptone (3–6 g l^?1) and glutamate (3.6 g l^?1). However, these improvements in the cellulase titers in the presence of the organic nitrogen sources appeared to be related to smaller changes in the pH of the medium. This was confirmed using stirred tank bioreactors with pH control. No significant differences were observed in the highest cellulase titers and the protein pattern (according to the SDS-PAGE) of supernatants from pH controlled stirred tank bioreactor cultivations, when different nitrogen sources were used in the medium. Here the cellulase activities (~1.0 ± 0.2 FPU ml^?1) were also much greater (8–150 times) than in shake flask cultivation. Consequently, the addition of ammonium sulphate as sole nitrogen source to Avicel basal medium is recommended when performing cultivations in stirred tank bioreactors with strict pH controlled conditions.     

Enhanced submerged Aspergillus ficuum phytase production by implementation of fed-batch fermentation

Phytase is an important feed and food additive, which is both used in animal and human diets. Phytase has been used to increase the absorption of several divalent ions, amino acids, and proteins in the bodies and to decrease the excessive phosphorus release in the manure to prevent negative effects on the environment. To date, microbial phytase has been mostly produced in solid-state fermentations with insignificant production volumes. There are only a few studies in the literature that phytase productions were performed in submerged bench-top reactor scale. In our previous studies, growth parameters (temperature, pH, and aeration) and important fermentation medium ingredients (glucose, Na-phytate, and CaSO₄) were optimized. This study was undertaken for further enhancement of phytase production with Aspergillus ficuum in bench-top bioreactors by conducting fed-batch fermentations. The results showed that addition of 60 g of glucose and 10 g of Na-phytate at 96 h of fermentation increased phytase activity to 3.84 and 4.82 U/ml, respectively. Therefore, the maximum phytase activity was further enhanced with addition of glucose and Na-phytate by 11 and 40 %, respectively, as compared to batch phytase fermentations. It was also reported that phytase activity increased higher in early log stage additions than late log stage additions because of higher microbial activity. In addition, the phytase activity in fed-batch fermentation did not drop significantly as compared to the batch fermentation. Overall, this study shows that fungal phytase can be successfully produced in submerged fed-batch fermentations.     

Bioprocess optimization for pectinase production using <Emphasis Type="Italic">Aspergillus niger</Emphasis> in a submerged cultivation system

Background

Pectinase enzymes present a high priced category of microbial enzymes with many potential applications in various food and oil industries and an estimated market share of $ 41.4 billion by 2020.

Results

The production medium was first optimized using a statistical optimization approach to increase pectinase production. A maximal enzyme concentration of 76.35 U/mL (a 2.8-fold increase compared with the initial medium) was produced in a medium composed of (g/L): pectin, 32.22; (NH₄)₂SO₄, 4.33; K₂HPO₄, 1.36; MgSO₄.5H₂O, 0.05; KCl, 0.05; and FeSO₄.5H₂O, 0.10. The cultivations were then carried out in a 16-L stirred tank bioreactor in both batch and fed-batch modes to improve enzyme production, which is an important step for bioprocess industrialization. Controlling the pH at 5.5 during cultivation yielded a pectinase production of 109.63 U/mL, which was about 10% higher than the uncontrolled pH culture. Furthermore, fed-batch cultivation using sucrose as a feeding substrate with a rate of 2 g/L/h increased the enzyme production up to 450 U/mL after 126 h.

Conclusions

Statistical medium optimization improved volumetric pectinase productivity by about 2.8 folds. Scaling-up the production process in 16-L semi-industrial stirred tank bioreactor under controlled pH further enhanced pectinase production by about 4-folds. Finally, bioreactor fed-batch cultivation using constant carbon source feeding increased maximal volumetric enzyme production by about 16.5-folds from the initial starting conditions.

     

Production of β-galactosidase by Streptococcus salivarius subsp thermophilus 11F

The production of β-galactosidase by an autolytic strain of Streptococcus salivarius subsp thermophilus 11F was investigated in batch and fed-batch 2-L working volume stirred tank bioreactors. β-Galactosidase was released into the medium upon cell lysis within 1–2 h after the maximum biomass quantity was reached. In batch fermentations the highest β-galactosidase activity of 69 U ml⁻¹ was obtained when the temperature was increased to 42°C after a 4-h growth period at 30°C. In fed-batch experiments the highest β-galactosidase activity of 74 U ml⁻¹ was obtained at a constant 37°C. Received 18 December 1997/ Accepted in revised form 03 February 1998     

Growth and recombinant protein expression with <Emphasis Type="Italic">Escherichia coli</Emphasis> in different batch cultivation media

Parallel operated milliliter-scale stirred tank bioreactors were applied for recombinant protein expression studies in simple batch experiments without pH titration. An enzymatic glucose release system (EnBase), a complex medium, and the frequently used LB and TB media were compared with regard to growth of Escherichia coli and recombinant protein expression (alcohol dehydrogenase (ADH) from Lactobacillus brevis and formate dehydrogenase (FDH) from Candida boidinii). Dissolved oxygen and pH were recorded online, optical densities were measured at-line, and the activities of ADH and FDH were analyzed offline. Best growth was observed in a complex medium with maximum dry cell weight concentrations of 14 g L⁻¹. EnBase cultivations enabled final dry cell weight concentrations between 6 and 8 g L⁻¹. The pH remained nearly constant in EnBase cultivations due to the continuous glucose release, showing the usefulness of this glucose release system especially for pH-sensitive bioprocesses. Cell-specific enzyme activities varied considerably depending on the different media used. Maximum specific ADH activities were measured with the complex medium, 6 h after induction with IPTG, whereas the highest specific FDH activities were achieved with the EnBase medium at low glucose release profiles 24 h after induction. Hence, depending on the recombinant protein, different medium compositions, times for induction, and times for cell harvest have to be evaluated to achieve efficient expression of recombinant proteins in E. coli. A rapid experimental evaluation can easily be performed with parallel batch operated small-scale stirred tank bioreactors.