l-asparaginase production by isolated Staphylococcus sp. ? 6A: design of experiment considering interaction effect for process parameter optimization

l-Asparaginase producing novel Streptomyces sp. HB2AG: optimization of process parameters and whole genome sequence analysis

l-asparaginase (ASNase) is a key enzyme widely used as an anti-cancer drug and is also used in the pharmaceutical and food processing industries. This enzyme's applications are determined by its source and nature. The production of the enzyme through the fermentation process is also crucial for economic feasibility. Searching for a new potent microbial strain is necessary for increased ASNase synthesis. In this work, a potent strain was isolated from the sediment of Chilika Lake and selected for its high ASNase production potential. It was recognized following Bergey's manual of determinative and phylogenetic analysis was carried out by 16S rDNA sequencing. The isolated organism was Streptomyces sp. HB2AG. Additionally, a genome-wide analysis of HB2AG was performed. The result showed that the HB2AG genome possesses a chromosome with 6,099,956 bp and GC content of 74.0%. The whole genome analysis of the strain HB2AG revealed the presence of ASNase (ansA, ansB) and Asparagine synthase (asnB) in the HB2AG genome. Optimization of media composition is crucial for microbial growth and obtaining the desired end product. The current effort focuses on the Taguchi orthogonal design to determine optimum factor combinations that would allow the strain to produce maximum ASNase enzyme. Results showed that compared to unoptimized media, approximately 1.76-fold higher ASNase production was observed in Sea Water Luria Bertani (SWLB) media, pH-5, 0.5% (w/v) of lactose, 0.5% (w/v) of casein, 2.5% (w/v) NaCl, 1 mM Ca2+ and 0.1% Tween 80.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03620-0.

Optimization, Purification and Antitumor Activity of Kodamaea ohmeri ANOMY L-Asparaginase Isolated from Banana Peel

OBJECTIVE

L-Asparaginase is an important enzyme that converts L-asparagine to L-aspartate and ammonia. Microbial L-asparaginase has important applications as anticancer and food processing agents.

METHODS

This study reported the isolation, screening of a local yeast isolate from banana peel for L-asparaginase production using submerged fermentation, optimization of the production, purification, and anticancer assay of L-asparaginase. The yeast isolate was identified as Kodamaea ohmeri ANOMY based on the analysis of nuclear large subunit (26S) rDNA partial sequences. It was a promising L-asparaginase producer with a specific activity of 3059±193 U/mg in a non-optimized medium. The classical one-variable-at-a-time method was used to optimize the production medium components, and it was found that the elimination of K2HPO4 from the medium increased L-asparaginase specific activity (3100.90±180 U/mg).

RESULTS

Statistical optimization of L-asparaginase production was done using Plackett-Burman and Box-Behnken designs. The production medium for the maximum L-asparaginase specific activity (8500±578U/mg) was as follows (g/L): L-asparagine (7.50), NaNO3 (0.50), MgSO₄.7H₂O (0.80), KCl (0.80) associated with an incubation period of 5 days, inoculum size of 5.60 %, and pH (7.0). The optimization process increased L-asparaginase production by 2.78-fold compared to the non-optimized medium. L-Asparaginase was purified using ammonium sulphate precipitation followed by gel filtration on a Sephadex G-100 column. Its molecular weight was 66 KDa by SDS-PAGE analysis.

CONCLUSION

The cell morphology technique was used to evaluate the anticancer activity of L-asparaginase against three different cell lines. L-Asparaginase inhibited the growth of HepG-2, MCF-7, and HCT-116 cells at a concentration of 20, 50, and 60 μL, respectively.

Production, characterization and bioinformatics analysis of L-asparaginase from a new Stenotrophomonas maltophilia EMCC2297 soil isolate

An exhaustive screening program was applied for scoring a promising l-asparaginase producing-isolate. The recovered isolate was identified biochemically and molecularly and its l-asparaginase productivity was optimized experimentally and by Response Surface Methodology. The produced enzyme was characterized experimentally for its catalytic properties and by bioinformatics analysis for its immunogenicity. The promising l-asparaginase producing-isolate was selected from 722 recovered isolates and identified as Stenotrophomonas maltophilia and deposited at Microbiological Resources Centre (Cairo Mircen) under the code EMCC2297. This isolate produces both intracellular (type I) and extracellular (type II) l-asparaginases with about 4.7 fold higher extracellular l-asparaginase productivity. Bioinformatics analysis revealed clustering of Stenotrophomonas maltophilial-asparaginase with those of Pseudomonas species and considerable closeness to the two commercially available l-asparaginases of E. coli and Erwinia chrysanthemi. Fourteen antigenic regions are predicted for Stenotrophomonas maltophilial-asparaginase versus 16 and 18 antigenic regions for the Erwinia chrysanthemi and E. colil-asparaginases. Type II l-asparaginase productivity of the test isolate reached 4.7 IU/ml/h and exhibited maximum activity with no metal ion requirement at 37 °C, pH 8.6, 40 mM asparagine concentration and could tolerate NaCl concentration up to 500 mM and retain residual activity of 55% at 70 °C after half an hour treatment period. Application both of random mutation by gamma irradiation and Response Surface Methodology that determined 38.11 °C, 6.89 pH, 19.85 h and 179.15 rpm as optimum process parameters could improve the isolate l-asparaginase productivity. Maximum production of about 8 IU/ml/h was obtained with 0.4% dextrose, 0.1% yeast extract and 10 mM magnesium sulphate. In conclusion l-asparaginase of the recovered Stenotrophomonas maltophilia EMCC2297 isolate has characters enabling it to be used for medical therapeutic application.

A comprehensive review on microbial l-asparaginase: Bioprocessing, characterization, and industrial applications

l-Asparaginase (E.C.3.5.1.1.) is a vital enzyme that hydrolyzes l-asparagine to l-aspartic acid and ammonia. This property of l-asparaginase inhibits the protein synthesis in cancer cells, making l-asparaginase a mainstay of pediatric chemotherapy practices to treat acute lymphoblastic leukemia (ALL) patients. l-Asparaginase is also recognized as one of the important food processing agent. The removal of asparagine by l-asparaginase leads to the reduction of acrylamide formation in fried food items. l-Asparaginase is produced by various organisms including animals, plants, and microorganisms, however, only microorganisms that produce a substantial amount of this enzyme are of commercial significance. The commercial l-asparaginase for healthcare applications is chiefly derived from Escherichia coli and Erwinia chrysanthemi. A high rate of hypersensitivity and adverse reactions limits the long-term clinical use of l-asparaginase. Present review provides thorough information on microbial l-asparaginase bioprocess optimization including submerged fermentation and solid-state fermentation for l-asparaginase production, downstream purification, its characterization, and issues related to the clinical application including toxicity and hypersensitivity. Here, we have highlighted the bioprocess techniques that can produce improved and economically viable yields of l-asparaginase from promising microbial sources in the current scenario where there is an urgent need for alternate l-asparaginase with less adverse effects.

The effect of Yarrowia lipolytical-asparaginase on apoptosis induction and inhibition of growth in Burkitt's lymphoma Raji and acute lymphoblastic leukemia MOLT-4 cells

l-Asparaginase (l-asparagine amidohydrolase; E.C.3.5.1.1) as an anticancer agent is used to treat acute lymphocytic leukemia (ALL), Human Burkitt's lymphoma and non-Hodgkin's lymphoma. The commercial asparaginases are obtained from bacteria Erwinia chrysanthemi and Escherichia coli now which had many side effects. In this study, the effects of a novel l-asparaginase from yeast Yarrowia lipolytica was investigated on human ALL and Burkitt's lymphoma cell lines. The l-asparaginase causes metabolic stress, cytotoxicity, and apoptosis due to the arrest of the G0 cell cycle, the activation of caspase-3 and the modulation of mitochondrial membrane integrity. The RT-PCR analysis showed a significant increase in the pro-apoptosis genes such as Bax, Caspase-3, Caspase-8, Caspase-9 and p53 (P < 0.05) while the anti-apoptotic marker Bcl-2 was significantly decreased (P < 0.05). Furthermore, Y. lipolytical-asparaginase causes autophagy and increased ROS. The l-asparaginase has cytotoxic and anticancer effects higher than commercial asparaginase. In conclusion, Y. lipolytical-asparaginase shows interesting anticancer activity and it can be introduced as a new eukaryotic and therapeutic agent and strategy for ALL and Burkitt's lymphoma treatment after the in vivo and clinical experiments.

l-Asparaginase production in rotating bed reactor from Rhizopus microsporus IBBL-2 using immobilized Ca-alginate beads

The present work reports on the production of extracellular l-asparaginase from Rhizopus microsporus IBBL-2 using submerged fermentation (SmF) process free of glutaminase and urease activities. Primary studies done in shake flask showed that the highest l-asparaginase activity of 12.68 U mL^-1 was produced at 72 h with optimized fermentation parameters such as pH 6.0, 4 × 10⁶ fungal cells mL^-1, and agitation of 180 rpm at 30 °C using one-factor-at-a-time (OFAT). Different substrates, nitrogen sources, temperature, pH, the initial number of cells and metal ions were tested to determine the impact on enzyme production. l-Asparaginase activity of 17.68 U mL^-1 was produced after 48 h using immobilized calcium-alginate (Ca-alginate) cells. 4 × 10⁶ cells mL^-1 was entrapped in 3% (W/V) of alginate bead of size 2 mm each at a temperature of 30 °C and pH of 6. The process was optimized using L9 (3⁴) Taguchi Orthogonal Array (OA) technique with a regression coefficient (R ²) value of 0.9709, F value of 33.34 and p value of 0.0025. Scale-up studies involving 200-mL and 1-L rotating bed reactor (RBR) using immobilized beads were done and the results obtained are 20.21 U mL^-1 and 19.13 U mL^-1, respectively, the increased activity with immobilization accounts for reduced shear on cells due to increased stability as compared to the free-flowing cells.

Microbial community design: methods, applications, and opportunities

Microbial communities can perform a variety of behaviors that are useful in both therapeutic and industrial settings. Engineered communities that differ in composition from naturally occurring communities offer a unique opportunity for improving upon existing community functions and expanding the range of microbial community applications. This has prompted recent advances in various community design approaches including artificial selection procedures, reduction from existing communities, combinatorial evaluation of potential microbial combinations, and model-based in silico community optimization. Computational methods in particular offer a likely avenue toward improved synthetic community development going forward. This review introduces each class of design approach and surveys their recent applications and notable innovations, closing with a discussion of existing design challenges and potential opportunities for advancement.

Experimental and bioinformatics study for production of L-asparaginase from Bacillus licheniformis: a promising enzyme for medical application

A Bacillus licheniformis isolate with high l-asparaginase productivity was recovered upon screening two hundred soil samples. This isolate produces the two types of bacterial l-asparaginases, the intracellular type I and the extracellular type II. The catalytic activity of type II enzyme was much higher than that of type I and reached about 5.5 IU/ml/h. Bioinformatics analysis revealed that l-asparaginases of Bacillus licheniformis is clustered with those of Bacillus subtilis, Bacillus haloterans, Bacillus mojavensis and Bacillus tequilensis while it exhibits distant relatedness to l-asparaginases of other Bacillus subtilis species as well as to those of Bacillus amyloliquefaciens and Bacillus velezensis species. Upon comparison of Bacillus licheniformisl-asparaginase to those of the two FDA approved l-asparaginases of E. coli (marketed as Elspar) and Erwinia chrysanthemi (marketed as Erwinaze), it observed in a cluster distinct from- and with validly predicted antigenic regions number comparable to those of the two mentioned reference strains. It exhibited maximum activity at 40 °C, pH 8.6, 40 mM asparagine, 10 mM zinc sulphate and could withstand 500 mM NaCl and retain 70% of its activity at 70 °C for 30 min exposure time. Isolate enzyme productivity was improved by gamma irradiation and optimized by RSM experimental design (Box–Behnken central composite design). The optimum conditions for maximum l-asparaginase production by the improved mutant were 39.57 °C, 7.39 pH, 20.74 h, 196.40 rpm, 0.5% glucose, 0.1% ammonium chloride, and 10 mM magnesium sulphate. Taken together, Bacillus licheniformisl-asparaginase can be considered as a promising candidate for clinical application as antileukemic agent.

Effect of four trace elements on Paenibacillus polymyxa Pp-7250 proliferation, activity and colonization in ginseng

Trace elements are essential nutrients for the growth of microorganisms and play an important role in their proliferation. Hence, the purpose of this paper is to explore the optimal C and N sources for large-scale culture of Paenibacillus polymyxa, and to screen trace elements that can promote their proliferation and improve the activity. First, the concentration of Paenibacillus polymyxa Pp-7250, the number of spores were used as evaluation index. It was found that the four trace elements Cu2+, Fe2+, Mn2+, and Zn2+ could promote the proliferation of Paenibacillus polymyxa at their optimal concentrations. Next, when using wheat starch as carbon source and soybean meal as nitrogen source, it was most suitable for large-scale culture. Finally, field experiments were carried out, and it was discovered that the combination of four trace elements plus the wheat soybean meal group could significantly improve the disease prevention, growth promotion ability of Pp-7250 and its colonization in ginseng. Moreover, the ability of Pp-7250 to transform ginseng roots and leaf saponins were also significantly improved. The group also affected the rhizosphere bacterial community of ginseng and the number showed a significant promotion or inhibition.

Batch and fed-batch bioreactor studies for the enhanced production of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428

The effect of dissolved oxygen (DO) level and pH (controlled/uncontrolled) was first studied to enhance the production of novel glutaminase-free L-asparaginase by Pectobacterium carotovorum MTCC 1428 in a batch bioreactor. The optimum level of DO was found to be 20%. The production of L-asparaginase was found to be maximum when pH of the medium was maintained at 8.5 after 12 h of fermentation. Under these conditions, P. carotovorum produced 17.97 U/mL of L-asparaginase corresponding to the productivity of 1497.50 U/L/h. The production of L-asparaginase was studied in fed-batch bioreactor by feeding L-asparagine (essential substrate for production) and/or glucose (carbon source for growth) at the end of the reaction period of 12 h. The initial medium containing both L-asparagine and glucose in the batch mode and L-asparagine in the feeding stream was found to be the best combination for enhanced production of glutaminase-free L-asparaginase. Under this condition, the L-asparaginase production was increased to 38.8 U/mL, which corresponded to a productivity of 1615.8 U/L/h. The production and productivity were increased by 115.8% and 7.9%, respectively, both of which are higher than those obtained in the batch bioreactor experiments.

Optimization of Culture Conditions for Production of the Anti-Leukemic Glutaminase Free L-Asparaginase by Newly Isolated Streptomyces olivaceus NEAE-119 Using Response Surface Methodology

Among the antitumor drugs, bacterial enzyme L-asparaginase has been employed as the most effective chemotherapeutic agent in pediatric oncotherapy especially for acute lymphoblastic leukemia. Glutaminase free L-asparaginase producing actinomycetes were isolated from soil samples collected from Egypt. Among them, a potential culture, strain NEAE-119, was selected and identified on the basis of morphological, cultural, physiological, and biochemical properties together with 16S rRNA sequence as Streptomyces olivaceus NEAE-119 and sequencing product (1509 bp) was deposited in the GenBank database under accession number KJ200342. The optimization of different process parameters for L-asparaginase production by Streptomyces olivaceus NEAE-119 using Plackett-Burman experimental design and response surface methodology was carried out. Fifteen variables (temperature, pH, incubation time, inoculum size, inoculum age, agitation speed, dextrose, starch, L-asparagine, KNO₃, yeast extract, K₂HPO₄, MgSO₄·7H₂O, NaCl, and FeSO₄·7H₂O) were screened using Plackett-Burman experimental design. The most positive significant independent variables affecting enzyme production (temperature, inoculum age, and agitation speed) were further optimized by the face-centered central composite design-response surface methodology.

Optimization of selective production media for enhanced production of xylanases in submerged fermentation by Thielaviopsis basicola MTCC 1467 using L16 orthogonal array

Enzymes have been the centre of attention for researchers/industrialists worldwide due to their wide range of physiological, analytical, food/feed and industrial based applications. Among the enzymes explored for industrial applications, xylanases play an instrumental role in food/feed, textile/detergent, paper and biorefinery based application sectors. This study deals with the statistical optimization of xylanase production by Thielaviopsis basicola MTCC 1467 under submerged fermentation conditions using rice straw, as sole carbon source. Different fermentation parameters such as carbon source, nitrogen source, inorganic salts like KH2PO4, MgSO4 and pH of the medium were optimized at the individual and interactive level by Taguchi orthogonal array methodology (L16). All selected fermentation parameters influenced the enzyme production. Rice straw, the major carbon source mainly influenced the production of xylanase (~34 %). After media optimization, the yield of enzyme improved from 38 to ~60 IU/ml (161.5 %) indicating the commercial production of xylanase by T. basicola MTCC 1467. This study shows the potential of T. basicola MTCC 1467 for the efficient xylanase production under the optimized set of conditions.

Laccase production by Coriolopsis caperata RCK2011: optimization under solid state fermentation by Taguchi DOE methodology

Laccase production by Coriolopsis caperata RCK2011 under solid state fermentation was optimized following Taguchi design of experiment. An orthogonal array layout of L18 (2(1) × 3(7)) was constructed using Qualitek-4 software with eight most influensive factors on laccase production. At individual level pH contributed higher influence, whereas, corn steep liquor (CSL) accounted for more than 50% of the severity index with biotin and KH2PO4 at the interactive level. The optimum conditions derived were; temperature 30°C, pH 5.0, wheat bran 5.0 g, inoculum size 0.5 ml (fungal cell mass = 0.015 g dry wt.), biotin 0.5% w/v, KH2PO4 0.013% w/v, CSL 0.1% v/v and 0.5 mM xylidine as an inducer. The validation experiments using optimized conditions confirmed an improvement in enzyme production by 58.01%. The laccase production to the level of 1623.55 Ugds(-1) indicates that the fungus C. caperata RCK2011 has the commercial potential for laccase.

R. Dasari RK, Sajja V, Jacob AS, Sri Rami Reddy D. Optimization of l-Asparaginase Production by Isolated Aspergillus niger C4 from Sesame (black) Oil Cake under SSF using Box–Behnken Design in Column Bioreactor

l-Asparaginase production was investigated in the isolated Aspergillus niger C4 on sesame (black) oil cake using solid state fermentation in a column bioreactor. The main objective of the present study is optimizing the environmental conditions for l-Asparaginase production in a column bioreactor. In order to determine the effect of process variables on the yield of l-Asparaginase, by the way of response surface methodology, an experimental plan (Box–Behnken design) involving a design matrix of 15 trails was sketched. The design results were fitted with response surfaces. Empirical quadratic equations were fitted to the experimental data (BBD) relevant to the yields of l-Asparaginase, with three chosen variables (aeration, bed thickness and temperature). The statistical analysis revealed a maximum l-Asparaginase yield of 310 U/gds at the points where aeration, bed thickness and temperature were 0.44 vvm, 17.35 cm and 29.31°C, respectively.

Development and optimization of neutralizing antibody assays to monitor clinical immunogenicity

The development of an unwanted immune response to a protein therapeutic is a constant concern and necessitates careful monitoring of this class of drugs during clinical development. Neutralizing antibodies can have a significant impact on bioavailability, efficacy and safety of a protein therapeutic. Consequently, immunogenicity testing is required prior to obtaining regulatory approval and in some cases even after a product is marketed. Given the importance of this testing, it is critical that sensitive and robust assays are developed for detection of clinically relevant neutralizing antibodies. This review will describe considerations and current best practices for developing assays to detect neutralizing antibodies to protein therapeutics.

Efficient production of L-asparaginase from Bacillus licheniformis with low-glutaminase activity: optimization, scale up and acrylamide degradation studies

L-Asparaginase has potential as an anti-cancer drug and for prevention of acrylamide formation in fried and baked foods. Production of the enzyme by Bacillus licheniformis (RAM-8) was optimized by process engineering using a statistical modeling approach and a maximum yield of 32.26 IU/ml was achieved. The L-asparaginase exhibited glutaminase activity of only 0.8 IU/ml and would therefore be less prone to cause the side effects associated with asparaginase therapy compared to enzyme preparations with higher glutaminase activities. When production was carried out in a 30-L bioreactor, enzyme production reached 29.94 IU/ml in 15 h. The enzyme inhibited poly-acrylamide formation in 10% acrylamide solution and reduced acrylamide formation in fried potatoes by 80%.

Optimizing anaerobic digestion by selection of the immobilizing surface for enhanced methane production

Maximizing methane production while maintaining an appreciable level of process stability is a crucial challenge in the anaerobic digestion industry. In this study, the role of six parameters: the type of immobilizing supports, loading rate, inoculum levels, C:N ratio, trace nutrients concentrations and mixing rate, on methane production were investigated under thermophilic conditions (55 ± 1°C) with synthetic substrate medium. The immobilizing supports were Silica gel, Sand, Molecular Sieve and Dowex Marathon beads. A Taguchi Design of Experiment (DOE) methodology was employed to determine the effects of different parameters using an L(16) orthogonal array. Overall, immobilizing supports influenced methane production substantially (contributing 61.3% of the observed variation in methane yield) followed by loading rate and inoculum which had comparable influence (17.9% and 17.7% respectively). Optimization improved methane production by 153% (from 183 to 463 ml CH(4)l(-1)d(-1)).

Effect of medium composition and kinetic studies on extracellular and intracellular production of L-asparaginase from Pectobacterium carotovorum

Microbial L-asparaginase occupies a prominent place among biocatalysts owing to their ability to catalyze the reaction that hydrolyze the asparagine molecule. Effect of various medium components on the production of L-asparaginase in submerged fermentation by Pectobacterium carotovorum was studied for optimal nutrient requirements. Six different media compositions were tested for the L-asparaginase production keeping fermentation conditions constant at temperature 30 °C, initial pH 7.0 and agitation speed of 120 rpm. Maximum intracellular and extracellular L-asparaginase activity was obtained in the medium containing tryptone, yeast extract, monosodium glutamate, K₂HPO₄ and L-asparagine. These medium components were further optimized by central composite experimental design using response surface methodology. Maximum intracellular and extracellular L-asparaginase activity of 2.282 U/mL and 0.587 U/mL were obtained respectively at the late logarithmic phase in optimized media. Unstructured kinetic models were used to describe the cell growth and product formation kinetics. The unstructured models predicted the cell growth and product formation profile accurately with high coefficient of determination.

Improved production of L-asparaginase by Bacillus brevis cultivated in the presence of oxygen-vectors

The efficiency of three oxygen-vectors liquid paraffin, silicone oil and n-dodecane in the production of L-asparaginase by Bacillus brevis was evaluated at 4% (v/v) concentration. All of the three oxygen-vectors were found to exhibit a stimulatory effect on L-asparaginase activity. Liquid paraffin at 6% (v/v) resulted in 34% increase in the L-asparaginase activity accompanied by a 48% increase in the production of cell mass at a 10 L scale. This improvement in L-asparaginase activity and cell mass production in the presence of liquid paraffin can be related to the fact that liquid paraffin was capable of maintaining dissolved O2 concentration above 28% through out the course of the fermentation. Maintenance of the dissolved O2 concentration above 28% could be viewed in terms of an adequate oxygen supply to the rapidly dividing cells of the bacterium, which in turn resulted in enhancement in cell mass production and l-asparaginase activity.

Development of balanced medium composition for improved rifamycin B production by isolated Amycolatopsis sp. RSP-3

AIM

To develop optimum fermentation environment for enhanced rifamycin B production by isolated Amycolatopsis sp. RSP-3.

METHODS AND RESULTS

The impact of different fermentation parameters on rifamycin B production by isolated Amycolatopsis sp. RSP-3 was investigated using Taguchi methodology. Controlling fermentation factors were selected based on one variable at a time methodology. The isolated strain revealed more than 25% higher production compared to literature reports. Five different nutritional components (soyabean meal, glucose, potassium nitrate, calcium carbonate and barbital) and inoculum concentration showed impact on rifamycin B production at individual and interactive level. At optimized environment, 65% contribution was observed from selected fermentation parameters.

CONCLUSIONS

Soyabean meal and calcium carbonate were the most significant factors among the selected factors followed by barbital and potassium nitrate. Glucose, however, showed the least significance on rifamycin B production with this strain. A maximum of 5.12 g l(-1) rifamycin B production was achieved with optimized medium containing (g l(-1)) soyabean meal, 27; glucose, 100; potassium nitrate, 4; calcium carbonate, 3 and barbital, 1.2.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study signifies identification of balanced medium component concentrations for improved rifamycin B production by isolated Amycolatopsis sp. RSP-3. This strain requires organic and inorganic nitrogen sources for effective product yield. Yet at individual level, organic nitrogen source has c. nine-fold higher influence compared to inorganic one.