Production Of Iturin Research Articles

Process optimized for production of iturin A in biofilm reactor by Bacillus velezensis ND.

In this research, to provide an optimal growth medium for the production of iturin A, the concentrations of key amino acid precursors were optimized in shake flask cultures using the response surface method. The optimized medium were applied in a biofilm reactor for batch fermentation, resulting in enhanced production of iturin A. On this basis, a step-wise pH control strategy and a combined step-wise pH and temperature control strategy were introduced to further improve the production of iturin A. Finally, the fed-batch fermentation was performed based on combined step-wise pH and temperature control. The titer and productivity of iturin A reached 7.86 ± 0.23g/L and 65.50 ± 1.92mg/L/h, respectively, which were 37.65 and 65.20% higher than that before process optimization.

Crude lipopeptides from culture of Bacillus subtilis strain ET-1 against Podosphaera xanthii on Cucumis melo

The aim of this work was to evaluate the effectiveness of partially purified Iturin A and cell free supernatant (CFS) produced by the Bacillus subtilis strain ET-1 on control of powdery mildew. For this purpose, B. subtilis ET-1 strain was grown in a 21-L stirred-tank bioreactor with 10 litres of an already designed substrate for the production of Iturin A named High Medium Broth (HMB). At the end of culture, an Iturin A amount of 396.86 mg L-1 was determined in the supernatant purified from the cells by centrifugation. Then, the effect of CFS against the cucurbit powdery mildew fungus, Podosphaera xanthii was assessed on plants of Cucumis melo L. (cv Amarillo Oro) in greenhouse and in open-field conditions. For the greenhouse experiments, three different dilutions of supernatant containing 400, 40 and 4 mg L-1 Iturin A were used. Significant dose-dependent control effects were observed. In particular, a control disease of 100% was achieved at the highest concentration tested. In the subsequent open-field trials, a crude lipopeptide extract obtained by acid precipitation was analysed in addition to the CFS. The two conditions were tested at intermediate concentrations containing 100 ppm of Iturin A on plants artificially inoculated with P. xanthii and both showed strong disease control, similar to that observed with chemical fungicide. In conclusion, the results of the present work, while needing further study, open promising scenarios in the use of microbial lipopeptides, like Iturin family, as alternative control agents of plant diseases.

Production of antifungal iturins from vegetable straw: A combined chemical-bacterial process

A combined chemical-bacterial process was developed to convert vegetable straw waste to high value antifungal iturins. Straws from three widely cultivated vegetable (cucumber, tomato and pepper) were evaluated as feedstocks for iturin production. Microwave assisted hydrolysis with very dilute acid (0.2% w/w H2SO4) achieved efficient reducing sugar recovery. The high glucose concentration in non-detoxified hydrolysate from pepper straw facilitated the optimal growth of Bacillus amyloliquefaciens strain Cas02 and stimulated the production of iturin. The fermentation parameters were optimised to enhance the iturin production efficiency. The obtained fermentation extract was further purified using macroporous adsorption resin, resulting in an iturin-rich extract that exhibited strong antifungal activity against Alternaria alternata with an IC50 of 176.44 μg/mL. Each iturin homologue was identified using NMR. Overall, 1.58 g iturin-rich extract containing 164.06 mg/g iturins was obtained from 100 g pepper straw, illustrating the great potential of valorising pepper straw via this process.

Enhanced iturin a production in a two-compartment biofilm reactor by Bacillus velezensis ND.

In this study, a two-compartment biofilm reactor was designed for iturin A production. The biofilm reactor consists of a stirred-tank fermentor containing exclusively suspended cells and a packing column where the biofilm is attached. Polyester fiber with sphere shape and rough surfaces was chosen as the carrier of biofilm in packing column. Batch, fed-batch, and repeated-batch fermentation using Bacillus velezensis ND in the biofilm reactor were studied. Compared to conventional suspended cell fermentations, the productivity of iturin A in batch and fed-batch biofilm fermentation were increased by 66.7% and 63.3%, respectively. Maximum itutin A concentration of 6.8 ± 0.1g/L and productivity of 46.9 ± 0.2mg/L/h were obtained in fed-batch biofilm fermentation. Repeated-batch fermentation showed high stability, with almost same profile as batch fermentation. After a step-wise temperature control strategy was introduced in the biofilm reactor, productivity of iturin A was increased by 131.9% compared to suspended cell reactor. This superior performance of biofilm reactor confirms that it has great potential in industrial production of iturin A.

Production of iturin A by Bacillus velezensis ND and its biological control characteristics.

Bacillus subtilis, as a biocontrol bacterium, possess a variety of biological functions and the capacity to control plant pathogens. Iturin A is a biosurfactant with broad-spectrum antifungal activity produced by fermentation of B. subtilis. In this study, the dynamic parameters of solid-state fermentation (SSF) and submerged fermentation (SMF) of Bacillus velezensis ND were compared, and a method for producing iturin A with a yield of 12.46 g/kg utilizing SSF was proposed. It has significant advantages over SMF and has the highest yield of all previously reported studies. B. velezensis ND also contains protease activity, cellulase activity, iron-carrying activity, the ability to synthesis 3-indoleacetic acid (IAA), fixation nitrogen, and degrade phosphorus. In cotton pot experiments, it can effectively increase cotton growth and minimize Verticillium wilt. This strain's superior fermentation efficiency, biological function, and biocontrol ability are sufficient to demonstrate its promise for the development and use of biocontrol agents.

Enhanced production of iturin A by strengthening fatty acid synthesis modules in Bacillus amyloliquefaciens.

Iturin A is a biosurfactant with various applications, and its low synthesis capability limits its production and application development. Fatty acids play a critical role in cellular metabolism and target product syntheses, and the relationship between fatty acid supplies and iturin A synthesis is unclear. In this study, we attempted to increase iturin A production via strengthening fatty acid synthesis pathways in Bacillus amyloliquefaciens. First, acetyl-CoA carboxylase AccAD and ACP S-malonyltransferase fabD were overexpressed via promoter replacement, and iturin A yield was increased to 1.36 g/L by 2.78-fold in the resultant strain HZ-ADF1. Then, soluble acyl-ACP thioesterase derived from Escherichia coli showed the best performance for iturin A synthesis, as compared to those derived from B. amyloliquefaciens and Corynebacterium glutamicum, the introduction of which in HZ-ADF1 further led to a 57.35% increase of iturin A yield, reaching 2.14 g/L. Finally, long-chain fatty acid-CoA ligase LcfA was overexpressed in HZ-ADFT to attain the final strain HZ-ADFTL2, and iturin A yield reached 2.96 g/L, increasing by 6.59-fold, and the contents of fatty acids were enhanced significantly in HZ-ADFTL2, as compared to the original strain HZ-12. Taken together, our results implied that strengthening fatty acid supplies was an efficient approach for iturin A production, and this research provided a promising strain for industrial production of iturin A.

Enhanced Production of Iturin A-2 Generated from Bacillus velezensis T701 and the Antitumor Activity of Iturin A-2 against Human Gastric Carcinoma Cells

Enhanced Production of Iturin A-2 Generated from Bacillus velezensis T701 and the Antitumor Activity of Iturin A-2 against Human Gastric Carcinoma Cells

Isolation and characterization of a high iturin yielding Bacillus velezensis UV mutant with improved antifungal activity.

To isolate Bacillus velezensis mutants with improved antifungal activity for use in the biological control of phytopathogenic fungi, wild-type Bacillus velezensis KRF-001 producing iturin, surfactin, and fengycin was irradiated by ultraviolet (UV) rays. The in vitro and in vivo antifungal activities of UV mutants and characterization of the cyclic lipopeptides produced by a selected mutant were examined. A mutant strain yielding high levels of iturin showed over 2-fold higher antifungal activity than the wild-type against Fusarium oxysporum. A potent suppressive effect of the mutant was also observed on spore germination of Botrytis cinerea, the causative agent of cucumber gray mold, at different butanol extract concentrations. Further analysis of the mutant by real-time PCR and high-performance liquid chromatography revealed increased expression of iturin and surfactin biosynthesis genes as well as enhanced production of iturin and surfactin metabolites. However, the amounts of fengycin obtained from the mutant strain BSM54 were significantly lesser than those of iturin and surfactin. Particularly, iturin A production by the mutant was 3.5-fold higher than that of the wild-type, suggesting that the higher antifungal activity of the mutant against F. oxysporum resulted from the increased expression of biosynthesis genes associated with iturin production. The commercial greenhouse experiment using soil naturally infested with Sclerotinia sclerotiorum (sclerotinia rot) and F. oxysporum (fusarium wilt) showed that the mutant strain reduced sclerotinia rot and fusarium wilt diseases (P = 0.05) more effectively than the wild-type and commercially available product Cillus® in Korea. These results suggest that the mutant with high iturin yield is a potential candidate for the development of a biological control agent in agriculture.

Simultaneous hydrolysis with lipase and fermentation of rapeseed cake for iturin A production by Bacillus amyloliquefaciens CX-20

BackgroundRapeseed cake (RSC), as the intermediate by-product of oil extraction from the seeds of Brassica napus, can be converted into rapeseed meal (RSM) by solvent extraction to remove oil. However, compared with RSM, RSC has been rarely used as a raw material for microbial fermentation, although both RSC and RSM are mainly composed of proteins, carbohydrates and minerals. In this study, we investigated the feasibility of using untreated low-cost RSC as nitrogen source to produce the valuable cyclic lipopeptide antibiotic iturin A using Bacillus amyloliquefaciens CX-20 in submerged fermentation. Especially, the effect of oil in RSC on iturin A production and the possibility of using lipases to improve the iturin A production were analyzed in batch fermentation.ResultsThe maximum production of iturin A was 0.82 g/L at the optimal initial RSC and glucose concentrations of 90 and 60 g/L, respectively. When RSC was substituted with RSM as nitrogen source based on equal protein content, the final concentration of iturin A was improved to 0.95 g/L. The production of iturin A was further increased by the addition of different lipase concentrations from 0.1 to 5 U/mL into the RSC medium for simultaneous hydrolysis and fermentation. At the optimal lipase concentration of 0.5 U/mL, the maximal production of iturin A reached 1.14 g/L, which was 38.15% higher than that without any lipase supplement. Although rapeseed oil and lipase were firstly shown to have negative effects on iturin A production, and the effect would be greater if the concentration of either was increased, their respective negative effects were reduced when used together.ConclusionsAppropriate relative concentrations of lipase and rapeseed oil were demonstrated to support optimal iturin A production. And simultaneous hydrolysis with lipase and fermentation was an effective way to produce iturin A from RSC using B. amyloliquefaciens CX-20.

Enhanced production of iturin A in Bacillus amyloliquefaciens by genetic engineering and medium optimization

Brown spot disease, caused by Alternaria alternate, is one of the most destructive leaf spot diseases that made a major impact on tobacco growing. Biocontrol has attracted increasing attentions as its features of environmental friendship, promoting plant growth, etc. Iturin A, with broad spectrum antifungal activity, is a kind of biosurfactant that mainly produced by Bacillus. In this study, the promoter of iturin A synthetase cluster of Bacillus amyloliquefaciens HZ-12 was respectively replaced by promoters P43, PbacA, PsrfA and Pylb, our results implied that transcriptional level of gene ituD and iturin A titer showed consistent change trends, and PbacA was proven as the most efficient promoter, iturin A titer of which reached 950.08 ± 19.43 mg/L. Furthermore, regulator gene abrB was deleted to release the repression effect of AbrB on PbacA, ituD transcriptional level and iturin A titer were increased by 133.25 % and 20.88 %, respectively. Then, the maximum iturin A titer reached 2013.43 ± 32.86 mg/L by optimizing fermentation medium, increased by 392.15 % compared to the original (408.97 ± 21.35 mg/L). Finally, our results demonstrated that enhancing iturin A synthetic capability benefited the suppression of A. alternate. Collectively, this study provided a promising strain with an efficient fermentation medium for large-scale industrial production of iturin A.

Influence of Phenotypic Dissociation in Bacillus subtilis Strain ET-1 on Iturin A Production.

Iturin A is a very important cyclic lipopeptide produced by several B. subtilis strains and has large commercial and therapeutic application potentials but its production on industrial scale has not been realized yet. In the present study, we have observed that the strain ET-1 of Bacillus subtilis, a producer of Iturin A, can present at least three different colony morphologies, which we arbitrarily called Rough, Smooth, and Mucoid morphotypes (R-, S-, and M-form). Performing HPLC analysis, a significant difference between the amounts of Iturin A produced by the three morphotypes was found. The morphotype R-form showed the highest productivity with yields about 10 and 100 times higher than morphotypes S and M, respectively. The results show that the production of Iturin A by B. subtilis could be strongly influenced by the phenotypic heterogeneity of cells within the inoculum. Indeed, we have observed that, pasteurizing the inoculum before seeding in order to improve the homogeneity removing the phenotypes less able to synthesize the Iturin A, its yields in a bench-scale production could be significantly improved. This can represent an important control factor also at industrial scale to improve the Iturin A yields, the robustness, the replicability, and consequently the cost-effectiveness of fermentation processes.

Enhanced production of antifungal lipopeptide iturin A by Bacillus amyloliquefaciens LL3 through metabolic engineering and culture conditions optimization

BackgroundIturins, which belong to antibiotic cyclic lipopeptides mainly produced by Bacillus sp., have the potential for application in biomedicine and biocontrol because of their hemolytic and antifungal properties. Bacillus amyloliquefaciens LL3, isolated previously by our lab, possesses a complete iturin A biosynthetic pathway as shown by genomic analysis. Nevertheless, iturin A could not be synthesized by strain LL3, possibly resulting from low transcription level of the itu operon.ResultsIn this work, enhanced transcription of the iturin A biosynthetic genes was implemented by inserting a strong constitutive promoter C2up into upstream of the itu operon, leading to the production of iturin A with a titer of 37.35 mg l−1. Liquid chromatography-mass spectrometry analyses demonstrated that the strain produced four iturin A homologs with molecular ion peaks at m/z 1044, 1058, 1072 and 1086 corresponding to [C14 + 2H]2+, [C15 + 2H]2+, [C16 + 2H]2+ and [C17 + 2H]2+. The iturin A extract exhibited strong inhibitory activity against several common plant pathogens. The yield of iturin A was improved to 99.73 mg l−1 by the optimization of the fermentation conditions using a response surface methodology. Furthermore, the yield of iturin A was increased to 113.1 mg l−1 by overexpression of a pleiotropic regulator DegQ.ConclusionsTo our knowledge, this is the first report on simultaneous production of four iturin A homologs (C14–C17) by a Bacillus strain. In addition, this study suggests that metabolic engineering in combination with culture conditions optimization may be a feasible method for enhanced production of bacterial secondary metabolites.

Components of rice husk biochar in promoting the growth, sporulation and iturin A production of Bacillus sp. strain IA.

In a previously study, the Bacillus sp. strain IA was successfully isolated with high sensitivity to rice husk biochar (RHB). Moreover, RHB promoted an antibiotic iturin A production by strain IA. In order to develop the biocontrol agent, we attempted to reveal the functions of the RHB in promoting the production of iturin A by strain IA. The promotion effects of growth, sporulation and iturin A production of strain IA by the RHB were explained as follows. First, the manganese ion, released from RHB, promoted the sporulation and iturin A production of strain IA. Second, the silicon dioxide contained in RHB adsorbed the metabolic inhibitor(s) and promoted the iturin A production of strain IA. Finally, the combination of manganese ion and silicon dioxide promoted the growth, sporulation and iturin A production of the Bacillus sp. strain IA. To culture strain IA in the medium combining manganese ion and silicon dioxide, the total cells, spore cells and iturin A production increased 15 times, 10,000 times and 18 times higher than the control medium, respectively.

Plant Growth Enhancement, Disease Resistance, and Elemental Modulatory Effects of Plant Probiotic Endophytic Bacillus sp. Fcl1.

Endophytic bacteria have already been studied for their beneficial support to plants to manage both biotic and abiotic stress through an array of well-established mechanisms. They have either direct or indirect impact on mobilizing diverse nutrients and elements from soil to plants. However, detailed insight into the fine-tuning of plant elemental composition by associated microorganism is very limited. In this study, endophytic Bacillus Fcl1 characterized from the rhizome of Curcuma longa was found to have broad range of plant growth-promoting and biocontrol mechanisms. The organism was found to have indole acetic acid and 1-aminocyclopropane-1-carboxylate deaminase production properties along with nitrogen fixation. The Bacillus Fcl1 could also inhibit diverse phytopathogens as confirmed by dual culture and well diffusion. By LC-MS/MS analysis, chemical basis of its antifungal activity has been proved to be due to the production of iturin A and a blend of surfactin compounds. Moreover, the organism was found to induce both plant growth and disease resistance in vivo in model plant system. Because of these experimentally demonstrated multiple plant probiotic features, Bacillus Fcl1 was selected as a candidate organism to study its role in modulation of plant elemental composition. ICP-MS analysis of Bacillus Fcl1-treated plants provided insight into relation of bacterial interaction with elemental composition of plants.

Agricultural potential of rhizospheric Bacillus subtilis strains exhibiting varied efficiency of surfactin production

Six Bacillus subtilis strains collected from broad-leaved trees rhizosphere and exhibiting an ability of surfactin production were investigated as potent plant biofertilizers with biocontrol activity. Lipopeptide (LP) biosurfactants were extracted by a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure proposed as a quick and effective method of isolating LP biosurfactants. Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF) was applied to detect the lipopeptides. Predominant peaks at m/z 1016, 1030, 1044, 1058 and 1072 were putatively assigned as surfactin Na adducts possess a Glu-Leu-Leu-Val-Asp-Leu–Leu peptide and the β-OH fatty acid with a different length (C13-C16) whereas m/z 1016 was C13 surfactin Na adduct with Val in position 7 on the peptide moiety. Four other ions m/z 1051, 1065, 1079 and 1093 were recognized as iturin A Na adducts. Five fengycin homologues with Na adducts (m/z 1471, 1485, 1499, 1513 and 1527) were also determined. The quantitative analyses of the compounds were performed with the use of liquid chromatography-mass spectrometry (LC–MS/MS). Strains IM 7, IM 16 and IM 17 cultivated in Luria-Bertani medium for 48h produced surfactin alone at the concentrations below 10mgl−1. In contrast, strains KP7, IM 13 and IM 14 produced surfactin much more efficiently. Surfactin concentrations in 72-h-old cultures reached 100.3, 55.3 and 124.4mgl−1, respectively and were accompanied by the production of iturin in concentrations 5.7, 142.5 and 2.3mgl−1, respectively. Additionally, in Cooper’s medium, strain KP7 increased twofold the production of surfactin and iturin. Only surfactin overproducers (KP7, IM 13 and IM 14) exhibited swarming motility and formed biofilms, limited the growth of Botrytis cinerea and Aspergillus flavus strains, produced cellulases and inulinases and enhanced cucumber seed germination in vitro. All examined surfactin overproducers produced siderophores and, additionally, KP7 and IM 14 solubilized phosphates. Among all examined surfactin overproducers only IM 13 during the growth in the presence of F. oxysporum mycelium (in dual liquid culture) increased about twofold surfactin and iturin secretion and almost completely suppressed fungal biomass growth. The obtained results revealed that the studied surfactin overproducers were equipped with various plant growth-promoting (PGP) traits allowing them to promote plant development in a diverse manner.

Preparation and characterization of iturin A microcapsules in sodium alginate/poly(γ-glutamic acid) by spray drying

ABSTRACTIturin A is a valuable biopesticide because of its strong antifungal effect, low toxicity, and wide antimicrobial spectrum. However, the current formulation for iturin A is unstable and not sustained in the field. Thus, the aim of this work was to develop stable microcapsules containing iturin A by spray drying. The optimal technical parameters for the production of iturin A microcapsules include sodium alginate and poly(γ-glutamic acid) for the wall materials (1:1(W:W)), 180°C for the inlet temperature, and 5:1 (V:W) for the core-to-wall ratio. The iturin A microcapsules have a spherical shape, good sustained release, high ultraviolet resistance, and are stable in storage.

Statistical optimization of antifungal iturin A production from Bacillus amyloliquefaciens RHNK22 using agro-industrial wastes.

Biosurfactants are secondary metabolites with surface active properties and have wide application in agriculture, industrial and therapeutic products. The present study was aimed to screen bacteria for the production of biosurfactant, its characterization and development of a cost effective media formulation for iturin A production. A total of 100 bacterial isolates were isolated from different rhizosphere soil samples by enrichment culture method and screened for biosurfactant activity. Twenty isolates were selected for further studies based on their biosurfactant activity [emulsification index (EI%), emulsification assay (EA), surface tension (ST) reduction] and antagonistic activity. Among them one potential isolate Bacillus sp. RHNK22 showed good EI% and EA with different hydrocarbons tested in this study. Using biochemical methods and 16S rRNA gene sequence, it was identified as Bacillus amyloliquefaciens. Presence of iturin A in RHNK22 was identified by gene specific primers and confirmed as iturin A by FTIR and HPLC. B. amyloliquefaciens RHNK22 exhibited good surface active properties and antifungal activity against Sclerotium rolfsii and Macrophomina phaseolina. For cost-effective production of iturin A, 16 different agro-industrial wastes were screened as substrates, and Sunflower oil cake (SOC) was favouring high iturin A production. Further, using response surface methodology (RSM) model, there was a 3-fold increase in iturin A production (using SOC 4%, inoculum size 1%, at pH 6.0 and 37 °C temperature in 48 h). This is the first report on using SOC as a substrate for iturin A production.

User-friendly optimization approach of fed-batch fermentation conditions for the production of iturin A using artificial neural networks and support vector machine

In the field of microbial fermentation technology, how to optimize the fermentation conditions is of great crucial for practical applications. Here, we use artificial neural networks (ANNs) and support vector machine (SVM) to offer a series of effective optimization methods for the production of iturin A. The concentration levels of asparagine (Asn), glutamic acid (Glu) and proline (Pro) (mg/L) were set as independent variables, while the iturin A titer (U/mL) was set as dependent variable. General regression neural network (GRNN), multilayer feed-forward neural networks (MLFNs) and the SVM were developed. Comparisons were made among different ANNs and the SVM. The GRNN has the lowest RMS error (457.88) and the shortest training time (1 s), with a steady fluctuation during repeated experiments, whereas the MLFNs have comparatively higher RMS errors and longer training times, which have a significant fluctuation with the change of nodes. In terms of the SVM, it also has a relatively low RMS error (466.13), with a short training time (1 s). According to the modeling results, the GRNN is considered as the most suitable ANN model for the design of the fed-batch fermentation conditions for the production of iturin A because of its high robustness and precision, and the SVM is also considered as a very suitable alternative model. Under the tolerance of 30%, the prediction accuracies of the GRNN and SVM are both 100% respectively in repeated experiments.

Direct bio-utilization of untreated rapeseed meal for effective iturin A production by Bacillus subtilis in submerged fermentation.

The feasibility of using untreated rapeseed meal as a nitrogen source for iturin A production by Bacillus subtilis 3–10 in submerged fermentation was first evaluated by comparison with two different commercial nitrogen sources of peptone and ammonium nitrate. A significant promoting effect of rapeseed meal on iturin A production was observed and the maximum iturin A concentration of 0.60 g/L was reached at 70 h, which was 20% and 8.0 fold higher than that produced from peptone and ammonium nitrate media, respectively. It was shown that rapeseed meal had a positive induction effect on protease secretion, contributing to the release of soluble protein from low water solubility solid rapeseed meal for an effective supply of available nitrogen during fermentation. Moreover, compared to raw rapeseed meal, the remaining residue following fermentation could be used as a more suitable supplementary protein source for animal feed because of the great decrease of major anti-nutritional components including sinapine, glucosinolate and its degradation products of isothiocyanate and oxazolidine thione. The results obtained from this study demonstrate the potential of direct utilization of low cost rapeseed meal as a nitrogen source for commercial production of iturin A and other secondary metabolites by Bacillus subtilis.

The artificial neural network approach based on uniform design to optimize the fed-batch fermentation condition: application to the production of iturin A.

BackgroundIturin A is a potential lipopeptide antibiotic produced by Bacillus subtilis. Optimization of iturin A yield by adding various concentrations of asparagine (Asn), glutamic acid (Glu) and proline (Pro) during the fed-batch fermentation process was studied using an artificial neural network-genetic algorithm (ANN-GA) and uniform design (UD). Here, ANN-GA based on the UD data was used for the first time to analyze the fed-batch fermentation process. The ANN-GA and UD methodologies were compared based on their fitting ability, prediction and generalization capacity and sensitivity analysis.ResultsThe ANN model based on the UD data performed well on minimal statistical designed experimental number and the optimum iturin A yield was 13364.5 ± 271.3 U/mL compared with a yield of 9929.0 ± 280.9 U/mL for the control (batch fermentation without adding the amino acids). The root-mean-square-error for the ANN model with the training set and test set was 4.84 and 273.58 respectively, which was more than two times better than that for the UD model (32.21 and 483.12). The correlation coefficient for the ANN model with training and test sets was 100% and 92.62%, respectively (compared with 99.86% and 78.58% for UD). The error% for ANN with the training and test sets was 0.093 and 2.19 respectively (compared with 0.26 and 4.15 for UD). The sensitivity analysis of both methods showed the comparable results. The predictive error of the optimal iturin A yield for ANN-GA and UD was 0.8% and 2.17%, respectively.ConclusionsThe satisfactory fitting and predicting accuracy of ANN indicated that ANN worked well with the UD data. Through ANN-GA, the iturin A yield was significantly increased by 34.6%. The fitness, prediction, and generalization capacities of the ANN model were better than those of the UD model. Further, although UD could get the insight information between variables directly, ANN was also demonstrated to be efficient in the sensitivity analysis. The results of these comparisons indicated that ANN could be a better alternative way for fermentation optimization with limited number of experiments.