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

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 ± 0.23 g/L and 65.50 ± 1.92 mg/L/h, respectively, which were 37.65 and 65.20% higher than that before process optimization.

Classification, application, multifarious activities and production improvement of lipopeptides produced by Bacillus

Lipopeptides, a class of compounds consisting of a peptide ring and a fatty acid chain, are secondary metabolites produced by Bacillus spp. As their hydrophilic and oleophilic properties, lipopeptides are widely used in food, medicine, environment and other industrial or agricultural fields. Compared with artificial synthetic surfactants, microbial lipopeptides have the advantages of low toxicity, high efficiency and versatility, resulting in urgent market demand and broad development prospect of lipopeptides. However, due to the complex metabolic network and precursor requirements of synthesis, the specific and strict synthesis pathway, and the coexistence of multiple homologous substances, the production of lipopeptides by microorganisms has the problems of high cost and low production efficiency, limiting the mass production of lipopeptides and large-scale application in industry. This review summarizes the types of Bacillus-produced lipopeptides and their biosynthetic pathways, introduces the versatility of lipopeptides, and describes the methods to improve the production of lipopeptides, including genetic engineering and optimization of fermentation conditions.

Enhanced Iturin A Production of Engineered Bacillus amyloliquefaciens by Knockout of Endogenous Plasmid and Rap Phosphatase Genes

Iturin A biosynthesis has garnered considerable interest, yet bottlenecks persist in its low productivity in wild strains and the ability to engineer Bacillus amyloliquefaciens producers. This study reveals that deleting the endogenous plasmid, plas1, from the wild-type B. amyloliquefaciens HM618 notably enhances iturin A synthesis, likely related to the effect of the Rap phosphatase gene within plas1. Furthermore, inactivating Rap phosphatase-related genes (rapC, rapF, and rapH) in the genome of the strain also improved the iturin A level and specific productivity while reducing cell growth. Strategic rap genes and plasmid elimination achieved a synergistic balance between cell growth and iturin A production. Engineered strain HM-DR13 exhibited an increase in iturin A level to 849.9 mg/L within 48 h, significantly shortening the production period. These insights underscore the critical roles of endogenous plasmids and Rap phosphatases in iturin A biosynthesis, presenting a novel engineering strategy to optimize iturin A production in B. amyloliquefaciens.

Unlocking the potential of biosurfactants: Production, applications, market challenges, and opportunities for agro-industrial waste valorization

Biosurfactants are eco-friendly compounds with unique properties and promising potential as sustainable alternatives to chemical surfactants. The current review explores the multifaceted nature of biosurfactant production and applications, highlighting key fermentative parameters and microorganisms able to convert carbon-containing sources into biosurfactants. A spotlight is given on biosurfactants' obstacles in the global market, focusing on production costs and the challenges of large-scale synthesis. Innovative approaches to valorizing agro-industrial waste were discussed, documenting the utilization of lignocellulosic waste, food waste, oily waste, and agro-industrial wastewater in the segment. This strategy strongly contributes to large-scale, cost-effective, and environmentally friendly biosurfactant production, while the recent advances in waste valorization pave the way for a sustainable society.

CRISPR-dCpf1 mediated whole genome crRNA inhibition library for high-throughput screening of growth characteristic genes in Bacillus amyloliquefaciens LB1ba02

Bacillus amyloliquefaciens LB1ba02 is generally recognized as food safe (GRAS) microbial host and important enzyme-producing strain in the industry. However, autolysis affects the growth of bacteria, further affecting the yield of target products. Besides, the restriction-modification system, existed in B. amyloliquefaciens LB1ba02, results in a low transformation efficiency, which further leads to a lack of high-throughput screening tools. Here, we constructed a genome-wide crRNA inhibition library based on the CRISPR/dCpf1 system and high-throughput screening of related genes affecting the cell growth and autolysis using flow cytometry in B. amyloliquefaciens LB1ba02. The whole genome crRNA library was first validated for resistance to the toxic chemical 5-fluorouracil, and then used for validation of essential genes. In addition, seven gene loci (oppD, flil, tuaA, prmA, sigO, hslU, and GE03231) that affect the growth characteristics of LB1ba02 were screened. Among them, the Opp system had the greatest impact on growth. When the expression of operon oppA-oppB-oppC-oppD-oppF was inhibited, the cell growth difference was most significant. Inhibition of other sites could also promote rapid growth of bacteria to varying degrees; however, inhibition of GE03231 site accelerated cell autolysis. Therefore, the whole genome crRNA inhibition library is well suited for B. amyloliquefaciens LB1ba02 and can be further applied to high-throughput mining of other functional genes.

Biosurfactants: Secondary Metabolites Involved in the Process of Bioremediation and Biofilm Removal

The search for environmentally friendly methods to remove persistent substances such as organic pollutants and sessile communities such as biofilms that severely affect the environment and human health resulted in biosurfactant discovery. Owing to their low level of toxicity and high biodegradability, biosurfactants are increasingly preferred to be used for removal of pollutants from nature. These amphipathic molecules can be synthesized inexpensively, employing cheap substrates such as agricultural and industrial wastes. Recent progress has been made in identifying various biosurfactants that can be used to remove organic pollutants and harmful microbial aggregates, as well as novel microbial strains that produce these surface-active molecules to survive in a hydrocarbon-rich environment. This review focuses on the identification and understanding the role of biosurfactants and the microorganisms involved in the removal of biofilms and remediation of xenobiotics and various types of hydrocarbons such as crude oil, aromatic hydrocarbons, n-alkanes, aliphatic hydrocarbons, asphaltenes, naphthenes, and other petroleum products. This property of biosurfactant is very important as biofilms are of great concern due to their impact on the environment, public health, and industries worldwide. This work also includes several advanced molecular methods that can be used to enhance the production of biosurfactants by the microorganisms studied.

Biotechnological potential of microbial bio-surfactants, their significance, and diverse applications

Globally, there is a huge demand for chemically available surfactants in many industries, irrespective of their detrimental impact on the environment. Naturally occurring green sustainable substances have been proven to be the best alternative for reducing reliance on chemical surfactants and promoting long-lasting sustainable development. The most frequently utilized green active biosurfactants, which are made by bacteria, yeast, and fungi, are discussed in this review. These biosurfactants are commonly originated from contaminated sites, the marine ecosystem, and the natural environment, and it holds great potential for environmental sustainability. In this review, we described the importance of biosurfactants for the environment, including their biodegradability, low toxicity, environmental compatibility, and stability at a wide pH range. In this review, we have also described the various techniques that have been utilized to characterize and screen the generation of microbial biosurfactants. Also, we reviewed the potential of biosurfactants and its emerging applications in the foods, cosmetics, pharmaceuticals, and agricultural industries. In addition, we also discussed the ways to overcome problems with expensive costs such as low-cost substrate media formulation, gravitational techniques, and solvent-free foam fractionation for extraction that could be employed during biosurfactant production on a larger scale.

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.

Sustainable production of biosurfactants via valorisation of industrial wastes as alternate feedstocks

Globally, the rapid increase in the human population has given rise to a variety of industries, which have produced a variety of wastes. Due to their detrimental effects on both human and environmental health, pollutants from industry have taken centre stage among the various types of waste produced. The amount of waste produced has therefore increased the demand for effective waste management. In order to create valuable chemicals for sustainable waste management, trash must be viewed as valuable addition. One of the most environmentally beneficial and sustainable choices is to use garbage to make biosurfactants. The utilization of waste in the production of biosurfactant provides lower processing costs, higher availability of feedstock and environmental friendly product along with its characteristics. The current review focuses on the use of industrial wastes in the creation of sustainable biosurfactants and discusses how biosurfactants are categorized. Waste generation in the fruit industry, agro-based industries, as well as sugar-industry and dairy-based industries is documented. Each waste and wastewater are listed along with its benefits and drawbacks. This review places a strong emphasis on waste management, which has important implications for the bioeconomy. It also offers the most recent scientific literature on industrial waste, including information on the role of renewable feedstock for the production of biosurfactants, as well as the difficulties and unmet research needs in this area.

Artificial consortia of Bacillus amyloliquefaciens HM618 and Bacillus subtilis for utilizing food waste to synthetize iturin A

Food waste is a cheap and abundant organic resource that can be used as a substrate for the production of the broad-spectrum antifungal compound iturin A. To increase the efficiency of food waste biotransformation, different artificial consortia incorporating the iturin A producer Bacillus amyloliquefaciens HM618 together with engineered Bacillus subtilis WB800N producing lipase or amylase were constructed. The results showed that recombinant B. subtilis WB-A13 had the highest amylase activity of 23406.4 U/mL, and that the lipase activity of recombinant B. subtilis WB-L01 was 57.5 U/mL. When strain HM618 was co-cultured with strain WB-A14, the higher yield of iturin A reached to 7.66 mg/L, representing a 32.9% increase compared to the pure culture of strain HM618. In the three-strain consortium comprising strains HM618, WB-L02, and WB-A14 with initial OD₆₀₀ values of 0.2, 0.15, and 0.15, respectively, the yield of iturin A reached 8.12 mg/L, which was 38.6% higher than the control. Taken together, artificial consortia of B. amyloliquefaciens and recombinant B. subtilis can produce an increased yield of iturin A, which provides a new strategy for the valorization of food waste.

S. R, Hameeda B, El Enshasy HA, Hanapi SZ, Sayyed RZ. Biosurfactant producing multifarious Streptomyces puniceus RHPR9 of Coscinium fenestratum rhizosphere promotes plant growth in chilli

The present study involves isolation of Streptomyces spp. from rhizosphere of Coscinium fenestratum Gaertn, an endangered medicinal plant from Western Ghats of Karnataka, India. Four potential isolates were identified by 16S rRNA sequencing as Streptomyces sp. RHPR3, Streptomyces puniceus RHPR9, Streptomyces sp. RHPR14 and Streptomyces mediolani RHPR25. An enrichment culture method was used for the isolation of Streptomyces spp. for biosurfactant activity. Among four potential Streptomyces spp., S. puniceus RHPR9 showed highest Emulsification index (EI) (78±0.2%) and Emulsification assay (EA) (223±0.2 EU mL^-1). Thin layer chromatography, Fourier transform infrared spectroscopy (FTIR) and mass spectrometric analysis revealed that as glycolipid. Further confirmed by presence of fatty acids like hexanoic acid methyl ester, decanoic acid by Gas chromatography mass spectroscopy (GC-MS) analysis. S. puniceus RHPR9 showed a significant IAA production (41μg mL^-1), solubilized P (749.1 μg mL^-1), growth promotion of chilli (Capsicum annuum L.) was evaluated using paper towel method and greenhouse conditions. S. puniceus RHPR9 showed a significant increase in seed vigor index (2047) and increase in plant biomass (65%) when compared to uninoculated control. To our knowledge, this is the first report on epiphytic S. puniceus RHPR9 isolated from an endangered medicinal plant C. fenestratum Gaertn, for biosurfactant production and plant growth promotion activities.

Lipopeptide Biosurfactants from Bacillus spp.: Types, Production, Biological Activities, and Applications in Food

Biosurfactants are a functionally and structurally heterogeneous group of biomolecules produced by multiple filamentous fungi, yeast, and bacteria, and characterized by their distinct surface and emulsifying ability. The genus Bacillus is well studied for biosurfactant production as it produces various types of lipopeptides, for example, lichenysins, bacillomycin, fengycins, and surfactins. Bacillus lipopeptides possess a broad spectrum of biological activities such as antimicrobial, antitumor, immunosuppressant, and antidiabetic, in addition to their use in skincare. Moreover, Bacillus lipopeptides are also involved in various food products to increase the antimicrobial, surfactant, and emulsification impact. From the previously published articles, it can be concluded that biosurfactants have strong potential to be used in food, healthcare, and agriculture. In this review article, we discuss the versatile functions of lipopeptide Bacillus species with particular emphasis on the biological activities and their applications in food.

Iturin: cyclic lipopeptide with multifunction biological potential

Iturin, a metabolite produced by Bacillus subtilis, has a broad-spectrum antibacterial effect, and because they are secreted in the rhizosphere of plants, iturins are often mixed with many organic molecules. In recent years, people have improved their separation and purification methods but still cannot achieve simple and effective procedures, making Iturins an ideal biological control agent for insects and bacteria; commercial value still cannot be realized. With the in-depth studies of Iturins, its anti-cancer, hemolysis and other biological activities have gradually been discovered. This article reviews the branches of the Iturin family, structural features of these metabolite, separation and purification methods used for producing it, culture optimization, and various biological activities of the Iturin family, such as insecticidal, antibacterial, hemolytic and anticarcinogenic properties, among others have been summarized. Furthermore, this review revealed some commercial applications of Iturins and their relevance in research works. For example, in food packaging, clean water has good development potential.This can promote the commercial application of Iturins instead of other chemical and biological control agents that are environmentally friendly, pollution-free and have no side effects on humans. Furthermore, work documented anticancer, hemolytic and other biological activities of Iturin.

Iturin A Induces Resistance and Improves the Quality and Safety of Harvested Cherry Tomato

The soft rot disease caused by Rhizopus stolonifer is an important disease in cherry tomato fruit. In this study, the effect of iturin A on soft rot of cherry tomato and its influence on the storage quality of cherry tomato fruit were investigated. The results showed that 512 μg/mL of iturin A could effectively inhibit the incidence of soft rot of cherry tomato fruit. It was found that iturin A could induce the activity of resistance-related enzymes including phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), glucanase (GLU), and chitinase (CHI), and active oxygen-related enzymes including ascorbate peroxidases (APX), superoxide dismutases (SOD), catalases (CAT), and glutathione reductase (GR) of cherry tomato fruit. In addition, iturin A treatment could slow down the weight loss of cherry tomato and soften the fruit. These results indicated that iturin A could retard the decay and improve the quality of cherry tomato fruit by both the inhibition growth of R. stolonifera and the inducing the resistance.

Two Novel Bacillus Strains (subtilis and simplex Species) with Promising Potential for the Biocontrol of Zymoseptoria tritici, the Causal Agent of Septoria Tritici Blotch of Wheat

Two novel Algerian field-collected isolates were selected for their antifungal activity against Zymoseptoria tritici (teleomorph Mycosphaerella graminicola). The novel strains, termed Alg.24B1 and Alg.24B2, were identified as Bacillus subtilis and Bacillus simplex since their respective nucleotide sequences of the 16S rRNA gene were 100% and 99.93% identical to those of B. subtilis and B. simplex, respectively. The antifungal activities of Alg.24B1 and Alg.24B2 were evaluated by the well diffusion method and compared to those of other Bacillus species. The maximum activity was obtained after two days of confrontation of the bacterial strain supernatants with the fungus for Alg.24B1 and three days for Alg.24B2. Furthermore, the metabolites responsible for the antifungal activity of both strains were detected by the investigation of either gene presence (PCR) or molecule production (activity detection of lytic enzymes and HPLC detection of lipopeptides). Overall, this study showed that in addition to their ability to produce lytic enzymes (protease and β-glucanase), both strains coproduce three types of lipopeptides viz. surfactin, iturin, and fengycin. Thus, the biofungicide activity of both strains may be a result of a combination of different mechanisms. Therefore, they had a great potential to be used as biocontrol agents to effectively manage septoria tritici blotch of wheat (STB).

Bioconversion of agro-industry sourced biowaste into biomaterials via microbial factories - A viable domain of circular economy

Global increase in demand for food supply has resulted in surplus generation of wastes. What was once considered wastes, has now become a resource. Studies were carried out on the conversion of biowastes into wealth using methods such as extraction, incineration and microbial intervention. Agro-industry biowastes are promising sources of carbon for microbial fermentation to be transformed into value-added products. In the era of circular economy, the goal is to establish an economic system which aims to eliminate waste and ensure continual use of resources in a close-loop cycle. Biowaste collection is technically and economically practicable, hence it serves as a renewable carbon feedstock. Biowastes are commonly biotransformed into value-added materials such as bioethanol, bioplastics, biofuels, biohydrogen, biobutanol and biogas. This review reveals the recent developments on microbial transformation of biowastes into biotechnologically important products. This approach addresses measures taken globally to valorize waste to achieve low carbon economy. The sustainable use of these renewable resources is a positive approach towards waste management and promoting circular economy.

Isolation and Characterization of Fengycins Produced by Bacillus amyloliquefaciens JFL21 and Its Broad-Spectrum Antimicrobial Potential Against Multidrug-Resistant Foodborne Pathogens

The continuing emergence and development of pathogenic microorganisms that are resistant to antibiotics constitute an increasing global concern, and the effort in new antimicrobials discovery will remain relevant until a lasting solution is found. A new bacterial strain, designated JFL21, was isolated from seafood and identified as B. amyloliquefaciens. The antimicrobial substance produced by B. amyloliquefaciens JFL21 showed low toxicity to most probiotics but exhibited strong antimicrobial activities against multidrug-resistant foodborne pathogens. The partially purified antimicrobial substance, Anti-JFL21, was characterized to be a multiple lipopeptides mixture comprising the families of surfactin, fengycin, and iturin. Compared with commercially available polymyxin B and Nisin, Anti-JFL21 not only could exhibit a wider and stronger antibacterial activity toward Gram-positive pathogens but also inhibit the growth of a majority of fungal pathogens. After further separation through gel filtration chromatography (GFC), the family of surfactin, fengycin, and iturin were obtained, respectively. The results of the antimicrobial test pointed out that only fengycin family presented marked antimicrobial properties against the indicators of L. monocytogenes, A. hydrophila, and C. gloeosporioides, which demonstrated that fengycins might play a major role in the antibacterial and antifungal activity of Anti-JFL21. Additionally, the current study also showed that the fengycins produced by B. amyloliquefaciens JFL21 not only maintained stable anti-Listeria activity over a broad pH and temperature range, but also remained active after treatment with ultraviolet sterilization, chemical reagents, and proteolytic enzymes. Therefore, the results of this study suggest the new strain and its antimicrobials are potentially useful in food preservation for the biological control of the multidrug-resistant foodborne pathogens.

Plant systemic acquired resistance compound salicylic acid as a potent inhibitor against SCF (SKP1-CUL1-F-box protein) mediated complex in Fusarium oxysporum by homology modeling and molecular dynamics simulations

Fusarium oxysporum causes significant economic losses in many crop plants by causing root rot, necrosis, and wilting symptoms. Homology and molecular dynamics studies are promising tools for the detection in F. oxysporum of the systemic resistance compound, salicylic acid, for control of the SKP1-CUL1-F-box protein complex. The structure of SKP1-CUL1-F-box subunit Skp1 from F. oxysporum is produced by Modeler 9v7 for the conduct of docking studies. The Skp1 structure is based on the yeast Cdc4/Skp1 (PDB ID: 3MKS A) crystal structure collected by the Protein data bank. Applying molecular dynamic model simulation methods to the final predicted structure and further evaluated by 3D and PROCHECK test programmers, the final model is verified to be accurate. Applying GOLD 3.0.1, SCF Complex Skp1 is used to prevent stress-tolerant operation. The SKP1-CUL1-F-box model is predicted to be stabilized and tested as a stable docking structure. The predicted model of the SCF structure has been stabilized and confirmed to be a reliable structure for docking studies. The results indicated that GLN8, LYS9, VAL10, TRP11, GLU48, ASN49 in SCF complex are important determinant residues in binding as they have strong hydrogen bonding with salicylic acid, which showed best docking results with SKP1-CUL1-F-box complex subunit Skp1 with docking score 25.25KJ/mol. Insilco studies have been used to determine the mode of action of salicylic acid for Fusarium control. Salicylic acid hinders the SKP1-CUL1-F-box complex, which is important in protein-like interactions through hydrogen bodings. Results from docking studies have shown that the best energy for SKP1-CUL1-F-box was salicylic acid.Communicated by Ramaswamy H. Sarma.

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.

Kinetic analysis on precursors for iturin A production from Bacillus amyloliquefaciens BPD1

In this study, the precursor effect for iturin A production was quantitatively analyzed. A strain identified as Bacillus amyloliquefaciens BPD1 (Ba-BPD1) was selected due to its ability to produce iturin A. The enhancement of iturin A production in a submerged culture was tested using various additives, including palmitic acid, oils, and complex amino acids. Among these, complex amino acids triggered the highest yield at 559 mg/L. The respective amino acids that contribute to the structure of iturin A were used as precursors. In fact, it was found that the addition of l-proline, l-glutamine, l-asparagine and l-serine could improve iturin A yield in the defined medium. However, during the kinetic analysis, all the amino acids exhibited a lower saturation level than l-serine, which exhibited a high saturation level at 1.2% resulting in an iturin A yield of 914 mg/L. In contrast, a negative effect was observed following the addition of l-tyrosine. To analyze the kinetic behavior of l-serine, three kinetic models were adopted: the kinetic order equation, the Langmuir kinetic equation, and a modified logistic equation. The regression results showed that the modified logistic model was the best fit for the kinetic behavior of l-serine as the major precursor, which could be further referred to the biosynthesis pathway of iturin A. Among the proposed processes for iturin A production, this study achieved the highest iturin A levels as a result of the addition of precursors.

Draft Genome Sequence of Bacillus amyloliquefaciens Strain RHNK22, Isolated from Rhizosphere with Biosurfactant (Surfactin, Iturin, and Fengycin) and Antifungal Activity

Bacillus amyloliquefaciens strain RHNK22 isolated from groundnut rhizosphere showed direct and indirect plant growth-promoting traits along with biosurfactant activity and reduction in surface tension of water. Biosurfactants were identified as lipopeptides (surfactin, iturin, and fengycin) by molecular and biochemical analysis in our studies.