Effect of medium components and culture conditions in Bacillus subtilis EA-CB0575 spore production

Design of an agro-industrial by-products-based media for the production of probiotic bacteria for fish nutrition

Probiotic production in commercial culture media is expensive, so, it is necessary to design culture media based on "low-cost" components like agro-industrial by-products. Therefore, this study aimed to design an agro-industrial by-product-based culture media using whey, sugarcane molasses, and palm kernel cake as components to produce Lactococcus lactis A12, Priestia megaterium M4, and Priestia sp. M10 isolated from Nile tilapia (Oreochromis niloticus) associated gut microbiota. Higher bacterial concentrations were achieved at high whey concentrations and low concentrations of sugarcane molasses and palm kernel cake (PKC) using agitation. The optimal conditions were whey, 3.84% w/v; sugarcane molasses, 7.39% w/v; PKC, 0.77% w/v; and agitation speed, 75 RPM. Bacterial growth under optimal conditions was compared to that in commercial Brain-Heart Infusion (BHI) broth. L. lactis A12 showed similar growth in the optimal media and BHI. The estimated cost of the culture media based on component prices was USD $ 3.01/L, which is 86.93% lower than BHI broth (USD $ 23.04/L). It was possible to design a "low-cost agro-industrial by-product-based culture media to produce L. lactis A12 and the two Priestia species under monoculture conditions.

Influence of PepF peptidase and sporulation on microcin J25 production in Bacillus subtilis

The lasso peptide microcin J25 (MccJ25) possesses strong antibacterial properties and is considered a potential effective component of bacterial disease treatment drugs and safe food preservatives. Although MccJ25 can be heterologously expressed in Bacillus subtilis as we have previously reported, its regulation and accumulation are yet to be understood. Here, we investigated the expression level and stability of MccJ25 in B. subtilis strains with disruption in peptidase genes pepA, pepF, and pepT. Oligoendopeptidase F (PepF) was found to be involved in reduction of the production of MccJ25 by degradation of its precursor peptide. In the pepF mutant, the MccJ25 reached a concentration of 1.68 µM after a cultivation time exceeding 60 hours, while the wild-type strain exhibited a concentration of only 0.14 µM. Moreover, the production of MccJ25 in B. subtilis downregulated the genes associated with sporulation, and this may contribute to its accumulation. Finally, this study provides a strategy to improve the stability and production of MccJ25 in B. subtilis.

IMPORTANCE

MccJ25 displays significant antibacterial activity, a well-defined mode of action, exceptional safety, and remarkable stability. Hence, it presents itself as a compelling candidate for an optimal antibacterial or anti-endotoxin medication. The successful establishment of exogenous production of MccJ25 in Bacillus subtilis provides a strategy for reducing its production cost and diversifying its utilization. In this study, we have provided evidence indicating that both peptidase PepF and sporulation are significant factors that limit the expression of MccJ25 in B. subtilis. The ΔpepF and ΔsigF mutants of B. subtilis express MccJ25 with higher production yield and enhanced stability. To sum up, this study developed several better engineered strains of B. subtilis, which greatly reduced the consumption of MccJ25 during the nutrient depletion stage of the host strain, improved its production, and elucidated factors that may be involved in reducing MccJ25 accumulation in B. subtilis.

Pilot-scale production of Bacillus subtilis MSCL 897 spore biomass and antifungal secondary metabolites in a low-cost medium

OBJECTIVES

Bacillus subtilis is a plant growth promoting bacterium (PGPB) that acts as a microbial fertilizer and biocontrol agent, providing benefits such as boosting crop productivity and improving nutrient content. It is able to produce secondary metabolites and endospores simultaneously, enhancing its ability to survive in unfavorable conditions and eliminate competing microorganisms. Optimizing cultivation methods to produce B. subtilis MSCL 897 spores on an industrial scale, requires a suitable medium, typically made from food industry by-products, and optimal temperature and pH levels to achieve high vegetative cell and spore densities with maximum productivity.

RESULTS

This research demonstrates successful pilot-scale (100 L bioreactor) production of a biocontrol agent B. subtilis with good spore yields (1.5 × 109 spores mL-1) and a high degree of sporulation (>80%) using a low-cost cultivation medium. Culture samples showed excellent antifungal activity (1.6-2.3 cm) against several phytopathogenic fungi. An improved methodology for inoculum preparation was investigated to ensure an optimal seed culture state prior to inoculation, promoting process batch-to-batch repeatability. Increasing the molasses concentration in the medium and operating the process in fed-batch mode with additional molasses feed, did not improve the overall spore yield, hence, process operation in batch mode with 10 g molasses L-1 is preferred. Results also showed that the product quality was not significantly impacted for up to 12 months of storage at room temperature.

CONCLUSION

An economically-feasible process for B. subtilis-based biocontrol agent production was successfully developed at the pilot scale.

Enhanced sporulation of B. licheniformis BF-002 through automatic co-feeding of carbon and nitrogen sources

Bacillus licheniformis formulations are effective for environmental remediation, gut microbiota modulation, and soil improvement. An adequate spore quantity is crucial for the activity of B. licheniformis formulations. This study investigated the synergistic effects of carbon/nitrogen source consumption and concentration on B. licheniformis BF-002 cultivation, with the aim of developing an automatic co-feeding strategy to enhance spore production. Initial glucose (10 g/L) and amino nitrogen (1.5 g/L) concentrations promote cell growth, followed by reduced glucose (2.0 g/L) and amino nitrogen (0.5 g/L) concentrations for sustained spore generation. The spore quantity reached 2.59 × 1010 CFU/mL. An automatic co-feeding strategy was developed and implemented in 5 and 50 L cultivations, resulting in spore quantities of 2.35 × 1010 and 2.86 × 1010 CFU/mL, respectively, improving by 6.81% and 30.00% compared to that with a fixed glucose concentration (10.0 g/L). The culture broth obtained at both the 5 and 50 L scales was spray-dried, resulting in bacterial powder with cell viability rates of 85.94% and 82.68%, respectively. Even after exposure to harsh conditions involving high temperature and humidity, cell viability remained at 72.80% and 69.89%, respectively. Employing the automatic co-feeding strategy increased the transcription levels of the spore formation-related genes spo0A, spoIIGA, bofA, and spoIV by 7.42%, 8.46%, 8.87%, and 9.79%, respectively. The proposed strategy effectively promoted Bacillus growth and spore formation, thereby enhancing the quality of B. licheniformis formulations.

Modeling and optimization of sporulation by Bacillus licheniformis BF-002 based on dynamics and recurrent neural networks

Bacillus licheniformis is widely utilized in disease prevention and environmental remediation. Spore quantity is a critical factor in determining the quality of microbiological agents containing vegetative cells. To improve the understanding of Bacillus licheniformis BF-002 strain culture, a hybrid model integrating traditional dynamic modeling and recurrent neural network was developed. This model enabled the optimization of carbon/nitrogen source feeding rates, pH, temperature and agitation speed using genetic algorithms. Carbon and nitrogen source consumption in the optimal duplicate batches showed no significant difference compared to the control batch. However, the spore quantity in the broth increased by 16.2% and 35.2% in the respective duplicate batches. Overall, the hybrid model outperformed the traditional dynamic model in accurately tracking the cultivation dynamics of Bacillus licheniformis, leading to increased spore production when used for optimizing cultivation conditions.

Bacillus genus industrial applications and innovation: First steps towards a circular bioeconomy

In recent decades, environmental concerns have directed several policies, investments, and production processes. The search for sustainable and eco-friendly strategies is constantly increasing to reduce petrochemical product utilization, fossil fuel pollution, waste generation, and other major ecological impacts. The concepts of circular economy, bioeconomy, and biorefinery are increasingly being applied to solve or reduce those problems, directing us towards a greener future. Within the biotechnology field, the Bacillus genus of bacteria presents extremely versatile microorganisms capable of producing a great variety of products with little to no dependency on petrochemicals. They are able to grow in different agro-industrial wastes and extreme conditions, resulting in healthy and environmentally friendly products, such as foods, feeds, probiotics, plant growth promoters, biocides, enzymes, and bioactive compounds. The objective of this review was to compile the variety of products that can be produced with Bacillus cells, using the concepts of biorefinery and circular economy as the scope to search for greener alternatives to each production method and providing market and bioeconomy ideas of global production. Although the genus is extensively used in industry, little information is available on its large-scale production, and there is little current data regarding bioeconomy and circular economy parameters for the bacteria. Therefore, as this work gathers several products' economic, production, and environmentally friendly use information, it can be addressed as one of the first steps towards those sustainable strategies. Additionally, an extensive patent search was conducted, focusing on products that contain or are produced by the Bacillus genus, providing an indication of global technology development and direction of the bacteria products. The Bacillus global market represented at least $18 billion in 2020, taking into account only the products addressed in this article, and at least 650 patent documents submitted per year since 2017, indicating this market's extreme importance. The data we provide in this article can be used as a base for further studies in bioeconomy and circular economy and show the genus is a promising candidate for a greener and more sustainable future.

Arabinose Plays an Important Role in Regulating the Growth and Sporulation of Bacillus subtilis NCD-2

A microbial fungicide developed from Bacillus subtilis NCD-2 has been registered for suppressing verticillium wilt in crops in China. Spores are the main ingredient of this fungicide and play a crucial role in suppressing plant disease. Therefore, increasing the number of spores of strain NCD-2 during fermentation is important for reducing the cost of the fungicide. In this study, five kinds of carbon sources were found to promote the metabolism of strain NCD-2 revealed via Biolog Phenotype MicroArray (PM) technology. L-arabinose showed the strongest ability to promote the growth and sporulation of strain NCD-2. L-arabinose increased the bacterial concentration and the sporulation efficiency of strain NCD-2 by 2.04 times and 1.99 times compared with D-glucose, respectively. Moreover, L-arabinose significantly decreased the autolysis of strain NCD-2. Genes associated with arabinose metabolism, sporulation, spore resistance to heat, and spore coat formation were significantly up-regulated, and genes associated with sporulation-delaying protein were significantly down-regulated under L-arabinose treatment. The deletion of msmX, which is involved in arabinose transport in the Bacillus genus, decreased growth and sporulation by 53.71% and 86.46% compared with wild-type strain NCD-2, respectively. Complementing the mutant strain by importing an intact msmX gene restored the strain's growth and sporulation.

Endospore production of Bacillus spp. for industrial use

The increased occurrence of antibiotic resistance and the harmful use of pesticides are a major problem of modern times. A ban on the use of antibiotics as growth promoters in animal breeding has put a focus on the probiotics market. Probiotic food supplements are versatile and show promising results in animal and human nutrition. Chemical pesticides can be substituted by biopesticides, which are very effective against various pests in plants due to increased research. What these fields have in common is the use of spore-forming bacteria. The endospore-forming Bacillus spp. belonging to this group offer an effective solution to the aforementioned problems. Therefore, the biotechnological production of sufficient qualities of such endospores has become an innovative and financially viable field of research. In this review, the production of different Bacillus spp. endospores will be reviewed. For this purpose, the media compositions, cultivation conditions and bioprocess optimization methods of the last 20 years are presented and reflected.

Bioprocess development for endospore production by Bacillus coagulans using an optimized chemically defined medium

Bacillus coagulans is a promising probiotic, because it combines probiotic properties of Lactobacillus and the ability of Bacillus to form endospores. Due to this hybrid relationship, cultivation of this organism is challenging. As the probiotics market continues to grow, there is a new focus on the production of these microorganisms. In this work, a strain-specific bioprocess for B. coagulans was developed to support growth on one hand and ensure sporulation on the other hand. This circumstance is not trivial, since these two metabolic states are contrary. The developed bioprocess uses a modified chemically defined medium which was further investigated in a one-factor-at-a-time assay after adaptation. A transfer from the shake flask to the bioreactor was successfully demonstrated in the scope of this work. The investigated process parameters included temperature, agitation and pH-control. Especially the pH-control improved the sporulation in the bioreactor when compared to shake flasks. The bioprocess resulted in a sporulation efficiency of 80%-90%. This corresponds to a sevenfold increase in sporulation efficiency due to a transfer to the bioreactor with pH-control. Additionally, a design of experiment (DoE) was conducted to test the robustness of the bioprocess. This experiment validated the beforementioned sporulation efficiency for the developed bioprocess. Afterwards the bioprocess was then scaled up from a 1 L scale to a 10 L bioreactor scale. A comparable sporulation efficiency of 80% as in the small scale was achieved. The developed bioprocess facilitates the upscaling and application to an industrial scale, and can thus help meet the increasing market for probiotics.

Response surface methodology based optimization of keratinase from Bacillus velezensis strain ZBE1 and nanoparticle synthesis, biological and molecular characterization

The increasing demands of keratinases for biodegradation of recalcitrant keratinaceous waste like chicken feathers has lead to research on newer potential bacterial keratinases to produce high-value products with biological activities. The present study reports a novel keratinolytic bacterium Bacillus velezensis strain ZBE1 isolated from deep forest soil of Western Ghats of Karnataka, which possessed efficient feather keratin degradation capability and induced keratinase production. Production kinetics depicts maximum keratinase production (11.65 U/mL) on 4th day with protein concentration of 0.61 mg/mL. Effect of various physico-chemical factors such as, inoculum size, metal ions, carbon and nitrogen sources, pH and temperature influencing keratinase production were optimized and 3.74 folds enhancement was evidenced through response surface methodology. Silver (AgNP) and zinc oxide (ZnONP) nanoparticles with keratin hydrolysate produced from chicken feathers by the action of keratinase were synthesized and verified with UV-Visible spectroscopy that revealed biological activities like, antibacterial action against Bacillus cereus and Escherichia coli. AgNP and ZnONP also showed potential antioxidant activities through radical scavenging activities by ABTS and DPPH. AgNP and ZnONP revealed cytotoxic effect against MCF-7 breast cancer cell lines with IC50 of 5.47 µg/ml and 62.26 µg/ml respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the thermostability, structure and surface attributes. The study suggests the prospective applications of keratinase to trigger the production of bioactive value-added products and significant application in nanotechnology in biomedicine.

Matrine-producing endophytic fungus Galactomyces candidum TRP-7: screening, identification, and fermentation conditions optimization for Matrine production

Matrine (MA) is an alkaloid extracted from the root of genus Sophora with various pharmacological activities. Production of MA by endophytic fungi offers an alternative challenge to reduce the massive consumption to meet the increasing demand of MA. In the current study, the positive strains with MA producing ability were screened from endophytic fungal isolated from the root of Sophora tonkinensis Gagnep. Chromatographic analyses verified the identity of the produced MA. Among these fungi, Galactomyces candidum strain TRP-7 was the most valuable strain for MA production with the initial yield 8.26 mg L^-1. The MA production was efficiently maximized up to 17.57 mg L^-1 of fermentation broth, after optimization of eight process parameters using Plackett-Burman and Box-Behnken designs. The statistical optimization resulted in a 1.127 times increase in MA production as compared to the initial yield of TRP-7. This is the first report to isolate endophytic fungi with MA-producing activity from S. tonkinensis Gagnep., and to identify an endophytic fungus G. candidum TRP-7 as a new promising start strain for a higher MA yield.

Effects of Dietary Supplementation with Bacillus amyloliquefaciens US573 on Intestinal Morphology and Gut Microbiota of European Sea Bass

Probiotics or direct-fed microbials (DFM) have proven strong potential for improving aquaculture sustainability. This study aims to evaluate the effects of dietary supplementation with the DFM Bacillus amyloliquefaciens US573 on growth performance, intestinal morphology, and gut microbiota (GM) of European sea bass. For this purpose, healthy fish were divided into two feeding trials in triplicate of 25 fish in each tank. The fish were fed with a control basal diet or a DFM-supplemented diet for 42 days. Results showed that, while no significant effects on growth performance were observed, the length and abundance of villi were higher in the DFM-fed group. The benefic effects of DFM supplementation included also the absence of cysts formation and the increase in number of goblet cells playing essential role in immune response. Through DNA metabarcoding analysis of GM, 5 phyla and 14 major genera were identified. At day 42, the main microbiome changes in response to B. amyloliquefaciens US573 addition included the significant decrease in abundance of Actinobacteria phylum that perfectly correlates with a decrease in Nocardia genus representatives which represent serious threat in marine and freshwater fish. On the contrary, an obvious dominance of Betaproteobacteria associated with the abundance in Variovorax genus members, known for their ability to metabolize numerous substrates, was recorded. Interestingly, Firmicutes, particularly species affiliated to the genus Sporosarcina with recent promising probiotic potential, were identified as the most abundant. These results suggest that B. amyloliquefaciens US573 can be effectively recommended as health-promoting DFM in European sea bass farming.

Production of Bacillus subtilis soil isolate as biocontrol agent under bioreactor conditions

This study aimed to investigate the biomass production of Bacillus subtilis in flask and bioreactor conditions. It is necessary to carry the culture from the shake flask to the pH, air, temperature and stirring controlled bioreactor in order to reduce the working time and increase the production efficiency and product quality. In this study, Bacillus was isolated from soil and grown under flask and bioreactor conditions as biocontrol agent against Botrytis cinerea and Fusarium oxysporum. In this process, a pH value of 7.5, 100% O₂ saturation, 30% dissolved O₂, at the temperature of 37 °C, total flow of 0.1 Lmin^-1 and mixing speed of 150 min^-1 were preferred for optimal concerning high production yield of B. subtilis in bioreactor. To test whether B. subtilis has antifungal activity on the growth of B. cinerea and F. oxysporum, a dual culture assay in a PDA medium was carried out. Ultimately, high biomass production in a short incubation period by reaching 2.2 µg/mL after 9 h in the bioreactor. It was observed that the bacteria produced in the bioreactor cultivation grew stronger and showed high antifungal activity which resulted 33.33% inhibition percentage against B. cinerea. It was concluded that B. subtilis can be used as a green-fungicide against B. cinerea and F. oxysporum, and bacterial metabolites from B. subtilis could pave the way for the development of next generation green/biopesticides.

Comparison of one-step with two-step production of Bacillus atrophaeus spores for use as bioindicators

The production method of spores significantly influences the resistance of spores used as bioindicators (BI) in the validation of sterilization of packaging material surfaces in aseptic food manufacturing. Therefore, the standardization of the spore production method represents an important and desirable goal in industrial BI production to ensure reliable validation test results. Previously, we recommended a two-step production approach for submerged spore production, in which the cultivation phase to obtain high cell mass was separate from the sporulation phase. In this work, a one-step manufacturing process was investigated to reduce production complexity and facilitate standardization of spore production. It was found that one-step BI production is technically possible but at the expense of spore yield. The two-step manufacturing process can realize almost 10-fold higher spore yields.

Multiple linear regression models to simulate spore yields of Bacillus amyloliquefaciens BS13 through optimization of medium composition

Bacillus amyloliquefaciens is a food spoilage spore-forming bacterium. Its spores are useful for multiple biotechnological applications. Nevertheless, few reports are available regarding the achievement of a high cell density and good sporulation effectiveness under fermentation conditions. Therefore, the current study was designed to optimize a low-cost fermentation medium allowing the highest sporulation yield by B. amyloliquefaciens strain BS13. Our data revealed that tryptone and starch were the best carbon and energy sources. In addition, two nitrogen sources namely, corn steep liquor (CSL) and yeast extract (YE), allowed a significant enhancement of spore production and they were both retained for further optimization. A combination of CaCl₂ , MgSO₄ , and MnSO₄ showed a positive impact on spores' production. The composition of the optimized medium was (in g/L); tryptone 3, starch 15, CSL 13.5, YE 1.5, CaCl₂ 0.1, MgSO₄ ·7H₂ O 0.012, and MnSO₄ ·7H₂ O 0.0012. Such medium was further validated in a 400-L fermentor. The spore yield by B. amyloliquefaciens strain BS13 was enhanced from 3.0 × 10¹⁰ spores/mL under flask culture conditions to 6.2 × 10¹⁰ spores/mL when cultures were performed on large scale. Therefore, strain BS13 spore preparation could be proposed as a promising probiotic and a biocontrol agent useful for plants, animals, and humans.

Mechanism insights into bacterial sporulation at natural sphalerite interface with and without light irradiation: The suppressing role in bacterial sporulation by photocatalysis

Unveiling the mechanisms of bacterial sporulation at natural mineral interfaces is crucial to fully understand the interactions of mineral with microorganism in aquatic environment. In this study, the bacterial sporulation mechanisms of Bacillus subtilis (B. subtilis) at natural sphalerite (NS) interface with and without light irradiation were systematically investigated for the first time. Under dark condition, NS was found to inactivate vegetative cells of B. subtilis and promote their sporulation simultaneously. The released Zn2+ from NS was mainly responsible for the bacterial inactivation and sporulation. With light irradiation, the photocatalytic effect from NS could increase the bacterial inactivation efficiency, while the bacterial sporulation efficiency was decreased from 8.1 % to 4.5 %. The photo-generated H2O2 and O2- played the major roles in enhancing bacterial inactivation and suppressing bacterial sporulation process. The intracellular synthesis of dipicolinic acid (DPA) as biomarker for sporulation was promoted by NS in dark, which was suppressed by the photocatalytic effect of NS with light irradiation. The transformation process from vegetative cells to spores was monitored by both 3D-fluerecence EEM and SEM observations. Compared with the NS alone system, the NS/light combined system induced higher level of intracellular ROSs, up-regulated antioxidant enzyme activity and decreased cell metabolism activity, which eventually led to enhanced inactivation of vegetative cells and suppressed bacterial sporulation. These results not only provide in-depth understanding about bacterial sporulation as a new mode of sub-lethal stress response at NS interface, but also shed lights on putting forward suitable strategies for controlling spore-producing bacteria by suppressing their sporulation during water disinfection.

Transcriptome analysis of the production enhancement mechanism of antimicrobial lipopeptides of Streptomyces bikiniensis HD-087 by co-culture with Magnaporthe oryzae Guy11

The lipopeptides produced by Streptomyces bikiniensis have a significant inhibitory effect on Magnaporthe oryzae, but the low yield limits its application. In this study, the anti-M. oryzae activity of the broth of S. bikiniensis HD-087 co-cultured with M. oryzae Guy11 mycelium has risen by 41.22% compared with pure culture, and under induction conditions of adding Guy11-inducer (cell-free supernatant of M. oryzae Guy11), the activity of strain HD-087 improved 61.76%. The result proved that the enhancement effect of Guy11 on the antimicrobial activity of HD-087 was mainly related to metabolites but mycelium cells. Under optimum induction conditions, NRPS gene expression levels of HD-087 were significantly increased by induction with Guy11-inducer, the biomass of HD-087 had no significant change, but crude extract of lipopeptide (CEL) production was 107.4% higher than pure culture, and TLC result under acid hydrolysis showed that the induced culture has one component more than pure culture. To clarify the regulation mechanism of improving lipopeptide production of HD-087 with Guy11-inducer, transcriptomic analysis was performed using RNAseq to compare the induced culture and pure culture. In the induced culture, 943 genes were up-regulated, while 590 genes were down-regulated in DEGs (differentially expressed genes). KEGG results showed that the expression of genes related to amino acid synthesis, fatty acid metabolism, TCA cycle and pyruvate metabolism pathway were significantly increased. The increased expression of genes related to these metabolic pathways provided sufficient precursors for lipopeptide synthesis. Accordingly, key enzyme genes responsible for the synthesis of lipopeptides Srf and NRPS was significantly increased. Quorum sensing related genes OppA and MppA were significantly up-regulated, and then ComP was activated and promoted lipopeptide synthesis. These results provided a scientific basis for using M. oryzae to induce the increase of the production of Streptomyces lipopeptides, and also laid a foundation for further exploring the co-culture mechanisms among different genera.

Fed-Batch Fermentation of Saccharomyces pastorianus with High Ribonucleic Acid Yield

(1) Background: The degradation products of ribonucleic acid (RNA)are widely used in the food and pharmaceutical industry for their flavoring and nutritional enhancement functions. Yeast is the main source for commercial RNA production, and an efficient strain is the key to reducing production costs; (2) Methods: A mutant Saccharomyces pastorianus G03H8 with a high RNA yield was developed via ARTP mutagenesis and fed-batch fermentation was applied to optimize production capacity. Genome sequencing analysis was used to reveal the underlying mechanism of higher RNA production genetic differences in the preferred mutant; (3) Results: Compared with the highest RNA content of the mutant strain, G03H8 increased by 40% compared with the parental strain G03 after response surface model optimization. Meanwhile, in fed-batch fermentation, G03H8′s dry cell weight (DCW) reached 60.58 g/L in 5 L fermenter by molasses flowing and RNA production reached up to 3.58 g/L. Genome sequencing showed that the ribosome biogenesis, yeast meiosis, RNA transport, and longevity regulating pathway were closely related to the metabolism of high RNA production; (4) Conclusion: S. pastorianus G03H8 was developed for RNA production and had the potential to greatly reduce the cost of RNA production and shorten the fermentation cycle. This work lays the foundation for efficient RNA content using S. pastorianus.

Optimization of industrial (3000 L) production of Bacillus subtilis CW-S and its novel application for minituber and industrial-grade potato cultivation

A commercial plant probiotic product was developed employing Bacillus subtilis CW-S in submerged fermentation. The effects of molasses and urea on cell growth were investigated with the goal of low-cost manufacturing. Plackett–Burman and Central-Composite Design (CCD) were utilized to optimize production parameters to maximize productivity. The stability of the formulated product and its efficacy in cultivating minituber in aeroponics and industrial-grade potatoes in the field were assessed. The results showed that the medium BS10 (molasses and urea) produced satisfactory cell density (7.19 × 10⁸ CFU/mL) as compared to the control (1.51 × 10⁷ CFU/mL) and BS1-BS9 (expensive) media (1.84 × 10⁷–1.37 × 10⁹ CFU/mL). According to validated CCD results, optimized parameters fitted well in pilot (300 L; 2.05 × 10⁹ CFU/mL) and industrial (3000 L; 2.01 × 10⁹ CFU/mL) bioreactors, resulting in a two-fold increase in cell concentration over laboratory (9.84 × 10⁸ CFU/mL) bioreactors. In aeroponics, CW-S produced excellent results, with a significant increase in the quantity and weight of minitubers and the survival rate of transplanted plantlets. In a field test, the yield of industrial-grade (> 55 mm) potatoes was increased with a reduction in fertilizer dose. Overall, the findings suggest that CW-S can be produced commercially utilizing the newly developed media and optimized conditions, making plant probiotics more cost-effective and accessible to farmers for crop cultivation, particularly in aeroponic minituber and industrial-grade potato production.

Medium for the Production of Bacillus-Based Biocontrol Agent Effective against Aflatoxigenic Aspergillus flavus: Dual Approach for Modelling and Optimization

One of the leading limiting factors for wider industrial production and commercialization of microbial biopesticides refers to the high costs of cultivation media. The selection of alternative sources of macronutrients crucial for the growth and metabolic activity of the producing microorganism is a necessary phase of the bioprocess development. Gaining a better understanding of the influence of the medium composition on the biotechnological production of biocontrol agents is enabled through bioprocess modelling and optimization. In the present study, after the selection of optimal carbon and nitrogen sources, two modelling approaches were applied to mathematically describe the behavior of the examined bioprocess—the production of biocontrol agents effective against aflatoxigenic Aspergillus flavus strains. The modelling was performed using four independent variables: cellulose, urea, ammonium sulfate and dipotassium phosphate, and the selected response was the inhibition-zone diameter. After the comparison of the results generated by the Response Surface Methodology (RSM) and the Artificial Neural Network (ANN) approach, the first model was chosen for the further optimization step due to the better fit of the experimental results. As the final investigation step, the optimal cultivation medium composition was defined (g/L): cellulose 5.0, ammonium sulfate 3.77, dipotassium phosphate 0.3, magnesium sulfate heptahydrate 0.3.

Identification and analysis of Rap-Phr system in Bacillus cereus 0-9

In this study, eight rap-related genes were found in the Bacillus cereus 0-9 genome; five rap genes were located on chromosomes and three on large plasmids. Five Rap proteins in B. cereus 0-9 were annotated as 'tetratricopeptide repeat proteins'. SMART Server analysis showed that the eight Rap proteins had typical tetrapeptide repeat sequence (TPR) domains. Biofilm assays and crystal violet staining showed that overexpression of the rapp1 and rap5 genes affected the biofilm formation of B. cereus 0-9, and the activities of Rapp1 and Rap5 proteins were inhibited by their corresponding cognate Phr, suggesting that the Rap-Phr quorum sensing (QS) system might also exist in the B. cereus 0-9 strain. In addition, overexpression of rap1 genes inhibited in the extracellular amylase decomposition capacity of B. cereus 0-9. The results of the sporulation assay indicated that overexpression of the eight rap genes inhibited the spore formation of B. cereus 0-9 to varying degrees. These results provide a reference for research on the regulation of the Rap-Phr QS system in B. cereus.

Optimization of an economical medium composition for the coculture of Clostridium butyricum and Bacillus coagulans

Clostridium butyricum is a spore-forming probiotic which can promote the enhancement of beneficial bacteria and maintain intestinal microecological balance. However, it is difficult to improve the production level of C. butyricum by conventional fermentation process. In this study, a co-fermentation process of C. butyricum DL-1 and Bacillus coagulans ZC2-1 was established to improve the viable counts and spore yield of C. butyricum, and the formula of coculture medium was optimized by flask fermentation. The results showed that the optimum medium composition is 10 g/L bran, 15 g/L corn steep powder, 15 g/L peptone, 1 g/L K₂HPO₄ and 0.5 g/L MnSO₄.Cultured stationarily in the optimal medium for 36 h, the number of viable bacteria of C. butyricum DL-1 reached 1.5 × 10⁸ cfu/mL, Which was 375 times higher than that incubated in the initial medium. The sporulation rate reach 92.6%. The results revealed an economical and effective medium composition for the coculture of C. butyricum and B. coagulans, which achieved a 64.6% cost reduction. The co-fermentation process established in this study provides a new fermentation mode for the industrial production of other absolute anerobic bacteria.

Optimization of Growth Conditions for the Production of Bacillus subtilis Using Central Composite Design and Its Antagonism Against Pathogenic Fungi

Today, the enhancement of spore yields of Bacillus subtilis has considerable interest and has been widely investigated. In this context, studies have been carried out to improve the spore yield as well as the production amount. In order to perform this, optimization studies are conducted for large-scale production of B. subtilis in bioreactors. The prokaryotic structure, high extracellular production potential, lack of pathogenic activity, well-known fermentation technology and short fermentation time are the prominent advantages for the production of B. subtilis in a bioreactor. The Bacillus species produce a wide variety of antifungal and antimicrobial compounds, making them ideal biological control agents. In this study, first, the growth conditions of the medium were investigated and then optimized using the central composite design approach to achieve the highest productivity for the growth of B. subtilis. In the experiments, the effect of temperature of 25, 30 and 35 °C and pH level of 6.0, 7.0 and 8.0 on spore yield was studied. Moreover, the antifungal activity of the B. subtilis culture was investigated against pathogenic fungi: Colletotrichum gloeosporioides, Botrytis cinerea and Aspergillus brasiliensis.

On-line monitoring of industrial interest Bacillus fermentations, using impedance spectroscopy

Impedance spectroscopy is a technique used to characterize electrochemical systems, increasing its applicability as well to monitor cell cultures. During their growth, Bacillus species have different phases which involve the production and consumption of different metabolites, culminating in the cell differentiation process that allows the generation of bacterial spores. In order to use impedance spectroscopy as a tool to monitor industrial interest Bacillus cultures, we conducted batch fermentations of Bacillus species such as B. subtilis, B. amyloliquefaciens, and B. licheniformis coupled with this technique. Each fermentation was characterized by the scanning of 50 frequencies between 0.5 and 5 MHz every 30 min. Pearson's correlation between impedance and phase angle profiles (obtained from each frequency scanned) with the kinetic profiles of each strain allowed the selection of fixed frequencies of 0.5, 1.143, and 1.878 MHz to follow-up of the fermentations of B. subtilis, B. amyloliquefaciens and B. licheniformis, respectively. Dielectric profiles of impedance, phase angle, reactance, and resistance obtained at the fixed frequency showed consistent changes with exponential, transition, and spore release phases.

Isocitrate dehydrogenase of Bacillus cereus is involved in biofilm formation

Isocitrate dehydrogenase (IDH), a key enzyme in the TCA cycle, participates in the formation of biofilms in Staphylococcus aureus, but it remains to be clarified whether it is involved in the formation of Bacillus cereus biofilms. In this study, we scanned the genome of B. cereus 0-9 and found a gene encoding isocitrate dehydrogenase (FRY47_22620) named icdH. The IcdH protein was expressed and purified. The enzyme activity assay showed that the protein had IDH activity dependent on NADP⁺, indicating that this gene encoded an IDH. The ΔicdH mutant and its complemented strains were obtained by a homologous recombination strategy, and crystal violet data and CLSM were measured. The results showed that the biofilm yield of the mutant ΔicdH decreased, and the biofilm morphology also changed, while the growth of ΔicdH was not affected. The extracellular pH and citric acid content results showed that the ΔicdH mutant exhibited citric acid accumulation and acidification of the extracellular matrix. In addition, the addition of excess Fe³⁺ restored the biofilm formation of the ΔicdH mutant. It is speculated that IDH in B. cereus may regulate biofilm formation by modulating intracellular redox homeostasis. In addition, we found that the icdH deletion of B. cereus 0-9 could result in a reduced sporulation rate, which was significantly different from sporulation in B. subtilis caused by interruption of the stage I sporulation process due to icdH loss. All the above results provide us with new insights for further research on IDH.

A Review of the Effects and Production of Spore-Forming Probiotics for Poultry

Simple Summary

Spore-forming probiotics are widely used in the poultry industry for their beneficial impact on host health. The main feature that separates spore-forming probiotics from the more common lactic acid probiotics is their high resistance to external and internal factors, resulting in higher viability in the host and correspondingly, greater efficiency. Their most important effect is the ability to confront pathogens, which makes them a perfect substitute for antibiotics. In this review, we cover and discuss the interactions of spore-forming probiotic bacteria with poultry as the host, their health promotion effects and mechanisms of action, impact on poultry productivity parameters, and ways to manufacture the probiotic formulation. The key focus of this review is the lack of reproducibility in poultry research studies on the evaluation of probiotics’ effects, which should be solved by developing and publishing a set of standard protocols in the professional community for conducting probiotic trials in poultry.

Abstract

One of the main problems in the poultry industry is the search for a viable replacement for antibiotic growth promoters. This issue requires a “one health” approach because the uncontrolled use of antibiotics in poultry can lead to the development of antimicrobial resistance, which is a concern not only in animals, but for humans as well. One of the promising ways to overcome this challenge is found in probiotics due to their wide range of features and mechanisms of action for health promotion. Moreover, spore-forming probiotics are suitable for use in the poultry industry because of their unique ability, encapsulation, granting them protection from the harshest conditions and resulting in improved availability for hosts’ organisms. This review summarizes the information on gastrointestinal tract microbiota of poultry and their interaction with commensal and probiotic spore-forming bacteria. One of the most important topics of this review is the absence of uniformity in spore-forming probiotic trials in poultry. In our opinion, this problem can be solved by the creation of standards and checklists for these kinds of trials such as those used for pre-clinical and clinical trials in human medicine. Last but not least, this review covers problems and challenges related to spore-forming probiotic manufacturing.

Design of experiments and design space approaches in the pharmaceutical bioprocess optimization

The optimization of pharmaceutical bioprocesses suffers from several challenges like complexity, upscaling costs, regulatory approval, leading to the risk of delivering substandard drugs to patients. Bioprocess is very complex and requires the evaluation of multiple components that need to be monitored and controlled in order to attain the desired state when the process ends. Statistical design of experiments (DoE) is a powerful tool for optimizing bioprocesses because it plays a critical role in the quality by design strategy as it is useful in exploring the experimental domain and providing statistics of interest that enable scientists to understand the impact of critical process parameters on the critical quality attributes. This review summarizes selected publications in which DoE methodology was used to optimize bioprocess. The main objective of the critical review was to clearly demonstrate potential benefits of using the DoE and design space methodologies in bioprocess optimization.

Antimicrobial and bacteriostatic activity of surfactants against B. subtilis for microbial cleaner formulation

Cleaning products containing live bacteria that form spores of Bacillus spp. as active substances are becoming increasingly common in probiotic cleaner formulation. The quality of cleaning performance for the production of probiotic cleaners does not only depend on the potential of the bacterial strains used, but also on the chemical components of the formulations. In this study, the surfactants and other additives were investigated as biocidal or bacteriostatic against B. subtilis, and the viability of B. subtilis was examined at different pH ranges for microbial cleaner formulation. As a result, it was discovered that the B. subtilis, which can be used in the microbial cleaner formulation, shows higher growth and viability at the neutral pH, and it passes into the death phase at pH 3. According to antagonistic activity results, the Gram-positive S. aureus and K. pneumoniae were the most sensitive bacteria while B. cereus was the most resistant bacteria. The anionic surfactants such as linear alkylbenzene sulfonic acid and sodium lauryl ether sulfate act as bacteriostatic on Bacillus spp. and do not cause cell death. In the view of these results, the usage of appropriate bacterial cultures and the correct stabilization of the formulations are also critical elements in the development of microbial cleaner formulations.

Metabolic strategies of dormancy of a marine bacterium Microbulbifer aggregans CCB-MM1: Its alternative electron transfer chain and sulfate-reducing pathway

Bacterial dormancy plays a crucial role in maintaining the functioning and diversity of microbial communities in natural environments. However, the metabolic regulations of the dormancy of bacteria in natural habitats, especially marine habitats, have remained largely unknown. A marine bacterium, Microbulbifer aggregans CCB-MM1 exhibits rod-to-coccus cell shape change during the dormant state. Therefore, to clarify the metabolic regulation of the dormancy, differential gene expression analysis based on RNA-Seq was performed between rod- (vegetative), intermediate, and coccus-shaped cells (dormancy). The RNA-Seq data revealed that one of two distinct electron transfer chains was upregulated in the dormancy. Dissimilatory sulfite reductase and soluble hydrogenase were also highly upregulated in the dormancy. In addition, induction of the dormancy of MM1 in the absence of MgSO₄ was slower than that in the presence of MgSO₄. These results indicate that the sulfate-reducing pathway plays an important role in entering the dormancy of MM1.

Phosphorus Solubilizing and Mineralizing Bacillus spp. Contribute to Rice Growth Promotion Using Soil Amended with Rice Straw

Rice (Oryza sativa L.) is a staple food for more than two billion people worldwide. Its cultivation demands large amounts of nutrients, particularly nitrogen and phosphorus (P). Consequently, low availability of these nutrients in the soil has led to the use of chemical fertilizers, generating increases in production costs and environmental damage. Soil host microorganisms known as plant growth-promoting rhizobacteria (PGPR) colonize the rhizosphere and facilitate the uptake of nutrients by the plants. In this study, rice seeds inoculated with PGPR were grown for 30 days in an inert substrate and fertilized with modified Hoagland nutrient solution with phosphate rock as a source of P. Treatments were repeated over time, obtaining five isolates which significantly increased plant length by up to 56% and dry weight of stems and roots up to 45% and 169% respectively relative to an uninoculated control. Selected strains showed in vitro tri-calcium phosphate solubilizing activity, mineralizing phytate activity, and phosphate release from rice straw (RS). Based on the above criteria, three isolates (IBUN-02755, -02,704 and -02,724) that contained β propeller phytase (BPP) genes, were selected to evaluate their effect as PGPR in rice seedlings. These were planted in a soil amended with RS under greenhouse conditions. The results showed that selected Bacillus spp. strains significantly increased plant length and dry weight or increased plant phosphate uptake up to two times compared to an un-inoculated control. This suggests that selected strains may have a capacity as PGPR using RS as carbon and a P amendment.

Imaging high-performance thin-layer chromatography as powerful tool to visualize metabolite profiles of eight Bacillus candidates upon cultivation and growth behavior

Imaging high-performance thin-layer chromatography (HPTLC) was explored with regard to its ability to visualize changes in the metabolite profile of bacteria. Bacillus subtilis has become a model organism in many fields. The increasing interest in these bacteria is driven by their attributed probiotic activity. However, growth behavior and metabolism of Bacillus species have a considerable influence on their activity and secondary metabolite profile. On the HPTLC plate, cultivation broths of Bacillus species (B. subtilis, B. licheniformis, B. pumilus and B. amyloliquefaciens) and some B. subtilis strains of high genetic similarity up to 99.5% were applied directly and compared with their respective liquid-liquid extracts. The latter as well as the cultivation in a minimal medium reduced the matrix load and improved the zone resolution. Cultivation parameters such as nutrient supply, cultivation temperature, cultivation time and rotational speed (oxygen level) as well as medium change were shown to have a considerable influence on the growth behavior and resulting metabolite profiles. Imaging HPTLC turned out to be an efficient and affordable tool to visualize such influences of cultivation parameters on the metabolite profiles. It converts the complexity of reaction processes occurring during cell cultivation in easy-to-understand images, which are helpful to figure out factors of influence and understand activity changes. The results highlighted that optimal cultivation conditions need to be found for the intended bacterial application, and in particular, these conditions have to be kept constant. It must be ensured that small variations in cultivation parameters of bacteria do not change the specified (probiotic) effect on the health of animals and humans. The HPTLC metabolite profiles represented the cultivation conditions of specific bacteria and were found to be a proof of the activity of distinct bacteria. In addition, HPTLC can also be used to optimize and streamline the culture media. The quality control of cultivation or fermentation processes can benefit from such a powerful tool, as a picture is worth a thousand words.

Proteomic analysis of secretomes from Bacillus sp. AR03: characterization of enzymatic cocktails active on complex carbohydrates for xylooligosaccharides production

Bacillus sp. AR03 have been described as an important producer of carbohydrate-active enzymes (CAZymes) when growing in a peptone-based medium supplemented with simple sugars and/or carboxymethyl cellulose (CMC) as carbon sources. This work aimed to identify the extracellular enzymatic cocktails through shotgun proteomics. The proteomic analysis showed that enzymes involved in cellulose and xylan degradation were among the most abundant proteins. These enzymes included an endo-glucanase GH5_2 and a glucuronoxylanase GH30_8, which were found in all conditions. In addition, several proteins were differentially expressed in the three evaluated culture media, indicating microbial metabolic changes due to the different supplied carbon sources, particularly, in the presence of CMC. Finally, the capability of the crude enzymatic cocktails from culture media to degrade birchwood xylan was assessed, which produced mostly xylooligosaccharides containing among 3-5 xylose units. Consequently, this work shows the potential of the extracellular enzymes from Bacillus sp. AR03 for producing emergent prebiotics.

Production and stability of a multi-strain Bacillus based probiotic product for commercial use in poultry

Probiotics can be effective alternatives to the prophylactic use of antibiotic growth promoters (AGPs) in response to industry and consumer concerns around their use in poultry. Studies on the suitability of Bacillus probiotics are emerging and showing benefits, but information on the production technology is limited. We developed the production process for a novel probiotic product previously shown to be effective in field trials. All strains were cultivated to a spore concentration exceeding 1 × 10¹⁰ CFU. mL^-1. The spores of each strain were harvested, processed into a powder intermediate and formulated into an end product with 100 % recoveries and a shelf life stability >1 year. The probiotic was shown to be incorporated into broiler feed exceeding the desired concentration of 1 × 10⁶ CFU. g^-1. Using efficient process technology and lower cost materials, this study presents a commercially relevant case for the potential adoption of probiotic products by the poultry industry.

Selection of plant growth promoting rhizobacteria sharing suitable features to be commercially developed as biostimulant products

Plant biostimulants (PBs) are an eco-friendly alternative to chemical fertilisers because of their minimal or null impact on human health and environment, while ensuring optimal nutrient uptake and increase of crop yield, quality and tolerance to abiotic stress. Although there is an increasing interest on microbial biostimulants, the optimal procedure to select and develop them as commercial products is still not well defined. This work proposes and validates a procedure to select the best plant growth promoting rhizobacteria (PGPR) as potential active ingredients of commercial PBs. The stepwise screening strategy was designed based on literature analysis and consists of six steps: (i) determination of the target crop and commercial strategy, (ii) selection of growth media for the isolation of microbial candidates, (iii) screening for traits giving major agronomical advantages, (iv) screening for traits related to product development, (v) characterisation of the mode of action of PGPR and (vi) assessment of plant growth efficacy. The strategy was validated using a case study: PGPR combined with humic acids to be applied on tomato plants. Among 200 bacterial strains isolated from tomato rhizosphere, 39 % were able to grow in presence of humic acids and shared the ability to solubilise phosphate. After the screening for traits related to product development, only 6 % of initial bacterial strains were sharing traits suitable for the further development as potential PBs. In fact, the selected bacterial strains were able to produce high cell mass and tolerated drought, aspects important for the mass production and formulation. These bacterial strains were not able to produce antibiotics, establish pathogenic interaction with plants and did not belong to bacterial species associated to human, animal and plant diseases. Most importantly, five of the selected bacterial strains were able to promote tomato seedling vigour in experiments carried out in vitro. These bacterial strains were furtherly characterised for their ability to colonize effectively tomato plant roots, produce phytohormones and solubilise soil minerals. This characterisation led to the selection of two candidates that showed the ability to promote tomato plant growth in experiments carried out in greenhouse conditions. Overall, this work provides a flow diagram for the selection of PGPR candidates to be successfully developed and commercialized as PBs. The validation of the flow diagram led to the selection of two bacterial strains belonging to Pantoea and Pseudomonas genera, potential active ingredients of new commercial PBs.

Improving probiotic spore yield using rice straw hydrolysate

Spore-forming Bacillus sp. has been extensively studied for their probiotic properties. In this study, an acid-treated rice straw hydrolysate was used as carbon source to produce the spores of Bacillus coagulans. The results showed that this hydrolysate significantly improved the spore yield compared with other carbon sources such as glucose. Three significant medium components including rice straw hydrolysate, MnSO₄ and yeast extract were screened by Plackett-Burman design. These significant variables were further optimized by response surface methodology (RSM). The optimal values of the medium components were rice straw hydolysate of 27% (v/v), MnSO₄ of 0·78 g l^-1 and yeast extract of 1·2 g l^-1 . The optimized medium and RSM model for spore production were validated in a 5 l bioreactor. Overall, this sporulation medium containing acid-treated rice straw hydrolysate has a potential to be used in the production of B. coagulans spores.

Characterizations and Fibrinolytic Activity of Serine Protease from Bacillus subtilis C10

BACKGROUND

Fibrinolytic enzymes, such as Nattokinases from Bacillus species are known to degrade the fibrin blood clots. They belong to serine protease group having commercial applications, such as therapeutic agents and functional food formulation.

OBJECTIVE

The present study reports some characteristics and fibrinolytic activity of serine protease from B. subtilis C10 strain that was isolated from shrimp shell.

METHODS

Extracellular enzyme from B. subtilis C10 culture was harvested and partially purified by ammonium sulphate precipitation. Fibrinolytic activity of the enzyme was determined by zymography and measured by spectrophotometry with fibrinogen and thrombin used as substrates. The optimal temperature and pH for fibrinolytic activity were studied in the range of 31-43ºC and 5-10, respectively. The thermal and pH stability of enzyme was studied by incubating enzyme for 30 min in the same range of temperature and pH as above. The effect of some metal ions and reagents on fibrinolytic activity of enzyme was evaluated by concentrations of 5 mM and 5%, respectively.

RESULTS

Zymogram analysis indicated the presence of four fibrinolytic enzymes with molecular weights of approximately 69, 67, 39 and 36 kDa. The optimal temperature and pH for enzyme activity were 37°C and 9, respectively. The thermal and pH stability ranged from 35-39°C and 8-10, respectively. Fibrinolytic activity reached a maximum value of about 400 U/mg protein after 16 h of C10 strain culture. Enzyme has been drastically inhibited by PMSF and SDS, and partially inhibited by EDTA, while Triton X-100 has significantly increased enzyme activity. Effects of ions such as Mg2+, Ca2+ and Mn2+ on enzyme were negligible, except Cu2+ and Zn2+ have strongly decreased its activity.

CONCLUSION

Results from the present study suggested that enzyme obtained from B. subtilis C10 could be serine protease that has a high fibrinolytic activity up to about 400 U/mg protein at the most appropriate temperature and pH of 37ºC and 9. This activity can be improved up to 142% by incubating enzyme with 5% Triton X-100 for 30 min.

Recent Advances in the Physiology of Spore Formation for Bacillus Probiotic Production

Spore-forming probiotic bacteria have received a wide and constantly increasing scientific and commercial interest. Among them, Bacillus species are the most studied and well-characterized Gram-positive bacteria. The use of bacilli as probiotic products is expanding especially rapidly due to their inherent ability to form endospores with unique survivability and tolerance to extreme environments and to produce a large number of valuable metabolites coupled with their bio-therapeutic potential demonstrating immune stimulation, antimicrobial activities and competitive exclusion. Ease of Bacillus spp. production and stability during processing and storage make them a suitable candidate for commercial manufacture of novel foods or dietary supplements for human and animal feeds for livestock, especially in the poultry and aquaculture industries. Therefore, the development of low-cost and competitive technologies for the production of spore-forming probiotic bacteria through understanding physiological peculiarities and mechanisms determining the growth and spore production by Bacillus spp. became necessary. This review summarizes the recent literature and our own data on the physiology of bacilli growth and spore production in the submerged and solid-state fermentation conditions, focusing on the common characteristics and unique properties of individual bacteria as well as on several approaches providing enhanced spore formation.

Solid-state Co-cultivation of Bacillus subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus Using Tobacco Waste Residue

Agro-industrial wastes are excellent sources for solid-state culture to produce spores of microorganisms, whereas microbial co-cultivation is not fully exploited in solid-state culture. In this work, the co-cultivation of different strains of Bacillus subtilis, and three microbes of B. subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus was studied using a solid medium only composed of water and tobacco waste residue after extraction of nicotine and solanesol. The influences of matrix thickness, moister, temperature, and ratio of three microbes in seed on the cell growth and spore formation were studied. The maximum viable cells and spores of each microbe reached 1013 cfu/g when cultured alone at 30 °C in a medium containing 58.3% moisture. Co-cultivation of microbes stimulated cell growth and maximum viable cells of each microbe reached 1014 cfu/g, while spore production was inhibited and decreased to 1011 cfu/g. With decreasing amount of P. lilacinus in seed, total amount of spores was increased. When the seed with a ratio of 6:3:1 for B. mucilaginosus, B. subtilis, and P. lilacinus was inoculated, the total amount of spores reached 4.14 × 1012 cfu/g and the ratio was 1.7:0.7:1. These results indicate the potential of solid-state cultivation in the high production of spores from tobacco waste residue at low cost.

Bacillus amyloliquefaciens Spore Production Under Solid-State Fermentation of Lignocellulosic Residues

This study was conducted to elucidate cultivation conditions determining Bacillus amyloliquefaciens B-1895 growth and enhanced spore formation during the solid-state fermentation (SSF) of agro-industrial lignocellulosic biomasses. Among the tested growth substrates, corncobs provided the highest yield of spores (47 × 10¹⁰ spores g^-1 biomass) while the mushroom spent substrate and sunflower oil mill appeared to be poor growth substrates for spore formation. Maximum spore yield (82 × 10¹⁰ spores g^-1 biomass) was achieved when 15 g corncobs were moistened with 60 ml of the optimized nutrient medium containing 10 g peptone, 2 g KH₂PO₄, 1 g MgSO₄·7H₂O, and 1 g NaCl per 1 l of distilled water. The cheese whey usage for wetting of lignocellulosic substrate instead water promoted spore formation and increased the spore number to 105 × 10¹⁰ spores g^-1. Addition to the cheese whey of optimized medium components favored sporulation process. The feasibility of developed medium and strategy was shown in scaled up SSF of corncobs in polypropylene bags since yield of 10 × 10¹¹ spores per gram of dry biomass was achieved. In the SSF of lignocellulose, B. amyloliquefaciens B-1895 secreted comparatively high cellulase and xylanase activities to ensure good growth of the bacterial culture.

Development of low-cost formulations of plant growth-promoting bacteria to be used as inoculants in beneficial agricultural technologies

Phosphorus is one of the main macronutrients for plant development. Despite its large deposits in soils, it is scarcely available for plants. Phosphate-solubilizing bacteria, belonging to the group of plant growth-promoting rhizobacteria (PGPR), are capable of mobilizing deposits of insoluble phosphates in the soil. The use of PGPR as inoculants provides an environmentally sustainable approach to increase crop production. The effectiveness of inoculants depends on their proper production, formulation and storage in order to ensure the application of the required number of viable microbial cells. In order to develop inexpensive technology, low-cost compounds for biomass production and protection should be used. After the biomass production process, the product should be formulated in a liquid or a solid form, taking into account required storage time, use of protectors/carriers, storage conditions (temperature, humidity, etc.), ease of application and maintenance of beneficial effects on crops. Careful determination of these optimal conditions would ensure a low-cost efficient inoculant that would promote the growth and yield of various crops.

Elucidation of Bacillus subtilis KATMIRA 1933 Potential for Spore Production in Submerged Fermentation of Plant Raw Materials

In this study, the effects of several key factors to increase spore production by Bacillus subtilis subsp. KATMIRA 1933 were evaluated in shake flask experiments. In a synthetic medium, glucose concentration played a crucial role in the expression of bacilli sporulation capacity. In particular, maximum spore yield (2.3 × 10⁹ spores/mL) was achieved at low glucose concentration (2 g/L), and further gradual increase of the carbon source content in the medium caused a decrease in sporulation capacity. Substitution of glucose with several inexpensive lignocellulosic materials was found to be a reasonable way to achieve high cell density and sporulation. Of the materials tested, milled mandarin peels at a concentration of 40 g/L served as the best growth substrate. In these conditions, bacilli secreted sufficient levels of glycosyl hydrolases, providing slow hydrolysis of the mandarin peel's polysaccharides to metabolizable sugars, providing the bacterial culture with an adequate carbon and energy source. Among nitrogen sources tested, peptone was found to favor spore production. Moreover, it was shown that cheese and cottage cheese whey usage, instead of distilled water, significantly increases spore formation. After optimization of the nutrient medium in the shake flask experiments, the technical feasibility of large-scale spore production by B. subtilis KATMIRA 1933 was confirmed in a laboratory fermenter. The spore yield (7 × 10¹⁰ spores/mL) obtained using a bioreactor was higher than those previously reported.

Fungal Competitors Affect Production of Antimicrobial Lipopeptides in Bacillus subtilis Strain B9-5

Bacillus subtilis has shown success in antagonizing plant pathogens where strains of the bacterium produce antimicrobial cyclic lipopeptides (CLPs) in response to microbial competitors in their ecological niche. To gain insight into the inhibitory role of these CLPs, B. subtilis strain B9-5 was co-cultured with three pathogenic fungi. Inhibition of mycelial growth and spore germination was assessed and CLPs produced by B. subtilis B9-5 were quantified over the entire period of microbial interaction. B. subtilis B9-5 significantly inhibited mycelial growth and spore germination of Fusarium sambucinum and Verticillium dahliae, but not Rhizopus stolonifer. LC-MS analysis revealed that B. subtilis differentially produced fengycin and surfactin homologs depending on the competitor. CLP quantification suggested that the presence of Verticillium dahliae, a fungus highly sensitive to the compounds, caused an increase followed by a decrease in CLP production by the bacterium. In co-cultures with Fusarium sambucinum, a moderately sensitive fungus, CLP production increased more gradually, possibly because of its slower rate of spore germination. With co-cultures of the tolerant fungus Rhizopus stolonifer, B. subtilis produced high amounts of CLPs (per bacterial cell) for the duration of the interaction. Variations in CLP production could be explained, in part, by the pathogens' overall sensitivities to the bacterial lipopeptides and/or the relative growth rates between the plant pathogen and B. subtilis. CLP production varied substantially temporally depending on the targeted fungus, which provides valuable insight concerning the effectiveness of B. subtilis B9-5 protecting its ecological niche against the ingress of these pathogens.

Rapid optimization of spore production from Bacillus amyloliquefaciens in submerged cultures based on dipicolinic acid fluorimetry assay

Some optimization techniques have been widely applied for spore fermentation based on the plate counting. This study optimized the culture medium for the spore production of Bacillus amyloliquefaciens BS-20 and investigated the feasibility of using a dipicolonic acid (DPA) fluorimetry assay as a simpler alternative to plate counting for evaluating spore yields. Through the single-factor experiment, the metal ions and agro-industrial raw materials that significantly enhanced spore production were determined. After conducting a response surface methodology (RSM) analysis of several metal ions, the combined use of optimum concentrations of Mn2+, Fe2+, and Ca2+ in culture media produced a 3.4-fold increase in spore yields. Subsequently, supplementing soybean meal and corn meal with optimum concentrations determined by another RSM analysis produced an 8.8-fold increase. The final spore concentration from a culture medium incorporating optimum concentrations of the metal ions and raw materials mentioned above was verified to reach (8.05 ± 0.70) × 109 CFU/mL by both DPA fluorimetry and plate counting. The results suggest that the use of DPA fluorescence intensity as an alternative value to colony counting provides a general method for assessing spore yields with less work and shorter time.

Manejo biológico del tamo de arroz bajo diferentes relaciones C:N empleando co-inóculos microbianos y promotores de crecimiento vegetal

El tamo de arroz es uno de los residuos agrícolas lignocelulósicos más abundantes en el planeta, luego de los residuos producidos por los cultivos de maíz y trigo, con una producción mundial estimada de 1000 millones de toneladas según estadísticas de la FAO. En el contexto de la agricultura moderna es determinante lograr un manejo ambientalmente sostenible de este recurso mediante su incorporación al suelo, de tal forma que se logre el reciclaje de nutrientes, evitando la incorporación de patógenos al sistema y la inmovilización de elementos como el nitrógeno por la comunidad microbiana. El objetivo de este trabajo consistió en la evaluación de un inoculo microbiano mixto a partir de productos comerciales basados en hongos del género Trichoderma y bacterias aerobias formadoras de endosporas, con potencial degradador del tamo de arroz, así como el empleo de bacterias promotoras de crecimiento vegetal al momento de la siembra, que pudieran aprovechar los nutrientes del proceso de descomposición del tamo de arroz, potenciando su actividad biológica. Los tratamientos fueron evaluados bajo diferentes relaciones C:N del tamo de arroz que favorecieran el proceso de degradación, mediante la adición de nitrógeno inorgánico. Los resultados del trabajo permitieron identificar que la aplicación de una enmienda de nitrógeno a una relación C:N 35 más una dosis adicional de urea al momento de la siembra de las semillas de arroz, fue el tratamiento más adecuado para potenciar el efecto de los microorganismos e incrementar las variables agronómicas obtenidas mediante un esquema de fertilización convencional del cultivo.