Cytotoxic potential of industrial strains of Bacillus sp

Evaluation of by-products from agricultural, livestock and fishing industries as nutrient source for the production of proteolytic enzymes

This study presents an approach that utilizes low-value agro-industrial by-products as culture media for producing high-value proteolytic enzymes. The objective was to assess the impact of six agro-industrial by-products as culture media on the production of proteolytic enzymes. Bacillus subtilis strains, confirmed through comprehensive biochemical, morphological, and molecular analyses, were isolated and identified. Enzymatic activity was evaluated using azocasein and casein substrates, and the molecular sizes of the purified extract components were determined. The results demonstrated that the isolated bacteria exhibited higher metabolic and enzymatic activity when cultured in media containing 1 % soybean oil cake or feather meal. Furthermore, higher concentrations of the culture media were found to hinder the production of protease. Optimal protease synthesis on soybean oil cake and feather meal media was achieved after 4 days, using both the azocasein and casein methods. Semi-purification of the enzymatic extract obtained from Bacillus subtilis in feather meal and soybean oil cake resulted in a significant increase in azocaseinolytic and caseinolytic activities. Gel electrophoresis analysis revealed multiple bands in the fractions with the highest enzymatic activity in soybean oil cake, indicating the presence of various enzymes with varying molecular sizes. These findings highlight the potential of utilizing low-value agro-industrial by-products as efficient culture media for the sustainable and economically viable production of proteolytic enzymes with promising applications in various industries.

Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future

The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.

Bacillus subtilis DSM29784 attenuates Clostridium perfringens-induced intestinal damage of broilers by modulating intestinal microbiota and the metabolome

Necrotic enteritis (NE), especially subclinical NE (SNE), without clinical symptoms, in chicks has become one of the most threatening problems to the poultry industry. Therefore, increasing attention has been focused on the research and application of effective probiotic strains as an alternative to antibiotics to prevent SNE in broilers. In the present study, we evaluated the effects of Bacillus subtilis DSM29784 (BS) on the prevention of subclinical necrotic enteritis (SNE) in broilers. A total of 480 1-day-old broiler chickens were randomly assigned to four dietary treatments, each with six replicates pens of twenty birds for 63 d. The negative (Ctr group) and positive (SNE group) groups were only fed a basal diet, while the two treatment groups received basal diets supplemented with BS (1 × 109 colony-forming units BS/kg) (BS group) and 10mg/kg enramycin (ER group), respectively. On days 15, birds except those in the Ctr group were challenged with 20-fold dose coccidiosis vaccine, and then with 1 ml of C. perfringens (2 × 108) at days 18 to 21 for SNE induction. BS, similar to ER, effectively attenuated CP-induced poor growth performance. Moreover, BS pretreatment increased villi height, claudin-1 expression, maltase activity, and immunoglobulin abundance, while decreasing lesional scores, as well as mucosal IFN-γ and TNF-α concentrations. In addition, BS pretreatment increased the relative abundance of beneficial bacteria and decreased that of pathogenic species; many lipid metabolites were enriched in the cecum of treated chickens. These results suggest that BS potentially provides active ingredients that may serve as an antibiotic substitute, effectively preventing SNE-induced growth decline by enhancing intestinal health in broilers.

Classification and Multifaceted Potential of Secondary Metabolites Produced by Bacillus subtilis Group: A Comprehensive Review

Despite their remarkable biosynthetic potential, Bacillus subtilis have been widely overlooked. However, their capability to withstand harsh conditions (extreme temperature, Ultraviolet (UV) and γ-radiation, and dehydration) and the promiscuous metabolites they synthesize have created increased commercial interest in them as a therapeutic agent, a food preservative, and a plant-pathogen control agent. Nevertheless, the commercial-scale availability of these metabolites is constrained due to challenges in their accessibility via synthesis and low fermentation yields. In the context of this rising in interest, we comprehensively visualized the antimicrobial peptides produced by B. subtilis and highlighted their prospective applications in various industries. Moreover, we proposed and classified these metabolites produced by the B. subtilis group based on their biosynthetic pathways and chemical structures. The biosynthetic pathway, bioactivity, and chemical structure are discussed in detail for each class. We believe that this review will spark a renewed interest in the often disregarded B. subtilis and its remarkable biosynthetic capabilities.

Safety evaluation of the food enzyme α‐amylase from the genetically modified Bacillus licheniformis strain NZYM‐AY

The food enzyme α‐amylase (4‐α‐d‐glucan glucanhydrolase; EC 3.2.1.1) is produced with the genetically modified Bacillus licheniformis strain NZYM‐AY by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is considered free from viable cells of the production organism and its DNA. It is intended to be used in starch processing for the production of glucose syrup and other starch hydrolysates, and distilled alcohol production. Since residual amounts of total organic solids are removed by distillation and by the purification steps applied during the production of glucose syrups, dietary exposure estimation was considered unnecessary. The production strain of the food enzyme fulfils the requirements for the qualified presumption of safety (QPS) approach to safety assessment. As no other concerns arising from the manufacturing process have been identified, the Panel considers that toxicological tests are not needed for the assessment of this food enzyme. A search for similarity of the amino acid sequence of the food enzyme to known allergens was made and one match was found. The Panel considered that, under the intended conditions of use (other than distilled alcohol production) the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is considered to be low. Based on the data provided, the Panel concluded that this food enzyme did not give rise to safety concerns under the intended conditions of use.

Polyketide-derived macrobrevins from marine macroalga-associated Bacillus amyloliquefaciens as promising antibacterial agents against pathogens causing nosocomial infections

Marine heterotrophs are treasured bio-resources of antimicrobial metabolites, and herein we report the biosynthetic potential of Bacillus amyloliquefaciens (ex. Fukumoto) Priest et al. (Bacillaceae) strain MTCC 12713 isolated from an intertidal macroalga Kappaphycus alvarezii (Doty) L.M.Liao (Rhodophyta: Solieriaceae). The bacterium showed promising biological activities against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. Genome mining of B. amyloliquefaciens MTCC 12713 predicted the gene clusters coding for biosynthesis of antibacterial metabolites. Bioactivity-guided purification was directed to isolate four homologous members of trans-acyltransferase polyketide synthase-derived antibiotics, which were classified as macrobrevin analogues. The compounds exhibited antibacterial activities against nosocomial pathogens, for example, methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Klebsiella pneumoniae and Pseudomonas aeruginosa with a range of MIC values from 1.56 to 6.25 μg/mL, although standard antibiotic chloramphenicol was active at 6.25-12.5 μg/mL. Conspicuously, the macrobrevin compound encompassing hexahydro-41-hydroxy-macrobrevin-31-acetate functionality, displayed considerably greater antagonistic activities against methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Vibrio parahaemolyticus, P. aeruginosa, K. pneumoniae, and Streptococcus pyogenes (MIC 1.56 μg/mL) compared to the positive controls and other macrobrevin analogues. Trans-AT polyketide synthase-stimulated biosynthetic pathway of macrobrevin compounds, through repetitive decarboxylative Claisen condensation between acetyl-S-KS domain and malonate-S-ACP units could corroborate the structural elucidation. In the genome mining study, among the 34 biosynthetic gene clusters, a hybrid trans-acyltransferase (trans-AT) pks/nrps gene cluster, which extends up to ∼81 Kb, was recognized in the genome of B. amyloliquefaciens MTCC 12713. The pks/nrps cluster revealed 46% similarity to trans-AT PKS-derived macrobrevin isolated from a mesophilic bacterium Brevibacillus sp. Leaf182 associated with the phyllosphere of the wild-type genotype of Arabidopsis thaliana. The binding positions for macrobrevins with S. aureus peptide deformylase showed docking score of larger than 14 kcal/mol, which was considerably greater than macrolactin N and actinonin (<10 kcal/mol). These present findings documented that the marine heterotrophic B. amyloliquefaciens MTCC 12713 could be used to develop prospective antibacterial agents belonging to macrobrevin analogues for biotechnological and pharmaceutical applications.

A Leap Forward Towards Unraveling Newer Anti-infective Agents from an Unconventional Source: a Draft Genome Sequence Illuminating the Future Promise of Marine Heterotrophic Bacillus sp. Against Drug-Resistant Pathogens

During the previous decade, genome-built researches on marine heterotrophic microorganisms displayed the chemical heterogeneity of natural product resources coupled with the efficacies of harnessing the genetic divergence in various strains. Herein, we describe the whole genome data of heterotrophic Bacillus amyloliquefaciens MB6 (MTCC 12,716), isolated from a marine macroalga Hypnea valentiae, a 4,107,511-bp circular chromosome comprising 186 contigs, with 4154 protein-coding DNA sequences and a coding ratio of 86%. Simultaneously, bioactivity-guided purification of the bacterial extract resulted in six polyketide classes of compounds with promising antibacterial activity. Draft genome sequence of B. amyloliquefaciens MB6 unveiled biosynthetic gene clusters (BGCs) engaged in the biosynthesis of polyketide-originated macrolactones with prospective antagonistic activity (MIC ≤ 5 µg/mL) against nosocomial pathogens. Genome analysis manifested 34 putative BGCs necessitated to synthesize biologically active polyketide-originated frameworks or their derivatives. These results provide insights into the genetic basis of heterotrophic B. amyloliquefaciens MTCC 12,716 as a prospective lead for biotechnological and pharmaceutical applications.

Safety evaluation of food enzymes produced by a safe strain lineage of Bacillussubtilis

The safety of microbially-derived food enzymes must be carefully assessed before market introduction. The production strain's safety is central to the assessment. In this paper, we have determined that DSM's Bacillus subtilis strain lineage can be considered safe for food enzyme production. The mutations introduced into this non-pathogenic and non-toxigenic microorganism do not lead to any safety concerns, as ensured by a thorough characterization of the strain lineage. The safety of both targeted and randomly introduced changes into the production strain's genome is confirmed by validating the absence of vector sequences and antibiotic resistance genes in all relevant production strains, and by demonstrating absence of cytotoxic peptide production. Furthermore, three food enzyme preparations produced by strains within this lineage did not show genotoxic potential. 90-day oral toxicity studies performed with the same enzyme preparations did not reveal toxicologically significant adverse effects. These results demonstrate absence of safety concerns from the introduced genetic modifications. Based on the establishment of this safe strain lineage, we postulate that future enzymes produced by current and new strains derived from the lineage can be safely developed without additional genotoxicity and systemic toxicity studies, allowing for a reduction of animal testing without compromising on product safety.

Safety evaluation of the food enzyme α-amylase from the genetically modified Bacillus licheniformis strain NZYM-KE

The food enzyme α‐amylase (4‐α‐d‐glucan glucanohydrolase; EC 3.2.1.1) is produced with the genetically modified Bacillus licheniformis strain NZYM‐KE by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. The α‐amylase is intended to be used in starch processing for the production of glucose syrups and other starch hydrolysates, and distilled alcohol production. Since residual amounts of the food enzyme are removed by the purification steps applied during the production of glucose syrups and distillation, no dietary exposure was calculated. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rats. The Panel identified a no observed adverse effect level at the highest dose of 1,100 mg TOS/kg body weight (bw) per day. A search for similarity of the amino acid sequence of the food enzyme to known allergens was made and one match was found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood is considered to be low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Bacillus subtilis natto as a potential probiotic in animal nutrition

The growing global demand for animal products and processed meat has created a challenge for the livestock sector to enhance animal productivity without compromising product quality. The restriction of antibiotics in animal feeds as growth promoters makes the use of probiotics a natural and safe alternative to obtain functional foods that provide animal health and quality and to maintain food safety for consumers. To incorporate these additives into the diet, detailed studies are required, in which in vitro and in vivo assays are used to prove the efficacy and to ensure the safety of probiotic candidate strains. Studies on the use of Bacillus subtilis natto as a spore-forming probiotic bacterium in animal nutrition have shown no hazardous effects and have demonstrated the effectiveness of its use as a probiotic, mainly due to its proven antimicrobial, anti-inflammatory, antioxidant, enzymatic, and immunomodulatory activity. This review summarizes the recent scientific background on the probiotic effects of B. subtilis natto in animal nutrition. It focuses on its safety assessment, host-associated efficacy, and industrial requirements.

Moving away from traditional antibiotic treatment: can macrocyclic lactones from marine macroalga-associated heterotroph be the alternatives?

Intertidal red algae Hypnea valentiae associated Bacillus amyloliquefaciens MTCC 12716 revealed potential inhibitory effects on the growth of drug-resistant pathogens. In the genome of B. amyloliquefaciens MTCC 12716, biosynthetic gene clusters encoding antibacterial metabolites were predicted, which might be expressed and contributed to the broad-spectrum anti-infective activity. Three homologue members of the 24-membered macrocyclic lactone family, named as bacvalactones 1-3 bearing 13-O-ethyl (1); 15-O-furanyl-13-O-isobutyl-7-O-propyl-propanoate (2); and 15-O-furanyl-13-O-isobutyl-7-O-propyl-propanoate-7,24-dimethyl (3) functionalities, were acquired through bioactivity-guided purification. The macrocyclic lactones displayed bactericidal activity against opportunistic pathogens causing nosocomial infections, for instance, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VREfs), and multidrug-resistant strains of Pseudomonas aeruginosa and Klebsiella pneumonia with MIC ≤ 3.0 μg/mL, whereas standard antibiotics ampicillin and chloramphenicol were active only at concentrations of ≥ 6.25 mg/mL. The biosynthetic pathway of macrocyclic lactones that are generated by trans-AT polyketide synthases through stepwise extension of an acetyl starter unit by eleven sequential Claisen condensations with malonyl-CoA was established, and the structures were correlated with the gene organization of the mln operon, which encompasses nine genes mln A-I (approximately 47 kb in size). The best binding poses for each compounds (1-3) with Staphylococcus aureus peptide deformylase (SaPDF) unveiled docking scores (≥ 9.70 kcal/mol) greater than that of natural peptide deformylase inhibitors, macrolactin N and actinonin (9.14 and 6.96 kcal/mol, respectively), which supported their potential in vitro bioactivities. Thus, the present work demonstrated the potential of macrocyclic lactone for biotechnological and pharmaceutical applications against emerging multidrug-resistant pathogens. Key Points •Three antibacterial bacvalactones were identified from the symbiotic bacterium. •The symbiotic bacterial genome was explored to identify the biosynthetic gene clusters. •Trans-AT pks-assisted mln biosynthetic pathway of the macrocyclic lactone was proposed. •In silicomolecular interactions of the bacvalactones with S. aureus PDF were analyzed.

Control of Foodborne Pathogenic Bacteria by Endophytic Bacteria Isolated from Ginkgo biloba L

Endophytic bacteria (EB) are a prospective source of natural and novel bioactive compounds with pharmaceutical relevance. In the present study, a total of 50 EB were isolated from the fruits and leaves of ginkgo tree (Ginkgo biloba L.), the only living species in the division Ginkgophyta and popularly known as a living fossil. All the isolated EB were screened for their antibacterial activity against five deleterious foodborne pathogenic bacteria namely Escherichia coli ATCC 43890, Salmonella Typhimurium ATCC 19586, Bacillus cereus ATCC 10876, Listeria monocytogenes ATCC19115, and Staphylococcus aureus ATCC 12600. Among the isolated EB, GbF-96, GbF-97, and GbF-98 exhibited antibacterial activity against all the pathogenic bacteria tested, with inhibition zone ranging from 33.47 to 9.55 mm. GbF-96, identified as Bacillus subtilis, exerted the highest antibacterial activity against all the tested bacteria. In contrast, the ethyl acetate extract of GbF-96 showed antibacterial activity against only B. cereus, E. coli, and Salmonella Typhimurium. Scanning electron microscopy results indicated cracked and irregular, swollen, shrunken, and lysed cell surfaces of the pathogenic bacteria treated with ethyl acetate extract of GbF-96 or B. subtilis, indicating that the metabolites of GbF-96 might penetrate the bacterial cell membranes and evoke pathways inducing cell lysis. Together, the data suggest that B. subtilis from G. biloba can be a potential candidate for controlling dreadful foodborne pathogenic bacteria, either by itself or by its metabolites.

Safety evaluation of the food enzyme endo-1,4-β-xylanase from a genetically modified Bacillus licheniformis (strain NZYM-CE)

The food enzyme endo-1,4-β-xylanase (4-β-d-xylan xylanohydrolase; EC 3.2.1.8) is produced with a genetically modified Bacillus licheniformis (strain NZYM-CE) by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. This xylanase is intended to be used in baking and cereal-based processes. Based on the maximum use levels recommended for the respective food processes and individual data from the EFSA Comprehensive European Food Consumption Database, dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.012 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not indicate a genotoxic concern. The systemic toxicity was assessed by a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level (NOAEL) of at least 1,020 mg TOS/kg bw per day, the highest dose tested. When the NOAEL value is compared to the estimated dietary exposure, this results in a margin of exposure (MoE) of at least 85,000. Similarity of the amino acid sequence to those of known allergens was searched and no match was found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood is considered to be low. Overall, the Panel concluded that based on the data provided and the derived MoE, this food enzyme does not give rise to safety concerns under the intended conditions of use.

Overview of the Antimicrobial Compounds Produced by Members of the Bacillus subtilis Group

Over the last seven decades, applications using members of the Bacillus subtilis group have emerged in both food processes and crop protection industries. Their ability to form survival endospores and the plethora of antimicrobial compounds they produce has generated an increased industrial interest as food preservatives, therapeutic agents and biopesticides. In the growing context of food biopreservation and biological crop protection, this review suggests a comprehensive way to visualize the antimicrobial spectrum described within the B. subtilis group, including volatile compounds. This classification distinguishes the bioactive metabolites based on their biosynthetic pathways and chemical nature: i.e., ribosomal peptides (RPs), volatile compounds, polyketides (PKs), non-ribosomal peptides (NRPs), and hybrids between PKs and NRPs. For each clade, the chemical structure, biosynthesis and antimicrobial activity are described and exemplified. This review aims at constituting a convenient and updated classification of antimicrobial metabolites from the B. subtilis group, whose complex phylogeny is prone to further development.

Secondary metabolite production and the safety of industrially important members of the Bacillus subtilis group

Members of the 'Bacillus subtilis group' include some of the most commercially important bacteria, used for the production of a wide range of industrial enzymes and fine biochemicals. Increasingly, group members have been developed for use as animal feed enhancers and antifungal biocontrol agents. The group has long been recognised to produce a range of secondary metabolites and, despite their long history of safe usage, this has resulted in an increased focus on their safety. Traditional methods used to detect the production of secondary metabolites and other potentially harmful compounds have relied on phenotypic tests. Such approaches are time consuming and, in some cases, lack specificity. Nowadays, accessibility to genome data and associated bioinformatical tools provides a powerful means for identifying gene clusters associated with the synthesis of secondary metabolites. This review focuses primarily on well-characterised strains of B. subtilis and B. licheniformis and their synthesis of non-ribosomally synthesised peptides and polyketides. Where known, the activities and toxicities of their secondary metabolites are discussed, together with the limitations of assays currently used to assess their toxicity. Finally, the regulatory framework under which such strains are authorised for use in the production of food and feed enzymes is also reviewed.

Safety evaluation of the food enzyme α-amylase from a genetically modified Bacillus licheniformis (strain NZYM-AV)

The food enzyme is an α‐amylase (4‐α‐d‐glucan glucanohydrolase; EC 3.2.1.1) produced with the genetically modified Bacillus licheniformis strain NZYM‐AV by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme does not contain the production microorganism or its DNA; therefore, there is no safety concern for the environment. The α‐amylase is intended to be used in starch processing for the production of glucose syrups and distilled alcohol production. Residual amounts of total organic solids (TOS) are removed by distillation and by the purification steps applied during the production of glucose syrups (by > 99%). Consequently, dietary exposure was not calculated. Genotoxicity tests did not raise a safety concern. The subchronic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rodents. The Panel derived a no observed adverse effect level (NOAEL) at the highest dose level of 796 mg TOS/kg body weight (bw) per day. The allergenicity was evaluated by comparing the amino acid sequence to those of known allergens and one match was found. The Panel considered that, under the intended condition of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood is considered low. Based on the microbial source, the genetic modifications, the manufacturing process, the compositional and biochemical data, the removal of TOS during the intended food production processes and the toxicological and genotoxicity studies, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme alpha-amylase from a genetically modified Bacillus licheniformis (strain NZYM-AN)

The food enzyme is an α‐amylase (4‐α‐d‐glucan glucanohydrolase; EC 3.2.1.1) produced with a genetically modified Bacillus licheniformis strain NZYM‐AN by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme does not contain the production organism or recombinant DNA; therefore, there is no safety concern for the environment. The α‐amylase is intended to be used in starch processing for the production of glucose syrups and distilled alcohol production. Residual amounts of total organic solids (TOS) are removed by distillation and by the purification steps applied during the production of glucose syrups (by > 99%). Consequently, dietary exposure was not calculated. Genotoxicity tests with the food enzyme did not raise a safety concern. The amino acid sequence of the food enzyme did not match to those of known allergens. The Panel considered that under the intended condition of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood is considered low. Based on the microbial source, the genetic modifications, the manufacturing process, the compositional and biochemical data, the removal of TOS during the intended food production processes and the findings in the genotoxicity studies, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme maltogenic amylase from a genetically modified Bacillus subtilis (strain NZYM‐SM)

The food enzyme considered is a maltogenic amylase (glucan 1,4‐α‐maltohydrolase; EC 3.2.1.133) produced with the genetically modified Bacillus subtilis strain NZYM‐SM by Novozymes A/S. The food enzyme contains neither the production organism nor recombinant DNA. The maltogenic amylase is intended for use in baking processes and starch processing for glucose syrups production. Based on the maximum use levels recommended for the food processes and individual consumption data from the EFSA Comprehensive European Food Consumption Database, dietary exposure to the food enzyme–Total Organic Solids (TOS) was estimated to be up to 0.168 mg TOS/kg body weight (bw) per day in European populations. The food enzyme did not induce gene mutations in bacteria or chromosomal aberrations in human lymphocytes. The subchronic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rodents. A no observed adverse effect level (NOAEL) was derived (320 mg TOS/kg bw per day), which, compared with the dietary exposure, results in a sufficiently high margin of exposure. The allergenicity was evaluated by searching for similarity of the amino acid sequence to those of known allergens. Three matches to occupational respiratory allergens were found, however, the Panel considered that there are no indications for food allergic reactions to the food enzyme. Based on the genetic modifications performed, the manufacturing process, the compositional and biochemical data provided, the dietary exposure assessment, the findings in the toxicological studies and allergenicity assessment, the Panel concluded that the food enzyme maltogenic amylase from Bacillus subtilis strain NZYM‐SM does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme xylanase from a genetically modified Bacillus subtilis strain TD160(229)

The food enzyme considered in this opinion is an endo-1,4-β-xylanase (EC 3.2.1.8) produced with a genetically modified Bacillus subtilis strain from Puratos N.V. (Belgium). The genetic modifications do not raise safety concerns. The food enzyme contains neither the production organism nor recombinant DNA. The endo-1,4-β-xylanase is intended to be used in baking processes. Based on the maximum use levels recommended for the baking processes, dietary exposure to the food enzyme-total organic solids (TOS) was estimated on the basis of individual data from the EFSA Comprehensive European Food Consumption Database. This exposure estimate is up to 0.008 mg TOS/kg body weight per day in European populations. The food enzyme did not induce gene mutations in bacteria nor clastogenic activity in human lymphocytes. Therefore, there is no concern with respect to genotoxicity. The subchronic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rodents. A no observed adverse effect level was derived, which, compared with the dietary exposure, results in a sufficiently high margin of exposure. The allergenicity was evaluated by searching for similarity of the amino acid sequence to those of known allergens; no matches were found. The Panel considered that there are no indications for food allergic reactions to this xylanase. Based on the microbial source, genetic modifications performed, the manufacturing process, the compositional and biochemical data provided, the findings in the toxicological studies and allergenicity assessment, this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme β-amylase from genetically modified Bacillus licheniformis strain NZYM-JA

The food enzyme considered in this opinion is a β-amylase (4-α-d-glucan maltohydrolase; EC 3.2.1.2), produced with genetically modified Bacillus licheniformis strain NZYM-JA by Novozymes A/S (Denmark). The β-amylase food enzyme is intended to be used in starch processing for the production of glucose syrups. Since the residual amounts of total organic solids (TOS) in glucose syrups after filtration and purification during starch processing were considered negligible, no dietary exposure was calculated. Toxicological tests made with the food enzyme under application indicated that there was no concern with respect to genotoxicity, mutagenicity or systemic toxicity. The allergenicity was evaluated by searching for similarity of the amino acid sequence to those of known allergens; no match was found. The Panel considers that there are no indications for allergic reactions. Based on the genetic modifications performed, the manufacturing process, the compositional and biochemical data provided, the findings in the toxicological studies and allergenicity assessment, the Panel concludes that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Safety evaluation of the food enzyme pullulanase from genetically modified Bacillus subtilis strain NZYM-AK

The food enzyme considered in this opinion is a pullulanase (pullulan 6-α-glucanohydrolase; EC 3.2.1.41), produced with the genetically modified Bacillus subtilis strain NZYM-AK by Novozymes A/S (Denmark). The pullulanase food enzyme is intended to be used in starch processing for the production of glucose syrups. Since the residual amounts of total organic solids (TOS) in glucose syrups after filtration and purification during starch processing were considered negligible, no dietary exposure was calculated. Genotoxicity tests made with the food enzyme indicated no genotoxic concern. A repeated dose 90-day oral toxicity study in rodents, carried out with a pullulanase produced with a predecessor strain, showed no concern with respect to systemic toxicity. The allergenicity was evaluated by searching for similarity of the amino acid sequence to those of known allergens; no match was found. The Panel considers that there are no indications for allergic reactions. Based on the microbial source, genetic modifications performed, the manufacturing process, the compositional and biochemical data provided, the findings in the toxicological studies and allergenicity assessment, the Panel concludes that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Isolation and Characterization of Phages Infecting Bacillus subtilis

Bacteriophages have been suggested as an alternative approach to reduce the amount of pathogens in various applications. Bacteriophages of various specificity and virulence were isolated as a means of controlling food-borne pathogens. We studied the interaction of bacteriophages with Bacillus species, which are very often persistent in industrial applications such as food production due to their antibiotic resistance and spore formation. A comparative study using electron microscopy, PFGE, and SDS-PAGE as well as determination of host range, pH and temperature resistance, adsorption rate, latent time, and phage burst size was performed on three phages of the Myoviridae family and one phage of the Siphoviridae family which infected Bacillus subtilis strains. The phages are morphologically different and characterized by icosahedral heads and contractile (SIOΦ, SUBω, and SPOσ phages) or noncontractile (ARπ phage) tails. The genomes of SIOΦ and SUBω are composed of 154 kb. The capsid of SIOΦ is composed of four proteins. Bacteriophages SPOσ and ARπ have genome sizes of 25 kbp and 40 kbp, respectively. Both phages as well as SUBω phage have 14 proteins in their capsids. Phages SIOΦ and SPOσ are resistant to high temperatures and to the acid (4.0) and alkaline (9.0 and 10.0) pH.

Bacillus subtilis subsp. subtilis CBMDC3f with antimicrobial activity against Gram-positive foodborne pathogenic bacteria: UV-MALDI-TOF MS analysis of its bioactive compounds

In this work a new Bacillus sp. strain, isolated from honey, was characterized phylogenetically. Its antibacterial activity against three relevant foodborne pathogenic bacteria was studied; the main bioactive metabolites were analyzed using ultraviolet matrix assisted laser desorption-ionization mass spectrometry (UV-MALDI MS). Bacillus CBMDC3f was phylogenetically characterized as Bacillus subtilis subsp. subtilis after rRNA analysis of the 16S subunit and the gyrA gene (access codes Genbank JX120508 and JX120516, respectively). Its antibacterial potential was evaluated against Listeria monocytogenes (9 strains), B. cereus (3 strains) and Staphylococcus aureus ATCC29213. Its cell suspension and cell-free supernatant (CFS) exerted significant anti-Listeria and anti-S. aureus activities, while the lipopeptides fraction (LF) also showed anti-B. cereus effect. The UV-MALDI-MS analysis revealed surfactin, iturin and fengycin in the CFS, whereas surfactin predominated in the LF. The CFS from CBMDC3f contained surfactin, iturin and fengycin with four, two and four homologues per family, respectively, whereas four surfactin, one iturin and one fengycin homologues were identified in the LF. For some surfactin homologues, their UV-MALDI-TOF/TOF (MS/MS; Laser Induced Decomposition method, LID) spectra were also obtained. Mass spectrometry analysis contributed with relevant information about the type of lipopeptides that Bacillus strains can synthesize. From our results, surfactin would be the main metabolite responsible for the antibacterial effect.

Purification, characterization and safety assessment of the introduced cold shock protein B in DroughtGard maize

DroughtGard maize was developed through constitutive expression of cold shock protein B (CSPB) from Bacillus subtilis to improve performance of maize (Zea mays) under water-limited conditions. B. subtilis commonly occurs in fermented foods and CSPB has a history of safe use. Safety studies were performed to further evaluate safety of CSPB introduced into maize. CSPB was compared to proteins found in current allergen and protein toxin databases and there are no sequence similarities between CSPB and known allergens or toxins. In order to validate the use of Escherichia coli-derived CSPB in other safety studies, physicochemical and functional characterization confirmed that the CSPB produced by DroughtGard possesses comparable molecular weight, immunoreactivity, and functional activity to CSPB produced from E. coli and that neither is glycosylated. CSPB was completely digested with sequential exposure to pepsin and pancreatin for 2 min and 30 s, respectively, suggesting that CSPB will be degraded in the mammalian digestive tract and would not be expected to be allergenic. Mice orally dosed with CSPB at 2160 mg/kg, followed by analysis of body weight gains, food consumption and clinical observations, showed no discernible adverse effects. This comprehensive safety assessment indicated that the CSPB protein from DroughtGard is safe for food and feed consumption.

Bacillus subtilis natto: a non-toxic source of poly-γ-glutamic acid that could be used as a cryoprotectant for probiotic bacteria

It is common practice to freeze dry probiotic bacteria to improve their shelf life. However, the freeze drying process itself can be detrimental to their viability. The viability of probiotics could be maintained if they are administered within a microbially produced biodegradable polymer - poly-γ-glutamic acid (γ-PGA) - matrix. Although the antifreeze activity of γ-PGA is well known, it has not been used for maintaining the viability of probiotic bacteria during freeze drying. The aim of this study was to test the effect of γ-PGA (produced by B. subtilis natto ATCC 15245) on the viability of probiotic bacteria during freeze drying and to test the toxigenic potential of B. subtilis natto. 10% γ-PGA was found to protect Lactobacillus paracasei significantly better than 10% sucrose, whereas it showed comparable cryoprotectant activity to sucrose when it was used to protect Bifidobacterium breve and Bifidobacterium longum. Although γ-PGA is known to be non-toxic, it is crucial to ascertain the toxigenic potential of its source, B. subtilis natto. Presence of six genes that are known to encode for toxins were investigated: three component hemolysin (hbl D/A), three component non-haemolytic enterotoxin (nheB), B. cereus enterotoxin T (bceT), enterotoxin FM (entFM), sphingomyelinase (sph) and phosphatidylcholine-specific phospholipase (piplc). From our investigations, none of these six genes were present in B. subtilis natto. Moreover, haemolytic and lecithinase activities were found to be absent. Our work contributes a biodegradable polymer from a non-toxic source for the cryoprotection of probiotic bacteria, thus improving their survival during the manufacturing process.

Co-production of surfactin and a novel bacteriocin by Bacillus subtilis subsp. subtilis H4 isolated from Bikalga, an African alkaline Hibiscus sabdariffa seed fermented condiment

Bikalga is a Hibiscus sabdariffa seed fermented condiment widely consumed in Burkina Faso and neighboring countries. The fermentation is dominated by Bacillus subtilis group species. Ten B. subtilis subsp. subtilis (six isolates) and Bacillus licheniformis (four isolates) isolated from traditional Bikalga were examined for their antimicrobial activity against a panel of 36 indicator organisms including Gram-positive and Gram-negative bacteria and yeasts. The Bacillus spp. isolates showed variable inhibitory abilities depending on the method used. Both Gram-positive and Gram-negative bacteria were inhibited in the agar spot assay while only Gram-positive pathogens were inhibited in the agar well diffusion assay. Cell free supernatants (CFS) of pure cultures of 3 B. subtilis subsp. subtilis (G2, H4 and F1) strains inhibited growth of Listeria monocytogenes, Micrococcus luteus, Staphylococcus aureus and Bacillus cereus, while CFS of 2 B. licheniformis (E3 and F9) strains only inhibited M. luteus. The antimicrobial substance(s) produced by B. subtilis subsp. subtilis H4 was further characterized. The antimicrobial substance(s) produced by H4 was detected from mid-exponential growth phase. The activity was sensitive to protease and trypsin, but resistant to the proteolytic action of proteinase K and papain. Treatment with α-amylase and lipase II resulted in a complete loss of antimicrobial effect, indicating that a sugar moiety and lipid moiety are necessary for the activity. Treatment with mercapto-ethanol resulted in a significant loss, indicative of the presence of disulfide bridges. The antimicrobial activity of H4 was heat resistant and active at pH3-10. PCR detection of yiwB, sboA, spoX, albA and spaS, etnS genes and genes coding for surfactins and plipastatins (fengycins) indicated a potential for subtilosin, subtilin and lipopeptide production, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was carried out and a single band of approximately 4kDa had antimicrobial activity. Ultra high performance liquid chromatography-time of flight mass spectrometry (UHPLC-TOFMS) analysis of the 4kDa band allowed identification of surfactin and a protein with a monoisotopic mass of 3346.59Da, which is dissimilar in size to subtilosin and subtilin. Surfactin is a cyclic lipoheptapeptide, which contains a β-hydroxy fatty acid, but no di-sulfide bridges or sugar residues. The complete loss of activity upon amylase treatment indicates that surfactin was not responsible for the observed antimicrobial effect. However, it cannot completely be ruled out that surfactin acts synergistically with the detected protein, though further investigations are needed to confirm this.

Production of the Bacillus licheniformis SubC protease using Lactococcus lactis NICE expression system

In this work the subC gene from Bacillus licheniformis encoding subtilisin was cloned into the nisin-controlled expression (NICE) vectors (pNZ8048 and pNZ8148) with or without the signal peptide SP Usp45 directing extracellular secretion via Sec machinery. Extracellular protease production and activity was tested using Lactococcus lactis NZ9000 as host, which could be used for rennet production. The efficiency of protein production was tested using purified nisin and the supernatant of L. lactis NZ970 nisin producer. Similar results were obtained for 1 ng/ml nisin and 10 000 diluted supernatant. SP Usp45 signal peptide effectively directed extracellular localization of active and stable protease. SubC signal for extracellular localization in B. licheniformis, was also recognized by L. lactis Sec pathway, although with lower efficiency, as shown by a 3-fold lower protease activity in the medium. Protease production and activity was optimized using parameters such as induction time, nutrients (glucose, casitone) supplementation during growth or protease stabilization by calcium ions. The results were also verified in fed-batch bioreactor for further scale-up of the expression system.

Evaluation of the immunogenicity and in vivo toxicity of the antimicrobial peptide P34

Immunogenicity and toxicity of antimicrobial peptide P34 were evaluated in vivo. BALB/c mice were inoculated intraperitoneally with peptide P34 alone and associated with Freund's adjuvant. For acute toxicity testing, different concentrations of the peptide P34 (82.5, 165.0, 247.5 and 330.0mg/kg) were orally administered. To evaluate the sub-chronic toxicity the tested dose of 0.825 mg/kg/day of the peptide P34 or nisin were administered for 21 days. There were no hypersensitivity reactions or significant increase in antibody titer during the immunogenicity experiment or death of animals during the acute or sub-chronic toxicity tests. The LD(50) was higher than 332.3 ± 0.76 mg/kg. No significant changes in serum biochemical parameters were observed in the animals treated with the peptide P34 unlike nisin-treated group showed a significant increase in alanine transaminase levels in comparison to controls. The group treated with 0.825 mg/kg/day of nisin showed histological changes in the spleen, skin and liver. In the group treated with peptide P34 histological changes in the spleen were observed, with the presence of megakaryocytes. Few studies report the use of animal models to evaluate the in vivo toxicity of antimicrobial peptides and such investigation is an essential step to ensure it safe use in foods.

Diversity and applications of Bacillus bacteriocins

Members of the genus Bacillus are known to produce a wide arsenal of antimicrobial substances, including peptide and lipopeptide antibiotics, and bacteriocins. Many of the Bacillus bacteriocins belong to the lantibiotics, a category of post-translationally modified peptides widely disseminated among different bacterial clades. Lantibiotics are among the best-characterized antimicrobial peptides at the levels of peptide structure, genetic determinants and biosynthesis mechanisms. Members of the genus Bacillus also produce many other nonmodified bacteriocins, some of which resemble the pediocin-like bacteriocins of the lactic acid bacteria (LAB), while others show completely novel peptide sequences. Bacillus bacteriocins are increasingly becoming more important due to their sometimes broader spectra of inhibition (as compared with most LAB bacteriocins), which may include Gram-negative bacteria, yeasts or fungi, in addition to Gram-positive species, some of which are known to be pathogenic to humans and/or animals. The present review provides a general overview of Bacillus bacteriocins, including primary structure, biochemical and genetic characterization, classification and potential applications in food preservation as natural preservatives and in human and animal health as alternatives to conventional antibiotics. Furthermore, it addresses their environmental applications, such as bioprotection against the pre- and post-harvest decay of vegetables, or as plant growth promoters.

Influence of pH and sodium chloride on kinetics of thermal inactivation of the bacteriocin-like substance P34

AIMS

To investigate the kinetics of thermal inactivation of the bacteriocin-like substance P34 at different pH and sodium chloride concentration.

METHODS AND RESULTS

Samples of bacteriocin were treated at different time-temperature combinations in the range of 0-300 min and 90-120°C and the kinetic parameters for bacteriocin inactivation were calculated. For all treatments, the thermal inactivation reaction fitted adequately to first-order model. D- and k-values were smaller and higher, respectively, for pH 4·5 than for 6·0 or 7·0, indicating that bacteriocin P34 was less thermostable at lower pH. At 120, 115 and 100°C, the addition of sodium chloride decreased thermal stability. For other temperatures, addition of NaCl increased stability of the peptide. The presence of greater amount of the salt (50 g l(-1) ) resulted in a higher thermal stability of bacteriocin P34, suggesting that the reduction in water activity of the solution interfered on the stability of the peptide.

CONCLUSIONS

Based on an isothermal experiment in the temperature range of 90-120°C, and by thermal death time models, bacteriocin P34 is less heat stable at low pH and has increased thermal stability in the presence of NaCl. Addition of NaCl improved the stability of the peptide P34 at high temperatures.

SIGNIFICANCE AND IMPACT OF THE STUDY

Studies on kinetics of thermal inactivation of bacteriocins are essential to allow their proper utilization in the food industry.

Health considerations regarding horizontal transfer of microbial transgenes present in genetically modified crops

The potential effects of horizontal gene transfer on human health are an important item in the safety assessment of genetically modified organisms. Horizontal gene transfer from genetically modified crops to gut microflora most likely occurs with transgenes of microbial origin. The characteristics of microbial transgenes other than antibiotic-resistance genes in market-approved genetically modified crops are reviewed. These characteristics include the microbial source, natural function, function in genetically modified crops, natural prevalence, geographical distribution, similarity to other microbial genes, known horizontal transfer activity, selective conditions and environments for horizontally transferred genes, and potential contribution to pathogenicity and virulence in humans and animals. The assessment of this set of data for each of the microbial genes reviewed does not give rise to health concerns. We recommend including the above-mentioned items into the premarket safety assessment of genetically modified crops carrying transgenes other than those reviewed in the present study.

Kinetic modeling of the thermal inactivation of bacteriocin-like inhibitory substance p34

Optimization of thermal processes relies on adequate degradation kinetic models to warrant food safety and quality. The knowledge on thermal inactivation kinetics of antimicrobial peptides is necessary to allow for their adequate use as natural biopreservatives in the food industry. In this work, thermal inactivation of the previously characterized bacteriocin-like inhibitory substance (BLIS) P34 was kinetically investigated within the temperature range of 90-120 degrees C. Listeria monocytogenes ATCC 7644 was used as the indicator microorganism for antimicrobial activity. Applicability of various inactivation models available in the literature was critically evaluated. The first-order model provided the best description of the kinetics of inactivation over the selected temperatures, with k values between 0.059 and 0.010 min(-1). D and k values decreased and increased, respectively, with increasing temperature, indicating a faster inactivation at higher temperatures. Results suggest that BLIS P34 is thermostable, with a z value of 37.74 degrees C and E(a) of 72 kJ mol(-1).

Safety evaluation of 1,4-alpha-glucan branching enzymes from Bacillus stearothermophilus and Aquifex aeolicus expressed in Bacillus subtilis

1,4-alpha-Glucan branching enzyme (BE; EC 2.4.1.18) is a key biocatalyst in the synthesis of polysaccharides, and is therefore useful in the production of food ingredients. The BEs evaluated in this study (BE-01 and BE-02) are obtained by fermentation of Bacillus subtilis expressing the BE gene from either Bacillus stearothermophilus strain TRBE14 or Aquifex aeolicus strain VF5. The safety of BE-01 and BE-02 have not been previously evaluated, and therefore, both were subjected to standard toxicological testing. In a battery of standard Salmonella typhimurium strains (TA98, TA100, TA1535, and TA1537) and in Escherichia coli WP2uvrA, both with and without metabolic activation, neither BE-01 nor BE-02 exhibited mutagenic activity. Similarly, neither was associated with clastogenic properties in Chinese hamster ovary cells in an in vitro chromosomal aberration assay. In rats, oral administration of BE-01 or BE-02 at doses of up to 15 mL/kg body weight/day (approximately 870 and 900 mg/kg body weight/day, respectively) for 13 weeks did not produce compound-related clinical signs or toxicity, changes in body weight gain, food consumption, hematology, clinical chemistry, urinalysis, organ weights, or in any gross and microscopic findings. The results of this study support the safety of BE-01 and BE-02 in food production.

Mode of action of antimicrobial peptide P45 on Listeria monocytogenes

The mode of action of an antimicrobial peptide produced by Bacillus sp. P45 isolated from the intestine of the Amazonian basin fish Piaractus mesopotamicus was investigated. The antimicrobial peptide was purified from culture supernatants by precipitation with ammonium sulfate and gel filtration chromatography. The peptide has an EC(50) of 300 AU (activity units) ml(-1) and kills all viable cells of Listeria monocytogenes with a concentration of 800 AU ml(-1). A decrease in OD was observed when L. monocytogenes cultures were treated with the peptide, suggesting that cells were lysed. Transmission electron microscopy showed damage of the cell envelope and loss of protoplasmic material. The peptide P45 was bactericidal and bacteriolytic to L. monocytogenes. There is evidence that the mode of action is interfering at cell membranes and the cell wall. The knowledge of the mode of action of antimicrobial peptides is an essential step to consider their utilization in food or clinic.

Identification of a non-pathogenic surrogate organism for chlorine dioxide (ClO2) gas treatment

The identification of non-pathogenic surrogate microorganisms is beneficial for determining and validating the efficacy of antimicrobial treatments in food manufacturing environments. A surrogate organism was identified to aid in the decontamination process of fresh produce when treated with chlorine dioxide (ClO(2)) gas. Thirty-two known strains of pathogenic and non-pathogenic microorganisms and seven unknown microbial isolates from mushroom, tomatoes, and strawberries were evaluated. The primary goal was to find alternative non-pathogenic organisms that had an equal or higher resistance compared to Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes. Among the strains tested, MR1 (mushroom isolate), E. coli O157:H7 C7927, E. coli O157:H7 204P, STB2 (strawberry isolate), and vegetative cells of Bacillus cereus 232 in wet inoculum were found to be the most resistant to gaseous ClO(2) treatment at 0.3 mg/l for 1 min and D-values at 0.3 mg/l ClO(2) were 3.53, 1.95, 1.72, 1.68, and 1.57 min, respectively. For identification, the MR1 and STB2 strains were identified using a Ribotyper with the EcoRI restriction enzyme of 16S rDNA sequence. MR1 was identified as Hafnia alvei with a similarity value of 94% using the ribotype pattern and with a 93.6% similarity using an API 20E strip, and with a 99% similarity using 16S rDNA analysis. The Ped-2E9-based cytotoxicity assay was conducted for the MRI strain extracellular toxin and whole cell toxicity and did not show cytotoxicity. Analysis, using multiplex PCR, was performed to verify absence of the eaeA gene. H. alvei is a suitable non-pathogenic surrogate, with higher resistance to ClO(2) gas compared to pathogens studied, that may be useful to establish optimum conditions of ClO(2) gas decontamination systems.

Inhibition of Listeria monocytogenes in dairy products using the bacteriocin-like peptide cerein 8A

The efficacy of the antimicrobial peptide cerein 8A to control the development of Listeria monocytogenes in milk and soft cheese was investigated. The addition of 160 AU ml(-1) cerein 8A to UHT milk resulted in a decrease of 3 log cycles in viable cells within the 14-day period at 4 degrees C. The viable counts of L. monocytogenes in pasteurized milk samples containing cerein 8A was lower than those observed in controls without bacteriocin. Addition of cerein 8A to Minas-type soft cheese caused a delay in the start of exponential growth phase, although similar counts were observed after day 6. When cerein 8A was used to control cheese surface contamination by L. monocytogenes, a decrease of 2 log cycles in viable counts of cerein-treated samples was observed during 30 days at 4 degrees C. This antimicrobial peptide shows potential use as a biopreservative for application in dairy products.