Spores of Bacillus coagulans GBI-30, 6086 show high germination, survival and enzyme activity in a dynamic, computer-controlled in vitro model of the gastrointestinal tract

Progress of research and application of Heyndrickxia coagulans (Bacillus coagulans) as probiotic bacteria

Probiotics are defined as living or dead bacteria and their byproducts that maintain the balance of the intestinal microbiome. They are non-toxic, non-pathogenic, and do not release any toxins either within or outside the body. Adequate consumption of probiotics can enhance metabolite production, increase immunity, maintain a balanced intestinal flora, and stimulate growth. Probiotics do not have negative antibiotic effects and help maintain the natural flora in animals in a balanced state or prevent dysbacteriosis. Heyndrickxia coagulans (H. coagulans) is a novel probiotic species that is gradually being used for the improvement of human health. Compared to commonly used probiotic lactic acid bacteria, H. coagulans can produce spores, which provide the species with high resistance to adverse conditions. Even though they are transient residents of the gut, beneficial bacteria can have a significant impact on the microbiota because they can outnumber harmful germs, and vice versa. This article discusses the probiotic mechanisms of H. coagulans and outlines the requirements for a substance to be classified as a probiotic. It also addresses how to assess strains that have recently been discovered to possess probiotic properties.

Nutritional Interventions with Bacillus coagulans Improved Glucose Metabolism and Hyperinsulinemia in Mice with Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is a metabolic disorder caused by mutations in the porphobilinogen deaminase (PBGD) gene, encoding the third enzyme of the heme synthesis pathway. Although AIP is characterized by low clinical penetrance (~1% of PBGD mutation carriers), patients with clinically stable disease report chronic symptoms and frequently show insulin resistance. This study aimed to evaluate the beneficial impact of nutritional interventions on correct carbohydrate dysfunctions in a mouse model of AIP that reproduces insulin resistance and altered glucose metabolism. The addition of spores of Bacillus coagulans in drinking water for 12 weeks modified the gut microbiome composition in AIP mice, ameliorated glucose tolerance and hyperinsulinemia, and stimulated fat disposal in adipose tissue. Lipid breakdown may be mediated by muscles burning energy and heat dissipation by brown adipose tissue, resulting in a loss of fatty tissue and improved lean/fat tissue ratio. Probiotic supplementation also improved muscle glucose uptake, as measured using Positron Emission Tomography (PET) analysis. In conclusion, these data provide a proof of concept that probiotics, as a dietary intervention in AIP, induce relevant changes in intestinal bacteria composition and improve glucose uptake and muscular energy utilization. Probiotics may offer a safe, efficient, and cost-effective option to manage people with insulin resistance associated with AIP.

Draft Genome Sequence of Weizmannia coagulans MB BCM9, a Stable Spore-Forming Probiotic

Weizmannia coagulans MB BCM9 (MTCC 25157) is a safe probiotic strain. Here, we announce a fully assembled draft genome sequence consisting of 3,450,803 bp, with 139 contigs. A total of 3,377 protein-coding genes, 15 rRNAs, 80 tRNAs, 5 noncoding RNAs (ncRNAs), and 107 pseudogenes were identified from this assembly.

Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 mediate via reshaping of microbiome gut-brain axis in rats

BACKGROUND

Due to the rising cases of treatment-refractory affective disorders, the discovery of newer therapeutic approaches is needed. In recent times, probiotics have garnered notable attention in managing stress-related disorders. Herein, we examined the effect of Bacillus coagulans Unique IS-2® probiotic on anxiety- and depression-like phenotypes employing maternal separation (MS) and chronic-unpredictable mild stress (CUMS) model in rats.

METHODS

Both male and female Sprague-Dawley rats were subjected to MS + CUMS. Probiotic treatment was provided for 6 weeks via drinking water. Anxiety- and depression-like phenotypes were assessed using sucrose-preference test (SPT), forced-swimming test (FST), elevated-plus maze test (EPM), and open-field test (OFT). Blood, brain, intestine, and fecal samples were obtained for biochemical and molecular studies.

RESULTS

Stress-exposed rats drank less sucrose solution, showed increased passivity, and explored less in open-arms in SPT, FST, and EPM, respectively. These stress-generated neurobehavioral aberrations were alleviated by 6-week of Bacillus coagulans Unique IS-2 treatment. The overall locomotor activity in OFT remained unchanged. The decreased levels of BDNF and serotonin and increased levels of C-reactive protein, TNF-α, IL-1β, and dopamine, in the hippocampus and/or frontal cortex of stress-exposed rats were reversed following probiotic treatment. Administration of probiotic also restored the systemic levels of L-tryptophan, L-kynurenine, kynurenic-acid, and 3-hydroxyanthranilic acid, villi/crypt ratio, goblet-cell count, Firmicutes to Bacteroides ratio, and levels of acetate, propionate, and butyrate in fecal samples. These results indicate remodeling of the microbiome gut-brain axis in Bacillus coagulans Unique IS-2 recipient rats. However, protein levels of doublecortin, GFAP, and zona occludens in the hippocampus and occludin-immunoreactivity in the intestine remained unchanged. No prominent sex-specific changes were noted.

CONCLUSION

Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 in MS + CUMS rat model may be mediated via reshaping the microbiome gut-brain axis.

W D, U. M K, S.D K. Bacillus Coagulans and its Spore as Potential Probiotics in the Production of Novel Shelf- Stable Foods

The synbiotic foods with therapeutic activities have been beneficial to gut health and immunity development, including Bacillus coagulans as the probiotic microorganism. It is preferred over other lactic acid bacteria (LAB) as it can produce spores. It is grown in the pH range of 5.5 to 6.2 and releases spores at 37 °C. These microbial spores can withstand environments with high temperatures, acidic conditions, and salinity, making it a viable probiotic organism for production of novel shelf-stable foods. It has become an essential ingredient in the functional food industry due to its probiotic characteristics and great resistance to stressful conditions. For extensive commercial use and a wide range of food applications, apart from probiotic characteristics, a probiotic organism must be cost-effective, convenient and remain viable throughout the processing, storage and consumption. The non-spore- forming lactic acid bacteria can be utilized to make probiotic products and fermented dairy products under controlled processing and storage conditions. The spore- forming probiotic organism can be delivered into the human gut through novel food products derived from cereals, legumes, fruits and vegetables, confectionery products, and meat and non-dairy products. This has led to the development of convenient and shelf-stable non-dairy probiotics. These non-dairy-based probiotics are cheaper, resilient against various processing conditions, high in bioactive components, and can mitigate the risk of lifestyle diseases and reduce. Further, lactose intolerance is associated with the consumption of dairy probiotics. Therefore, this review aimed to assess the utilization of probiotic Bacillus coagulans spores in emerging shelf-stable novel non-dairy products with probiotic potential.

Application of Weizmannia coagulans in the medical and livestock industry

Purpose

Products enriched with probiotics have always been fashionable. Weizmannia coagulans has become a hot research topic in the academic community due to their multiple functional properties and high resistance to stress, which can retain their activity in a variety of harsh environments. This review aims to evaluate the probiotic effects of different strains of Weizmannia coagulans in animals and humans and to inspire better exploitation of the value of this strain.

Methods

This review summarizes the latest research progress of Weizmannia coagulans from two major applications in animal breeding and human health.

Results

The functional properties of Weizmannia coagulans are extensively recognized. In animals, the strain can promote nutrient absorption, reduce mortality, and enhance the slaughter rate in livestock and poultry. In humans, the strain can be used to treat gastrointestinal disorders, immunomodulation, depressive symptoms, and non-alcoholic fatty liver. Weizmannia coagulans is projected as an ideal substitute for antibiotics and other chemical drugs.

Conclusion

Despite the outstanding functional properties of Weizmannia coagulans, there are numerous strains of Weizmannia coagulans and significant differences between strains in functional and physiological properties. Currently, there are few literature reports on the probiotic mechanism and functional gene identification of Weizmannia coagulans, which is crucial for the commercialization of Weizmannia coagulans and the benefit of human society.

Effective gossypol removal from cottonseed meal through optimized solid-state fermentation by Bacillus coagulans

BACKGROUND

Cottonseed meal (CSM) is the main by-product of the cottonseed oil extraction process with high protein content, which is an important protein source for feed industry. However, CSM contains free gossypol (FG), a toxic substance that is detrimental to animal health and greatly limits its application. Microbial fermentation is currently considered to be one of the most effective methods to reduce FG and other anti-nutritional factors in CSM. Previously, yeast and bacteria species are used for degradation of FG in CSM, but showing less detoxification efficiency. Bacillus coagulans combines the properties of both lactic acid bacteria and Bacillus, producing both lactic acid and spores, and is considered a potential probiotic. In this study, we aimed to evaluate and optimize the effect of the solid-state fermentation process using a Bacillus coagulans to gossypol removal contained cottonseed meal.

RESULTS

36 B. coagulans strains were isolated and found to have the ability to remove free gossypol. Through the evaluation of strains and optimization of fermentation conditions including fermentation temperature, ratio of material to water, inoculation amount, fermentation time and pH, we have established a solid-state fermentation process using a Bacillus coagulans strain S17 on CSM substrate with 1:1 of the material-to-water ratio, 15% (v/w) seed inoculation, 2% expanded corn flour, 1% bran, and 0.3%-0.8% metal irons at 40 °C for 52 h. After fermentation, the FG content in CSM was reduced from 923.80 to 167.90 mg/kg with 81.83% detoxification efficiency. Meanwhile, the crude protein content in CSM increased from 47.98 to 52.82%, and importantly, the spore concentration of strain S17 reached 1.68 × 10¹⁰ CFU/g dry material.

CONCLUSION

The study showed that B. coagulans have the potential strong ability to degrade free gossypol through cottonseed meal fermentation. This study presents a feasible process for improving the resource utilization rate and nutritional value of CSM via solid-state fermentation through B. coagulans S17.

Throughput screening of Bacillus subtilis strains that abundantly secrete surfactin in vitro identifies effective probiotic candidates

Since the prohibition of antibiotics as animal growth promoters, demand for effective probiotic strains has steadily increased. The goal is to maintain productivity and mitigate environmental concerns in the livestock industry. There are many probiotic animal-diet supplements available, over 2,000 products in the Republic of Korea alone, with little explanation about the desirable properties of each probiotic strain. The purpose of this study was to describe the underlying logic and methods used to select two novel strains of probiotic candidates. To economically screen these candidates, the abundance of surfactin secreted was used as an in vitro marker. We used a modified oil-misting method to screen ~2,000 spore-forming bacteria for novel strains of Bacillus subtilis. Of these, 18 strains were initially selected based on the semiquantitative criterion that they secreted more surfactin than B. subtilis ATCC21322 on Luria-Berani (LB) agar plates. The whole genome sequence was determined for two of the 18 strains to verify their identity. A phylogeny of 1,162 orthologous genes, genome contents, and genome organization confirmed them as novel strains. The surfactin profiles produced by these two strains consisted of at least four isoforms similar to standard surfactin and enhanced cellulase activities up to 50%. Four fractionated individual isoforms of surfactin suppressed inflammation induced by lipopolysaccharides. The half-maximal inhibitory concentration (IC50) was about 20 μM for each isoform. Both selected strains were susceptible to seven important antibiotics. Our results implied that an abundant secretion of surfactin was a useful biomarker in vitro and could be utilized for mining probiotic candidates through high-throughput screening of environmental samples.

In situ, in vivo, and in vitro approaches for studying AMR plasmid conjugation in the gut microbiome

Antimicrobial resistance (AMR) is a global threat, with evolution and spread of resistance to frontline antibiotics outpacing the development of novel treatments. The spread of AMR is perpetuated by transfer of antimicrobial resistance genes (ARGs) between bacteria, notably those encoded by conjugative plasmids. The human gut microbiome is a known 'melting pot' for plasmid conjugation, with ARG transfer in this environment widely documented. There is a need to better understand the factors affecting the incidence of these transfer events, and to investigate methods of potentially counteracting the spread of ARGs. This review describes the use and potential of three approaches to studying conjugation in the human gut: observation of in situ events in hospitalized patients, modelling of the microbiome in vivo predominantly in rodent models, and the use of in vitro models of various complexities. Each has brought unique insights to our understanding of conjugation in the gut. The use and development of these systems, and combinations thereof, will be pivotal in better understanding the significance, prevalence, and manipulability of horizontal gene transfer in the gut microbiome.

Bacillus-derived probiotics: metabolites and mechanisms involved in bacteria-host interactions

Bacillus probiotics have a sporulation capacity that makes them more suitable for processing and storage and for surviving passage through the gastrointestinal tract. The probiotic functions and regulatory mechanisms of different Bacillus have been exploited in many reports, but little is known about how various Bacillus probiotics perform different functions. This knowledge gap results in a lack of specificity in the selection and application of Bacillus. The probiotic properties are strain-specific and cell-type-specific, and are related to the germination potential and to the diversity of metabolites produced following intestinal germination, as this causes the variation in probiotic function and mechanisms. In this review, we discuss the Bacillus metabolites produced during germination and sporulation in the GI tract, as well as possible processes affecting intestinal homeostasis. We conclude that the oxygen-capturing capability and the production of antimicrobials, exoenzymes, competence and sporulation factors (CSF), exopolysaccharides, lactic acid, and cell components are specifically associated with the functional mechanisms of probiotic Bacillus. The aim of this review is to guide the screening of potential Bacillus strains for probiotics and their application in nutrition research. The information provided will also promote further research on Bacillus-derived functional metabolites in human nutrition.

In Vitro Evaluation of Weizmannia coagulans Strain LMG S-31876 Isolated from Fermented Rice for Potential Probiotic Properties, Safety Assessment and Technological Properties

Simple Summary

Weizmanniacoagulans strain LMG S-31876, isolated from fermented rice, is Gram-positive bacilli, a spore-forming, motile, and facultative anaerobe, with an optimum temperature requirement of 40 °C. The strain is able to tolerate acidic gastric juice, bile, and pancreatin. It is non-virulent and exhibits sensitivity to most of the tested antibiotics. The strain shows antagonistic activity against pathogenic bacteria. The 16S rDNA gene sequence of W.coagulans strain LMG S-31876 has been submitted to NCBI–GenBank, archiving accession number MZ687045. The strain has also been deposited to BCCM/LMG and MTCC-IDA with reference numbers LMG S-31876 and MTCC 25396, respectively.

Abstract

Bacillus coagulans, which has been taxonomically reclassified as Weizmannia coagulans, has been the focus of research due to its wide distribution in fermented foods, probiotic properties, and tolerance to extreme environments. The purpose of this study was to characterise putative probiotic bacteria in a fermented rice sample, followed by an in vitro screening of presumptive probiotic properties and a safety assessment to ensure their safety for human consumption. The predominant isolate was Gram-positive, rod-shaped, catalase-positive, spore-forming, motile, and facultatively anaerobic. The biochemical test and 16S rDNA sequencing identify the isolate as Weizmannia coagulans strain LMG S-31876. The strain showed significant viability in acidic gastric juice, pancreatin, and bile. The strain showed tolerance to 5% NaCl, and a low-to-moderate percentage of hydrophobicity and auto-aggregation was recorded. It met all safety criteria, including haemolytic activity, DNase activity, antibiotic sensitivity, and growth inhibition of other bacteria. Evaluation of its technological properties showed positive results for amylolytic and lipolytic activities; however, negative results were obtained for proteolytic activity. It could be concluded from the gathered data that W. coagulans strain LMG S-31876 isolated from fermented rice, might serve as a potential functional probiotic food. However, extended follow-up durations and larger-scale trials by assessing the therapeutic effects in managing various clinical gastrointestinal conditions are required to warranty such effects.

Different effects of Bacillus coagulans vegetative cells and spore isolates on constipation-induced gut microbiota dysbiosis in mice

Bacillus coagulans (B. coagulans) can improve and prevent functional gastrointestinal disorders. However, there has been little discussion in the literature on the difference between spores and vegetative cells for relieving constipation. The purpose of this study was to determine the efficacy of Bacillus coagulans (B. coagulans) vegetative cells and spores against loperamide-induced constipation in mice. According to our findings, B. coagulans vegetative cells and spores differ in their ability to relieve loperamide-induced constipation. Two of the three strains of B. coagulans spores used in this experiment, B. coagulans GBI-30 6086 and B. coagulans 90, were significantly different from the model group in relieving constipation. This mainly manifested as a decreased time required for first black stool defecation (by 52 and 79 min, respectively), and increased counts of the first black stools in 5 h (by 15 and 8, respectively), the small intestine transit rate (by 23.31% and 20.52%, respectively), and the concentration of SCFAs. While the administration of vegetative cells could only relieve some indicators of intestinal transit disorders and dysbacteriosis caused by constipation. Spores of B. coagulans GBI-30 6086 and B. coagulans 90 had higher survival rates in the simulated gastrointestinal tract environment, which indicated that the functional modes of the three strains were different and had a strong relationship with the morphology of the bacteria. B. coagulans GBI-30 6086 and B. coagulans 90 spores alleviate constipation by increasing the abundances of Actinobacteria, Deferribacteres, and Lachnospiraceae UCG-006 (which were positively correlated with SCFAs) and decreasing the abundances of Cyanobateria and Rikenellaceae_RC9_gut group (which were negatively correlated with SCFAs) and the levels of Ruminococcaceae UGC-014 and Alistipes. In this study, the effects of probiotics in the form of spore or vegetative cell were compared, and the optimal preparation form was determined, providing a theoretical basis for the application of probiotics of B. coagulans to relieve constipation.

Beneficial Effects of Spore-Forming Bacillus Probiotic Bacteria Isolated From Poultry Microbiota on Broilers' Health, Growth Performance, and Immune System

Probiotics are known for their beneficial effects on poultry health and wellbeing. One promising strategy for discovering Bacillus probiotics is selecting strains from the microbiota of healthy chickens and subsequent screening for potential biological activity. In this study, we focused on three probiotic strains isolated from the gastrointestinal tract of chickens bred in different housing types. In addition to the previously reported poultry probiotic Bacillus subtilis KATMIRA1933, three strains with antimutagenic and antioxidant properties Bacillus subtilis KB16, Bacillus subtilis KB41, and Bacillus amyloliquefaciens KB54, were investigated. Their potential effects on broiler health, growth performance, and the immune system were evaluated in vivo. Two hundred newly hatched Cobb500 broiler chickens were randomly divided into five groups (n = 40). Four groups received a standard diet supplemented with the studied bacilli for 42 days, and one group with no supplements was used as a control. Our data showed that all probiotics except Bacillus subtilis KATMIRA1933 colonized the intestines. Treatment with Bacillus subtilis KB54 showed a significant improvement in growth performance compared to other treated groups. When Bacillus subtilis KB41 and Bacillus amyloliquefaciens KB54 were applied, the most significant immune modulation was noticed through the promotion of IL-6 and IL-10. We concluded that Bacillus subtilis KB54 supplementation had the largest positive impact on broilers' health and growth performance.

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.

Evaluation of graded levels of Bacillus coagulans GBI-30, 6086 on apparent nutrient digestibility, stool quality, and intestinal health indicators in healthy adult dogs

Bacillus coagulans GBI-30, 6086 is a commercially available spore-forming non-toxigenic microorganism approved for use in dog foods with high resiliency to stresses associated with commercial manufacturing. The objectives of this research were to examine the effect of B. coagulans on stool quality, nutrient digestibility, and intestinal health markers in healthy adult dogs. Extruded diets containing graded levels of B. coagulans applied either to the base ration before extrusion or to the exterior of the kibble as a topical coating after extrusion were randomly assigned to 10 individually housed adult beagle dogs (7 castrated males and 3 spayed females) of similar age (5.75 ± 0.23 yr) and body weight (12.3 ± 1.5 kg). The study was designed as a 5 × 5 replicated Latin square with 16-d adaptation followed by 5-d total fecal collection for each period. Five dietary treatments were formulated to deliver a dose of 0-, 6-, 7-, 8-, and 9-log10 colony-forming units (CFU) per dog per day for the control (CON), extruded B. coagulans (PEX), and low, moderate, and high B. coagulans coating levels (PCL, PCM, and PCH), respectively. Food-grade TiO2 was added to all diets at a level of 0.4% to serve as an indigestible dietary marker for digestibility calculations. Data were analyzed using a mixed model through SAS (version 9.4, SAS Institute, Inc., Cary, NC) with treatment as a fixed effect and room (i.e., replicate), period, and dog(room) as random effects. Apparent total tract digestibility of organic matter, crude protein, crude fat, and gross energy calculated by the marker method were numerically greatest for dogs fed the 9-log10 dose treatment with increases (P < 0.05) observed in gross energy and organic matter digestibility compared with the negative control. No significant differences were observed in food intake, stool quality, fecal pH, fecal ammonia, fecal short-chain fatty acids, or branched-chain fatty acids for the extruded B. coagulans treatment (PEX) or the coated B. coagulans treatments (PCL, PCM, and PCH) compared with CON. These results suggest that B. coagulans has a favorable impact on nutrient digestibility and no apparent adverse effects when added to extruded diets at a daily intake level of up to 9-log10 CFU in healthy adult dogs.

Complete Genome Sequence of Bacillus coagulans BC01, a Promising Human Probiotic Strain Isolated from Thick Broad Bean Sauce

We report the whole-genome sequence of a promising human probiotic, Bacillus coagulans BC01, isolated from thick broad bean sauce. B. coagulans BC01 is widely used in China, where it is considered a treatment for diarrhea, constipation, and allergies and an immunity booster. The complete genome sequence of B. coagulans BC01 will help future research to provide more molecular information about its features and safety.

Combined Use of Bacillus subtilis yb-114,246 and Bacillus licheniformis yb-214,245 Improves Body Growth Performance of Chinese Huainan Partridge Shank Chickens by Enhancing Intestinal Digestive Profiles

The aim of our study was to unveil the promoting function of compound Bacillus sp. in improving chicken digestion-induced higher body growth performance. Strains of Bacillus subtilis and B. licheniformis were jointly supplemented to the chick diet. Digestive enzyme activities in the digesta improved, development of intestinal villus enhanced, and duodenum and ileum villous height increased, while their crypt depth declined, and the cecum's bacterial composition optimized after 56 days of supplementation. Bacterial composition at the phylum level changed significantly, more Firmicutes, Proteobacteria, Epsilonbacteraeota, and Tenericutes, but fewer Bacteroidetes were detected in cecum digesta in the compound Bacillus supplemented group. Bacterial composition diversity, which improves the abundances of metabolic genes through KEGG pathway classification, became more abundant. Results indicated that the Ruminococcaceae UCG-005, unclassified Ruminococcaceae, and unclassified Lachnospiraceae species are actively correlated with body growth, promoting higher final body weight. In conclusion, owing to digestive enzyme secretion, the development of intestinal villus was stimulated and gastrointestinal bacterial composition optimized, and two combined Bacillus sp. improved chicken body growth. Our findings show the promoting action of Bacillus subtilis and B. licheniformis on digestion, which can be an alternative to antibiotics.