Screening and characterization of Bacillus velezensis LB-Y-1 toward selection as a potential probiotic for poultry with multi-enzyme production property

Comprehensive Phenotypic Characterization and Genomic Analysis Unveil the Probiotic Potential of Bacillus velezensis K12

Bacillus spp. have emerged as pivotal sources of probiotic preparations, garnering considerable attention in recent years owing to their vigorous bacteriostatic activity and antimicrobial resistance. This study aimed to investigate these probiotic characteristics in depth and verify the safety of Bacillus velezensis K12, a strain isolated from broiler intestine. The K12 strain was identified as Bacillus velezensis based on its morphology and 16S rDNA sequence homology analysis. Subsequently, B. velezensis K12 was evaluated for acid resistance, bile salt resistance, gastrointestinal tolerance, drug sensitivity, and antimicrobial activity. Additionally, whole-genome sequencing technology was employed to dissect its genomic components further, aiming to explore its potential applications as a probiotic strain. B. velezensis K12 was sensitive to six antibiotics and had acid tolerance. Furthermore, it showed potent antimicrobial activity against a wide range of pathogenic bacteria, including Escherichia coli (E. coli), Staphylococcus aureus, Salmonella, Clostridium perfringens, Bacillus cereus, and Vibrio parahaemolyticus. The complete genome sequencing of B. velezensis K12 revealed a genomic length of 3,973,105 base pairs containing 4123 coding genes, among which 3973 genes were functionally annotated. The genomic analysis identified genes associated with acid and bile tolerance, adhesion, antioxidants, and secondary metabolite production, whereas no functional genes related to enterotoxins or transferable antibiotic resistance were detected, thereby confirming the probiotic properties of B. velezensis K12. B. velezensis K12 exhibits broad-spectrum bacteriostatic activity and in vitro safety, positioning it as a potential candidate strain for developing probiotic Bacillus preparations.

Characterization and application of Bacillus velezensis D6 co-producing α-amylase and protease

BACKGROUND

Research on the co-production of multiple enzymes by Bacillus velezensis as a novel species is still a topic that needs to be studied. This study aimed to investigate the fermentation characteristics of B. velezensis D6 co-producing α-amylase and protease and to explore their enzymatic properties and applications in fermentation.

RESULTS

The maximum co-production of α-amylase and protease reached 13.13 ± 0.72 and 2106.63 ± 64.42 U mL-1, respectively, under the optimal fermented conditions (nutrients: 20.0 g L-1 urea, 20.0 g L-1 glucose, 0.7 g L-1 MnCl2; incubation conditions: initial pH 7.0, temperature 41 °C, 8% inoculation size and 30% working volume). Moreover, the genetic co-expression of α-amylase and protease increased from 0 to 24 h and then decreased after 36 h at the transcriptional level, which coincided with the growth trend of B. velezensis D6. The optimal reaction temperature of α-amylase was 55-60 °C, while that of protease was 35-40 °C. The activities of α-amylase and protease were retained by over 80% after thermal treatment (90 °C, 1 h), which indicated that two enzymes co-produced by B. velezensis D6 demonstrated excellent thermal stability. Moreover, the two enzymes were stable over a wide pH range (pH 4.0-8.0 for α-amylase; pH 4.0-9.0 for protease). Finally, the degrees of hydrolysis of corn, rice, sorghum and soybeans by α-amylase from B. velezensis D6 reached 44.95 ± 2.95%, 57.16 ± 2.75%, 52.53 ± 4.01% and 20.53 ± 2.42%, respectively, suggesting an excellent hydrolysis effect on starchy raw materials. The hydrolysis degrees of mackerel heads and soybeans by protease were 43.93 ± 2.19% and 26.38 ± 1.72%, respectively, which suggested that the protease from B. velezensis D6 preferentially hydrolyzed animal-based protein.

CONCLUSION

This is a systematic study on the co-production of α-amylase and protease by B. velezensis D6, which is crucial in widening the understanding of this species co-producing multi-enzymes and in exploring its potential application. © 2024 Society of Chemical Industry.

The Resistance of Bacillus Spores: Implications for the Strain-Specific Response to High-Performance Disinfectants

Bacterial spores in materials and equipment pose significant biosecurity risks, making effective disinfection crucial. This study evaluated Ortho-phthalaldehyde (OPA) and a quaternary ammonia-glutaraldehyde solution (AG) for inactivating spores of Bacillus thuringiensis (BT), B. cereus (BC), and two strains of B. velezensis (BV1 and BV2). Spores of BV1 and BT were treated with 22.5 mg/m3 OPA by dry fumigation or 1 mg/mL AG by spray for 20 min, according to the manufacturer's recommendation. As no sporicidal effect was observed, OPA was tested at 112.5 mg/m3 for 40 min, showing effectiveness for BT but not for BV1. Minimum bactericidal concentration (MBC) tests revealed higher MBC values for glutaraldehyde, prompting an overnight test with 112.5 mg/m3 OPA by dry fumigation and 50 mg/mL AG by spray, using formaldehyde as a control. AG reduced all Bacillus strains, but with limited sporicidal effect. OPA was sporicidal for BT and BV1 but not for BC and BV2, indicating a strain-dependent effect. Formaldehyde performed better overall but did not completely inactivate BV2 spores. Our findings suggest that OPA and AG have potential as formaldehyde replacements in wet disinfection procedures.

A New Bacillus velezensis Strain CML532 Improves Chicken Growth Performance and Reduces Intestinal Clostridium perfringens Colonization

Bacillus velezensis has gained increasing recognition as a probiotic for improving animal growth performance and gut health. We identified six B. velezensis strains from sixty Bacillus isolates that were isolated from the cecal samples of fifteen different chicken breeds. We characterized the probiotic properties of these six B. velezensis strains. The effect of a selected strain (B. velezensis CML532) on chicken growth performance under normal feeding and Clostridium perfringens challenge conditions was also evaluated. The results revealed that the six B. velezensis strains differed in their probiotic properties, with strain CML532 exhibiting the highest bile salt and acid tolerance and high-yield enzyme and antibacterial activities. Genomic analyses showed that genes related to amino acid and carbohydrate metabolism, as well as genes related to starch and cellulose hydrolysis, were abundant in strain CML532. Dietary supplementation with strain CML532 promoted chicken growth, improved the gut barrier and absorption function, and modulated the gut microbiota. Under the C. perfringens challenge condition, strain CML532 alleviated intestinal damage, reduced ileal colonization of C. perfringens, and also improved chicken growth performance. Collectively, this study demonstrated that the newly isolated B. velezensis strain is a promising probiotic with beneficial effects on chicken growth performance and gut health.

Targeted Screening of Fiber Degrading Bacteria with Probiotic Function in Herbivore Feces

Cellulolytic bacteria with probiotic functions play a crucial role in promoting the intestinal health in herbivores. In this study, we aimed to correlate the 16S rRNA gene amplicon sequencing and fiber-degrading enzyme activity data from six different herbivore feces samples. By utilizing the separation and screening steps of probiotics, we targeted and screened high-efficiency fiber-degrading bacteria with probiotic functions. The animals included Maiwa Yak (MY), Holstein cow (CC), Tibetan sheep (TS), Southern Sichuan black goat (SG), Sichuan white rex rabbit (CR), and New Zealand white rabbit (ZR). The results showed that the enzymes associated with fiber degradation were higher in goat and sheep feces compared to cattle and rabbit's feces. Correlation analysis revealed that Bacillus and Fibrobacter were positively correlated with five types of fiber-degrading related enzymes. Notably, the relative abundance of Bacillus in the feces of Tibetan sheep was significantly higher than that of other five herbivores. A strain TS5 with good cellulose decomposition ability from the feces of Tibetan sheep by Congored staining, filter paper decomposition test, and enzyme activity determination was isolated. The strain was identified as Bacillus velezensis by biological characteristics, biochemical analysis, and 16S rRNA gene sequencing. To test the probiotic properties of Bacillus velezensis TS5, we evaluated its tolerance to acid and bile salt, production of digestive enzymes, antioxidants, antibacterial activity, and adhesion ability. The results showed that the strain had good tolerance to pH 2.0 and 0.3% bile salts, as well as good potential to produce cellulase, protease, amylase, and lipase. This strain also had good antioxidant capacity and the ability to antagonistic Staphylococcus aureus BJ216, Salmonella SC06, Enterotoxigenic Escherichia coli CVCC196, and Escherichia coli ATCC25922. More importantly, the strain had good self-aggregation and Caco-2 cell adhesion rate. In addition, we tested the safety of Bacillus velezensis TS5 by hemolysis test, antimicrobial susceptibility test, and acute toxicity test in mice. The results showed that the strain had no hemolytic phenotype, did not develop resistance to 19 commonly used antibiotics, had no cytotoxicity to Caco-2, and did not have acute toxic harm to mice. In summary, this study targeted isolated and screened a strain of Bacillus velezensis TS5 with high fiber-degrading ability and probiotic potency. This strain can be used as a potential probiotic for feeding microbial preparations for ruminants.

Complete genome analysis of Bacillus velezensis TS5 and its potential as a probiotic strain in mice

Introduction

In recent years, a large number of studies have shown that Bacillus velezensis has the potential as an animal feed additive, and its potential probiotic properties have been gradually explored.

Methods

In this study, Illumina NovaSeq PE150 and Oxford Nanopore ONT sequencing platforms were used to sequence the genome of Bacillus velezensis TS5, a fiber-degrading strain isolated from Tibetan sheep. To further investigate the potential of B. velezensis TS5 as a probiotic strain, in vivo experiments were conducted using 40 five-week-old male specific pathogen-free C57BL/6J mice. The mice were randomly divided into four groups: high fiber diet control group (H group), high fiber diet probiotics group (HT group), low fiber diet control group (L group), and low fiber diet probiotics group (LT group). The H and HT groups were fed high-fiber diet (30%), while the L and LT groups were fed low-fiber diet (5%). The total bacteria amount in the vegetative forms of B. velezensis TS5 per mouse in the HT and LT groups was 1 × 109 CFU per day, mice in the H and L groups were given the same volume of sterile physiological saline daily by gavage, and the experiment period lasted for 8 weeks.

Results

The complete genome sequencing results of B. velezensis TS5 showed that it contained 3,929,788 nucleotides with a GC content of 46.50%. The strain encoded 3,873 genes that partially related to stress resistance, adhesion, and antioxidants, as well as the production of secondary metabolites, digestive enzymes, and other beneficial nutrients. The genes of this bacterium were mainly involved in carbohydrate metabolism, amino acid metabolism, vitamin and cofactor metabolism, biological process, and molecular function, as revealed by KEGG and GO databases. The results of mouse tests showed that B. velezensis TS5 could improve intestinal digestive enzyme activity, liver antioxidant capacity, small intestine morphology, and cecum microbiota structure in mice.

Conclusion

These findings confirmed the probiotic effects of B. velezensis TS5 isolated from Tibetan sheep feces and provided the theoretical basis for the clinical application and development of new feed additives.

Exploring Microorganisms from Plastic-Polluted Sites: Unveiling Plastic Degradation and PHA Production Potential

The exposure of microorganisms to conventional plastics is a relatively recent occurrence, affording limited time for evolutionary adaptation. As part of the EU-funded project BioICEP, this study delves into the plastic degradation potential of microorganisms isolated from sites with prolonged plastic pollution, such as plastic-polluted forests, biopolymer-contaminated soil, oil-contaminated soil, municipal landfill, but also a distinctive soil sample with plastic pieces buried three decades ago. Additionally, samples from Arthropoda species were investigated. In total, 150 strains were isolated and screened for the ability to use plastic-related substrates (Impranil dispersions, polyethylene terephthalate, terephthalic acid, and bis(2-hydroxyethyl) terephthalate). Twenty isolates selected based on their ability to grow on various substrates were identified as Streptomyces, Bacillus, Enterococcus, and Pseudomonas spp. Morphological features were recorded, and the 16S rRNA sequence was employed to construct a phylogenetic tree. Subsequent assessments unveiled that 5 out of the 20 strains displayed the capability to produce polyhydroxyalkanoates, utilizing pre-treated post-consumer PET samples. With Priestia sp. DG69 and Neobacillus sp. DG40 emerging as the most successful producers (4.14% and 3.34% of PHA, respectively), these strains are poised for further utilization in upcycling purposes, laying the foundation for the development of sustainable strategies for plastic waste management.