Risk Comparison of the Diarrheal and Emetic Type of Bacillus cereus in Tofu

Aerobic spore-forming bacteria associated with ropy bread: Identification, characterization and spoilage potential assessment

Aerobic spore-forming (ASF) bacteria have been reported to cause ropiness in bread. Sticky and stringy degradation, discoloration, and an odor reminiscent of rotting fruit are typical characteristics of ropy bread spoilage. In addition to economic losses, ropy bread spoilage may lead to health risks, as virulent strains of ASF bacteria are not uncommon. However, the lack of systematic approaches to quantify physicochemical spoilage characteristics makes it extremely difficult to assess rope formation in bread. To address this problem, the aim of this study was to identify, characterize and objectively assess the spoilage potential of ASF bacteria associated with ropy bread. Hence, a set of 82 ASF bacteria, including isolates from raw materials and bakery environments as well as strains from international culture collections, were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and their species identity confirmed by 16S rRNA and gyrA or panC gene sequencing. A standardized approach supported by objective colorimetric measurements was developed to assess the rope-inducing potential (RIP) of a strain by inoculating autoclaved bread slices with bacterial spores. In addition, the presence of potential virulence factors such as swarming motility or hemolysis was investigated. This study adds B. velezensis, B. inaquosorum and B. spizizenii to the species potentially implicated of causing ropy bread spoilage. Most importantly, this study introduces a standardized classification protocol for assessing the RIP of a bacterial strain. Colorimetric measurements are used to objectively quantify the degree of breadcrumb discoloration. Furthermore, our results indicate that strains capable of inducing rope spoilage in bread often exhibit swarming motility and virulence factors such as hemolysis, raising important food quality considerations.

Using fresh vegetable waste from Chinese traditional wet markets as animal feed: Material feasibility and utilization potential

To develop new animal feed sources and establish a sustainable food upcycling system, the material feasibility and feeding potential of fresh vegetable waste (FVW) were clarified in this study. First, the FVW output of wet markets in Hangzhou, China was tracked and predicted. The results showed that the retail waste ratio of FVW in wet markets reached 9.3 %, predicting that China's FVW will reach 9034 kt in 2030. Second, the study revealed that the nutritive value of FVW was comparable to that of traditional alfalfa feed, suitable for use as animal feed. However, we found a high probability of microbial contamination. Therefore, FVW should have stricter classification and collection methods. Under this premise, the feeding utilization potential of FVW in wet markets is large. In 2030, the crude protein content may replace 2737 kt of alfalfa, saving 7.7 E + 08 m3 of water and 75,018 ha of land.

UV-C and wet heat resistance of Bacillus thuringiensis biopesticide endospores compared to foodborne Bacillus cereus endospores

Bacillus endospores (spores) are generally resistant to environmental and food processing-related stress including thermal and non-thermal processing in the food industry, such as pasteurization, and UV-C inactivation. Bacillus thuringiensis insecticidal crystals and spores as the active substances in commercial biopesticides can also be introduced to vegetable foods and their food processing environment due to pre-harvest treatment of edible crops. The resistance of B. thuringiensis biopesticide spores in comparison to the genetically closely related foodborne B. cereus against heat and UV-C treatment is investigated in this study. The results show that B. thuringiensis biopesticide spores with the commercial granulated product formulation are better protected and as such more resistant to both wet heat (D values at 90 °C: 50.1-79.5 min) and UV-C treatment (D values at 0.6 mW/cm2: 7.5-8.9 min) than the pure spore suspension. The enhanced UV-C resistance properties of B. thuringiensis-formulated spores also indicate that the B. thuringiensis spores in powder or granule formulation applied in the field might not be effectively inactivated by solar radiation (UV-A and UV-B) in a short period. Furthermore, the spores of one emetic B. cereus toxin-producing strain (LFMFP 254; a Belgian outbreak strain) were found more resistant to the wet heat at 90 °C (D90-value = 71.2 min) than other tested pure spore suspensions, although the spores of B. cereus 254 did not show different behavior against UV-C treatment. This result suggests that UV-C treatment can be applied as an effective inactivation method against B. cereus 254 spores.

Post-Cooking Growth and Survival of Bacillus cereus Spores in Rice and Their Enzymatic Activities Leading to Food Spoilage Potential

Bacillus cereus strains vary in their heat resistance, post-processing survival and growth capacity in foods. Hence, this study was carried out to determine the effect of cooking on the survival and growth of eight B. cereus spores in rice at different temperatures in terms of their toxigenic profiles and extracellular enzyme activity. Samples of rice inoculated with different B. cereus spores were cooked and stored at 4 °C, 25 °C and 30 °C for up to 7 days, 48 h and 24 h, respectively. Out of eight B. cereus strains, four and three spore strains were able to grow at 30 °C and 25 °C post-cooking, respectively. Rapid growth was observed after a minimum of 6 h of incubation at 30 °C. All strains possessed proteolytic activity, whereas lipolytic and amylolytic activities were exhibited by 50% and 12.5% of the strains, respectively. The post-cooking survival and growth capacity of the B. cereus strains appeared to be independent of their toxigenic profiles, whereas extracellular enzymatic activities were required for their vegetative growth. Due to the B. cereus spores' abilities to survive cooking and return to their active cellular form, great care should be taken when handling ready-to-eat foods.

Antibacterial and physical effects of cationic starch nanofibers containing carvacrol@casein nanoparticles against Bacillus cereus in soy products

Bacillus cereus (B. cereus) is a recognized foodborne pathogen widely distributed in various protein-rich foods, which is a huge challenge to food safety. Herein, a novel enzyme-responsive nanomaterial based on cationic starch (CSt) nanofibers loaded with carvacrol@casein nanoparticles (CL@CSNPs) was constructed (CL@CS/CSt nanofiber) to prevent the contamination of B. cereus in soybean products. Considering the excellent antibacterial activity of carvacrol (CL) against B. cereus, CL@CSNPs were prepared by electrostatic adsorption and hydrophobic interaction and characterized by SEM and FTIR.CL@CS/CSt nanofibers with better performance were determined by comparing the physical properties of the electrospinning solution and the prepared nanofiber. Nanofibers were prepared by electrospinning technology and analyzed by SEM and AFM to investigate the size and structural morphology of fibers. FTIR analyses were done to confirm the successful embedding of CL@CSNPs in CSt nanofibers. Subsequently, the controlled release of CL was verified by GC-MS and disc diffusion method. The application experiment results indicated that the treatment based on CL@CS/CSt nanofibers reduced the B. cereus in soy products by 2 log CFU/g, which reflected a significant antibacterial activity. In addition, CL@CS/CSt nanofibers could also prevent texture and chroma changes under refrigeration and maintain the sensory quality of soy products. Thus, CL@CS/CSt nanofibers appear to have great potential in controlling the contamination of soybean products by B. cereus while maintaining the physical quality.

Impact of Bacillus in fermented soybean foods on human health

PURPOSE

Fermented soybean foods (FSF) is popularly consumed in the South-East Asian countries. Bacillus species, a predominant microorganism present in these foods, have demonstrated beneficial and deleterious impacts on human health. These microorganisms produce bioactive compounds during fermentation that have beneficial impacts in improving human health. However, the health risks associated with FSF, food pathogens, biogenic amines (BAs) production, and late-onset anaphylaxis, remain a concern. The purpose of this review is to present an in-depth analysis of positive and negative impacts as a result of consumption of FSF along with the measures to alleviate health risks for human consumption.

METHODS

This review was composed by scrutinizing contemporary literature of peer-reviewed publications related to Bacillus and FSF. Based on the results from academic journals, this review paper was categorized into FSF, role of Bacillus species in these foods, process of fermentation, beneficial, and adverse influence of these foods along with methods to improve food safety. Special emphasis was given to the potential benefits of bioactive compounds released during fermentation of soybean by Bacillus species.

RESULTS

The nutritional and functional properties of FSF are well-appreciated, due to the release of peptides and mucilage, which have shown health benefits: in managing cardiac disease, gastric disease, cancer, allergies, hepatic disease, obesity, immune disorders, and especially microbial infections due to the presence of probiotic property, which is a potential alternative to antibiotics. Efficient interventions were established to mitigate pitfalls like the techniques to reduce BAs and food pathogens and by using a defined starter culture to improve the safety and quality of these foods.

CONCLUSION

Despite some of the detrimental effects produced by these foods, potential health benefits have been observed. Therefore, soybean foods fermented by Bacillus can be a promising food by integrating effective measures for maintaining safety and quality for human consumption. Further, in vivo analysis on the activity and dietary interventions of bioactive compounds among animal models and human volunteers are yet to be achieved which is essential to commercialize them for safe consumption by humans, especially immunocompromised patients.

Vancomycin-modified poly-l-lysine magnetic separation combined with multiplex polymerase chain reaction assay for efficient detection of Bacillus cereus in milk

In this study, a new vancomycin (Van)-modified poly-l-lysine (PLL) magnetic bead (MB) technique was developed for isolation of gram-positive bacteria. The method combines magnetic separation with a multiplex PCR (mPCR) assay and gel electrophoresis for easy and rapid detection of Bacillus cereus. Vancomycin was used as a molecular ligand between the MB and the d-alanyl-d-alanine moieties on the cell wall surface of B. cereus. The PLL served as a flexible molecular tether between the MB and Van that reduced steric hindrance maintaining the biological activity of Van. The MB-PLL-Van capture nanoprobes exhibited excellent capture and isolation efficiency for B. cereus in spiked milk matrix samples without interference from the complex food matrix. The subsequent mPCR assay showed high specificity for the 4 target genes in B. cereus, the entFM, cesB, cer, and 16S rRNA genes, that were used to achieve efficient genotyping and detection. Under optimum conditions, the limit of detection reached 10³ cfu/mL, with a dynamic range of detection at 10³ to 10⁷ cfu/mL in pure culture. Application of the MB-PLL-Van mediated mPCR assay for B. cereus in milk matrix samples achieved results similar to those of the pure culture. In addition, with a 6-h pre-enrichment of B. cereus that was spiked in milk matrix samples, the limit of detection reached 10¹ cfu/mL. The MB-PLL-Van mediated mPCR assay developed in this study could be used as a universal technology platform for the efficient enrichment and genotyping of gram-positive bacteria.

The Bacillus cereus Food Infection as Multifactorial Process

The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.