Detoxification of Aflatoxin B1 by a Potential Probiotic Bacillus amyloliquefaciens WF2020

Microbial Composition of Water Kefir Grains and Their Application for the Detoxification of Aflatoxin B1

Water kefir grains (WKGs), the starter used to develop a traditional beverage named water kefir, consist of a symbiotic mixture of probiotics with diverse bioactivities, but little is known about their abilities to remove mycotoxins that have serious adverse effects on humans and animals. This study investigated the ability of WKGs to remove aflatoxin B1 (AFB1), one of the most toxic mycotoxins, under different settings, and determined the mechanism of absorption mediated by WKGs and the effect of WKGs on the toxicity induced by AFB1 and the reduction in AFB1 in cow milk and tea soups. The results showed the WKGs used herein were dominated by Lactobacillus, Acetobacter, Phenylobacterium, Sediminibacterium, Saccharomyces, Issatchenkia, and Kodamaea. HPLC analysis demonstrated that the WKGs effectively removed AFB1 at concentrations ranging from 1 to 5 µg/mL, pH values ranging from 3 to 9, and temperatures ranging from 4 to 45 °C. Additionally, the removal of AFB1 mainly depended on absorption, which was consistent with the Freundlich and pseudo-second-order kinetic models. Moreover, only 49.63% of AFB1 was released from the AFB1-WKG complex after four washes when the release of AFB1 was non-detectable. Furthermore, WKG treatment caused a dramatic reduction in the mutagenicity induced by AFB1 according to an Ames test and reduced more than 54% of AFB1 in cow milk and three tea soups. These results suggested that WKGs can act as a potential bio-absorbent with a high binding ability to detoxify AFB1 in food and feed via a chemical action step and multi-binding sites of AFB1 absorption in a wide range of scenarios.

Mechanism Underlying Bacillus subtilis BS-Z15 Metabolite-Induced Prevention of Grain Contamination by Aspergillus flavus

Aspergillus flavus can cause mildew in corn, peanuts, and other foods as well as animal feed, which seriously endangers human and livestock health; thus, preventing A. flavus contamination is imperative. Previous studies have found that the secondary metabolites of Bacillus subtilis BS-Z15 have broad-spectrum-inhibiting fungal activity, further confirming that the main active inhibiting fungal substance is Mycosubtilin (Myco). In this paper, corn and peanuts were treated with 0, 100, and 200 μg/mL BS-Z15 secondary metabolites (BS-Z15-SMA) for 7 days, and the aflatoxin contamination prevention effect was examined. The results showed that with increasing BS-Z15-SMA concentration, the aflatoxin contamination prevention effect was significantly enhanced. The above toxicity phenomena became more significant with extended BS-Z15-SMA treatment time. Scanning electron microscopy showed that 4 μg/mL Myco treatment resulted in a dented A. flavus surface and breakage of both the conidial stem and the mycelium. Transcriptome results showed that Myco significantly affected gene expression in A. flavus spores. The downregulated genes were significantly enriched in cell wall synthesis, transcription and translation, transmembrane transport pathways, and pathways related to key enzymes for aflatoxin synthesis. These results suggest that Myco could be used as a new bioactive material to prevent aflatoxin synthesis and contamination.

Optimizing the Fermentation Conditions of Cudrania tricuspidata Fruit Using Bacillus amyloliquefaciens for Anti-Inflammatory Activity and GC-MS-Based Volatile Component Characteristics

The aim of this study is to optimize the performance conditions used for maximum anti-inflammatory activity and to clarify in vitroanti-inflammatory properties of fermented C. tricuspidata fruit. Based on the single-factor experiment and Box-Behnken design, the optimized fermentation conditions of C. tricuspidata fruit for maximum anti-inflammatory activity were 3.8 d fermentation period, 8.4% (v/w) inoculation concentration, and 29.2°C fermentation temperature. Under optimal conditions, anti-inflammatory activity-based nitric oxide of fermented C. tricuspidata fruit reached 93.9%. Moreover, this study provides a theoretical basis and experimental data containing β-hexosaminidase and reactive oxygen species for the medical use and industrialization of C. tricuspidata fruit fermentation. Interestingly, the results of GC-MS analysis confirmed that fermented C. tricuspidata fruits detect volatile components different from unfermented C. tricuspidata fruits. We suggested that this volatile component may have been involved in the anti-inflammatory reaction, but scientific verification of this is needed later. Therefore, an in-depth study of volatile components detected from fermented C. tricuspidata fruits will need to be conducted later.

Protective Effect of Long-Term Fermented Soybeans with Abundant Bacillus subtilis on Glucose and Bone Metabolism and Memory Function in Ovariectomized Rats: Modulation of the Gut Microbiota

We investigated the effects of different types of long-term fermented soybeans (traditionally made doenjang; TMD) on glucose and bone metabolism and memory function in ovariectomized (OVX) rats. The rats were categorized into six groups: Control, cooked unfermented soybeans (CSB), and four TMDs based on Bacillus subtilis (B. subtilis) and biogenic amine contents analyzed previously: high B. subtilis (HS) and high biogenic amines (HA; HSHA), low B. subtilis (LS) and HA (LSHA), HS and low biogenic amines (LA; HSLA), and LS and LA (LSLA). The rats in the CSB and TMD groups fed orally had a 4% high-fat diet for 12 weeks. Rats in the Control (OVX rats) and Normal-control (Sham-operated rats) groups did not consume CSB or TMD, although macronutrient contents were the same in all groups. Uterine weight and serum 17β-estradiol concentrations were much lower in the Control than the Normal-control group, but CSB and TMD intake did not alter them regardless of B. subtilis and biogenic amine contents. HOMA-IR, a measure of insulin resistance, decreased with TMD with high B. subtilis (HSLA and HSHA) compared to the Control group. In OGTT and IPGTT, serum glucose concentrations at each time point were higher in the Control than in the Normal-control, and HSLA and HSHA lowered them. Memory function was preserved with HSHA and HSLA administration. Bone mineral density decline measured by DEXA analysis was prevented in the HSHA and HSLA groups. Bone metabolism changes were associated with decreased osteoclastic activity, parathyroid hormone levels, and osteoclastic activity-related parameters. Micro-CT results demonstrated that TMD, especially HSLA and HSHA, preserved bone structure in OVX rats. TMD also modulated the fecal bacterial community, increasing Lactobacillus, Ligalactobacillus, and Bacillus. In conclusion, through gut microbiota modulation, TMD, particularly with high B. subtilis content, acts as a synbiotic to benefit glucose, bone, and memory function in OVX rats. Further research is needed to make specific recommendations for B. subtilis-rich TMD for menopausal women.

AFB1 Microbial Degradation by Bacillus subtilis WJ6 and Its Degradation Mechanism Exploration Based on the Comparative Transcriptomics Approach

Aflatoxin pollution poses great harm to human and animal health and causes huge economic losses. The biological detoxification method that utilizes microorganisms and their secreted enzymes to degrade aflatoxin has the advantages of strong specificity, high efficiency, and no pollution inflicted onto the environment. In this study, Bacillus subtilis WJ6 with a high efficiency in aflatoxin B₁ degradation was screened and identified through molecular identification, physiological, and biochemical methods. The fermentation broth, cell-free supernatant, and cell suspension degraded 81.57%, 73.27%, and 8.39% of AFB₁, respectively. The comparative transcriptomics analysis indicated that AFB₁ led to 60 up-regulated genes and 31 down-regulated genes in B. subtilis WJ6. A gene ontology (GO) analysis showed that the function classifications of cell aggregation, the organizational aspect, and the structural molecule activity were all of large proportions among the up-regulated genes. The down-regulated gene expression was mainly related to the multi-organism process function under the fermentation condition. Therefore, B. subtilis WJ6 degraded AFB₁ through secreted extracellular enzymes with the up-regulated genes of structural molecule activity and down-regulated genes of multi-organism process function.

Biocontrol Capabilities of Bacillus subtilis E11 against Aspergillus flavus In Vitro and for Dried Red Chili (Capsicum annuum L.)

As a condiment with extensive nutritional value, chili is easy to be contaminated by Aspergillus flavus (A. flavus) during field, transportation, and storage. This study aimed to solve the contamination of dried red chili caused by A. flavus by inhibiting the growth of A. flavus and detoxifying aflatoxin B₁ (AFB₁). In this study, Bacillus subtilis E11 (B. subtilis) screened from 63 candidate antagonistic bacteria exhibited the strongest antifungal ability, which could not only inhibit 64.27% of A. flavus but could also remove 81.34% of AFB₁ at 24 h. Notably, scanning electron microscopy (SEM) showed that B. subtilis E11 cells could resist a higher concentration of AFB₁, and the fermentation supernatant of B. subtilis E11 could deform the mycelia of A. flavus. After 10 days of coculture with B. subtilis E11 on dried red chili inoculated with A. flavus, the mycelia of A. flavus were almost completely inhibited, and the yield of AFB₁ was significantly reduced. Our study first concentrated on the use of B. subtilis as a biocontrol agent for dried red chili, which could not only enrich the resources of microbial strains for controlling A. flavus but also could provide theoretical guidance to prolong the shelf life of dried red chili.