Isolation and Characterization of EndophyticBacilliBacterium from Maize Grains Able to Detoxify Aflatoxin B1

Rice Weevil (Sitophilus oryzae L.) Gut Bacteria Inhibit Growth of Aspergillus flavus and Degrade Aflatoxin B1

In this study, bacteria residing in the gut of the rice weevils (Sitophilus oryzae L.) (Coleoptera: Curculionidae) feeding on aflatoxin-contaminated corn kernels were isolated and evaluated for their ability to suppress Aspergillus flavus and to remove/degrade aflatoxin B1 (AFB1). Four morphologically distinct S. oryzae gut-associated bacterial isolates were isolated and identified as Bacillus subtilis (RWGB1), Bacillus oceanisediminis (RWGB2), Bacillus firmus (RWGB3), and Pseudomonas aeruginosa (RWGB4) based on 16S rRNA gene sequence analysis. These bacterial isolates inhibited A. flavus growth in the dual culture assay and induced morphological deformities in the fungal hyphae, as confirmed by scanning electron microscopy. All four bacterial isolates were capable of removing AFB1 from the nutrient broth medium. In addition, culture supernatants of these bacterial isolates degraded AFB1, and the degradation of toxin molecules was confirmed by liquid chromatography-mass spectrometry. The bacterial isolates, B. subtilis RWGB1, B. oceanisediminis RWGB2, and P. aeruginosa RWGB4, were capable of producing antifungal volatile organic compounds that inhibited A. flavus growth. These results suggest that the bacterial isolates from S. oryzae gut have the potential to bind and/or degrade AFB1. Further research on their application in the food and feed industries could enhance the safety of food and feed production.

Does the Use of Different Types of Probiotics Possess Detoxification Properties Against Aflatoxins Contamination in Rabbit Diets?

The present work was carried out to study the ability of five probiotics on the in vitro degradation of Aflatoxins B1 (AFB1). The best results of in vitro were tested on the detoxification of AFB1 in rabbits. A total of 40 growing New Zealand White (NZW) male rabbits were assigned to five experimental groups. Animals were fed the following diets: basal diet (control), basal diet contaminated with 300 ppb AFB1, basal diet contaminated with 300 ppb AFB1. + probiotic 3 (0.5 g/kg diet), basal diet contaminated with 300 ppb AFB1 + ajowan (0.5 g/kg diet), and basal diet contaminated with 300 ppb AFB1 + probiotic 3 (0.5 g/kg diet) + ajowan (0.5 g/kg diet). Live body weight significantly (P < 0.05) decreased in rabbits fed AFB1 contaminated diet compared to the control rabbits. All additives improved (P < 0.05) the live body weight. The best improvement occurred with probiotics + ajowan. The addition of probiotics increased (P < 0.05) daily body weight gain in all weeks except the first week. Adding ajowan or ajowan + probiotic led to a significant (P < 0.05) increase in live body weight gain and feed intake compared to rabbits fed AFB1 alone. The digestion coefficients of dry matter (DM), organic matter (OM), crude fiber (CF), ether extract (EE), nitrogen-free extract (NFE), and digestible crude protein (DCP) significantly (P < 0.05) decreased in rabbits fed AFB1 contaminated diet. All additives improved (P < 0.05) the digestibility coefficients of DM, OM, EE, CF, NFE, and total digested nutrients (TDN)%. The best improvement occurred with probiotics + ajowan. Concentrations of serum total protein, albumin and globulin significantly (P < 0.05) decreased in rabbits fed AFB1 contaminated diet compared with the control rabbits. In conclusion, the addition of probiotic 3 (AVI-5-BAC) + ajowan could be recommended to eliminate the toxicity of AFB1 and improve growth performance criteria in rabbits.

Degradation mechanism of aflatoxin B1 and aflatoxin G1 by salt tolerant Bacillus albus YUN5 isolated from 'doenjang', a traditional Korean food

Aflatoxins are the mycotoxins that contaminate food and feed and pose health hazards to humans and animals. Here, Bacillus albusYUN5 was isolated from doenjang (Korean fermented soybean paste) and examined for aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1) degradation capabilities. The highest degradation of AFB1 (76.28 ± 0.15%) and AFG1 (98.98 ± 0.00%) was observed in the cell-free supernatant (CFS) ofB. albusYUN5, whereas negligible degradation was observed in intracellular fraction, viable cells, and cell debris. Furthermore, heat (100 °C) and proteinase K treated CFS possessed AFB1 and AFG1 degradation ability, suggesting that substances other than proteins or enzymes are responsible for the degradation. Optimal degradation of AFB1 and AFG1 by the CFS was achieved at 55 °C and 45 °C, respectively, and at pH 7-10 and salt concentration of 0-20%. Liquid chromatography-mass spectroscopy analysis of the degraded products revealed that either the difuran or lactone ring of AFB1 and lactone ring of AFG1 is the main target site by CFS of B. albus YUN5. A slightly better reduction of AFB1 and AFG1 was observed in doenjang treated with CFS and viable cells of B. albus YUN5 compared to those without CFS and B. albus YUN5 treated doenjang during one year of fermentation, suggesting the applicability of B. albus in real food.

Detoxification of Aflatoxin B1 by a Potential Probiotic Bacillus amyloliquefaciens WF2020

Microbial degradation is considered as an attractive method to eliminate exposure to aflatoxin B1 (AFB1), the most toxic mycotoxin that causes great economic losses and brings a serious threat to human and animal health, in food and feed. In this study, Bacillus amyloliquefaciens WF2020, isolated from naturally fermented pickles, could effectively degrade AFB1 ranging from 1 to 8 μg/ml, and the optimum temperature and pH value were 37–45°C and 8.0, respectively. Moreover, B. amyloliquefaciens WF2020 was considered to be a potential probiotic due to the synthesis of active compounds, absence of virulence genes, susceptibility to various antibiotics, and enhanced lifespan of Caenorhabditis elegans. Extracellular enzymes or proteins played a major role in AFB1 degradation mediated by B. amyloliquefaciens WF2020 into metabolites with low or no mutagenicity and toxicity to C. elegans. AFB1 degradation by the cell-free supernatant was stable up to 70°C, with an optimal pH of 8.0, and the cell-free supernatant could still degrade AFB1 by 37.16% after boiling for 20 min. Furthermore, B. amyloliquefaciens WF2020 caused a slight defect in fungal growth and completely inhibited AFB1 production when co-incubated with Aspergillus flavus. Additionally, B. amyloliquefaciens WF2020 suppressed the expression of 10 aflatoxin pathway genes and 2 transcription factors (alfR and alfS), suggesting that B. amyloliquefaciens WF2020 might inhibit AFB1 synthesis in A. flavus. These results indicate that B. amyloliquefaciens WF2020 and/or its extracellular enzymes or proteins have a promising potential to be applied in protecting food and feed from AFB1 contamination.

Endophytic Bacteria Bacillus subtilis, Isolated from Zea mays, as Potential Biocontrol Agent against Botrytis cinerea

Simple Summary

Plant–microorganism associations date back more than 400 million years. Plants host microorganisms that establish many different relationships with them, some negative and others very positive for both organisms. A type of this relationship is established with microorganisms that live inside them, known as endophytic microorganisms; they can include bacteria, yeasts, and fungi. In this study, we isolate endophytic bacteria from maize plants, and we characterize them in order to check their potential for being used as biocontrol agents against Botrytis cinerea, one of the most important phytopathogenic fungi in the world. The endophytic bacteria showed this antagonistic effect during in vitro assay and also during in vivo assay in Phaseolus vulgaris. At the same time, they showed the capacity for promoting growth in Zea mays plants.

Abstract

Plant diseases are one of the main factors responsible for food loss in the world, and 20–40% of such loss is caused by pathogenic infections. Botrytis cinerea is the most widely studied necrotrophic phytopathogenic fungus. It is responsible for incalculable economic losses due to the large number of host plants affected. Today, B. cinerea is controlled mainly by synthetic fungicides whose frequent application increases risk of resistance, thus making them unsustainable in terms of the environment and human health. In the search for new alternatives for the biocontrol of this pathogen, the use of endophytic microorganisms and their metabolites has gained momentum in recent years. In this work, we isolated endophytic bacteria from Zea mays cultivated in Colombia. Several strains of Bacillus subtilis, isolated and characterized in this work, exhibited growth inhibition against B. cinerea of more than 40% in in vitro cultures. These strains were characterized by studying several of their biochemical properties, such as production of lipopeptides, potassium solubilization, proteolytic and amylolytic capacity, production of siderophores, biofilm assays, and so on. We also analyzed: (i) its capacity to promote maize growth (Zea mays) in vivo, and (ii) its capacity to biocontrol B. cinerea during in vivo infection in plants (Phaseolus vulgaris).

Biodegradation of aflatoxin by bacterial species isolated from poultry farms

Aflatoxins are carcinogenic compounds produced by certain Aspergillus spp and naturally contaminate poultry rations. Exposure to low levels of Aflatoxin B1 (AFB1) in poultry feeds is the second most threatening issue facing the poultry industry in Egypt; it can cause a reduction in growth, egg production, and compromised immune functions, resulting in significant economic loss. Hence, a safe, effective and eco-friendly detoxification method is strongly required. Biological decontamination is a promising approach to reduce aflatoxin levels within threshold limits. This study explores the biodegradation capacity of bacteria isolated from the moldy feed, soil and poultry feces in various poultry farms against AFB1 (100 ppb), G1 (100 ppb), B2 (30 ppb), G2 (30 ppb). Sixty-five bacterial isolates were initially screened using coumarin media with a concentration of (0.01%-0.5%) coumarin. Only one soil isolate (SZ1) grew at the highest concentration (0.5%). Coumarin and Aflatoxin degradation rates of ten promising isolates were measured using spectrophotometry and HPLC. Six isolates reduced AFG1 by more than 90% in the liquid medium, five reduced AFB2 while only four did the same with AFB1& AFG2. Impressively, isolate SZ1 (identified as Pseudomonas fluorescens) exhibited the best degradation capacity to both coumarin and aflatoxin with 100% degradation of AFG1 and 99% degradation of AFB1, AFB2 and AFG2. Biochemical and molecular identification of the ten isolates revealed that they belong to four genera; Bacillus (6), Pseudomonas (2), Enterococcus (1) and Stenotrophomonas (1). Factors affecting Pseudomonas fluorescens SZ1 degradation activity was further investigated. Optimum temperature, time and pH for maximum aflatoxin degradation were at 37 °C, 72 h and 7, respectively. Treatment with proteinase K reduced the degradation activity of G1 (31% ± 1.438), B1 (42% ± 1.438), G2 (19% ± 1.097), and B2 (25% ± 1.732), suggesting that the effective component in aflatoxin degradation may be protein in nature. Our study suggests the biocontrol potential of several different species isolated from poultry farms; B. haynesii, B. licheniformis, B. tequilensis, B. subtilis, B. amyloliquefaciens, Pseudomonas fluorescens, Enterococcus casseliflavus, and Stenotrophomonas maltophilia. The results proposed Pseudomonas fluorescens SZ1 as an excellent candidate for bioremediation and decontamination of aflatoxin in feed matrices. To the best of our knowledge, this is the first report identifying B. haynesii, Enterococcus casseliflavus, B. tequilensis and B. amyloliquefaciens with aflatoxin degradation activity.

Novel strategies for degradation of aflatoxins in food and feed: A review

Aflatoxins are toxic secondary metabolites mainly produced by Aspergillus fungi, posing high carcinogenic potency in humans and animals. Dietary exposure to aflatoxins is a global problem in both developed and developing countries especially where there is poor regulation of their levels in food and feed. Thus, academics have been striving over the decades to develop effective strategies for degrading aflatoxins in food and feed. These strategies are technologically diverse and based on physical, chemical, or biological principles. This review summarizes the recent progress on novel aflatoxin degradation strategies including irradiation, cold plasma, ozone, electrolyzed oxidizing water, organic acids, natural plant extracts, microorganisms and enzymes. A clear understanding of the detoxification efficiency, mechanism of action, degradation products, application potential and current limitations of these methods is presented. In addition, the development and future perspective of nanozymes in aflatoxins degradation are introduced.

Microbiological Detoxification of Mycotoxins: Focus on Mechanisms and Advances

Some fungal species of the genera Aspergillus, Penicillium, and Fusarium secretes toxic metabolites known as mycotoxins, have become a global concern that is toxic to different species of animals and humans. Biological mycotoxins detoxification has been studied by researchers around the world as a new strategy for mycotoxin removal. Bacteria, fungi, yeast, molds, and protozoa are the main living organisms appropriate for the mycotoxin detoxification. Enzymatic and degradation sorptions are the main mechanisms involved in microbiological detoxification of mycotoxins. Regardless of the method used, proper management tools that consist of before-harvest prevention and after-harvest detoxification are required. Here, in this review, we focus on the microbiological detoxification and mechanisms involved in the decontamination of mycotoxins.

Aflatoxin B1 Degradation and Detoxification by Escherichia coli CG1061 Isolated From Chicken Cecum

Aflatoxin B₁ (AFB₁) is one of the most hazardous mycotoxins contamination in food and feed products, which leads to hepatocellular carcinoma in humans and animals. In the present study, we isolated and characterized an AFB₁ degrading bacteria CG1061 from chicken cecum, exhibited an 93.7% AFB₁ degradation rate by HPLC. 16S rRNA gene sequence analysis and a multiplex PCR experiment demonstrated that CG1061 was a non-pathogenic Escherichia coli. The culture supernatant of E. coli CG1061 showed an 61.8% degradation rate, whereas the degradation rates produced by the intracellular extracts was only 17.6%, indicating that the active component was constitutively secreted into the extracellular space. The degradation rate decreased from 61.8 to 37.5% when the culture supernatant was treated with 1 mg/mL proteinase K, and remained 51.3% when that treated with 100°C for 20 min. We postulated that AFB₁ degradation was mediated by heat-resistant proteins. The content of AFB₁ decreased rapidly when it was incubated with the culture supernatant during the first 24 h. The optimal incubation pH and temperature were pH 8.5 and 55°C respectively. According to the UPLC Q-TOF MS analysis, AFB₁ was bio-transformed to the product C₁₆H₁₄O₅ and other metabolites. Based on the results of in vitro experiments on chicken hepatocellular carcinoma (LMH) cells and in vivo experiments on mice, we confirmed that CG1061-degraded AFB₁ are less toxic than the standard AFB₁. E. coli CG1061 isolated from healthy chicken cerum is more likely to colonize the animal gut, which might be an excellent candidate for the detoxification of AFB₁ in food and feed industry.

Effective Biodegradation of Aflatoxin B1 Using the Bacillus licheniformis (BL010) Strain

Aflatoxin B1 (AFB1), a pollutant of agricultural products, has attracted considerable attention in recent years, due to its potential impact on health. In the present study, Bacillus licheniformis (BL010) was demonstrated to efficiently degrade AFB1, reducing over 89.1% of the toxin content within 120 h. A crude enzyme solution of BL010 exhibited the highest degradation level (97.3%) after three induction periods. However, uninduced BL010 bacteria was not capable of reducing AFB1. Furthermore, high performance liquid chromatography (HPLC) analysis showed that while a cell-free extract caused a significant decrease in AFB1 content (93.6%, p < 0.05), cell culture fluid treatment did not significantly degrade AFB1. The biotransformation products of AFB1 were detected and further identified by quadrupole time-of-flight liquid chromatography⁻mass spectrometry (LC-Q-TOF/MS); these corresponded to a molecular formula of C12H14O₄. A sequence analysis of whole BL010 genes with a bioinformatics approach identified the secondary structures of two degrading enzymes (Chia010 and Lac010), providing an important basis for subsequent homology modeling and functional predictions.

Biological Degradation of Aflatoxin B₁ by Cell-Free Extracts of Bacillus velezensis DY3108 with Broad PH Stability and Excellent Thermostability

(1) Background: Aflatoxin contamination in food and grain poses serious problems both for economic development and public health protection, thus leading to a focus on an effective approach to control it; (2) Methods: Aflatoxin B₁ (AFB₁) degrading bacteria were isolated using a medium containing coumarin as the sole carbon source, and the biodegradation of AFB₁ by the isolate was examined by high performance liquid chromatography, and liquid chromatography mass spectrometry; (3) Results: a bacterial strain exhibiting strong AFB1 degradation activity (91.5%) was isolated and identified as Bacillusvelezensis DY3108. The AFB₁ degrading activity was predominantly attributed to the cell-free supernatant of strain DY3108. Besides, it was heat-stable and resistant to proteinase K treatment but sensitive to sodium dodecyl sulfate treatment. The optimal temperature for the maximal degradation of AFB₁ was 80 °C. Even more notable, the supernatant showed a high level of activity over a broad pH (4.0 to 11.0) and exhibited the highest degradation (94.70%) at pH 8.0. Cytotoxicity assays indicated that the degradation products displayed significantly (p < 0.05) lower cytotoxic effects than the parent AFB₁; (4) Conclusions: B.velezensis DY3108 might be a promising candidate for exploitation in AFB₁ detoxification and bioremediation in food and feed matrices.

Strategies and Methodologies for Developing Microbial Detoxification Systems to Mitigate Mycotoxins

Mycotoxins, the secondary metabolites of mycotoxigenic fungi, have been found in almost all agricultural commodities worldwide, causing enormous economic losses in livestock production and severe human health problems. Compared to traditional physical adsorption and chemical reactions, interest in biological detoxification methods that are environmentally sound, safe and highly efficient has seen a significant increase in recent years. However, researchers in this field have been facing tremendous unexpected challenges and are eager to find solutions. This review summarizes and assesses the research strategies and methodologies in each phase of the development of microbiological solutions for mycotoxin mitigation. These include screening of functional microbial consortia from natural samples, isolation and identification of single colonies with biotransformation activity, investigation of the physiological characteristics of isolated strains, identification and assessment of the toxicities of biotransformation products, purification of functional enzymes and the application of mycotoxin decontamination to feed/food production. A full understanding and appropriate application of this tool box should be helpful towards the development of novel microbiological solutions on mycotoxin detoxification.