Biodegradation of ochratoxin A byAlcaligenes faecalisisolated from soil

Biodegradation of ochratoxin A by Brevundimonas diminuta HAU429: Characterized performance, toxicity evaluation and functional enzymes

Ochratoxin A (OTA) is a notorious mycotoxin commonly contaminating food products worldwide. In this study, an OTA-degrading strain Brevundimonas diminuta HAU429 was isolated by using hippuryl-L-phenylalanine as the sole carbon source. The biodegradation of OTA by strain HAU429 was a synergistic effect of intracellular and extracellular enzymes, which transformed OTA into ochratoxin α (OTα) through peptide bond cleavage. Cytotoxicity tests and cell metabolomics confirmed that the transformation of OTA into OTα resulted in the detoxification of its hepatotoxicity since OTA but not OTα disturbed redox homeostasis and induced oxidative damage to hepatocytes. Genome mining identified nine OTA hydrolase candidates in strain HAU429. They were heterologously expressed in Escherichia coli, and three novel amidohydrolase BT6, BT7 and BT9 were found to display OTA-hydrolyzing activity. BT6, BT7 and BT9 showed less than 45 % sequence identity with previously identified OTA-degrading amidohydrolases. BT6 and BT7 shared 60.9 % amino acid sequence identity, and exhibited much higher activity towards OTA than BT9. BT6 and BT7 could completely degrade 1 μg mL-1 of OTA within 1 h and 50 min, while BT9 hydrolyzed 100 % of OTA in the reaction mixture by 12 h. BT6 was the most thermostable retaining 38 % of activity after incubation at 70 °C for 10 min, while BT7 displayed the highest tolerance to ethanal remaining 76 % of activity in the presence of 6 % ethanol. This study could provide new insights towards microbial OTA degradation and promote the development of enzyme-catalyzed OTA detoxification during food processing.

Structural and functional analysis of the key enzyme responsible for the degradation of ochratoxin A in the Alcaligenes genus

The potential to degrade ochratoxin A (OTA), a highly poisonous mycotoxin, was investigated in cultures from Alcaligenes-type strains. Genome sequence analyses from different Alcaligenes species have permitted us to demonstrate a direct, causal link between the gene coding a known N-acyl-L-amino acid amidohydrolase from A. faecalis (AfOTH) and the OTA-degrading activity of this bacterium. In agreement with this finding, we found the gene coding AfOTH in two additional species included in the Alcaligenes genus, namely, A. pakistanensis, and A. aquatilis, which also degraded OTA. Notably, A. faecalis subsp. faecalis DSM 30030T was able to transform OTα, the product of OTA hydrolysis. AfOTH from A. faecalis subsp. phenolicus DSM 16503T was recombinantly over-produced and enzymatically characterized. AfOTH is a Zn2+-containing metalloenzyme that possesses structural features and conserved residues identified in the M20D family of enzymes. AfOTH is a tetramer in solution that shows both aminoacylase and carboxypeptidase activities. Using diverse potential substrates, namely, N-acetyl-L-amino acids and carbobenzyloxy-L-amino acids, a marked preference towards C-terminal Phe and Tyr residues could be deduced. The structural basis for this specificity has been determined by in silico molecular docking analyses. The amidase activity of AfOTH on C-terminal Phe residues structurally supports its OTA and OTB degradation activity.

Comprehensive Insights into Ochratoxin A: Occurrence, Analysis, and Control Strategies

Ochratoxin A (OTA) is a toxic mycotoxin produced by some mold species from genera Penicillium and Aspergillus. OTA has been detected in cereals, cereal-derived products, dried fruits, wine, grape juice, beer, tea, coffee, cocoa, nuts, spices, licorice, processed meat, cheese, and other foods. OTA can induce a wide range of health effects attributable to its toxicological properties, including teratogenicity, immunotoxicity, carcinogenicity, genotoxicity, neurotoxicity, and hepatotoxicity. OTA is not only toxic to humans but also harmful to livestock like cows, goats, and poultry. This is why the European Union and various countries regulate the maximum permitted levels of OTA in foods. This review intends to summarize all the main aspects concerning OTA, starting from the chemical structure and fungi that produce it, its presence in food, its toxicity, and methods of analysis, as well as control strategies, including both fungal development and methods of inactivation of the molecule. Finally, the review provides some ideas for future approaches aimed at reducing the OTA levels in foods.

Isolation, identification, degradation mechanism and exploration of active enzymes in the ochratoxin A degrading strain Acinetobacter pittii AP19

Ochratoxin A (OTA) is a polyketide mycotoxin that commonly contaminates agricultural products and causes significant economic losses. In this study, the efficient OTA-degrading strain AP19 was isolated from vineyard soil and was identified as Acinetobacter pittii. Compared with growth in nutrient broth supplemented with OTA (OTA-NB), strain AP19 grew faster in nutrient broth (NB), but the ability of the resulting cell lysates to remove OTA was weaker. After cultivation in NB, the cell lysate of strain AP19 was able to remove 100% of 1 mg/L OTA within 18 h. The cell lysate fraction > 30 kDa degraded 100% of OTA within 12 h, while the fractions < 30 kDa were practically unable to degrade OTA. Further anion exchange chromatography of the > 30 kDa fraction yielded two peaks exhibiting significant OTA degradation activity. The degradation product was identified as OTα. Amino acid metabolism exhibited major transcriptional trends in the response of AP19 to OTA. The dacC gene encoding carboxypeptidase was identified as one of the contributors to OTA degradation. Soil samples inoculated with strain AP19 showed significant OTA degradation. These results provide significant insights into the discovery of novel functions in A. pittii, as well as its potential as an OTA decomposer.

Biodegradation of low-density polyethylene (LDPE) through application of indigenous strain Alcaligenes faecalis ISJ128

The resiliency of plastic products against microbial degradation in natural environment often creates devastating changes for humans, plants, and animals on the earth's surface. Biodegradation of plastics using indigenous bacteria may serve as a critical approach to overcome this resulting environmental stress. In the present work, a polyethylene degrading bacterium Alcaligenes faecalis strain ISJ128 (Accession No. MK968769) was isolated from partially degraded polyethylene film buried in the soil at plastic waste disposal site. The biodegradation studies were conducted by employing various methods such as hydrophobicity assessment of the strain ISJ128, measurement of viability and total protein content of bacterial biofilm attached to the polyethylene surface. The proliferation of bacterial cells on polyethylene film, as indicated by high growth response in terms of protein content (85.50 µg mL-1) and viability (1010 CFU mL-1), proposed reasonable suitability of our strain A. faecalis ISJ128 toward polyethylene degradation. The results of biodegradation assay revealed significant degradation (10.40%) of polyethylene film within a short period of time (i.e., 60 days), whereas no signs of degradation were seen in control PE film. A. faecalis strain ISJ128 also demonstrated a removal rate of 0.0018 day-1 along with half-life of 462 days. The scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy studies not only displayed changes on polyethylene surface but also altered level of intensity of functional groups and an increase in the carbonyl indexes justifying the degradation of polyethylene film due to bacterial activity. In addition, the secondary structure prediction (M fold software) of 16SrDNA proved the stable nature of the bacterial strain, thereby reflecting the profound scope of A. faecalis strain ISJ128 as a potential degrader for the eco-friendly disposal of polyethylene waste. Schematic representation of methodology.

Mechanisms by which microbial enzymes degrade four mycotoxins and application in animal production: A review

Mycotoxins are toxic compounds that pose a serious threat to animal health and food safety. Therefore, there is an urgent need for safe and efficient methods of detoxifying mycotoxins. As biotechnology has continued to develop, methods involving biological enzymes have shown great promise. Biological enzymatic methods, which can fundamentally destroy the structures of mycotoxins and produce degradation products whose toxicity is greatly reduced, are generally more specific, efficient, and environmentally friendly. Mycotoxin-degrading enzymes can thus facilitate the safe and effective detoxification of mycotoxins which gives them a huge advantage over other methods. This article summarizes the newly discovered degrading enzymes that can degrade four common mycotoxins (aflatoxins, zearalenone, deoxynivalenol, and ochratoxin A) in the past five years, and reveals the degradation mechanism of degrading enzymes on four mycotoxins, as well as their positive effects on animal production. This review will provide a theoretical basis for the safe treatment of mycotoxins by using biological enzyme technology.

Cryo-EM structure and rational engineering of a superefficient ochratoxin A-detoxifying amidohydrolase

Ochratoxin A (OTA) is among the most prevalent mycotoxins detected in agroproducts, posing serious threats to human and livestock health. Using enzymes to conduct OTA detoxification is an appealing potential strategy. The recently identified amidohydrolase from Stenotrophomonas acidaminiphila, termed ADH3, is the most efficient OTA-detoxifying enzyme reported thus far and can hydrolyze OTA to nontoxic ochratoxin α (OTα) and L-β-phenylalanine (Phe). To elucidate the catalytic mechanism of ADH3, we solved the single-particle cryo-electron microscopy (cryo-EM) structures of apo-form, Phe- and OTA-bound ADH3 to an overall resolution of 2.5-2.7 Å. The role of OTA-binding residues was investigated by structural, mutagenesis and biochemical analyses. We also rationally engineered ADH3 and obtained variant S88E, whose catalytic activity was elevated by 3.7-fold. Structural analysis of variant S88E indicates that the E88 side chain provides additional hydrogen bond interactions to the OTα moiety. Furthermore, the OTA-hydrolytic activity of variant S88E expressed in Pichia pastoris is comparable to that of Escherichia coli-expressed enzyme, revealing the feasibility of employing the industrial yeast strain to produce ADH3 and its variants for further applications. These results unveil a wealth of information about the catalytic mechanism of ADH3-mediated OTA degradation and provide a blueprint for rational engineering of high-efficiency OTA-detoxifying machineries.

Purification and characterization of the enzymes from Brevundimonas naejangsanensis that degrade ochratoxin A and B

Ochratoxin A (OTA) and Ochratoxin B (OTB) co-contaminate many types of agricultural products. Screening enzymes that degrade both OTA and OTB has significance in food safety. In this study, four novel OTA and OTB degrading enzymes, namely BnOTase1, BnOTase2, BnOTase3, and BnOTase4, were purified from the metabolites of the Brevundimonas naejangsanensis ML17 strain. These four enzymes hydrolyzed OTA into OTα and hydrolyzed OTB into OTβ. BnOTase1, BnOTase2, BnOTase3, and BnOTase4 have the apparent K_m values for hydrolyzing OTA of 19.38, 0.92, 12.11, 1.09 μmol/L and for hydrolyzing OTB of 0.76, 2.43, 0.60, 0.64 μmol/L respectively. OTα and OTβ showed no significant cytotoxicity to HEK293 cells, suggesting that these enzymes mitigate the toxicity of OTA and OTB. The discovery of the novel OTA and OTB degrading enzymes enriches the research on ochratoxin control and provides objects for protein rational design.

Research progress of ochratoxin a bio-detoxification

Ochratoxins (OTs) is an extremely toxic mycotoxin in which Ochratoxin A (OTA) is the most toxic and prevalent in the ochratoxin family. OTA is among the five most critical mycotoxins that are subject to legal regulations. Animals and humans may be exposed to OTA through dietary intake, inhalation, and dermal contact. OTA is considered nephrotoxic, genotoxic, cytotoxic, teratogenic, carcinogenic, mutagenic, immunotoxic, and myelotoxic. So, intake of OTA contaminated foods and feeds can impact the productivity of animals and health of people. According to this review, several studies have reported on the approaches that have been established for OTA removal. This review focused on the control approaches to mitigate OTA contamination, OTA bio-detoxification materials and their applicable techniques, recombinant strains for OTA bio-detoxification, and their detoxification effects, recombinant OTA-degrading enzymes and their sources, recombinant fusion enzymes for OTA, ZEN and AFB1 mycotoxins detoxification, as well as the current application and commercialized OTA bio-detoxification products. However, there is no single technique that has been approved to detoxify OTA by 100% to date. Some preferred current strategies for OTA bio-detoxification have been recombinant degrading enzymes and genetic engineering technology due to their efficiency and safety. Therefore, prospective studies should focus on standardizing pure enzymes from genetically engineered microbial strains that have great potential for OTA detoxification.

Biodegradation of ochratoxin A by endophytic Trichoderma koningii strains

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus spp. and Penicillium spp. that causes a threat to food safety and human health. Fungal biodegradation might be a promising strategy for reducing the OTA contamination in the future. In this study, the ability of Trichoderma koningii strains to degrade OTA produced by Aspergillus niger T2 (MW513392.1) isolated from tomato seeds was investigated. Among T. koningii strains tested, three strains; AUMC11519, AUMC11520 and AUMC11521 completely eliminated OTA from the culture medium, while AUMC11522 strain eliminated only 41.82% of OTA. OTα-amide, 3-phenylpropionic acid, OTα and phenylalanine were assayed as degradation products by FTIR analysis and LC-MS/MS spectra. Carboxypeptidase A (CPA) was found responsible for OTA degradation when a metal ion chelator, EDTA, was added to cell free supernatants of the three effective strains. OTA detoxification by T. koningii could present new prospective strategies for a possible application in food commodities intoxicated with ochratoxin.

Unveiling ochratoxin a controlling and biodetoxification molecular mechanisms: Opportunities to secure foodstuffs from OTA contamination

Anarchic growth of ochratoxin A (OTA) producing fungi during crop production, prolonged storage, and processing results in OTA contamination in foodstuffs. OTA in food exacerbates the risk of health and economic problems for consumers and farmers worldwide. Although the toxic effects of OTA on human health have not been well established, comprehensive preventive and remedial measures will be essential to eliminate OTA from foodstuffs. Strict regulations, controlling OTA at pre- or post-harvest stage, and decontamination of OTA have been adopted to prevent human and animal OTA exposure. Biological control of OTA and bio-decontamination are the most promising strategies due to their safety, specificity and nutritional value. This review addresses the current understanding of OTA biodegradation mechanisms and recent developments in OTA control and bio-decontamination strategies. Additionally, this review analyses the strength and weaknesses of different OTA control methods and the contemporary approaches to enhance the efficiency of biocontrol agents. Overall, this review will support the implementation of new strategies to effectively control OTA in food sectors. Further studies on efficacy-related issues, production issues and cost-effectiveness of OTA biocontrol are to be carried out to improve the knowledge, develop improved delivery technologies and safeguard the durability of OTA biocontrol approaches.

A Newly Isolated Alcaligenes faecalis ANSA176 with the Capability of Alleviating Immune Injury and Inflammation through Efficiently Degrading Ochratoxin A

Ochratoxin A (OTA) is one of the most prevalent mycotoxins that threatens food and feed safety. Biodegradation of OTA has gained much attention. In this study, an Alcaligenes faecalis strain named ANSA176, with a strong OTA-detoxifying ability, was isolated from donkey intestinal chyme and characterized. The strain ANSA176 could degrade 97.43% of 1 mg/mL OTA into OTα within 12 h, at 37 °C. The optimal levels for bacterial growth were 22–37 °C and pH 6.0–9.0. The effects of ANSA176 on laying hens with an OTA-contaminated diet were further investigated. A total of 36 laying hens were assigned to three dietary treatments: control group, OTA (250 µg/kg) group, and OTA + ANSA176 (6.2 × 10⁸ CFU/kg diet) group. The results showed that OTA decreased the average daily feed intake (ADFI) and egg weight (EW); meanwhile, it increased serum alanine aminopeptidase (AAP), leucine aminopeptidase (LAP), β2-microglobulin (β2-MG), immunoglobulin G (IgG), tumor necrosis factor-α (TNF-α), and glutathione reductase (GR). However, the ANSA176 supplementation inhibited or attenuated the OTA-induced damages. Taken together, OTA-degrading strain A. faecalis ANSA176 was able to alleviate the immune injury and inflammation induced by OTA.

Characterization of Bacillus velezensis E2 with abilities to degrade ochratoxin A and biocontrol against Aspergillus westerdijkiae fc-1

Ochratoxin A (OTA), primarily produced by the fungi belonging to the species of Aspergillus and Penicillium, is one of the most common mycotoxins found in cereals and fruits. In addition to resulting in huge economic losses, OTA contamination also poses considerable threat to human and livestock health. Microbial degradation of mycotoxins has been considered with great potential in mycotoxins decontamination. In a previous study, Bacillus velezensis E2 was isolated by our laboratory and showed appreciable inhibitory effect on Aspergillus flavus growth and aflatoxin production in rice grains. In this study, B. velezensis E2 was investigated for its ability to remove OTA and biocontrol against the ochratoxigenic Aspergillus westerdijkiae fc-1. The results revealed that B. velezensis E2 has considerable inhibitory effect on A. westerdijkiae fc-1 both on PDA medium and pear fruits, with inhibitory rate of 51.7% and 73.9%, respectively. In addition, its ability to remove OTA was evaluated in liquid medium and the results showed that more than 96.1% of OTA with an initial concentration of 2.5 μg/mL could be removed by B. velezensis E2 in 48 h. Further experiments revealed that enzymatic transformation and alkaline hydrolysis might be the main mechanisms related to OTA degradation by B. velezensis E2, with ring open ochratoxin α (OP-OTα) as a possible degradation product. Our study indicated that the B. velezensis E2 strain could be a potential bacterial candidate in biodegradation of OTA and biocontrol against A. westerdijkiae fc-1.

Genomic and resistome analysis of Alcaligenes faecalis strain PGB1 by Nanopore MinION and Illumina Technologies

Background

Drug-resistant bacteria are important carriers of antibiotic-resistant genes (ARGs). This fact is crucial for the development of precise clinical drug treatment strategies. Long-read sequencing platforms such as the Oxford Nanopore sequencer can improve genome assembly efficiency particularly when they are combined with short-read sequencing data.

Results

Alcaligenes faecalis PGB1 was isolated and identified with resistance to penicillin and three other antibiotics. After being sequenced by Nanopore MinION and Illumina sequencer, its entire genome was hybrid-assembled. One chromosome and one plasmid was assembled and annotated with 4,433 genes (including 91 RNA genes). Function annotation and comparison between strains were performed. A phylogenetic analysis revealed that it was closest to A. faecalis ZD02. Resistome related sequences was explored, including ARGs, Insert sequence, phage. Two plasmid aminoglycoside genes were determined to be acquired ARGs. The main ARG category was antibiotic efflux resistance and β-lactamase (EC 3.5.2.6) of PGB1 was assigned to Class A, Subclass A1b, and Cluster LSBL3.

Conclusions

The present study identified the newly isolated bacterium A. faecalis PGB1 and systematically annotated its genome sequence and ARGs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08507-7.

Ochratoxin A as alarming health in livestock and human: A review on molecular interactions, mechanism of toxicity, detection, detoxification, and dietary prophylaxis

Ochratoxin A (OTA) is a toxic metabolite produced by Aspergillus and Penicillium fungi commonly found in raw plant sources and other feeds. This review comprises an extensive evaluation of the origin and proprieties of OTA, toxicokinetics, biotransformation, and toxicodynamics of ochratoxins. In in vitro and in vivo studies, the compatibility of OTA with oxidative stress is observed through the production of free radicals, resulting in genotoxicity and carcinogenicity. The OTA leads to nephrotoxicity as the chief target organ is the kidney. Other OTA excretion and absorption rates are observed, and the routes of elimination include faeces, urine, and breast milk. The alternations in the Phe moiety of OTA are the precursor for the amino acid alternation, bringing about Phe-hydroxylase and Phe-tRNA synthase, resulting in the complete dysfunction of cellular metabolism. Biodetoxification using specific microorganisms decreased the DNA damage, lipid peroxidation, and cytotoxicity. This review addressed the ability of antioxidants and the dietary components as prophylactic measures to encounter toxicity and demonstrated their capability to counteract the chronic exposure through supplementation as feed additives.

Ochratoxin A: Occurrence and recent advances in detoxification

Ochratoxin A (OTA), one of the most important mycotoxins, is mainly produced by fungi in the genera Aspergillus and Penicillium, and commonly found in food and agricultural products. In addition to causing significant economic losses, the occurrence of OTA in foods poses a serious threat to human health. Therefore, it is very important to develop approaches to control or detoxify OTA contamination and thus ensure food safety. In this paper, we review the source and occurrence of OTA in food and agricultural products and the latest achievements in the removal and detoxification of OTA using physical, chemical, and biological methods, with specific attention to influencing factors and mechanisms related to the biodetoxification of OTA. Moreover, the advantages and disadvantages of these methods and their potential application prospect were also discussed.

Bio-control on the contamination of Ochratoxin A in food: Current research and future prospects

Ochratoxin A (OTA) is a secondary metabolite of several fungi and widely exists in various species of foods. The establishment of effective methods for OTA reduction is a key measure to ensure food processing and human health. This article reviews the current research of OTA reduction by biological approaches, summarizes the characteristics and efficiency of them, and evaluates the transformation pathways and metabolites safety of each degradation technology. The shortcomings of various methods are pointed out and future prospects are also proposed. Biological methods are the most promising approaches for OTA control. The defect of them is the long processing time and the growth of microbial cells may affect the product quality. Therefore, the control of OTA contamination should be conducted according to the food processing and their product types. Besides, it is significant for the exploitation of new strains, enzyme and novel adsorbents.

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The application of physical and chemical methods has been restricted.

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Existing biological methods can effectively detoxify OTA.

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OTA reduction systems should be established for different food.

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The exploitation of novel equipment, enzyme and adsorbents is essential.

Microbiological Decontamination of Mycotoxins: Opportunities and Limitations

The contamination of food and feeds with mycotoxins poses a global health risk to humans and animals, with major economic consequences. Good agricultural and manufacturing practices can help control mycotoxin contamination. Since these actions are not always effective, several methods of decontamination have also been developed, including physical, chemical, and biological methods. Biological decontamination using microorganisms has revealed new opportunities. However, these biological methods require legal regulations and more research before they can be used in food production. Currently, only selected biological methods are acceptable for the decontamination of feed. This review discusses the literature on the use of microorganisms to remove mycotoxins and presents their possible mechanisms of action. Special attention is given to Saccharomyces cerevisiae yeast and lactic acid bacteria, and the use of yeast cell wall derivatives.

A superefficient ochratoxin A hydrolase with promising potential for industrial applications

As the most seriously controlled mycotoxin produced by Aspergillus spp. and Penicillium spp., ochratoxin A (OTA) results in various toxicological effects and widely contaminates agro-products. Biological detoxification of OTA is the most priority in food and feed industry, but currently available detoxification enzymes are relatively low effectiveness in time and cost. Here we show a superefficient enzyme ADH3 identified from Stenotrophomonas acidaminiphila with a strong ability to transform OTA into non-toxic ochratoxin-α by acting as an amidohydrolase. Recombinant ADH3 (1.2 μg/mL) completely degrades 50 μg/L OTA within 90 seconds, while the availably most efficient OTA hydrolases takes several hours. The kinetic constant showed that rADH3 (Kcat/Km) catalytic efficiency was 56.7-35000 times higher than those of previous hydrolases rAfOTase, rOTase and commercial carboxypeptidase A (CPA). Protein structure-based assay suggested that ADH3 has a preference for hydrophobic residues to form a larger hydrophobic area than other detoxifying enzymes at the cavity of the catalytic sites, and this structure makes the OTA easier to access to catalytic sites. In addition, ADH3 shows considerable temperature adaptability to exert hydrolytic function at the temperature down to 0°C or up to 70°C. Collectively, we report a superefficient OTA detoxifying enzyme with promising potential for industrial applications. IMPORTANCE Ochratoxin A (OTA) can result in various toxicological effects and widely contaminates agro-products and feedstuffs. OTA detoxifications by microbial strains and bio-enzymes are significant to food safety. Although previous studies showed OTA could be transformed through several pathways, the ochratoxin-α pathway is recognized as the most effective one. However, the most currently available enzymes are not efficient enough. Here, a superefficient hydrolase ADH3 which can completely transform 50 μg/L OTA into ochratoxin-α within 90 seconds was screened and characterized. The hydrolase ADH3 shows considerable temperature adaptability (0-70°C) to exert the hydrolytic function. Findings of this study supplied an efficient OTA detoxifying enzyme and predicted the superefficient degradation mechanism which lay a foundation for future industrial applications.

Bacillus subtilis ANSB168 Producing d-alanyl-d-alanine Carboxypeptidase Could Alleviate the Immune Injury and Inflammation Induced by Ochratoxin A

Ochratoxin A (OTA) is toxic to animals and threatens food safety through residues in animal tissues. A novel degrading strain Bacillus subtilis ANSB168 was isolated and further investigated. We cloned d-alanyl-d-alanine carboxypeptidase DacA and DacB from ANSB168 and over-expressed them in Escherichia coli Rosetta (DE3). Then, we characterized the OTA degradation mechanism of DacA and DacB, which was degrading OTA into OTα. A total of 45 laying hens were divided into three equal groups. The control group was fed basal feed, and other groups were administered with OTA (250 μg/kg of feed). A freeze-dried culture powder of ANSB168 (3 × 10⁷ CFU/g, 2 kg/T of feed) was added to one of the OTA-fed groups for 28 days from day one of the experiment. We found that OTA significantly damaged the kidney and liver, inducing inflammation and activating the humoral immune system, causing oxidative stress in the layers. The ANSB168 bioproduct was able to alleviate OTA-induced kidney and liver damage, relieving OTA-induced inflammation and oxidative stress. Overall, DacA and DacB derived from ANSB168 degraded OTA into OTα, while the ANSB168 bioproduct was able to alleviate damages induced by OTA in laying hens.

Biodegradation of Deoxynivalenol by Nocardioides sp. ZHH-013: 3-keto-Deoxynivalenol and 3-epi-Deoxynivalenol as Intermediate Products

Deoxynivalenol (DON) is one of the most devastating and notorious contaminants in food and animal feed worldwide. A novel DON-degrading strain, Nocardioides sp. ZHH-013, which exhibited complete mineralization of DON, was isolated from soil samples. The intermediate products of DON generated by this strain were identified by high-performance liquid chromatography and ultra-performance liquid chromatography tandem mass spectrometry analyses. It was shown that, on an experimental level, 3-keto-DON was a necessary intermediate product during the conversion from DON to 3-epi-DON. Furthermore, the ZHH-013 strain could also utilize 3-epi-DON. This DON degradation pathway is a safety concern for food and feed. The mechanism of DON and 3-epi-DON elimination will be further studied, so that new enzymes for DON degradation can be identified.

Genome mining reveals the genes of carboxypeptidase for OTA-detoxification in Bacillus subtilis CW14

Bacillus subtilis CW14, isolated from fresh elk droppings in Beijing Zoo, is a Gram-positive, conferred Generally Recognized as Safe (GRAS) bacterium with the capacity of ochratoxin A (OTA) detoxification. The genome sequence of the CW14 strain showed a size of 4,287,522 bp with 44.06% GC content. It was predicted many putative enzymes involved in degrading mycotoxin by analyzing the signal peptides and the transmembrane regions. Nine extracellular enzymes were predicted relating to OTA detoxification, including four D-Ala-D-Ala carboxypeptidases, two hydrolases, two amidases, and one lactamase. Indeed, two of the carboxypeptidase genes dacA and dacB, expressed in Escherichia coli, were verified contributing to OTA detoxification. DacA and OTA were mixed incubated for 24 h, and the degradation rate reached 71.3%. After purification, the concentration of recombinant DacA protein was 0.5 mg/mL. Bacillus subtilis CW14 and its carboxypeptidases may be used as OTA detoxification agents in food and feed industry production.

Co-Occurrence of Regulated and Emerging Mycotoxins in Corn Silage: Relationships with Fermentation Quality and Bacterial Communities

Sixty-four corn silages were characterized for chemicals, bacterial community, and concentrations of several fungal metabolites. Silages were grouped in five clusters, based on detected mycotoxins, and they were characterized for being contaminated by (1) low levels of Aspergillus- and Penicillium-mycotoxins; (2) low levels of fumonisins and other Fusarium-mycotoxins; (3) high levels of Aspergillus-mycotoxins; (4) high levels of non-regulated Fusarium-mycotoxins; (5) high levels of fumonisins and their metabolites. Altersetin was detected in clusters 1, 3, and 5. Rugulusovin or brevianamide F were detected in several samples, with the highest concentration in cluster 3. Emodin was detected in more than 50.0% of samples of clusters 1, 3 and 5, respectively. Kojic acid occurred mainly in clusters 1 and 2 at very low concentrations. Regarding Fusarium mycotoxins, high occurrences were observed for FB3, FB4, FA1, whereas the average concentrations of FB6 and FA2 were lower than 12.4 µg/kg dry matter. Emerging Fusarium-produced mycotoxins, such as siccanol, moniliformin, equisetin, epiequisetin and bikaverin were detected in the majority of analyzed corn silages. Pestalotin, oxaline, phenopirrozin and questiomycin A were detected at high incidences. Concluding, this work highlighted that corn silages could be contaminated by a high number of regulated and emerging mycotoxins.

Ochratoxin A-induced genotoxic and epigenetic mechanisms lead to Alzheimer disease: its modulation with strategies

Ochratoxin A (OTA) is a naturally occurring mycotoxin mostly found in food items including grains and coffee beans. It induces DNA single-strand breaks and has been considered to be carcinogenic. It is recognized as a serious threat to reproductive health both in males and females. OTA is highly nephrotoxic and carcinogenic, and its potency changes evidently between species and sexes. There is a close association between OTA, mutagenicity, carcinogenicity, and genotoxicity, but the underlying mechanisms are not clear. Reports regarding genotoxic effects in relation to OTA which leads to the induction of DNA adduct formation, protein synthesis inhibition, perturbation of cellular energy production, initiation of oxidative stress, induction of apoptosis, influences on mitosis, induction of cell cycle arrest, and interference with cytokine pathways. All these mechanisms are associated with nephrotoxicity, hepatotoxicity, teratotoxicity, immunological toxicity, and neurotoxicity. OTA administration activates various mechanisms such as p38 MAPK, JNKs, and ERKs dysfunctions, BDNF disruption, TH overexpression, caspase-3 and 9 activation, and ERK-1/2 phosphorylation which ultimately lead to Alzheimer disease (AD) progression. The current review will focus on OTA in terms of recent discoveries in the field of molecular biology. The main aim is to investigate the underlying mechanisms of OTA in regard to genotoxicity and epigenetic modulations that lead to AD. Also, we will highlight the strategies for the purpose of attenuating the hazards posed by OTA exposure.

Integrative, genome-wide association study identifies chemicals associated with common women's malignancies

BACKGROUND

Breast cancer, cervical cancer, and ovarian cancer are three of the most commonly diagnosed malignancies in women, and more cancer prevention research is urgently needed.

METHODS

Summary data of a large genome-wide association study of female cancers were derived from the UK biobank. We performed a transcriptome-wide association study and a gene set enrichment analysis to identify correlations between chemical exposure and aberrant expression, repression, or mutation of genes related to cancer using the Comparative Toxicogenomics Database.

RESULTS

We identified five chemicals (NSC668394, glafenine, methylnitronitrosoguanidine, fenofibrate, and methylparaben) that were associated with the incidence of both breast cancer and cervical cancer.

CONCLUSION

Using a transcriptome-wide association study and gene set enrichment analysis we identified environmental chemicals that are associated with an increased risk of breast cancer, cervical cancer, and ovarian cancer.

Minimizing Ochratoxin A Contamination through the Use of Actinobacteria and Their Active Molecules

Ochratoxin A (OTA) is a secondary metabolite produced by fungal pathogens such as Penicilliumverrucosum, which develops in food commodities during storage such as cereals, grapes, and coffee. It represents public health concerns due to its genotoxicity, carcinogenicity, and teratogenicity. The objective of this study was to evaluate the ability of actinobacteria and their metabolites to degrade OTA and/or to decrease its production. Sixty strains of actinobacteria were tested for their ability to prevent OTA formation by in vitro dual culture assays or with cell free extracts (CFEs). In dual culture, 17 strains strongly inhibited fungal growth, although it was generally associated with an increase in OTA specific production. Seventeen strains inhibited OTA specific production up to 4% of the control. Eleven actinobacteria CFEs reduced OTA specific production up to 62% of the control, while no substantial growth inhibition was observed except for two strains up to 72% of the control. Thirty-three strains were able to degrade OTA almost completely in liquid medium whereas only five were able to decrease it on solid medium, and two of them reduced OTA to an undetectable amount. Our results suggest that OTA decrease could be related to different strategies of degradation/metabolization by actinobacteria, through enzyme activities and secretion of secondary metabolites interfering with the OTA biosynthetic pathway. CFEs appeared to be ineffective at degrading OTA, raising interesting questions about the detoxification mechanisms. Common degradation by-products (e.g., OTα or L-β-phenylalanine) were searched by HPLC-MS/MS, however, none of them were found, which implies a different mechanism of detoxification and/or a subsequent degradation into unknown products.

Degradation of ochratoxin A by supernatant and ochratoxinase of Aspergillus niger W-35 isolated from cereals

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus spp. and Penicillium spp. and poses a threat to food safety. Biodegradation may be a promising strategy for reducing the OTA contamination in the future. In this study, Aspergillus niger strain W-35 was isolated from cereals and studied for its ability to degrade OTA. Results showed that the supernatant of W-35 could degrade OTA both in vitro and in commercial feeds after incubation at 37 °C for 12 h by 78.0 and 37.0%, respectively. Ochratoxin α (OTα) was assayed as a degradation product by HPLC-FLD. Furthermore, an enzyme specific for OTA degradation (ochratoxinase, OTase) obtained from W-35 was successfully expressed in Escherichia coli BL21, and degraded OTA at a rate of 85.1% for 12 h. These results indicated that this OTA degradation is enzymatic and that the responsible enzyme is extracellular OTase. Reliable degradation of OTA has the potential for wide-ranging applications in the food and feed industries.

Detoxification of ochratoxin A by Lysobacter sp. CW239 and characteristics of a novel degrading gene carboxypeptidase cp4

Ochratoxin A (OTA) is a potent mycotoxin that frequently contaminates agro-products and threatens food safety. A highly efficient OTA degrading strain Lysobacter sp. CW239 was isolated, and the OTA degradation characteristics were investigated. A novel OTA degrading gene carboxypeptidase cp4 was successfully cloned and characterized from CW239. The heterologous recombinant was constructed by gene cp4 and expression vector pET-32a⁽⁺⁾ and overexpressed by E. coli BL21 CodonPlus™ (DE3). The recombinant protein rCP4 was purified, and the OTA-degrading activity was evaluated. Although OTA was efficiently degraded by CW239 (24-h degradation ratio of 86.2%), the 24-h OTA degradation ratio for rCP4 was only 36.8% at fairly high concentration (0.25 mg/mL) protein. The degraded product was obtained by immune affinity column (IAC) and determined by mass spectrometry (MS), and the degraded product was the less toxic ochratoxin α (OTα). Based on the serial investigations of this study, OTA might be simultaneously co-degraded by CP4 and another unknown degrading agent in that degrading strain.

Selenium Yeast Alleviates Ochratoxin A-Induced Hepatotoxicity via Modulation of the PI3K/AKT and Nrf2/Keap1 Signaling Pathways in Chickens

The aim of this study was to investigate the protective effects of selenium yeast (Se-Y) against hepatotoxicity induced by ochratoxin A (OTA). The OTA-induced liver injury model was established in chickens by daily oral gavage of 50 µg/kg OTA for 21 days. Serum biochemistry analysis, antioxidant analysis, as well as the qRT-PCR and Western blot (WB) analyses were then used to evaluate oxidative damage and apoptosis in chicken liver tissue. The results showed that Se-Y significantly increased liver coefficient induced by OTA (P < 0.05). OTA + Se-Y treated group revealed that Se-Y reduced the OTA-induced increase in glutamic pyruvic transaminase (ALT), glutamic oxaloacetic transaminase (AST) and malonaldehyde (MDA) content, and reversed the decrease in antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) and total superoxide dismutase (T-SOD) (P < 0.05). In this study, we found that OTA is involved in the mRNA expression levels about Nrf2/Keap1 and PI3K/AKT signaling pathways, such as oxidative stress-related genes (Nrf2, GSH-Px, GLRX2 and Keap1) and apoptosis-related genes (Bax, Caspase3, P53, AKT, PI3K and Bcl-2). Besides, significant downregulations of protein expression of HO-1, MnSOD, Nrf2 and Bcl-2, as well as a significant upregulation of Caspase3 and Bax levels were observed after contaminated with OTA (P < 0.05). Notably, OTA-induced apoptosis and oxidative damage in the liver of chickens were reverted back to normal level in the OTA + Se-Y group. Our findings indicate that pretreatment with Se-Y effectively ameliorates OTA-induced hepatotoxicity.

Detoxification of Mycotoxins through Biotransformation

Mycotoxins are toxic fungal secondary metabolites that pose a major threat to the safety of food and feed. Mycotoxins are usually converted into less toxic or non-toxic metabolites through biotransformation that are often made by living organisms as well as the isolated enzymes. The conversions mainly include hydroxylation, oxidation, hydrogenation, de-epoxidation, methylation, glycosylation and glucuronidation, esterification, hydrolysis, sulfation, demethylation and deamination. Biotransformations of some notorious mycotoxins such as alfatoxins, alternariol, citrinin, fomannoxin, ochratoxins, patulin, trichothecenes and zearalenone analogues are reviewed in detail. The recent development and applications of mycotoxins detoxification through biotransformation are also discussed.

Heterologous Expression and Characterization of A Novel Ochratoxin A Degrading Enzyme, N-acyl-L-amino Acid Amidohydrolase, from Alcaligenes faecalis

Ochratoxin A (OTA) is a well-known, natural contaminant in foods and feeds because of its toxic effects, such as nephrotoxicity in various animals. Recent studies have revealed that Alcaligenes faecalis could generate enzymes to efficiently degrade OTA to ochratoxin α (OTα) in vitro. In an effort to obtain the OTA degrading mechanism, we purified and identified a novel degrading enzyme, N-acyl-L-amino acid amidohydrolase (AfOTase), from A. faecalis DSM 16503 via mass spectrometry. The same gene of the enzyme was also encountered in other A. faecalis strains. AfOTase belongs to peptidase family M20 and contains metal ions at the active site. In this study, recombination AfOTase was expressed and characterized in Escherichia coli. The molecular mass of recombinant rAfOTase was approximately 47.0 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited a wide temperature range (30-70 °C) and pH adaptation (4.5-9.0) and the optimal temperature and pH were 50 °C and 6.5, respectively.

Long-term operation of electroactive biofilms for enhanced ciprofloxacin removal capacity and anti-shock capabilities

Few studies have focused on the feasibility of microbial fuel cells (MFCs) for removing quinolones antibiotics and their anti-shock capabilities. After 1.5 years of operation, the removal efficiency of 10 mg/L ciprofloxacin in MFCs increased to 99.00% in 88 h. These results are in accordance with the enhanced activity of biofilms and voltage output of MFCs. Additionally, the anti-shock capacities of the biofilms in MFCs were evaluated by treating ofloxacin and enrofloxacin and operating at different temperature and salinity. These MFCs can remove 87.31% and 40.81% of ofloxacin and enrofloxacin in 72 h, respectively. Even exposed to a low temperature of 10 °C or a salinity of 3%, the MFCs can achieve greater than 50% and nearly 80% of ciprofloxacin removal efficiency, respectively. The enrichment of Alcaligenes and Chryseobacterium contributed mostly to the removal of quinolones antibiotics. This study provides scientific evidences for treating wastewater containing quinolones antibiotics using MFCs.

Removal of ochratoxin A by a carboxypeptidase and peptides present in liquid cultures of Bacillus subtilis CW14

Ochratoxin A (OTA) is an important mycotoxin that contaminates a variety of agricultural products. The cell-free supernatant of Bacillus subtilis CW14 liquid cultures were reported previously to be capable of removing OTA efficiently. In this work, we examined several substances that are probably involved in this removal of OTA using in vitro experiments. The strain CW14 culture supernatant that was separated by ultrafiltration showed that the fractions collected at >10 kDa and <3 kDa had a significant ability to reduce OTA (84.9 and 74.8%, respectively) when incubated with 6 μg/ml OTA at 37 °C for 24 h. A putative metalloenzyme was responsible for the activity of the >10-kDa fraction, which was confirmed by the detrimental effects of heat treatments or addition of SDS, proteinase K, or EDTA. Subsequently, a carboxypeptidase (CP) gene that was likely related to the enzymatic conversion of OTA by the >10-kDa fraction was cloned from the B. subtilis CW14 genome, and over-expressed in Escherichia coli. The recombinant CP degraded 71.3% of OTA at 37 °C for 24 h, and ochratoxin α (OTα) was confirmed as a degradation product. From the <3-kDa fraction, some small peptides (1.7 kDa >Mw >0.7 kDa) were purified and decreased OTA by 45.0% under the same conditions, but no product was detected. These peptides were presumed to be capable of binding OTA due to their affinity with the OTA molecule, and the OTA-peptide complexes escaped from the extraction procedures for OTA quantification. These results indicated there was a probable synergistic effect that was involved in removal of OTA by the strain CW14 culture supernatant, which included enzymatic degradation by a CP and physical adsorption by some small peptides.

Advances in Biodetoxification of Ochratoxin A-A Review of the Past Five Decades

Ochratoxin A (OTA) is a toxic secondary fungal metabolite that widely takes place in various kinds of foodstuffs and feeds. Human beings and animals are inevitably threatened by OTA as a result. Therefore, it is necessary to adopt various measures to detoxify OTA-contaminated foods and feeds. Biological detoxification methods, with better safety, flavor, nutritional quality, organoleptic properties, availability, and cost-effectiveness, are more promising than physical and chemical detoxification methods. The state-of-the-art research advances of OTA biodetoxification by degradation, adsorption, or enzymes are reviewed in the present paper. Researchers have discovered a good deal of microorganisms that could degrade and/or adsorb OTA, including actinobacteria, bacteria, filamentous fungi, and yeast. The degradation of OTA to non-toxic or less toxic OTα via the hydrolysis of the amide bond is the most important OTA biodegradation mechanism. The most important influence factor of OTA adsorption capacity of microorganisms is cell wall components. A large number of microorganisms with good OTA degradation and/or adsorption ability, as well as some OTA degradation enzymes isolated or cloned from microorganisms and animal pancreas, have great application prospects in food and feed industries.