Simultaneous degradation of two mycotoxins enabled by a fusion enzyme in food-grade recombinant Kluyveromyces lactis

Mycotoxin management: exploring natural solutions for mycotoxin prevention and detoxification in food and feed

Mycotoxins, secondary metabolites produced by various fungi, pose a significant threat to food and feed safety worldwide due to their toxic effects on human and animal health. Traditional methods of mycotoxin management often involve chemical treatments, which may raise concerns about residual toxicity and environmental impact. In recent years, there has been growing interest in exploring natural alternatives for preventing mycotoxin contamination and detoxification. This review provides an overview of the current research on the use of natural products for mitigating mycotoxin risks in food and feed. It encompasses a wide range of natural sources, including plant-derived compounds, microbial agents, and enzymatic control. The mechanisms underlying the efficacy of these natural products in inhibiting mycotoxin synthesis, adsorbing mycotoxins, or enhancing detoxification processes are discussed. Challenges and future directions in the development and application of natural products for mycotoxin management are also addressed. Overall, this review highlights the promising role of natural products as sustainable and eco-friendly alternatives for combating mycotoxin contamination in the food and feed supply chain.

Bioenzymatic detoxification of mycotoxins

Mycotoxins are secondary metabolites produced during the growth, storage, and transportation of crops contaminated by fungi and are physiologically toxic to humans and animals. Aflatoxin, zearalenone, deoxynivalenol, ochratoxin, patulin, and fumonisin are the most common mycotoxins and can cause liver and nervous system damage, immune system suppression, and produce carcinogenic effects in humans and animals that have consumed contaminated food. Physical, chemical, and biological methods are generally used to detoxify mycotoxins. Although physical methods, such as heat treatment, irradiation, and adsorption, are fast and simple, they have associated problems including incomplete detoxification, limited applicability, and cause changes in food characteristics (e.g., nutritive value, organoleptic properties, and palatability). Chemical detoxification methods, such as ammonification, ozonation, and peroxidation, pollute the environment and produce food safety risks. In contrast, bioenzymatic methods are advantageous as they achieve selective detoxification and are environmentally friendly and reusable; thus, these methods are the most promising options for the detoxification of mycotoxins. This paper reviews recent research progress on common mycotoxins and the enzymatic principles and mechanisms for their detoxification, analyzes the toxicity of the degradation products and describes the challenges faced by researchers in carrying out enzymatic detoxification. In addition, the application of enzymatic detoxification in food and feed is discussed and future directions for the development of enzymatic detoxification methods are proposed for future in-depth study of enzymatic detoxification methods.

Enzymatic characterization and application of soybean hull peroxidase as an efficient and renewable biocatalyst for degradation of zearalenone

Zearalenone (ZEN) is a notorious mycotoxin commonly found in Fusarium-contaminated crops, which causes great loss in livestock farming and serious health problems to humans. In the present work, we found that crude peroxidase extraction from soybean hulls could use H2O2 as a co-substate to oxidize ZEN. Molecular docking and dynamic simulation also supported that ZEN could bind to the active site of soybean hull peroxidase (SHP). Subsequently, SHP extracted from soybean hulls was purified using a combined purification protocol involving ammonium sulfate precipitation, ion exchange chromatography and size exclusion chromatography. The purified SHP showed wide pH resistance and high thermal stability. This peroxidase could degrade 95 % of ZEN in buffer with stepwise addition of 100 μM H2O2 in 1 h. The two main ZEN degradation products were identified as 13-OH-ZEN and 13-OH-ZEN-quinone. Moreover, SHP-catalyzed ZEN degradation products displayed much less cytotoxicity to human liver cells than ZEN. The application of SHP in various food matrices obtained 54 % to 85 % ZEN degradation. The findings in this study will promote the utilization of SHP as a cheap and renewable biocatalyst for degrading ZEN in food.

Intervention mechanism of marine-based chito-oligosaccharide on acute liver injury induced by AFB1 in rats

Aflatoxin B1 (AFB1) is extremely hepatotoxic, a causative agent of liver cancer, and can cause symptoms of acute or chronic liver damage. Chito-oligosaccharides (COS), obtained from the degradation of chitosan derived from shrimp and crab shells, is a natural antioxidant substance and its antitumor properties have been widely studied, but less research has been done on the prevention of AFB1-induced acute liver injury. In this study, rats were acutely exposed to 1 mg/kg BW AFB1 and simultaneously gavaged with different doses of COS for 8 days. The results showed that COS attenuated the hepatic histopathological changes and reduced serum biochemical indices (ALT, AST, ALP, and TBIL) in rats. It significantly inhibited MDA content and promoted SOD and GSH-Px activity production. Moreover, it also improved hepatocyte apoptosis. Furthermore, AFB1-vs-HCOS differential genes were enriched with 622 GO entries, and 380 were Biological Processes, 170 were Molecular Functions, 72 were Cellular Components. Differentially expressed genes (DEGs) analyzed by KEGG enrichment were more enriched in pathways, such as metabolism, PPAR signaling pathway, and peroxisome. Q-PCR technique verified that Lama5, Egr1, Cyp2b1, and Gadd45g in DEGs were associated with oxidative stress damage and apoptosis. In conclusion, COS intervention reduces the effect of AFB1 on hepatic genes and thus reduces the changes in hepatic gene function.

Capacity and kinetics of zearalenone adsorption by Geotrichum candidum LG-8 and its dried fragments in solution

The application of LG-8 and its dry fragments as zearalenone (ZEN) adsorbents was investigated. The study showed that Geotrichum candidum LG-8 and its fragments dried at 55°C or through lyophilization are able to adsorb around 80% of ZEN. However, besides in water and 55°C-drying conditions, SEM indicated that higher 90% of ZEN binding tended to occur when cell walls of fragments were intact with less adhesion among themselves. Notably, ZEN/LG-8 fragments complexes were quite stable, as only 1.262% and 1.969% of ZEN were released after successive pH treatments for 4 h and 5 min. The kinetic data signified that adsorption of ZEN onto LG-8 fragments followed well the pseudo-first-order kinetic model. Isotherm calculations showed Langmuir model was favourable and monolayer adsorption of ZEN occurred at functional binding sites on fragments surface. Therefore, we conclude that it can be an alternative biosorbent to treat water contained with ZEN, since LG-8 is low-cost biomass and its fragments have a considerable high biosorption capacity avoiding impacting final product quality and immunodeficient patients.

Recent advances in biosynthesis of mycotoxin-degrading enzymes and their applications in food and feed

Mycotoxins are secondary metabolites produced by fungi in food and feed, which can cause serious health problems. Bioenzymatic degradation is gaining increasing popularity due to its high specificity, gentle degradation conditions, and environmental friendliness. We reviewed recently reported biosynthetic mycotoxin-degrading enzymes, traditional and novel expression systems, enzyme optimization strategies, food and feed applications, safety evaluation of both degrading enzymes and degradation products, and commercialization potentials. Special emphasis is given to the novel expression systems, advanced optimization strategies, and safety considerations for industrial use. Over ten types of recombinases such as oxidoreductase and hydrolase have been studied in the enzymatic hydrolysis of mycotoxins. Besides traditional expression system of Escherichia coli and yeasts, these enzymes can also be expressed in novel systems such as Bacillus subtilis and lactic acid bacteria. To meet the requirements of industrial applications in terms of degradation efficacy and stability, genetic engineering and computational tools are used to optimize enzymatic expression. Currently, registration and technical difficulties have restricted commercial application of mycotoxin-degrading enzymes. To overcome these obstacles, systematic safety evaluation of both biosynthetic enzymes and their degradation products, in-depth understanding of degradation mechanisms and a comprehensive evaluation of their impact on food and feed quality are urgently needed.

Simultaneous degradation of aflatoxin B1 and zearalenone by Porin and Peroxiredoxin enzymes cloned from Acinetobacter nosocomialis Y1

Mycotoxin contamination can cause severe health issues for both humans and animals. This study examined the potential of enzymes derived from Acinetobacter nosocomialis Y1 to simultaneously degrade aflatoxin B1 (AFB1) and zearalenone (ZEN), which could have significant implications in reducing mycotoxin contamination. Two enzymes, Porin and Peroxiredoxin, were identified with molecular weights of 27.8 and 20.8 kDa, respectively. Porin could completely degrade 2 µg/mL of AFB1 and ZEN within 24 h at 80 °C and 60 °C, respectively. Peroxiredoxin could completely degrade 2 µg/mL of AFB1 and reduce ZEN by 91.12% within 24 h. The addition of Na+, Cu2+, and K+ ions enhanced the degradation activities of both enzymes. LC-MS/MS analysis revealed that the molar masses of the degradation products of AFB1 and ZEN were 286 g/mol and 322.06 g/mol, and the products were identified as AFD1 and α or β-ZAL, respectively. Vibrio fischeri bioluminescence assays further confirmed that the cytotoxicity of the two degradation products was significantly lower than that of AFB1 and ZEN. Based on these results, it can be inferred that the degradation product of ZEN is β-ZAL. These findings suggest that both enzymes have the potential to be utilized as detoxification enzymes in food and feed.

Degradation of zearalenone by microorganisms and enzymes

Mycotoxins are toxic metabolites produced by fungi that may cause serious health problems in humans and animals. Zearalenone is a secondary metabolite produced by fungi of the genus Fusarium, widely exists in animal feed and human food. One concern with the use of microbial strains and their enzyme derivatives for zearalenone degradation is the potential variability in the effectiveness of the degradation process. The efficiency of degradation may depend on various factors such as the type and concentration of zearalenone, the properties of the microbial strains and enzymes, and the environmental conditions. Therefore, it is important to carefully evaluate the efficacy of these methods under different conditions and ensure their reproducibility. Another important consideration is the safety and potential side effects of using microbial strains and enzymes for zearalenone degradation. It is necessary to evaluate the potential risks associated with the use of genetically modified microorganisms or recombinant enzymes, including their potential impact on the environment and non-target organisms. Additionally, it is important to ensure that the degradation products are indeed harmless and do not pose any health risks to humans or animals. Furthermore, while the use of microbial strains and enzymes may offer an environmentally friendly and cost-effective solution for zearalenone degradation, it is important to explore other methods such as physical or chemical treatments as well. These methods may offer complementary approaches for zearalenone detoxification, and their combination with microbial or enzyme-based methods may improve overall efficacy. Overall, the research on the biodegradation of zearalenone using microorganisms and enzyme derivatives is promising, but there are important considerations that need to be addressed to ensure the safety and effectiveness of these methods. Development of recombinant enzymes improves enzymatic detoxification of zearalenone to a non-toxic product without damaging the nutritional content. This review summarizes biodegradation of zearalenone using microorganisms and enzyme derivatives to nontoxic products. Further research is needed to fully evaluate the potential of these methods for mitigating the impact of mycotoxins in food and feed.

Isolation and Characterization of the Zearalenone-Degrading Strain, Bacillus spizizenii B73, Inspired by Esterase Activity

Zearalenone (ZEN) is a widespread mycotoxin found in grain and feed, presenting a serious threat to animal and human health. This study investigated the ability of the novel strain B73, isolated from petroleum-contaminated soil, to detoxify ZEN. B73 was identified as Bacillus spizizenii through physiological and biochemical tests, and further confirmed based on the 16S rRNA gene sequence and the complete genome sequence. B. spizizenii B73 was capable of degrading up to 99.3% of ZEN at a concentration of 10 μg/mL in a minimal medium (pH = 7.0) within 8 h at 37 °C via HPLC-UV. In addition, B. spizizenii B73 was used to treat ZEN-contaminated wheat bran, dried distillers grains (DDGS), and corn meal, whereby the respective degradation rates reached 96.32%, 98.73%, and 80.31% after 36 h of treatment. HPLC-Q-Exactive-MS/MS analysis revealed one of the degradation products to have the formula C17H24O4. B. spizizenii B73 is a novel strain isolated from petroleum-contaminated soil, and the extracellular enzymes secreted by this strain show a remarkable ability to degrade ZEN.

Post-Harvest Prevention of Fusariotoxin Contamination of Agricultural Products by Irreversible Microbial Biotransformation: Current Status and Prospects

Biological degradation of mycotoxins is a promising environmentally-friendly alternative to chemical and physical detoxification methods. To date, a lot of microorganisms able to degrade them have been described; however, the number of studies determining degradation mechanisms and irreversibility of transformation, identifying resulting metabolites, and evaluating in vivo efficiency and safety of such biodegradation is significantly lower. At the same time, these data are crucial for the evaluation of the potential of the practical application of such microorganisms as mycotoxin-decontaminating agents or sources of mycotoxin-degrading enzymes. To date, there are no published reviews, which would be focused only on mycotoxin-degrading microorganisms with the proved irreversible transformation of these compounds into less toxic compounds. In this review, the existing information about microorganisms able to efficiently transform the three most common fusariotoxins (zearalenone, deoxinyvalenol, and fumonisin B1) is presented with allowance for the data on the corresponding irreversible transformation pathways, produced metabolites, and/or toxicity reduction. The recent data on the enzymes responsible for the irreversible transformation of these fusariotoxins are also presented, and the promising future trends in the studies in this area are discussed.

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.

Microbial Enzymes Involved in the Biotransformation of Major Mycotoxins

Mycotoxins, the most researched biological toxins, can contaminate food and feed, resulting in severe health implications for humans and animals. Physical, chemical, and biological techniques are used to mitigate mycotoxin contamination. The biotransformation method using whole microbial cells or isolated enzymes is the best choice to mitigate mycotoxins. Using specific enzymes may avoid the disadvantages of utilizing a full microbe, such as accidental harm to the product's organoleptic characteristics and hazardous safety features. Moreover, the degradation rates of the isolated enzymes are higher than those of the whole-cell reactions, and they are substrate-specific. Their specificity is comprehensive and is shown at the positional and/or chiral center in many circumstances. Currently, only a few enzymes of microbial origin are commercially available. Therefore, there is a need to identify more novel enzymes of microbial origin that can mitigate mycotoxins. In this review, we conducted an in-depth summary of the microbial enzymes involved in the biotransformation of mycotoxins.

The potential of cold-shock promoters for the expression of recombinant proteins in microbes and mammalian cells

BACKGROUND

Low-temperature expression of recombinant proteins may be advantageous to support their proper folding and preserve bioactivity. The generation of expression vectors regulated under cold conditions can improve the expression of some target proteins that are difficult to express in different expression systems. The cspA encodes the major cold-shock protein from Escherichia coli (CspA). The promoter of cspA has been widely used to develop cold shock-inducible expression platforms in E. coli. Moreover, it is often necessary to employ expression systems other than bacteria, particularly when recombinant proteins require complex post-translational modifications. Currently, there are no commercial platforms available for expressing target genes by cold shock in eukaryotic cells. Consequently, genetic elements that respond to cold shock offer the possibility of developing novel cold-inducible expression platforms, particularly suitable for yeasts, and mammalian cells.

CONCLUSIONS

This review covers the importance of the cellular response to low temperatures and the prospective use of cold-sensitive promoters to direct the expression of recombinant proteins. This concept may contribute to renewing interest in applying white technologies to produce recombinant proteins that are difficult to express.

Zearalenone lactonase: characteristics, modification, and application

Zearalenone (ZEN) and its derivatives are one of the most contaminated fungal toxins worldwide, posing a severe threat to food security and human life. Traditional physical and chemical detoxifying methods are unsatisfactory due to incomplete detoxification, nutrient loss, and secondary pollutants. In recent years, bioremediation for eliminating fungal toxins has been gradually investigated. ZEN lactone hydrolase (lactonase) has been widely studied because of its high activity, mild conditions, and non-toxic product property. This review comprehensively represents the gene mining, characterization, molecular modification, and application of microbial-derived ZEN lactonases. It is aimed to elucidate the advantages and challenges of ZEN lactonases in industrial application, which also provides perspectives on obtaining innovative and promising biocatalysts for ZEN degradation. KEY POINTS: • A timely and concise review related to enzymatic elimination towards ZEN is shown. • The catalytic conditions and mechanism of ZEN lactonase is presented. • The modification and application of ZEN lactonase are exhibited also.

Microbial and enzymatic battle with food contaminant zearalenone (ZEN)

Zearalenone (ZEN) contamination of various foods and feeds is an important global problem. In some animals and humans, ZEN causes significant health issues in addition to massive economic losses, annually. Therefore, removal or degradation of the ZEN in foods and feeds is required to be done. The conventional physical and chemical methods have some serious issues including poor efficiency, decrease in nutritional value, palatability of feed, and use of costly equipment. Research examined microbes from diverse media for their ability to degrade zearalenone and other toxins, and the findings of several investigations revealed that enzymes produced from microbes play a significant role in the degradation of mycotoxins. In established bacterial hosts, genetically engineered technique was used to enhance heterologously produced degrading enzymes. Then, the bio-degradation of ZEN by the use of micro-organisms or their enzymes is much more advantageous and is close to nature and ecofriendly. Furthermore, an effort is made to put forward the work done by different scientists on the biodegradation of ZEN by the use of fungi, yeast, bacteria, and/or their enzymes to degrade the ZEN to non-toxic products. KEY POINTS: •Evolved microbial strains degraded ZEA more quickly •Different degrading properties were studied.

Design of Artificial Enzymes Bearing Several Active Centers: New Trends, Opportunities and Problems

Harnessing enzymes which possess several catalytic activities is a topic where intense research has been carried out, mainly coupled with the development of cascade reactions. This review tries to cover the different possibilities to reach this goal: enzymes with promiscuous activities, fusion enzymes, enzymes + metal catalysts (including metal nanoparticles or site-directed attached organometallic catalyst), enzymes bearing non-canonical amino acids + metal catalysts, design of enzymes bearing a second biological but artificial active center (plurizymes) by coupling enzyme modelling and directed mutagenesis and plurizymes that have been site directed modified in both or in just one active center with an irreversible inhibitor attached to an organometallic catalyst. Some examples of cascade reactions catalyzed by the enzymes bearing several catalytic activities are also described. Finally, some foreseen problems of the use of these multi-activity enzymes are described (mainly related to the balance of the catalytic activities, necessary in many instances, or the different operational stabilities of the different catalytic activities). The design of new multi-activity enzymes (e.g., plurizymes or modified plurizymes) seems to be a topic with unarguable interest, as this may link biological and non-biological activities to establish new combo-catalysis routes.

Preparation of recombinant Kluyveromyces lactis agents for simultaneous degradation of two mycotoxins

Aflatoxin B1 (AFB1) and zearalenone (ZEN) are widely distributed in corns, peanuts, and other cereals, causing serious threat to food safety and human health. As shown by our previous studies, the recombinant yeast strain Kluyveromyces lactis GG799(pKLAC1-ZPF1) had the ability of degrading AFB1 and ZEN simultaneously. In this work, the agent preparation process was optimized for K. lactis GG799(pKLAC1-ZPF1), and the storage conditions of the prepared yeast agents were investigated, for obtaining the products with high storage activities and potent mycotoxin degradation efficiency. The optimal preparation process was as follows: centrifugation at 6000 rpm for 15 min for collection of the yeast cells, spray drying with the ratio of protective compounds to yeast cells at 3:1 (w/w) and then stored at - 20 °C. Simultaneous degradation tests of AFB1 and ZEN were performed using the supernatants of reactivated yeast agents after three months of storage, and the degradation ratios for AFB1 and ZEN in reaction system 1 (70.0 mmol/L malonic buffer, pH 4.5, with 1.0 mmol/L MnSO4, 0.1 mmol/L H2O2, 5.0 μg/mL AFB1 and ZEN, respectively) were 48.2 ± 3.2% and 34.8 ± 2.8%, while that for ZEN in reaction system 2 (50.0 mmol/L Tris-HCl, pH 7.5, with 5.0 μg/mL AFB1 and ZEN, respectively) was 30.1 ± 2.7%. Besides, the supernatants of reactivated yeast agents degraded more than 80% of AFB1 and 55% of ZEN in contaminated peanuts after twice treatments. Results of this work suggested that the optimized process for K. lactis GG799(pKLAC1-ZPF1) was with high value for industrial applications.

Improvement of the enzymatic detoxification activity towards mycotoxins through structure-based engineering

Mycotoxin contamination of food and feed is posing a serious threat to the global food safety and public health. Biological detoxification mediated by enzymes has emerged as a promising approach, as they can specifically degrade mycotoxins into non-toxic ones. However, the low degradation efficiency and stability limit their further application. To optimize the enzymes for mycotoxin removal, modification strategies that combine computational design with their structural data have been developed. Accordingly, this review will comprehensively summarize the recent trends in structure-based engineering to improve the enzyme catalytic efficiency, selectivity and stability in mycotoxins detoxification, which also provides perspectives in obtaining innovative and effective biocatalysts for mycotoxins degradation.

Food-Grade Expression of Manganese Peroxidases in Recombinant Kluyveromyces lactis and Degradation of Aflatoxin B1 Using Fermentation Supernatants

Aflatoxins are naturally occurring high-toxic secondary metabolites, which cause worldwide environmental contaminations and wastes of food and feed resources and severely threaten human health. Thus, the highly efficient methods and technologies for detoxification of aflatoxins are urgently needed in a long term. In this work, we report the construction of recombinant Kluyveromyces lactis strains GG799(pKLAC1-Phsmnp), GG799(pKLAC1-Plomnp), GG799(pKLAC1-Phcmnp), and then the food-grade expression of the three manganese peroxidases in these strains, followed by the degradation of aflatoxin B1 (AFB1) using the fermentation supernatants. The expression of the manganese peroxidases was achieved in a food-grade manner since Kluyveromyces lactis is food-safe and suitable for application in food or feed industries. The inducible expression process of the optimal recombinant strain GG799(pKLAC1-Phcmnp) and the aflatoxin B1 degradation process were both optimized in detail. After optimization, the degradation ratio reached 75.71%, which was an increase of 49.86% compared to the unoptimized results. The degradation product was analyzed and determined to be AFB1-8,9-dihydrodiol. The recombinant strain GG799(pKLAC1-Phcmnp) supernatants degraded more than 90% of AFB1 in the peanut samples after twice treatments. The structural computational analysis for further mutagenesis of the enzyme PhcMnp was also conducted in this work. The food-grade recombinant yeast strain and the enzyme PhcMnp have potential to be applied in food or feed industries.

Recent technological advances in mechanism, toxicity, and food perspectives of enzyme-mediated aflatoxin degradation

Aflatoxins are carcinogenic secondary metabolites produced by Aspergillus section Flavi that contaminates a wide variety of food and feed products and is responsible for serious health and economic consequences. Fermented foods are prepared with a wide variety of substrates over a long fermentation time and are thus vulnerable to contamination by aflatoxin-producing fungi, leading to the production of aflatoxin B1. The mitigation and control of aflatoxin is currently a prime focus for developing safe aflatoxin-free food. This review summarizes the role of major aflatoxin-degrading enzymes such as laccase, peroxidase, and lactonase, and microorganisms in the context of their application in food. A putative mechanism of enzyme-mediated aflatoxin degradation and toxicity evaluation of the degraded products are also extensively discussed to evaluate the safety of degradation processes for food applications. The review also describes aflatoxin-degrading microorganisms isolated from fermented products and investigates their applicability in food as aflatoxin preventing agents. Furthermore, a summary of recent technological advancements in protein engineering, nanozymes, in silico and statistical optimization approaches are explored to improve the industrial applicability of aflatoxin-degrading enzymes.