Biodegradation of ochratoxin A and ochratoxin B by Brevundimonas naejangsanensis isolated from soil

Efficient Secretory Expression and Purification on Three Insoluble Amidohydrolases for Ochratoxin A Hydrolysis by Pichia pastoris

As a highly toxic mycotoxin, ochratoxin A (OTA) is widely contaminating agricultural products and has various toxicological effects. Bioenzymes for OTA degradation have shown promising potential for detoxification. Other than the efficient amidohydrolase ADH3 previously, two novel amidohydrolases ADH1 and AMD3 were obtained in this study. During Escherichia coli expression, the expressed protein solubility was very low and will limit future industrial application. Here, high copy number integrations were screened, and the amidohydrolases were efficiently secretory expressed by Pichia pastoris GS115. The protein yields from 1.0 L of fermentation supernatant were 53.5 mg for ADH1, 89.15 mg for ADH3, and 79.5 mg for AMD3. The catalytic efficiency (Kcat/Km) of secretory proteins was 124.95 s-1 mM-1 for ADH3, 123.21 s-1 mM-1 for ADH1, and 371.99 s-1 mM-1 for AMD3. In comparison to E. coli expression, the active protein yields substantially increased 15.78-51.53 times. Meanwhile, two novel amidohydrolases (ADH1 and AMD3) showed much higher activity than ADH3 that produced by secretory expression.

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.

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.

Diazo-functionalised immunoelectrochemical sensor for the detection of ochratoxin a in foods

Ochratoxin A (OTA) is a toxic fungal metabolite that is commonly found in cereals and animal feed. It is economically damaging and potentially hazardous to human health. Herein, we propose an electrochemical immunosensor for the rapid detection of OTA using anti-OTA antibodies and diazonium-functionalized, screen-printed electrodes. We attached 4-aminobenzoic acid to an electrode surface, activated the carboxyl groups on the surface with carbodiimide, and attached an antibody to the diazo layer. Subsequently, we used bovine serum protein as a blocker to prevent non-specific antigens from binding to the antibody. We evaluated the performance of the sensor by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. The sensor is highly specific and sensitive, has good linear responses in the range 20-200 ng/mL, a limit of detection of 0.5 ng/mL, and good recoveries of 90.5%-100.9% in spiked samples. It can be stored at 4 °C for approximately 2 weeks, and is highly stable, with a current response variation of no more than 4.6%.

Selective Isolation and Identification of Microorganisms with Dual Capabilities: Leather Biodegradation and Heavy Metal Resistance for Industrial Applications

Tanning, crucial for leather production, relies heavily on chromium yet poses risks due to chromium's oxidative conversion, leading to significant wastewater and solid waste generation. Physico-chemical methods are typically used for heavy metal removal, but they have drawbacks, prompting interest in eco-friendly biological remediation techniques like biosorption, bioaccumulation, and biotransformation. The EU Directive (2018/850) mandates alternatives to landfilling or incineration for industrial textile waste management, highlighting the importance of environmentally conscious practices for leather products' end-of-life management, with composting being the most researched and viable option. This study aimed to isolate microorganisms from tannery wastewater and identify those responsible for different types of tanned leather biodegradation. Bacterial shifts during leather biodegradation were observed using a leather biodegradation assay (ISO 20136) with tannery and municipal wastewater as the inoculum. Over 10,000 bacterial species were identified in all analysed samples, with 7 bacterial strains isolated from tannery wastewaters. Identification of bacterial genera like Acinetobacter, Brevundimonas, and Mycolicibacterium provides insights into potential microbial candidates for enhancing leather biodegradability, wastewater treatment, and heavy metal bioremediation in industrial applications.

Dynamic Succession of Natural Microbes during the Ecolly Grape Growth under Extremely Simplified Eco-Cultivation

The composition and continuous succession of natural microbial communities during grape growth play important roles in grape health and flavor quality as well as in characterizing the regional wine terroir. This study explored the diversity and dynamics of fruit epidermal microbes at each growth and developmental stage of Ecolly grapes under an extremely simplified eco-cultivation model, analyzed microbial interactions and associations of weather parameters to specific communities, and emphasized metabolic functional characteristics of microecology. The results indicated that the natural microbial community changed significantly during the grape growth phase. The dominant fungal genera mainly included Gibberella, Alternaria, Filobasidium, Naganishia, Ascochyta, Apiotrichum, Comoclathris, and Aureobasidium, and the dominant bacterial genera mainly contained Sediminibacterium, Ralstonia, Pantoea, Bradyrhizobium, Brevundimonas, Mesorhizobium, Planococcus, and Planomicrobium. In summary, filamentous fungi gradually shifted to basidiomycetous yeasts along with fruit ripening, with a decline in the number of Gram-negative bacteria and a relative increase in Gram-positive bacteria. The community assembly process reflects the fact that microbial ecology may be influenced by a variety of factors, but the fungal community was more stable, and the bacterial community fluctuated more from year to year, which may reflect their response to weather conditions over the years. Overall, our study helps to comprehensively profile the ecological characteristics of the grape microbial system, highlights the natural ecological viticulture concept, and promotes the sustainable development of the grape and wine industry.

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.

Solvent directed morphogenesis of a peptidic-benzimidazolium dipodal receptor: ratiometric detection and catalytic degradation of ochratoxin A

Ochratoxin A (OTA) is the most abundant and harmful toxin found in agriculture and processed food. The environment and human health are both harmed by this mycotoxin. As a result, in various scenarios, selective detection and biodegradation of ochratoxin A are essential. The current study reveals the morphogenesis of a peptidic-benzimidazolium dipodal receptor (SS4) and its application as a catalytic and sensing unit for the detection and degradation of OTA in an aqueous medium. Initially, a facile and scalable method was executed to synthesize SS4, and solvent-directed morphogenesis were examined under SEM analysis. Consequently, molecular recognition properties of self-assembled architectures were explored using UV-visible absorption, fluorescence spectroscopy, and atomic force microscopy (AFM). The designed probe showed a ratiometric response for OTA and served as a catalytic unit for the degradation of OTA at a short interval of 25 min. The biodegradation pathway for OTA was accomplished using LC-MS analysis. Furthermore, the reliability of the developed method was checked by determining the spiked concentrations of the OTA in cereals and wine samples. The results obtained are in good agreement with the % recovery and RSD values. The present work provides a robust, selective, and sensitive method of detection and degradation for OTA.

Degradation of ochratoxins A and B by lipases: A kinetic study unraveled by molecular modeling

Mycotoxins are toxic substances produced by fungi and, frequently, different mycotoxins cooccur in food commodities. Ochratoxin A (OTA) and Ochratoxin B (OTB) may co-occur in a variety of foods, like red wines and wheat, presenting a significant risk of population exposure. In this study, we investigated the potential of five lipases (Candida rugosa Lipase, Candida antarctica B Lipase, Thermomyces lanuginosus Lipase, Amano Lipase A from Aspergillus niger (ANL) and Porcine Pancreas Lipase (PPL)) to hydrolyze OTA and OTB into non-hazardous products. Only ANL and PPL degraded both substrates, however, with varying degrees of efficiency. PPL completely degraded OTB (9 h), but only 43% of OTA (25 h). Molecular simulations indicated a high binding energy of OTA to PPL, that can be explained by the impact of the chlorine group, impairing hydrolysis. ANL was able to completely degrade both mycotoxins, OTA in 3 h and OTB in 10 h. The ANL enzyme showed also high specificity to OTA, however, the activity of this enzyme is not affected by chlorine and hydrolyzes OTA faster than OTB. These two enzymes were found to be able to detoxify co-occurring ochratoxins A and B, making isolated enzymes an alternative to the direct use of microorganisms for mycotoxin mitigation in food.

Enhancing the thermostability of carboxypeptidase A by a multiple computer-aided rational design based on amino acids preferences at β-turns

Carboxypeptidase A (CPA) with efficient hydrolysis ability has shown vital potential in food and biological fields. In addition, it is also the earliest discovered enzyme with Ochratoxin A (OTA) degradation activity. Thermostability plays an imperative role to catalyze the reactions at high temperatures in industry, but the poor thermostability of CPA restricts its industrial application. In order to improve the thermostability of CPA, flexible loops were predicted through molecular dynamics (MD) simulation. Based on the amino acid preferences at β-turns, three ΔΔG-based computational programs (Rosetta, FoldX and PoPMuSiC) were employed to screen three variants from plentiful candidates and MD simulations were then used to verify two potential variants with enhanced thermostability (R124K and S134P). Results showed that compared to the wild-type CPA, the variants S134P and R124K exhibited rise of 4.2 min and 7.4 min in half-life (t1/2) at 45 °C, 3 °C and 4.1 °C in the half inactivation temperature (T5010), in addition to increase by 1.9 °C and 1.2 °C in the melting temperature (Tm), respectively. The mechanism responsible for the enhanced thermostability was elucidated through the comprehensive analysis of molecular structure. This study shows that the thermostability of CPA can be improved by the multiple computer-aided rational design based on amino acid preferences at β-turns, broadening its industrial applicability of OTA degradation and providing a valuable strategy for the protein engineering of mycotoxin degrading enzymes.

Diversity of the Bacterial Community Associated with Hindgut, Malpighian Tubules, and Foam of Nymphs of Two Spittlebug Species (Hemiptera: Aphrophoridae)

Spittlebugs are xylem-sap feeding insects that can exploit a nutrient-poor diet, thanks to mutualistic endosymbionts residing in various organs of their body. Although obligate symbioses in some spittlebug species have been quite well studied, little is known about their facultative endosymbionts, especially those inhabiting the gut. Recently, the role played by spittlebugs as vectors of the phytopathogenetic bacterium Xylella fastidiosa aroused attention to this insect group, boosting investigations aimed at developing effective yet sustainable control strategies. Since spittlebug nymphs are currently the main target of applied control, the composition of gut bacterial community of the juveniles of Philaenus spumarius and Lepyronia coleoptrata was investigated using molecular techniques. Moreover, bacteria associated with their froth, sampled from different host plants, were studied. Results revealed that Sodalis and Rickettsia bacteria are the predominant taxa in the gut of P. spumarius and L. coleoptrata nymphs, respectively, while Rhodococcus was found in both species. Our investigations also highlighted the presence of recurring bacteria in the froth. Furthermore, the foam hosted several bacterial species depending on the host plant, the insect species, or on soil contaminant. Overall, first findings showed that nymphs harbor a large and diverse bacterial community in their gut and froth, providing new accounts to the knowledge on facultative symbionts of spittlebugs.

Small Peptides in the Detection of Mycotoxins and Their Potential Applications in Mycotoxin Removal

Mycotoxins pose significant risks to humans and livestock. In addition, contaminated food- and feedstuffs can only be discarded, leading to increased economic losses and potential ecological pollution. Mycotoxin removal and real-time toxin level monitoring are effective approaches to solve this problem. As a hot research hotspot, small peptides derived from phage display peptide libraries, combinatorial peptide libraries, and rational design approaches can act as coating antigens, competitive antigens, and anti-immune complexes in immunoassays for the detection of mycotoxins. Furthermore, as a potential approach to mycotoxin degradation, small peptides can mimic the natural enzyme catalytic site to construct artificial enzymes containing oxidoreductases, hydrolase, and lyase activities. In summary, with the advantages of mature synthesis protocols, diverse structures, and excellent biocompatibility, also sharing their chemical structure with natural proteins, small peptides are widely used for mycotoxin detection and artificial enzyme construction, which have promising applications in mycotoxin degradation. This paper mainly reviews the advances of small peptides in the detection of mycotoxins, the construction of peptide-based artificial enzymes, and their potential applications in mycotoxin control.

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.

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.