Browsing by Author "Gupta TB"

Now showing 1 - 7 of 7
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    Antibacterial efficacy and possible mechanism of action of 2-hydroxyisocaproic acid (HICA)
    (PLOS, 2022-04-01) Pahalagedara ASNW; Flint S; Palmer J; Brightwell G; Gupta TB; Nevárez-Moorillón GV
    The exploitation of natural antimicrobial compounds that can be used in food preservation has been fast tracked by the development of antimicrobial resistance to existing antimicrobials and the increasing consumer demand for natural food preservatives. 2-hydroxyisocaproic acid (HICA) is a natural compound produced through the leucine degradation pathway and is produced in humans and by certain microorganisms such as lactic acid bacteria and Clostridium species. The present study investigated the antibacterial efficacy of HICA against some important bacteria associated with food quality and safety and provided some insights into its possible antimicrobial mechanisms against bacteria. The results revealed that HICA was effective in inhibiting the growth of tested Gram-positive and Gram-negative bacteria including a multi-drug resistant P. aeruginosa strain in this study. The underlying mechanism was investigated by measuring the cell membrane integrity, membrane permeability, membrane depolarisation, and morphological and ultrastructural changes after HICA treatment in bacterial cells. The evidence supports that HICA exerts its activity via penetration of the bacterial cell membranes, thereby causing depolarisation, rupture of membranes, subsequent leakage of cellular contents and cell death. The current study suggests that HICA has potential to be used as an antibacterial agent against food spoilage and food-borne pathogenic bacteria, targeting the bacterial cell envelope.
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    Culture and genome-based analysis of four soil Clostridium isolates reveal their potential for antimicrobial production
    (BioMed Central Ltd, 2021-12) Pahalagedara ASNW; Jauregui R; Maclean P; Altermann E; Flint S; Palmer J; Brightwell G; Gupta TB
    BACKGROUND: Soil bacteria are a major source of specialized metabolites including antimicrobial compounds. Yet, one of the most diverse genera of bacteria ubiquitously present in soil, Clostridium, has been largely overlooked in bioactive compound discovery. As Clostridium spp. thrive in extreme environments with their metabolic mechanisms adapted to the harsh conditions, they are likely to synthesize molecules with unknown structures, properties, and functions. Therefore, their potential to synthesize small molecules with biological activities should be of great interest in the search for novel antimicrobial compounds. The current study focused on investigating the antimicrobial potential of four soil Clostridium isolates, FS01, FS2.2 FS03, and FS04, using a genome-led approach, validated by culture-based methods. RESULTS: Conditioned/spent media from all four Clostridium isolates showed varying levels of antimicrobial activity against indicator microorganism; all four isolates significantly inhibited the growth of Pseudomonas aeruginosa. FS01, FS2.2, and FS04 were active against Bacillus mycoides and FS03 reduced the growth of Bacillus cereus. Phylogenetic analysis together with DNA-DNA hybridization (dDDH), average nucleotide identity (ANI), and functional genome distribution (FGD) analyses confirmed that FS01, FS2.2, and FS04 belong to the species Paraclostridium bifermentans, Clostridium cadaveris, and Clostridium senegalense respectively, while FS03 may represent a novel species of the genus Clostridium. Bioinformatics analysis using antiSMASH 5.0 predicted the presence of eight biosynthetic gene clusters (BGCs) encoding for the synthesis of ribosomally synthesized post-translationally modified peptides (RiPPs) and non-ribosomal peptides (NRPs) in four genomes. All predicted BGCs showed no similarity with any known BGCs suggesting novelty of the molecules from those predicted gene clusters. In addition, the analysis of genomes for putative virulence factors revealed the presence of four putative Clostridium toxin related genes in FS01 and FS2.2 genomes. No genes associated with the main Clostridium toxins were identified in the FS03 and FS04 genomes. CONCLUSIONS: The presence of BGCs encoding for uncharacterized RiPPs and NRPSs in the genomes of antagonistic Clostridium spp. isolated from farm soil indicated their potential to produce novel secondary metabolites. This study serves as a basis for the identification and characterization of potent antimicrobials from these soil Clostridium spp. and expands the current knowledge base, encouraging future research into bioactive compound production in members of the genus Clostridium.
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    Effectiveness of mānuka and rosemary oils as natural and green antioxidants in wagyu and normal beef
    (John Wiley and Sons Ltd on behalf of Institute of Food, Science and Technology (IFSTTF), 2023-02-28) Kaur R; Kaur L; Gupta TB; Bronlund J
    Essential oils possessing antioxidant characteristics have acquired broad interest as an alternative to synthetic food antioxidants like butylated hydroxytoluene (BHT). In this study, mānuka (with 5, 25 and 40% triketone content) (MO), rosemary (RO) and kānuka (KO) oils were characterised and screened through DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric radical absorbing power) assays for their antioxidant efficacies. Different triketone levels were selected to examine their effect on the antioxidant activity of MO. All MOs showed higher phenolic content and antioxidant activities than KO and RO. Based on the obtained results, the MO with 25% triketone content and RO were chosen to study their antioxidant effects in pastes prepared from New Zealand normal (3% fat) and wagyu (12% fat) beef during refrigerated storage (7 days). No significant effect of the oils was observed on lipid oxidation in normal pastes during storage. However, MO and BHT significantly reduced lipid oxidation in wagyu pastes, showing the potential of mānuka oil as a natural antioxidant in high-fat meat products.
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    Mānuka Oil vs. Rosemary Oil: Antimicrobial Efficacies in Wagyu and Commercial Beef against Selected Pathogenic Microbes
    (MDPI (Basel, Switzerland), 2023-03-21) Kaur R; Kaur L; Gupta TB; Bronlund J; Monteils V; Gagaoua M
    Essential oils possessing antimicrobial characteristics have acquired considerable interest as an alternative to chemical preservatives in food products. This research hypothesizes that mānuka (MO) and kānuka (KO) oils may possess antimicrobial characteristics and have the potential to be used as natural preservatives for food applications. Initial experimentation was conducted to characterize MOs (with 5, 25, and 40% triketone contents), rosemary oil (RO) along with kanuka oil (KO) for their antibacterial efficacy against selected Gram-negative (Salmonella spp. and Escherichia coli), and Gram-positive (Listeria monocytogenes and Staphylococcus aureus) bacteria through disc diffusion and broth dilution assays. All MOs showed a higher antimicrobial effect against L. monocytogenes and S. aureus with a minimum inhibitory concentration below 0.04%, compared with KO (0.63%) and RO (2.5%). In chemical composition, α-pinene in KO, 1, 8 cineole in RO, calamenene, and leptospermone in MO were the major compounds, confirmed through Gas-chromatography-mass spectrometry analysis. Further, the antimicrobial effect of MO and RO in vacuum-packed beef pastes prepared from New Zealand commercial breed (3% fat) and wagyu (12% fat) beef tenderloins during 16 days of refrigerated storage was compared with sodium nitrate (SN) and control (without added oil). In both meat types, compared with the SN-treated and control samples, lower growth of L. monocytogenes and S. aureus in MO- and RO- treated samples was observed. However, for Salmonella and E. coli, RO treatment inhibited microbial growth most effectively. The results suggest the potential use of MO as a partial replacement for synthetic preservatives like sodium nitrate in meats, especially against L. monocytogenes and S. aureus.
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    Multitarget preservation technologies for chemical-free sustainable meat processing
    (Wiley Periodicals LLC on behalf of Institute of Food Technologists, 2022-10-19) Kaur R; Kaur L; Gupta TB; Singh J; Bronlund J
    Due to the growing consumer demand for safe and naturally processed meats, the meat industry is seeking novel methods to produce safe-to-consume meat products without affecting their sensory appeal. The green technologies can maintain the sensory and nutritive characteristics and ensure the microbial safety of processed meats and, therefore, can help to reduce the use of chemical preservatives in meat products. The use of chemical additives, especially nitrites in processed meat products, has become controversial because they may form carcinogenic N-nitrosamines, a few of which are suspected as cancer precursors. Thus, the objective of reducing or eliminating nitrite is of great interest to meat researchers and industries. This review, for the first time, discusses the influence of processing technologies such as microwave, irradiation, high-pressure thermal processing (HPTP) and multitarget preservation technology on the quality characteristics of processed meats, with a focus on their sensory quality. These emerging technologies can help in the alleviation of ingoing nitrite or formed nitrosamine contents in meat products. The multitarget preservation technology is an innovative way to enhance the shelf life of meat products through the combined use of different technologies/natural additives. The challenges and opportunities associated with the use of these technologies for processing meat are also reviewed.
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    Non-Targeted Metabolomic Profiling Identifies Metabolites with Potential Antimicrobial Activity from an Anaerobic Bacterium Closely Related to Terrisporobacter Species.
    (MDPI (Basel, Switzerland), 2023-02-09) Pahalagedara ASNW; Flint S; Palmer J; Brightwell G; Luo X; Li L; Gupta TB; Eisenreich W
    This work focused on the metabolomic profiling of the conditioned medium (FS03CM) produced by an anaerobic bacterium closely related to Terrisporobacter spp. to identify potential antimicrobial metabolites. The metabolome of the conditioned medium was profiled by two-channel Chemical Isotope Labelling (CIL) LC-MS. The detected metabolites were identified or matched by conducting a library search using different confidence levels. Forty-eight significantly changed metabolites were identified with high confidence after the growth of isolate FS03 in cooked meat glucose starch (CMGS) medium. Some of the secondary metabolites identified with known antimicrobial activities were 4-hydroxyphenyllactate, 3-hydroxyphenylacetic acid, acetic acid, isobutyric acid, valeric acid, and tryptamine. Our findings revealed the presence of different secondary metabolites with previously reported antimicrobial activities and suggested the capability of producing antimicrobial metabolites by the anaerobic bacterium FS03.
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    Synthesis and characterisation of Mānuka and rosemary oil-based nano-entities and their application in meat
    (Elsevier Ltd, 2024-03-15) Kaur R; Gupta TB; Bronlund J; Singh J; Kaur L
    Mānuka (MO) and rosemary oils (RO) -containing nanoemulsions and nanocapsules made of sodium alginate and whey protein, were designed and compared for their antioxidant effect. Mānuka oil-nanoemulsions and nanocapsules had smaller particle sizes (343 and 330 nm), less negative zeta potential (-12 mV and -10 mV), higher phenolic content, and antiradical characteristics than RO-nano-entities. However, nano-entities of both oils showed more thermostability and sustained release than free oils. Further, the antioxidant effect of essential oils and their nano-entities was compared against sodium nitrite (SN)-added and without antioxidants-added (controls) and Wagyu and crossbred beef pastes (14 days refrigerated storage). No significant difference among MO, RO and their nano-entities was noticed in crossbred pastes, while in Wagyu, nanoemulsions showed the lowest oxidation values than controls and SN-added pastes. Hence, nano-entities can be alternatives to chemical preservatives as natural antioxidants in meat preservation, along with improved thermal stability and release than free oils.