Food Preservative Agent Research Articles

Investigation on L-rhamnose metabolism of Loigolactobacillus coryniformis subsp. coryniformis DSM 20001 and its propionate-containing fermentates.

Propionate is an important short-chain carboxylic acid (SCCA) that serves as an effective antimicrobial agent for food preservation. Previous research has highlighted that few Lactobacillaceae can synthesize propionate by metabolizing deoxyhexoses via the fermentation intermediate 1,2-propanediol (1,2-PD). In this study, we investigated propionate production by Loigolactobacillus coryniformis subsp. coryniformis DSM 20001 while utilizing L-rhamnose as the primary carbon source. We cultivated L. coryniformis in small-scale anaerobic bioreactors at 30°C and pH 6.5 for 72 h and monitored the expression of key genes associated with deoxyhexose metabolism using quantitative PCR. In addition, we assessed the contribution of individual SCCA to the antimicrobial activity of the fermentate against common foodborne pathogens, including Escherichia coli, Salmonella enterica, Klebsiella oxytoca, Staphylococcus aureus, Candida albicans, Aspergillus niger, Penicillium roqueforti, and Penicillium purpurogenum using broth dilution assays. During cultivation, we observed the production of up to 16 mM propionate, alongside other metabolites such as lactate (26 mM), formate (2 mM), and acetate (4 mM), derived from 32 mM L-rhamnose. Genes related to L-rhamnose utilization were upregulated within the initial 48 h, while genes involved in 1,2-PD utilization remained highly transcribed throughout fermentation. Comparing the antimicrobial efficacy of the fermentates to synthetic SCCA mixtures, bacterial indicator strains were more sensitive than molds and yeast. Propionate was the primary SCCA responsible for inhibitory activity; inhibition was reduced if indicator strains were able to use lactate.IMPORTANCEWorldwide, approximately 30% of food produced is lost. Despite the application of complementary treatment methods, microbial food spoilage can occur along the entire value chain. The rising concern about food waste has led to increasing interest in natural preservation approaches. Lactobacillaceae fermentative systems produce a variety of short-chain carboxylic acid (SCCA) with antimicrobial potential, and we present here fundamental insight into the only recently discovered deoxyhexose metabolism of Loigolactobacillus coryniformis producing the antimicrobial SCCA propionate. We developed a bioprocess to produce propionate from L-rhamnose under controlled conditions as a first step toward the exploitation of L-rhamnose metabolism in the production of antimicrobial fermentates for use in the food industry, potentially replacing chemical alternatives. Our investigations highlight the major contribution of propionate in antimicrobial activity but also indicate the issue of co-occurring fermentable metabolites, which can affect the efficiency of fermentates.

Enhanced physicochemical characteristics and biological activities of low-temperature ethylenediamine/urea pretreated lignin.

Low-temperature ethylenediamine (EDA)/urea pretreatment had been demonstrated to be an efficient pretreatment method for enzymatic hydrolysis and bioethanol production. For high-value utilization of the third main components of lignocellulosic biomass, the physicochemical structure characteristics and biological activities of low-temperature EDA/urea pretreated lignin (EUL) were comprehensively investigated in the present study. The results demonstrated that the pretreatment process facilitated the depolymerization of lignin, resulting in notable reduction in molecular weight and polydispersity index from 2.32 to 1.42kg/mol and 1.44 to 1.20, respectively. The EDA/urea pretreated lignin (EUL) exhibited enhanced ultraviolet absorption capacity and the most significant DPPH radical scavenging and inhibition of Staphylococcus aureus in comparison to the primary lignin (PL) and the NaOH pretreated lignin (NL). Enhanced physicochemical characteristics and biological activities of EUL make it more suitable to be developed as sunscreen ingredient or antioxidant and antimicrobial agent in food preservation and conservation.

Chemical Composition, Biological Activity, and Application of Rosa damascena Essential Oil as an Antimicrobial Agent in Minimally Processed Eggplant Inoculated with Salmonella enterica.

Rosa damascena is mostly grown for its usage in the food, medical, and perfume industries, while it is also used as an attractive plant in parks, gardens, and homes. The use of R. damascena essential oil may yield new results in relation to the antimicrobial activity of essential oils and their use mainly in extending the shelf life of foods. This study investigates the chemical composition and antimicrobial properties of Rosa damascena essential oil (RDEO) using gas chromatography-mass spectrometry (GC-MS) and various bioassays to explore its potential applications in food preservation and microorganism growth control. The GC-MS analysis revealed that RDEO is predominantly composed of phenylethyl alcohol (70%), which is known for its antimicrobial and aromatic properties. Additionally, other significant constituents were identified, including nerol, citronellol, and geraniol, which may contribute to the EOs overall bioactivity. The antimicrobial activity was assessed through the minimal inhibition concentration against five Candida yeast strains, four Gram-positive, and four Gram-negative bacteria, including biofilm-forming Salmonella enterica. Determination of minimum inhibitory concentrations (MIC) revealed the strongest effects of RDEO's on Gram-negative species, with MIC50 values as low as 0.250 mg/mL for S. enterica. Moreover, an in situ assessment utilizing fruit and vegetable models demonstrated that the vapor phase of RDEO significantly suppressed microbial growth, with the most substantial reductions observed on kiwi and banana models. As a result of our study, the antimicrobial effect of RDEO on the microbiota of sous vide processed eggplant was detected, as well as an inhibitory effect on S. enterica during storage. The insecticidal activity against Megabruchidius dorsalis Fahreus, 1839, was also studied in this work and the best insecticidal activity was found at the highest concentrations. These results suggest that RDEO has the potential to serve as a natural antimicrobial agent in food preservation and safety applications, providing an alternative to synthetic preservatives.

Antibacterial effects and mechanisms of quercetin-β-cyclodextrin complex mediated photodynamic on Escherichia coli O157:H7.

Quercetin is a natural flavonoid with antioxidant, anti-inflammatory, and antibacterial properties. This work aimed to formulate quercetin-cyclodextrin microcapsules (QT-β-CD) while examining their photodynamic antibacterial effects and underlying mechanisms in detail. Characterization of the QT-β-CD was conducted using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The bacteriostatic effects of UV-A irradiation on Escherichia coli O157:H7 (E. coli O157:H7) were investigated. The photodynamic impact of QT-β-CD was assessed by analyzing hydrogen peroxide (H₂O₂) production. The antimicrobial activity was further elucidated through examinations of cell membrane integrity, protein damage, changes in cellular motility, biofilm formation, and extracellular polysaccharide reduction. The effect of QT-β-CD on LuxS and motA gene expression in E. coli O157:H7 was investigated by RT-qPCR. The findings demonstrated that QT-β-CD exhibited potent photodynamic properties and functioned as an efficient photosensitizer, causing substantial damage to E. coli O157:H7 cells. These results underscore the potential of quercetin as an antimicrobial agent for food preservation.

Modification of physicochemical, antioxidant, and antibacterial properties of chitosan film with curcumin-loaded TA/Fe nanoparticles

The aim of this study is to fabricate novel chitosan-based film loaded with curcumin loaded metal-phenolic nanoparticles (MPN@Cur NPs) as an active agent for food preservation. The average particle size and ζ-potential of the MPN@Cur NPs were determined to be 205.9 nm and −26.8 mV, respectively. The impact of incorporating MPN@Cur NPs upon the morphology, microstructure, physicochemical characteristics, and functional activities of CS-based films were investigated through scanning electron microscope, infrared spectrometer, X-ray diffractometer, ultraviolet spectrometer, antioxidant activity and antibacterial activity analysis. The outcomes indicated that MPN@Cur NPs exhibited good mechanical compatibility with chitosan, effectively filling voids within the film matrix and significantly enhancing its mechanical characteristics (e.g., elongation at break improved from 22.6% to 37.3%; tensile strength improved from 31.1 MPa to 43.6 MPa). Additionally, films incorporating MPN@Cur NPs displayed superior barrier properties (e.g., water vapor and oxygen transmission), enhanced thermal stability, and improved UV-blocking capabilities compared to pure CS films (transmittance for UV decreased from 93.6% to 35.3%). Moreover, these films exhibited a marked increase in antibacterial efficacy against the foodborne pathogens Staphylococcus aureus and Escherichia coli, as well as elevated antioxidant activity (e.g., scavenging capability for DPPH increased from 9.22% to 85.19%, ABTS increased from 8.62% to 80.02%). Ultimately, the CS-based film significantly prolonged the shelf life of milk stored at 25 °C. Therefore, nanocomposite films provide an attractive and promising pathway for the high value-added commercial use of chitosan in food conservation.

Progress in essential oil extraction and their applications in food packaging and preservation

AbstractEssential oils (EOs) are secondary metabolites synthesised by many aromatic plants, which have good antimicrobial and antioxidant activities making them popular functional agents for food preservation and packaging applications. In recent years, novel extraction techniques, such as super critical fluid extraction, pulsed electric field assisted extraction and ultrasound assisted extraction have been explored as alternatives to the conventional solvent‐based extraction methods. This review mainly discusses on recent progresses in sustainable extraction of essential oil (EO) from aromatic plants and food processing wastes and their functional properties, and applications in food preservation have also been summarised. Sustainable extraction techniques yield better‐quality EO due to low temperature and short time process compared to the conventional extraction. Despite efficacy of EOs as good active agents, their low water solubility, volatile nature, strong flavour, and susceptibility to food processing parameters are major challenges against their applications in food. These challenges can be mitigated by advanced techniques such as encapsulation and nanoemulsification of EO, which provide dual functions of enhanced applicability and improved functional properties. Incorporation of EO in the biopolymer‐based films and coatings can open avenues for sustainable food packaging and preservation.

Potential and application of tandem mass spectrometry (MS/MS) in the analysis and identification of novel bacteriocins: a review

SummaryBacteriocins are antimicrobial peptides synthesised ribosomally by Gram‐positive or Gram‐negative bacteria to gain a competitive advantage. The majority of bacteriocins are derived from Gram‐positive bacteria, with lactic acid bacteria being the most common source. Because they are considered ‘natural’, there is currently significant development of bacteriocins for application as food preservative agents. As a preservative agent, bacteriocin activity is highly dependent on purity, down to the amino acid profile and sequence. Therefore, bacteriocin identification is important. Currently, MS is a cutting‐edge tool in bacteriocin identification. This method has high selectivity, sensitivity and resolution. To the best of our knowledge, systematic reviews focusing on the application of MS for bacteriocin identification are currently limited. In light of this, the objective of this study is to provide a comprehensive review and summary of MS technologies in bacteriocin research, with a particular focus on the discovery and characterisation of novel sources of bacteriocin. Additionally, studies related to the discovery of bacteriocins from various sources, their role as antimicrobial agents, and their synthesis are emphasised. Thus, this study presents a comprehensive analysis of the advantages, limitations, and future perspectives of the methods employed.

EFFICACY OF SHRIMP SHELL SYNTHESIZED CHITOSAN AGAINSTPOST-HARVEST SPOILAGE FUNGI OF Sesamum indicum

Contamination of Agricultural commodities by moulds poses significant challenges due to conducive climatic conditions. Mycotoxins produced by moulds like Aspergillus, Penicillium, and Fusarium present health risks and economic losses. Traditional control measures such as the use of fungicides have drawbacks, necessitating the exploration of eco-friendly alternatives. One such alternatives is the use of Chitosan, a biopolymer derived from chitin found in crustacean exoskeletons. This study evaluated the efficacy of chitosan synthesized from shrimp shells in inhibiting the growth of Aspergillus niger, a common food borne mould of oil seeds such as Sesame. Synthesized Chitosan was characterized using FTIR spectroscopy, UV-visible spectroscopy, and the degree of deacetylation was determined. FTIR analysis showed characteristic absorption peaks ranging from 3911.77 cm-1 to 794.70 cm-1, with higher wave numbers corresponding to stretching vibrations of the C-H, O-H, and N-H bonds functional groups. UV-visible spectroscopy displayed an absorbance peak at 232 nm with an absorbance value of 2.15. The degree of deacetylation of synthesized chitosan was determined to be 98.99%. In vitro experiments showed a concentration-dependent inhibition of A. niger growth by shrimp shell synthesized chitosan. The highest level of inhibition was seen at day 3 with 0.75mg/ml (50%) and 1.0mg/ml (52.1%), meaning the higher the concentration of shrimp shell synthesized chitosan the higher the inhibition. Results suggest chitosan as a potential anti-fungal agent for food preservation and agricultural protection against mould contamination and mitigate post harvest losses and ensure food safety.

Entrapment of antimicrobial compounds in a metal matrix for crop protection.

Agricultural yields are often limited by damage caused by pathogenic microorganisms, including plant-pathogenic bacteria. The chemical control options to cope with bacterial diseases in agriculture are limited, predominantly relying on copper-based products. These compounds, however, possess limited efficacy. Therefore, there is an urgent need to develop novel technologies to manage bacterial plant diseases and reduce food loss. In this study, a new antimicrobial agent was developed using a doping method that entraps small bioactive organic molecules inside copper as the metal matrix. The food preservative agent lauroyl arginate ethyl ester (ethyl lauroyl arginate; LAE) was chosen as the doped organic compound. The new composites were termed LAE@[Cu]. Bactericidal assays against Acidovorax citrulli, a severe plant pathogen, revealed that LAE and copper in the composites possess a synergistic interaction as compared with each component individually. LAE@[Cu] composites were further characterised in terms of chemical properties and in planta assays demonstrated their potential for further development as crop protection agents.

Exploring ethyl pyruvate as an antifungal and antibacterial agent for food preservation: an in vitro and in silico study

SummaryFood pathogens are one of the microbiological problems that have negative effects on both economic and human health by causing spoilage and decay of important foods such as fruits and vegetables. The adverse effects of chemical residues left by synthetic biocides on human health and the development of resistance mechanisms in microorganisms have directed research towards bio‐fungicide. This study aimed to develop an effective bio‐fungicide using varying concentrations of ethyl pyruvate (1–18 μL disc−1). Additionally, the interaction of EP with several proteins in pathogenic bacteria and fungi was investigated through in silico molecular docking. According to the obtained results, an increase in EP concentration resulted in larger inhibition zone diameters. In this context, at an EP concentration of 18 μL disc−1, the inhibition zones formed against E. coli, S. aureus, L. monocytogenes and S. typhimurium bacteria were measured as 27.50 ± 0.50 mm, 31.00 ± 1.00 mm, 30.00 ± 1.00 mm and 32.66 ± 1.15 mm, respectively. EP at a concentration of 9 μL disc−1 showed a fungicidal effect against B. cinerea and P. expansum and a fungistatic effect against C. gloeosporioides. As a result of in silico tests, the molecular binding energies of EP with E. coli dihydrofolate reductase, S. aureus DNA Gyrase B and B. cinerea 14 alpha‐demethylase were determined to be −4.62, −4.26 and −3.95 kcal mol−1, respectively. Our results holistically revealed that EP has great potential for use in food preservation due to its antifungal and antibacterial properties.

Chlorophyll-Enriched Chitosan-CuO-ZnO Nanoparticles for Antimicrobial Activities

<p>Chitosan-doped copper oxide and zinc oxide nanoparticles (CuO-CS-ZnO NPs) were prepared utilizing sol-gel synthesis route. Chlorophyll was added in the process of making NPs to enhance the effects of these NPs. The prepared NPs were thoroughly analyzed using advanced techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Structural analysis revealed the successful synthesis of irregular shaped NPs with average crystallite size of 10.7 nm. In optical properties, UV-Vis showed the absorption bands associated with different absorption centers in the sample and FTIR revealed various function groups associated with the preparation procedure and chemical used while synthesizing these NPs. On applications side, these NPs efficiently resist the growth of X. axanopodis pv punicea bacteria within 24-48 hours of investigation. Same NPs showed effective antifungal effects on the Alternaria solani. Finally, these NPs were used as food preservative agents where tomatoes were used as the target fruit. Tomatoes coated with NPs exhibited better preservation and a longer shelf life.</p>

Synthesis, Characterization, and Antifungal Activity of Benzimidazole-Grafted Chitosan against Aspergillus flavus.

Aspergillus flavus contamination in agriculture and food industries poses threats to human health, leading to a requirement of a safe and effective method to control fungal contamination. Chitosan-based nitrogen-containing derivatives have attracted much attention due to their safety and enhanced antimicrobial applications. Herein, a new benzimidazole-grafted chitosan (BAC) was synthesized by linking the chitosan (CS) with a simple benzimidazole compound, 2-benzimidazolepropionic acid (BA). The characterization of BAC was confirmed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy (1H and 13C NMR). Then, the efficiency of BAC against A. flavus ACCC 32656 was investigated in terms of spore germination, mycelial growth, and aflatoxin production. BAC showed a much better antifungal effect than CS and BA. The minimum inhibitory concentration (MIC) value was 1.25 mg/mL for BAC, while the highest solubility of CS (16.0 mg/mL) or BA (4.0 mg/mL) could not completely inhibit the growth of A. flavus. Furthermore, results showed that BAC inhibited spore germination and elongation by affecting ergosterol biosynthesis and the cell membrane integrity, leading to the permeabilization of the plasma membrane and leakage of intracellular content. The production of aflatoxin was also inhibited when treated with BAC. These findings indicate that benzimidazole-derived natural CS has the potential to be used as an ideal antifungal agent for food preservation.

Monitoring and risk assessment for some quaternary ammonium compounds as antimicrobial agents in some processed and packaged food

ABSTRACT Quaternary ammonium compounds (QACs) might be applied as fungicides, herbicides, and algaecide in agriculture or as antimicrobial agents in food preservation. There are risks either from the application of QACs as food additives or the contamination during the disinfection and sterilisation of the food production lines by QACs in food production factories. Exceeding the maximum residue limits (MRLs) wasn’t accepted by European legislation and Codex guidelines, leading to several risks in human health. Inspecting and monitoring of QACs in 143 packaged food products, such as liquid milk, juices, baby food products, herbal drinks, and frozen vegetables and fruits were carried out in some Egyptian local markets during 2022–2023. The In-house validated QuEChERS extraction method was operated and followed by LC-MS/MS analysis. Only one violated baby food sample that was contaminated with 0.064 mg/kg DDAC and 0.335 mg/kg BACs. According to the EU MRLs, there were no higher residue levels of QACs in juices, milk products, and frozen vegetables with acceptable concentrations. All analysed samples have acceptable results with concentrations less than 0.1 mg/kg, which means that they were all safe for human consumption and health. Our study supported the analytical procedure for the routine inspection of QACs in food.

Nanofabrication of citronellal with chitosan biopolymer to boost its efficacy against aflatoxin B1 and Aspergillus flavus mediated biodeterioration of active ingredient of Piper longum

The study reports the efficacy of nanofabricated citronellal inside the chitosan biopolymer (NeCn) against Aspergillus flavus growth, aflatoxin B1 (AFB1) production, and active ingredient biodeterioration (Piperine) in Piper longum L. The prepared NeCn was characterized by Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and Fourier Transform Infrared Spectroscopy (FTIR). The results revealed that the NeCn exhibited distantly improved antifungal (1.25 μL/mL) and AFB1 inhibition (1.0 μL/mL) compared to free Cn. The perturbances in membrane function, mitochondrial membrane potential, antioxidant defense system, and regulatory genes (Ver-1 and Nor-1) of AFB1 biosynthesis were reported as probable modes of action of NeCn. The NeCn (1.25 μL/mL) effectively protects the P. longum from A. flavus (78.8%), AFB1 contamination (100%), and deterioration of Piperine (62.39%), thus demonstrating its potential as a promising novel antifungal agent for food preservation.

Synergistic stabilization of garlic essential oil nanoemulsions by carboxymethyl chitosan/Tween 80 and application for coating preservation of chilled fresh pork

Garlic essential oil (GEO) is a potential natural antioxidant and antimicrobial agent for food preservation, but its intrinsic low water-solubility, high volatility and poor stability severely limit its application and promotion. In this work, we investigated the synergistic stabilization of the GEO-in-water nanoemulsion using carboxymethyl chitosan (CCS) and Tween 80 (TW 80). Additionally, the nanoemulsion was fabricated through high-pressure microfluidization and utilized for the coating-mediated preservation of chilled pork. The garlic essential oil nanoemulsion (GEON) with 3.0 % CCS and 3.0 % TW 80 exhibited more homogeneous droplet size (around 150 nm) and narrower size distribution, while maintained long-term stability with no significant change in size during 30 d storage. Compared with free GEO, the GEONs exhibited a higher scavenging capacity to DPPH and ABTS free radicals as well as higher inhibitory effects against Escherichia coli and Staphylococcus aureus, suggesting that the encapsulation of GEO in nanoemulsion considerably improved its antioxidant and antibacterial activities. Furthermore, the results of coating preservation experiments showed that the GEON coating effectively expanded the shelf-life of chilled fresh pork for approximately one week. Altogether, this study would guide the development of GEO-loaded nanoemulsions, and promote GEON as a promising alternative for coating preservation of chilled fresh meat.

Sulforaphane-Enriched Extracts from Broccoli Exhibit Antimicrobial Activity against Plant Pathogens, Promising a Natural Antimicrobial Agent for Crop Protection.

Sulforaphane (SFN) is one of the hydrolysates of glucosinolates (GSLs), primarily derived from Brassica vegetables like broccoli. In clinical therapy, SFN has been proven to display antimicrobial, anticancer, antioxidant, and anti-inflammatory properties. However, the antimicrobial effects and mechanism of SFN against plant pathogens need to be further elucidated, which limits its application in agriculture. In this study, the genetic factors involved in SFN biosynthesis in 33 B. oleracea varieties were explored. The finding showed that besides the genetic background of different B. oleracea varieties, myrosinase and ESP genes play important roles in affecting SFN content. Subsequently, the molecular identification cards of these 33 B. oleracea varieties were constructed to rapidly assess their SFN biosynthetic ability. Furthermore, an optimized protocol for SFN extraction using low-cost broccoli curds was established, yielding SFN-enriched extracts (SFN-ee) containing up to 628.44 μg/g DW of SFN. The antimicrobial activity assay confirmed that SFN-ee obtained here remarkably inhibit the proliferation of nine tested microorganisms including four plant pathogens by destroying their membrane integrity. Additionally, the data demonstrated that exogenous application of SFN-ee could also induce ROS accumulation in broccoli leaves. These results indicated that SFN-ee should play a dual role in defense against plant pathogens by directly killing pathogenic cells and activating the ROS signaling pathway. These findings provide new evidence for the antimicrobial effect and mechanism of SFN against plant pathogens, and suggest that SFN-ee can be used as a natural plant antimicrobial agent for crop protection and food preservation.

Fuji apple ( Malus domestica Borkh. cv. Red Fuji) pomace extracts as a source of antimicrobial and antioxidant polyphenols

This study aimed to assess the antibacterial and antioxidant properties of both crude polyphenol extract (CPE) and purified polyphenol extract (PPE) obtained from Fuji apple pomace. The antibacterial capacity of both extracts against Staphylococcus aureus was investigated by evaluating the inhibition zones, minimum bactericidal concentrations (MBC), growth curves and bacterial morphology of S. aureus treated with CPE or PPE, as well as the performance in simulated food systems. The antioxidant activity of CPE or PPE was assessed using the ABTS radical scavenging and ferric reducing antioxidant power (FRAP) assays. The results showed that PPE exhibited potent antibacterial activity against S. aureus, which was further confirmed by the bacterial morphology. It was revealed that PPE only exerted strong antibacterial effect in starch-based food system while CEP did not show such effect in all systems. The results of the ABTS and FRAP assays indicated that both PPE and CPE possess strong antioxidant activity, from which PPE showed much higher capacity than that of CPE. Therefore, PPE from Fuji apple pomace can be used as a novel antibacterial agent for food preservation and natural antioxidant for functional food and nutraceutical products.

Characteristics and Antibacterial Activities of Bacteriocin Produced by Lactid Acid Bacteria Isolate LG-50 and LG-90

Biopreservative agents is natural food preservative agent derived from microbes such as bacteriocin produced by lactic acid bacteria (LAB). Bacteriocin is a protein compound that has a small molecular weight and has antibacterial activity because it is effective in preventing the growth of pathogenic bacteria in food and beverages. Escherichia coli and Staphylococcus aureus are pathogenic bacteria that can contaminate seafood products because they can cause infection and food toxication. Isolates LG-50 and LG-90 are LAB, bacterial collection of the Microbiology Laboratory, Faculty of Biology, Isolate from mangrove sediment in Logending beach. Both isolates are not yet known for their potencies to synthesize bacteriocin and its inhibitory capability to the growth E. coli and S. aureus. The research aimed to determine the ability of LG-50 and LG-90 isolates to produce bacteriocin, to determine the ability of LG-50 and LG-90 isolates to inhibit the growth of E. coli and S. aureus bacteria invitro, to identity the characteristics of isolate LG-50 and LG-90 from Logending beach mangrove sediment. The results of this research show that the bacteriocins LG-50 and LG-90 were able to inhibit the growth of E.coli with inhibition zone diameters of 13.5 mm and 13 mm, in S. aureus with inhibition zone diameters of 15 mm and 15.5 mm.

Anti-bacterial activity of essential oils against multidrug-resistant foodborne pathogens isolated from raw milk.

The presence of pathogenic bacteria in food is considered as a primary cause of food-borne illness and food quality deterioration worldwide. The present study aimed to determine the effectiveness of five essential oils (EOs) against multidrug-resistant foodborne pathogens. In the current study Gram-negative bacteria (Escherichia, Enterobacter, Citrobacter, Proteus, Pseudomonas, and Klebsiella) and the Gram-positive bacteria Staphylococcus were isolated from raw milk and biochemically characterized. The anti-bacterial effect of different antibiotics and EOs (thyme, oregano, lemongrass, mint, and rosemary) was determined using the standard disc diffusion method. The antibiogram study revealed that Gram-negative bacteria were highly resistant to penicillin while Staphylococcus was resistant to streptomycin, amoxicillin, and lincomycin. Moderate resistance was observed to doxycycline, amikacin, enrofloxacin, kanamycin and cefixime. Isolates were found less resistant to gentamycin, chloramphenicol, and ciprofloxacin. EOs showed a broad range of antimicrobial activity against all bacteria except P. aeruginosa. Of these, thyme was more effective against most of the multi-drug resistant bacterial strains and formed the largest zone of inhibition (26 mm) against Escherichia followed by oregano oil (18 mm) against Staphylococcus (p<0.05). Klebsiella spp and Citrobacter spp showed resistance to mint and lemongrass oil respectively. The EOs such as lemongrass, mint and rosemary were less active against all the bacteria. The findings of the recent study suggest the use of EOs as natural antibacterial agents for food preservation.

Biosynthesis of the phycocyanin β-subunit in Escherichia coli BL21 and its antioxidant activity and application in the preservation of fresh-cut apples

In this study, the biosynthesis of phycocyanin β-subunit (CpcB) in Escherichia coli BL21 was investigated, and its antioxidant activity and application in anti-browning of fresh-cut apples was explored. Four genes (cpcB, cpeS, hox1 and pcyA) involved in the biosynthesis of CpcB were cloned and transformed into E. coli BL21 by constructing recombinant plasmid pETDuet-5. The positive transformant was screened by ampicillin resistance. The analysis of SDS-PAGE and zinc fluorescence spectrum showed that CpcB was successfully expressed in E. coli BL21 with a molecular weight of 21 kDa. The purified CpcB had a maximum absorption peak at 615 nm, and its maximum florescence emission wavelength was 640 nm. It exhibited a stronger ability to scavenge four free radicals than Vc. The color change in fresh-cut apples was obviously delayed by the CpcB treatment. These results suggest that CpcB may be used as a potential anti-browning agent for food preservation.