Food Spoilage Microorganisms Research Articles

Antimicrobial activity of bioactive compounds extract from Saussurea costus against food spoilage microorganisms

Saussurea costus had a wide range of antimicrobial activities which used as alternative for synthetic preservatives that threaten human health. This study aimed to identify the bioactive compounds in S. costus extract (SCE) and to evaluate its antimicrobial activity against some pathogenic microorganisms. HPLC and GC-MS were used to quantify the bioactive compounds in SCE. The results indicated that ethanol and ethyl acetate extracts had the highest levels of polyphenols followed by n-butanol, and then n-hexane extracts. The main phenolic compounds are Naringenin, Chlorogenic acid, Ferulic acid, Ellagic acid, Gallic acid and coffeic acid followed by taxifolin, catechin, syringic acid, methyl gallate, vanillin, kaempferol, cinnamic acid and rutin. GC-MS results showed 14 compounds in S. costus extract. The antibacterial activity of S. costus ethanol extract increased by increasing the concentration of extract from 10 µl to 50 µl for each wells .The inhibition zones were 13 mm and 23mm for S. typhi and Staphylococccus aureus, respectively. Gram (+ve) bacteria found to be more sensitive to SCE than Gram (-ve) bacteria. Similarly; the antifungal activity was increased by increasing the concentration of SCE the inhibition zones were 15.5 mm and 22.5 mm for P. verecossum and A. ochraceous, respectively. A. ochraceous appeared to be more sensitive towards all concentration of the extract. The minimum inhibitory concentration (MIC) of SCE for both bacteria and fungi strains ranged from 0.08 - 0.3 mg/ml and 0.25 -1.17 mg/ml, respectively. The results revealed that the SCE can play an important role against the human multi-drug resistant pathogens and can alternate the antibiotics as well as chemical preservatives to control infection and food spoilage contaminants.

Antimicrobial activity of different types of Centella asiatica extracts against foodborne pathogens and food spoilage microorganisms

The present study focused on the antimicrobial assessments of Centella asiatica for different extracts (ethanol, methanol, water, and hexane) against Bacillus cereus, Escherichia coli O157: H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Aspergillus niger, and Candida albicans. Ethanol achieved the highest extraction yields, total phenolic, and flavonoids contents, followed by those achieved with methanol, water, and hexane. The ethanolic extract exhibited the highest antimicrobial activity in agar disc diffusion assays. The minimum inhibitory concentrations (MIC) ranged from 7.81 for C. albicans to 125 mg/mL for A. niger. The minimum bactericidal concentration (MBC) was ranged from 15.63 for S. aureus and S. Typhimurium to 62.50 mg/mL for E. coli O157: H7. The minimum fungicidal concentration (MFC) was ranged 7.81 for C. albicans and 250 mg/mL for A. niger. No MBC and MFC could be established for the methanolic and aqueous extract, and the hexane extract did not show any antimicrobial activity. Ethanolic extract could potentially be an alternative for synthetic preservatives against foodborne pathogens.

A Critical Review of Disinfection Processes to Control SARS-CoV-2 Transmission in the Food Industry.

Industries of the food sector have made a great effort to control SARS-CoV-2 indirect transmission, through objects or surfaces, by updating cleaning and disinfection protocols previously focused on inactivating other pathogens, as well as food spoilage microorganisms. The information, although scarce at the beginning of the COVID-19 pandemic, has started to be sufficiently reliable to avoid over-conservative disinfection procedures. This work reviews the literature to propose a holistic view of the disinfection process where the decision variables, such as type and concentration of active substances, are optimised to guarantee the inactivation of SARS-CoV-2 and other usual pathogens and spoilage microorganisms while minimising possible side-effects on the environment and animal and human health.

Zinc Oxide Nanoparticle Synthesis, Characterization, and Their Effect on Mechanical, Barrier, and Optical Properties of HPMC-Based Edible Film

Zinc oxide nanoparticles (ZnO NPs) have been explored for controlling food spoilage microorganism. ZnO NPs were prepared by wet chemical synthesis using zinc nitrate as a precursor and sodium hydroxide as reducing agent. Nanorods and hexagonal plate shape ZnO NPs were obtained for different reaction time of 2 h and 24 h, respectively. Effect of hydroxypropyl methylcellulose (HPMC) as capping material on the morphology, size distribution, and optical properties of ZnO nanoparticles was studied by FESEM, TEM, DLS, UV-visible spectroscopy, and XRD analyses. Results showed that HPMC as capping material prevent the agglomeration of nanoparticles during synthesis and maintained uniformity in ZnO NPs size. Strong antimicrobial activity of prepared ZnO NPs was observed and minimum inhibitory concentration (MIC) for food application was determined. MIC for Staphylococcus aureus was 0.5 mg/ml. For Penicillium expansum 1 mg/ml showed approximately 80% inhibition and 2 mg/ml concentration showed 95% inhibition at the twelfth day for all ZnO NPs. HPMC-ZnO bio-nanocomposite films, prepared by incorporating capped ZnO NPs in HPMC biopolymer, showed improved mechanical and barrier properties and decreased transparency of film. Results showed that capped ZnO NPs obtained from 24 h reaction time were more effective in improving the barrier properties of HPMC film.

Antimicrobial Activity of Lipopeptide Biosurfactants Against Foodborne Pathogen and Food Spoilage Microorganisms and Their Cytotoxicity.

Lipopeptide biosurfactants produced by Bacillus sp. were assessed regarding their antimicrobial activity against foodborne pathogenic and food spoilage microorganisms. Both Gram-positive and Gram-negative bacteria were found not to be susceptible to these lipopeptides. However, mycosubtilin and mycosubtilin/surfactin mixtures were very active against the filamentous fungi Paecilomyces variotti and Byssochlamys fulva, with minimum inhibitory concentrations (MICs) of 1–16 mg/L. They were also active against Candida krusei, MIC = 16–64 mg/L. Moreover it was found that the antifungal activity of these lipopeptides was not affected by differences in isoform composition and/or purity. Furthermore their cytotoxicity tested on two different cell lines mimicking ingestion and detoxification was comparable to those of approved food preservatives such as nisin. Overall, for the first time here mycosubtilin and mycosubtilin/surfactin mixtures were found to have high antifungal activity against food relevant fungi at concentrations lower than their toxicity level hence, suggesting their application for extending the shelf-life of products susceptible to these moulds. In addition combining nisin with mycosubtilin or mycosubtiliin/surfactin mixtures proved to be an effective approach to produce antimicrobials with broader spectrum of action.

THE EFFECT OF LEAF TYPE AND SOLUTION ON THE RENDER OF PAPAYA SAPONINDA EXTRACT (CARICA PAPAYA LINN.)

Food safety issues can not be separated from the microbial pathogens that can cause health problems and food spoilage. Their presence in food product should be prevented and controlled. One of the efforts to improve food safety is the utilization of antimicrobial compounds, that can inhibit the growth of pathogenic microbes and food spoilage microorganism like Saponin. Saponins are triterpenic or steroidal glycosides which have many biological properties, and largely distributed in papaya leaves abundantly grown in Indonesia. This research aimed to compare the extraction procedure of saponin from papaya leaves by the difference of papaya leaves (young and old) and solvent (methanol, ethanol) that be used.The results showed that extraction by etanol provided higher yields (5.7 %) than by metanol (3.2 %). The yields of saponin-rich-extract from young and old leaves were not significantly different.

Exploring the Biodiversity of Red Yeasts for In Vitro and In Vivo Phenotypes Relevant to Agri-Food-Related Processes

Red yeasts grow on food wastes, show antagonistic activity against food-spoilage microorganisms, produce food supplements, and may be utilized as feed-supplements themselves to positively modulate the quali-quantitative composition of intestinal microbiota. Therefore, they show a variety of possible biotechnological applications in agri-food-related processes. Here, to further explore the biotechnological potential of red yeasts, eleven strains ascribed to different species of the genera Rhodotorula and Sporobolomyces, differing for biomass and carotenoids production, were characterized in vitro for biofilm formation, invasive growth, and growth at the temperature range of 20–40 °C and in vivo for their antagonistic activity against the fungal pathogen and patulin producer Penicillium expansum. Most of them formed cellular MAT and showed invasive growth as well as adhesion to plastic materials. Four strains determined a significant reduction of fruit decay caused by P. expansum on apple fruit while the remaining seven showed different degrees of biocontrol activity. Finally, none of them grew at body temperature (>37 °C). Statistical analyses of both qualitative and quantitative phenotypic data, including biomass and carotenoids production, gathered further information on the most interesting strains for the biotechnological exploitation of red yeasts in agri-food-related process.

EVALUTION OF ANTIMICROBIAL ACTIVITY OF PARTIAL PURIFIED BACTERIOCIN FROM LOCAL ISOLATE OF BACILLUS LICHENIFORIMS HJ2020 MT192715.1

This study was aimed to produce bacteriocin from Bacillus. licheniformis isolated from local soil of corn and sunflower fields and using as antimicrobial agent . Fourteen of local isolates of Bacillus sp. were obtained and ability of these isolates for growth on Brain heart infusion agar (BHI) at 550C were tested. Isolate C4 was revealed high growth density in comparison with other isolates. Isolate C4 was identified as Bacillus licheniformis according to morphological, cultural and biochemical tests, Moreover genetic analysis for 16S rRNA gene and given accession number MT192715.1 in GenBank of NCBI . Production of bacteriocin from this isolate was carried out in Luria Broth (LB) and partially purified by precipitation with 30-70 % saturation of ammonium sulfate followed by concentrated using poly ethylene glycol (PEG).The antimicrobial activity of partially purified bacteriocin was assayed against many species of food spoilage microorganism. Results were revealed that anitimicrobial activity of bacteriocin were between (0 - 360 ) units / ml. Stability of antimicrobial activity of partially purified bacteriocin toward Staphylococcus aureus were tested after incubation at different values of pH, temperature and some of enzyme which included proteolytic enzymes, α-amylase and lipase .The results indicated that residual inhibition activity of bacteriocin were varied according to conditions of incubation and type of treatment .

Antimicrobial activity of orange juice processing waste in powder form and its suitability to produce antimicrobial packaging

Orange peel essential oil is a common value-added product from orange juice processing waste. It is antimicrobial and used to produce antimicrobial films and coatings. This study reports the first development of antimicrobial films using orange peel as powder (OPP) instead of the extracted essential oil. The OPP amount needed for antimicrobial films was determined by studying the OPP effects on conidia germination inhibition (minimum inhibitory concentration (MIC)) and mycelial growth reduction for Botrytis cinerea, Aspergillus niger, and Penicillium sp. This amount was incorporated into linear low-density polyethylene using plastic processing machinery. The resulting LLDPE/OPP composite film was characterized for antimicrobial activity against Botrytis cinerea, antimicrobial compound release, and mechanical, barrier, and optical properties. We found the same OPP MIC (8.4 mg OPP/mL air) for the three fungi although their mycelial growth kinetics and conidia germination inhibition periods varied with OPP amount differently. 21.1 mg OPP/mL air completely inhibited the germination of Penicillium sp., B. cinerea, and A. niger conidia for 3, 2, and 1 days. The antimicrobial film was a LLDPE/OPP composite with 46% plastic replacement that reduced B. cinerea growth by 30% over a 7-day storage period at 23 °C, less than OPP due to limonene/citral reduction during processing. Plastic replacement resulted in films with the barrier and mechanical properties of plastics commonly used in food packaging. This study demonstrates the OPP antimicrobial capacity against food spoilage microorganisms and its suitability to produce antimicrobial packaging for food applications and presents a novel approach to utilizing orange juice processing waste.

Evaluation of Antimicrobial Activity of Buforin I and Nisin and the Synergistic Effect of Their Combination as a Novel Antimicrobial Preservative

One of the most effective methods for increasing the antimicrobial activity of a substance is to combine it with one or more other antimicrobial agents. The aim of the present study was to evaluate the antimicrobial effect of buforin I and nisin alone and investigate the synergistic action of these compounds against the most important food spoilage microorganisms in clouding B. subtilis, S. epidermidis, L. innocua, E. coli, S. Enteritidis, A. oryzae, R. glutinis and G. candidum. The results of MIC and MBC/MFC examinations showed that buforin I had higher antimicrobial activity than nisin on all the microbial strains used in this study (p≤0.5). E.coli was the most resistant to both antimicrobial agents, while Listeria innocua and Staphylococcus epidermidis were the most sensitive to nisin and buforin I, respectively. The results of synergistic interaction between buforin I and nisin indicated that the combination of buforin I and nisin on B. subtilis, S. epidermidis and A. oryzae showed synergistic effect, while it had no effect on S. Enteritidis and Geotrichum candidum. The combination of buforin I and nisin showed partial synergistic effect on Listeria innocua, Escherichia coli, Rhodotorula glutinis. Assessment of viability of the microorganisms under the antimicrobial agents alone and in combination with each other at MICs and FICs indicated that use of these antimicrobial agents in combination enhances antimicrobial activity at lower concentrations of both agents. The present study investigated the antimicrobial properties of buforin I against food spoilage microorganisms for the first time and suggests that its use alone or in combination with nisin may provide a clear horizon for the application of antimicrobial peptides as natural preservatives. Thus, the combination of antimicrobial peptides and traditional antimicrobial food preservative could be a promising option for the prevention of contamination, spoilage, and infestation of food and beverage products.

Immunomagnetic separation: An effective pretreatment technology for isolation and enrichment in food microorganisms detection.

The high efficiency and accurate detection of foodborne pathogens and spoilage microorganisms in food are a task of great social, economic, and public health importance. However, the contamination levels of target bacteria in food samples are very low. Owing to the background interference of food ingredients and negative impact of nontarget flora, the establishment of efficient pretreatment techniques is very crucial for the detection of food microorganisms. With the significant advantages of high specificity and great separation efficiency, immunomagnetic separation (IMS) assay based on immunomagnetic particles (IMPs) has been considered as a powerful system for the separation and enrichment of target bacteria. This paper mainly focuses on the development of IMS as well as their application in food microorganisms detection. First, the basic principle of IMS in the concentration of food bacteria is presented. Second, the effect of different factors, including the sizes of magnetic particles (MPs), immobilization of antibody and operation parameters (the molar ratio of antibody to MPs, the amount of IMPs, incubation time, and bacteria concentration) on the immunocapture efficiency of IMPs are discussed. The performance of IMPs in different food samples is also evaluated. Finally, the combination of IMS and various kinds of detection methods (immunology-based methods, nucleic acid-based methods, fluorescence methods, and biosensors) to detect pathogenic and spoilage organisms is summarized. The challenges and future trends of IMS are also proposed. As an effective pretreatment technique, IMS can improve the detection sensitivity and shorten their testing time, thus exhibiting broad prospect in the field of food bacteria detection.

New insights into the role of nanotechnology in microbial food safety.

Today, the role of nanotechnology in human life is undeniable as a broad range of industries, particularly food and medicine sectors, have been dramatically influenced. Nanomaterials can contribute to food safety by forming new nano-sized ingredients with modified physicochemical characteristics. Nanotechnologies can inhibit the growth of food spoilage microorganisms by recruiting novel and unique agents that are involved in removal of microbes from foods or prevent adhesion of microbial cells to food surfaces. Hence, nanotechnology could be considered as a high-potential tool in food packaging, safety, and preservation. Moreover, the prevention of biofilm formation by disturbing the attachment of bacteria to the food surface is another useful nanotechnological approach. Recently, nanoparticle-based biosensors have been designed and developed to detect the food-borne pathogens and hazardous substances through complicated mechanisms. During the past half-century, many methods such as freeze-drying and spray drying have been employed for increasing the viability in food industries; however, the other novel approaches such as encapsulation methods have also been developed. Admittedly, some beneficial bacteria such as probiotics bring diverse benefits for human health if only they are in a sufficient number and viability in the food products and gastrointestinal tract (GI). Encapsulation of these valuable microbial strains by nanoparticles improves the survival of probiotics under harsh conditions such as extreme levels of temperature, pH, and salinity during the processing of food products and within the GIT tract. The survival and effectiveness of encapsulated microorganisms depends on different factors including function of cell wall components in bacteria and type of coating materials. This review aims to broadly explore the potential of different aspects of nanotechnology in food industry, especially for packaging, preservation, safety, and viability.

Eucalyptus globulus Essential Oil as a Natural Food Preservative: Antioxidant, Antibacterial and Antifungal Properties In Vitro and in a Real Food Matrix (Orangina Fruit Juice)

The potential application of Eucalyptus globulus essential oil (EGEO) as a natural beverage preservative is described in this research. The chemical composition of EGEO was determined using gas chromatography analyses and revealed that the major constituent is 1,8-cineole (94.03% ± 0.23%). The in vitro antioxidant property of EGEO was assessed using different tests. Percentage inhibitions of EGEO were dose-dependent. In addition, EGEO had a better metal ion chelating effect with an IC50 value of 8.43 ± 0.03 mg/mL, compared to ascorbic acid (140.99 ± 3.13 mg/mL). The in vitro antimicrobial effect of EGEO was assessed against 17 food spoilage microorganisms. The diameter of the inhibitory zone (DIZ) ranged from 15 to 85 mm for Gram-positive bacteria and from 10 to 49 mm for yeast strains. Candida albicans, C.parapsilosis and Saccharomyces cerevisiae were the most sensitive fungal species to the EGEO vapor with DIZ varying from 59 to 85 mm. The anti-yeast effectiveness of EGEO alone and in association with heat processing was estimated in a real juice matrix (Orangina fruit juices) in a time-dependent manner. The combination of EGEO-heat treatment (70 °C for 2 min) at different concentrations (0.8 to 4 µL/mL) was effective at reducing S. cerevisiae growth in the fruit juice of Orangina, compared to juice preserved with synthetic preservatives. Current findings suggest EGEO as an effective and potent inhibitor of food spoilage fungi in a real Orangina juice, and might be a potential natural source of preservative for the food industry.

Bioprospecting of a novel endophytic Bacillus velezensis FZ06 from leaves of Camellia assamica: Production of three groups of lipopeptides and the inhibition against food spoilage microorganisms

Food contamination caused by microorganisms has become a threat to consumers' health. Exploring antagonistic endophytes from plants of food raw-material and applying bioactive metabolites to inhibit the contamination has been an alternative and safer solution. In this study, we isolated and screened potential antagonistic endophytes from fresh Camellia assamica leaves, which were widely used in tea beverage production. We focused on a strain that showed visible inhibitory activity to Gram-positive bacteria, Gram-negative bacteria, and fungi. It was identified as a member of Bacillus velezensis and named FZ06. The results of genome analysis showed the strain FZ06 had 167 single-copy specific genes, much higher than those of most related strains. Also, 11 potential gene clusters of antimicrobial metabolites were found. Three groups of lipopeptides (surfactin, iturin, and fengycin) were identified by UPLC-MS/MS in purified antimicrobial methanol fraction of strain FZ06. The results of minimum inhibitory concentration (MIC) test proved the lipopeptide extract showed significant inhibitory effect on food spoilage bacteria (MIC 512−2048 μg/mL) and toxigenic fungi (MIC 128−256 μg/mL). In conclusion, this study suggests that the endophytic B. velezensis FZ06 and its lipopeptide extract hold great potential applications in the inhibition of food spoilage bacteria and toxic fungi in food industry.

Biocontrol of Food Spoilage Microorganisms using Leaf extracts from Magnifera indica (Mango) and Psidium guajava (Guava).

The shelf life of processed food is greatly reduced by spoilage microorganisms, which has resulted in great losses to food processors, wholesalers, retailers and even consumers. This study was aimed at controlling food spoilage microorganisms using leaf extracts from mango and guava. Fried meat (beef, chicken, grass-cutter, and goat meat), fried fish and fresh bread were purchased from Benin City, and left to spoil, after which spoilage organisms were isolated, identified and characterized using standard microbiological techniques. Mango and guava leaf extracts (ethanolic and aqueous), with Potassium sorbate and sodium nitrite was used. Significant highest (<0.05) (15.67±0.88 mg/ml) antibacterial activity of Mango leaf extract was recorded against Escherichia coli, and significant highest (<0.05) antifungal activity (19.67±0.33) was recorded against Penicillium oxalicum. Ethanolic leaf extracts of mango had better MICs (6.25 mg/ml) against E. coli tested than guava (25 mg/ml). In addition, ethanolic leaf extracts from Mango did not have any effect on Bacillus polymyxa. This study suggests that extracts from Mango and Guava leaves can be explored for controlling spoilage organisms; however, ethanolic extracts are more potent than aqueous extracts.

Assessment of the Antimicrobial, Antioxidant, and Antiproliferative Potential of Sideritis raeseri subps. raeseri Essential Oil.

The aim of the present study was to investigate the antimicrobial potential of Sideritis raeseri subps. raeseri essential oil (EO) against common food spoilage and pathogenic microorganisms and evaluate its antioxidant and antiproliferative activity. The EO was isolated by steam distillation and analyzed by GC/MS. The main constituents identified were geranyl-p-cymene (25.08%), geranyl-γ-terpinene (15.17%), and geranyl-linalool (14.04%). Initially, its activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Listeria monocytogenes, Salmonella Enteritidis, Salmonella Typhimurium, Pseudomonas fragi, Saccharomyces cerevisiae, and Aspergillus niger was screened by the disk diffusion method. Subsequently, minimum inhibitory concentration (MIC), non-inhibitory concentration (NIC), and minimum lethal concentration (MLC) values were determined. Growth inhibition of all microorganisms tested was documented, although it was significantly lower compared to gentamycin, ciproxin, and voriconazole, which were used as positive controls. In a next step, its direct antioxidant properties were examined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, and the IC50 values were determined. The potential cytoprotective activity of the oil against H2O2–induced oxidative stress and DNA damage was studied in human immortalized keratinocyte (HaCaT) cells using the comet assay. Finally, the antiproliferative activity of the oil was evaluated against a panel of cancer cell lines including A375, Caco2, PC3, and DU145 and the non-cancerous HaCaT cell line using the sulforhodamine B (SRB) assay, and the EC50 values were determined. The oil demonstrated weak radical scavenging activity, noteworthy cytoprotective activity against H2O2–induced oxidative stress and DNA damage in HaCaT cells, and antiproliferative activity against all cell lines tested, being more sensitive against the in vitro model of skin melanoma.

Bacterial and Fungal Dynamics During the Fermentation Process of Sesotho, a Traditional Beer of Southern Africa.

Sesotho is an indigenous cereal-based fermented drink traditionally produced in the mountain kingdom of Lesotho, Southern Africa. The present study sought to examine the microbial (bacterial and fungal) community composition of Sesotho at five fermentation stages in five different locations. Using culture-independent (Illumina sequencing) techniques it was found that the bacterial communities followed similar successional patterns during the fermentation processes, regardless of geographical location and recipe variation between breweries. The most abundant bacterial taxa belonged to the phyla Firmicutes (66.2% of the reads on average) and Proteobacteria (22.1%); the families Lactobacillaceae (54.9%), Enterobacteriaceae (14.4%) and Leoconostrocaceae (8.1%); and the genera Lactobacillus (54%), Leuconostoc (10.7%), Leptotrichia (8.5%), and Weissella (5.5%). Most fungal taxa were from the phyla Ascomycota (60.7%) and Mucoromycota (25.3%); the families Rhizopodaceae (25.3%), Nectriaceae (24.2%), Saccharomycetaceae (16%) and Aspergillaceae (6.7%); and the genera Rhizopus (25.3%), Saccharomyces (9.6%), and Aspergillus (2.5%). Lactic acid bacteria (LAB) such as Enterococcus, Pediococcus, Lactobacillus, Leuconostoc, and Wiesella; as well as yeasts belonging to the genus Saccharomyces, were dominant in all breweries during the production of Sesotho. Several pathogenic and food spoilage microorganisms (e.g., Escherichia, Shigella, Klebsiella, etc.) were also present, but the study demonstrated the safety potential of the Sesotho fermentation process, as these microbial groups decline throughout Sesotho production. The functional profiles of the different brewing steps showed that the process is dominated by chemoheterotrophic and fermentative metabolisms. This study reveals, for the first time, the complex microbial dynamics that occur during Sesotho production.

The complex multicellular morphology of the food spoilage bacteria Brochothrix thermosphacta strains isolated from ground chicken.

Herein we describe a highly structured, filamentous growth phenotype displayed by an isolate of the food spoilage microorganism Brochothrix thermosphacta. The growth morphology of this B. thermosphacta strain (strain BII) was dependent on environmental factors such as the growth media, incubation temperatures, and the inoculum concentration. Inoculation of cultures in highly dilute suspensions resulted in the formation of isolated, tight aggregates resembling fungal growth in liquid media. This same strain also formed stable, mesh-like structures in 6-well tissue culture plates under specific growth conditions. The complex growth phenotype does not appear to be unique to strain BII but was common among B. thermosphacta strains isolated from chicken. Light and electron micrographs showed that the filaments of multiple BII cells can organize into complex, tertiary structures resembling multistranded cables. Time-lapse microscopy was employed to monitor the development of such aggregates over 18 h and revealed growth originating from short filaments into compact ball-like clusters that appeared fuzzy due to protruding filaments or cables. This report is the first to document this complex filamentous growth phenotype in a wild-type bacterial isolate of B. thermosphacta.

Biogenic Amine Contents and Microbial Characteristics of Cambodian Fermented Foods.

Naturally fermented foods are an important part of the typical diet in Cambodia. However, the food safety status of these products has not been widely studied. The aim of this study was, therefore, to provide an overview of the quality of these foods in relation to microbiology and biogenic amines. Additionally, the obtained results were compared to the habits and practices of Cambodians in handling this type of food. A total of 57 fermented foods (42 fishery and 15 vegetable products) were collected from different retail markets in the capital of Cambodia. Pathogenic Salmonella spp., Listeria spp., and Listeria monocytogenes were not detected in 25 g samples. Generally, less than 102 cfu/g of Staphylococcus aureus, Escherichia coli, Pseudomonas spp., Enterobacteriaceae, and molds were present in the fermented foods. Bacillus cereus group members (<102 to 2.3 × 104 cfu/g), lactic acid bacteria (<102 to 1.1 × 107 cfu/g), halophilic and halotolerant bacteria (<102 to 8.9 × 106 cfu/g), sulfite-reducing Clostridium spp. (<102 to 3.5 × 106 cfu/g), and yeasts (<102 to 1.1 × 106 cfu/g) were detected in this study. Still, the presence of pathogenic and spoilage microorganisms in these fermented foods was within the acceptable ranges. Putrescine, cadaverine, tyramine, and histamine were detected in 100%, 89%, 81%, and 75% of the tested products, respectively. The concentrations of histamine (>500 ppm) and tyramine (>600 ppm) were higher than the recommended maximum levels in respectively four and one of 57 fermented foods, which represents a potential health risk. The results suggest that the production process, distribution, and domestic handling of fermented foods should be re-evaluated. Further research is needed for the establishment of applicable preservation techniques in Cambodia.

Evaluation of the Potential of Biofilm Formation of Bifidobacterium longum subsp. infantis and Lactobacillus reuteri as Competitive Biocontrol Agents Against Pathogenic and Food Spoilage Bacteria.

This study proposes to exploit the in vivo metabolism of two probiotics (Bifidobacterium longum subsp. infantis and Lactobacillus reuteri) which, upon adhesion on a solid surface, form a biofilm able to control the growth of pathogenic and food spoilage bacteria. The results showed that pathogenic cell loads were always lower in presence of biofilm (6.5–7 log CFU/cm2) compared to those observed in its absence. For Escherichia coli O157:H7, a significant decrease (>1–2 logarithmic cycles) was recorded; for Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica, cell load reductions ranged from 0.5 to 1.5 logarithmic cycles. When tested as active packaging, the biofilm was successfully formed on polypropylene, polyvinyl chloride, greaseproof paper, polyethylene and ceramic; the sessile cellular load ranged from 5.77 log CFU/cm2 (grease-proof paper) to 6.94 log CFU/cm2 (polyethylene, PE). To test the potential for controlling the growth of spoilage microorganisms in food, soft cheeses were produced, inoculated with L. monocytogenes and Pseudomonas fluorescens, wrapped in PE pellicles with pre-formed biofim, packed both in air and under vacuum, and stored at 4 and 15 °C: an effective effect of biofilms in slowing the decay of the microbiological quality was recorded.