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Microbial Safety of Fermented Products

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A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Food Microbiology".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 59833

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Special Issue Editor

Dr. Marta Laranjo

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Guest Editor

MED-Mediterranean Institute for Agriculture, Environment and Development, IIFA-Instituto de Investigação e Formação Avançada & Departamento de Medicina Veterinária, Escola de Ciências e Tecnologia, Universidade de Évora, Évora, Portugal
Interests: food microbiology; food science & technology; food fermentation; molecular biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fermented food products comprise very diverse fermented foods and beverages with a long history of worldwide importance for human nutrition, health, and economy.

The main groups of fermented food products include the following: cereals (bread and sake); vegetables, fruits, and legumes (table olives, pickles, and vinegar); milk (cheese, yogurt, and kefir); meat and meat products (ham and sausages); fish products (anchovies and herring); and alcoholic beverages (wine and beer).

A huge diversity of indigenous microorganisms, mostly bacteria and yeasts, is associated with this vast variety of fermented food products. They not only differ according to the raw materials or the obtained final products, but also in their distinct fermentative behavior.

The microbial safety of these fermented food products is, however, menaced by the potential presence of microbial pathogens, which are included in the aforementioned microbial diversity. Pathogens may not only be harmful per se, but also through the toxins and other secondary products they release, such as mycotoxins or biogenic amines.

To assure the quality and safety of fermented food products, different approaches are not only needed to successfully control the indigenous microbiota and conduct fermentations, which include the use of a starter culture, but also to effectively preservative methodologies.

All manuscripts that fall under these specific topics are welcome.

Dr. Marta Laranjo
Guest Editor

Manuscript Submission Information

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Published Papers (14 papers)

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Research

16 pages, 3849 KiB

Open AccessArticle

Functional Properties and Sustainability Improvement of Sourdough Bread by Lactic Acid Bacteria

by Vera Fraberger, Claudia Ammer and Konrad J. Domig

Microorganisms 2020, 8(12), 1895; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8121895 - 30 Nov 2020

Cited by 22 | Viewed by 3499

Abstract

Preventing food spoilage without the addition of chemical food additives, while increasing functional properties of wheat-based bakery products, is an increasing demand by the consumers and a challenge for the food industry. Within this study, lactic acid bacteria (LAB) isolated from sourdough were screened in vitro for the ability to utilize the typical wheat carbohydrates, for their antimicrobial and functional properties. The dual culture overlay assay revealed varying levels of inhibition against the examined fungi, with Lactiplantibacillus plantarum S4.2 and Lentilactobacillusparabuchneri S2.9 exhibiting the highest suppression against the indicator strains Fusarium graminearum MUCL43764, Aspergillus fumigatus, A. flavus MUCL11945, A. brasiliensis DSM1988, and Penicillium roqueforti DSM1079. Furthermore, the antifungal activity was shown to be attributed mainly to the activity of acids produced by LAB. The antibacillus activity was evaluated by the spot-on-the-lawn method revealing a high inhibition potential of the majority of LAB isolated from sourdough against Bacillus cereus DSM31, B. licheniformis DSM13, B. subtilis LMG7135, and B. subtilis S15.20. Furthermore, evaluating the presence of the glutamate decarboxylase gen in LAB isolates by means of PCR showed a strain dependency of a potential GABA production. Finally, due to improved functional activities, LAB isolated from sourdoughs exhibit promising characteristics for the application as natural preservatives in wheat-based bakery products. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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15 pages, 1243 KiB

Open AccessArticle

Bacterial Populations in International Artisanal Kefirs

by Abrar Sindi, Md. Bahadur Badsha and Gülhan Ünlü

Microorganisms 2020, 8(9), 1318; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8091318 - 29 Aug 2020

Cited by 25 | Viewed by 5567

Abstract

Artisanal kefir is a traditional fermented dairy product made using kefir grains. Kefir has documented natural antimicrobial activity and health benefits. A typical kefir microbial community includes lactic acid bacteria (LAB), acetic acid bacteria, and yeast among other species in a symbiotic matrix. In the presented work, the 16S rRNA gene sequencing was used to reveal bacterial populations and elucidate the diversity and abundance of LAB species in international artisanal kefirs from Fusion Tea, Britain, the Caucuses region, Ireland, Lithuania, and South Korea. Bacterial species found in high abundance in most artisanal kefirs included Lactobacillus kefiranofaciens, Lentilactobacillus kefiri,Lactobacillus ultunensis, Lactobacillus apis, Lactobacillus gigeriorum, Gluconobacter morbifer, Acetobacter orleanensis, Acetobacter pasteurianus, Acidocella aluminiidurans, and Lactobacillus helveticus. Some of these bacterial species are LAB that have been reported for their bacteriocin production capabilities and/or health promoting properties. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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34 pages, 5798 KiB

Open AccessArticle

Monitoring and Optimization of Cupuaçu Seed Fermentation, Drying and Storage Processes

by Joana M. L. Souza, João M. Rocha, Cleísa B. C. Cartaxo, Marcus A. M. Vasconcelos, Virginia S. Álvares, Matheus M. Nascimento, Renata T. B. Yomura and Simara Kaefer

Microorganisms 2020, 8(9), 1314; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8091314 - 28 Aug 2020

Cited by 7 | Viewed by 3206

Abstract

Cupuaçu [Theobroma grandiflorum (Wild ex Spreng.) K. Schum] seeds have been employed for a long time in the Amazon region for food purposes. Similar to cocoa, processed cupuaçu pulp and seeds can be used to produce juices, ice creams, confectionary products and cupulate^®, which is a similar product to chocolate. However, its market penetration requires the mastery of all processing stages to improve the food quality and safety and to make possible an efficient technology transfer to the local small farmers and communities. Based on the above, the current research work aimed at monitoring and optimizing the consecutive fermentation and drying processes of cupuaçu seeds over 7 days each, as well as storage for 90 days. A greenhouse structure incorporating the fermenter and solar drying terrace was designed to be inexpensive, versatile, easily scalable, and easy to maintain and operate by the local small farmers after a short period of training. This research effort also aimed at giving a vision for the future creation of an integrative and sustainable cupuaçu system covering the economic, social, cultural and environmental vectors. The experimental design comprised 5 batches of 100 kg of seeds each. Several microbiological and physicochemical parameters were performed and correlated with processing variables. Microbiological parameters encompassed viable counts of mesophilic microorganisms, coliforms, yeasts, and molds, whereas physicochemical measures included fermentation and drying temperature, pH, acidity, dry matter, ashes, water activity, color, total proteins, lipids and carbohydrates, and energy. The average seed fermentation temperature varied from ca. 28 to 44 °C, reaching the maximum on day 3 and a final value of ca. 31 °C. Regarding solar drying, the average seed temperatures ranged from ca. 24 °C (at the end) to 39 °C on day 3, and an initial value of ca. 29 °C. The average final seed pH value of drying was 5.34 and was kept during storage. During storage, results demonstrated the existence of significant correlations among several experimental parameters under scrutiny. Finally, bean viable counts obtained during storage unfolded acceptable values of total mesophilic bacteria well below the maximum limit. Viable counts of yeast and molds were generally found between 3 and 4 log(CFU/g_sample), and total coliforms were also detected, although both were at acceptable levels and well beneath the established maximum limits for food safety. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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12 pages, 1544 KiB

Open AccessArticle

Antimicrobial Activity of Six International Artisanal Kefirs against Bacillus cereus, Listeria monocytogenes, Salmonella enterica Serovar Enteritidis, and Staphylococcus aureus

by Abrar Sindi, Md. Bahadur Badsha, Barbara Nielsen and Gülhan Ünlü

Microorganisms 2020, 8(6), 849; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8060849 - 04 Jun 2020

Cited by 13 | Viewed by 3442

Abstract

Kefir, a fermented dairy beverage, exhibits antimicrobial activity due to many metabolic products, including bacteriocins, generated by lactic acid bacteria. In this study, the antimicrobial activities of artisanal kefir products from Fusion Tea (A), Britain (B), Ireland (I), Lithuania (L), the Caucuses region (C), and South Korea (K) were investigated against select foodborne pathogens. Listeria monocytogenes CWD 1198, Salmonella enterica serovar Enteritidis ATCC 13076, Staphylococcus aureus ATCC 25923, and Bacillus cereus ATCC 14579 were inhibited by artisanal kefirs made with kefir grains from diverse origins. Kefirs A, B, and I inhibited all bacterial indicator strains examined at varying levels, except Escherichia coli ATCC 12435 (non-pathogenic, negative control). Kefirs K, L, and C inhibited all indicator strains, except S. aureus ATCC 25923 and E. coli ATCC 12435. Bacteriocins present in artisanal kefirs were determined to be the main antimicrobials in all kefirs examined. Kefir-based antimicrobials are being proposed as promising natural biopreservatives as per the results of the study. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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19 pages, 313 KiB

Open AccessArticle

Autochthonous Starter Cultures Are Able to Reduce Biogenic Amines in a Traditional Portuguese Smoked Fermented Sausage

by Igor Dias, Marta Laranjo, Maria Eduarda Potes, Ana Cristina Agulheiro-Santos, Sara Ricardo-Rodrigues, Ana Rita Fialho, Joana Véstia, Maria João Fraqueza, Margarida Oliveira and Miguel Elias

Microorganisms 2020, 8(5), 686; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8050686 - 08 May 2020

Cited by 23 | Viewed by 3082

Abstract

Traditional smoked fermented sausages are highly appreciated in Portugal and are mostly manufactured according to traditional procedures. The aim of the present work was to evaluate the effect of autochthonous starter cultures on the safety and quality of a smoked fermented sausage, Painho da Beira Baixa (PBB), preserving its sensory quality. Physicochemical parameters, namely pH and water activity (a_W), microbiological parameters, biogenic amines, colour, texture profile and sensory attributes were assessed. Different starters were selected based on our previous work. Staphylococcus equorum S2M7, Staphylococcus xylosus CECT7057, Lactobacillus sakei CV3C2, Lactobacillus sakei CECT7056 and a yeast strain (2RB4) were co-inoculated in meat batters at defined concentrations. Starters had a significant effect on the reduction of pH. Enterobacteria and Listeria monocytogenes were not detected in inoculated end-product sausages. Moreover, sausages inoculated with S. equorum S2M7/L. sakei CV3C2/yeast 2RB4 showed a significant reduction in the total content of biogenic amines. No significant differences between treatments were observed for colour and texture parameters, except for adhesiveness. The studied starters did not compromise the sensory characteristics of PBB. To our knowledge, this is the first comprehensive study on the quality and safety of this type of smoked fermented sausage from the central region of Portugal. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

29 pages, 2008 KiB

Open AccessArticle

Selection of Wild Lactic Acid Bacteria Strains as Promoters of Postbiotics in Gluten-Free Sourdoughs

by Bogdan Păcularu-Burada, Luminița Anca Georgescu, Mihaela Aida Vasile, João Miguel Rocha and Gabriela-Elena Bahrim

Microorganisms 2020, 8(5), 643; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8050643 - 28 Apr 2020

Cited by 35 | Viewed by 4601

Abstract

The occurrence of inflammatory responses in humans is frequently associated with food intolerances and is likely to give rise to irritable bowel disease. The use of conventional or unconventional flours to produce gluten-free baking doughs brings important technological and nutritional challenges, and the use of the sourdough biotechnology has the potential to overcome such limitations. In addition, the typical metabolic transformations carried out by Lactic Acid Bacteria (LAB) can become an important biotechnological process for the nutritional fortification and functionalization of sourdoughs due to the resulting postbiotics. In such a context, this research work aimed at isolating and selecting new LAB strains that resort to a wide range of natural environments and food matrices to be ultimately employed as starter cultures in gluten-free sourdough fermentations. Nineteen LAB strains belonging to the genera of Lactobacillus, Leuconostoc, Pediococcus, and Streptococcus were isolated, and the selection criteria encompassed their acidification capacity in fermentations carried out on chickpea, quinoa, and buckwheat flour extracts; the capacity to produce exopolysaccharides (EPS); and the antimicrobial activity against food spoilage molds and bacteria. Moreover, the stability of the LAB metabolites after the fermentation of the gluten-free flour extracts submitted to thermal and acidic treatments was also assessed. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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13 pages, 503 KiB

Open AccessArticle

Screening of Bacteriocinogenic Lactic Acid Bacteria and Their Characterization as Potential Probiotics

by Ana Pinto, Joana Barbosa, Helena Albano, Joana Isidro and Paula Teixeira

Microorganisms 2020, 8(3), 393; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8030393 - 11 Mar 2020

Cited by 41 | Viewed by 6319

Abstract

Probiotics are living microorganisms used as nutritional additives that confer health benefits on the host. Their use in food products is very attractive, especially if they could also inhibit important foodborne pathogens. In this study, antimicrobial activity against several foodborne pathogens was screened for 280 lactic acid bacteria (LAB) isolated from different food products and the probiotic characteristics of bacteriocinogenic isolates were evaluated. Seven out of 280 LAB isolates were selected due to their bacteriocinogenic properties and identified by 16S rRNA gene sequence analysis as Pediococcus pentosaceus (n = 6) and Lactobacillus plantarum (n = 1). Virulence factors and antibiotic resistances were not detected for any of the isolates. Except for L. plantarum R23, all the isolates were able to survive through the simulated gastrointestinal tract conditions. Only P. pentosaceus CFF4 was able to adhere to Caco-2 cells after the simulated gastrointestinal tract passage. In conclusion, even though in vivo studies should be performed, P. pentosaceus CFF4, which was also able to inhibit the growth of foodborne pathogens in vitro, seems to be a potential probiotic to be used in the food industry. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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11 pages, 618 KiB

Open AccessCommunication

Preliminary Survey of Alternaria Toxins Reduction during Fermentation of Whole Wheat Dough

by Elizabet Janić Hajnal, Lato Pezo, Dejan Orčić, Ljubiša Šarić, Dragana Plavšić, Jovana Kos and Jasna Mastilović

Microorganisms 2020, 8(2), 303; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8020303 - 21 Feb 2020

Cited by 5 | Viewed by 2363

Abstract

The aim of this study was to investigate the fate of the most common Alternaria toxins found in wheat—tenuazonic acid (TeA), alternariol (AOH), and alternariol monomethyl ether (AME) during sourdough processing. For this purpose, spiked whole wheat flour, 3% sourdough starter, 0.5% of baker’s yeast, and 105% of water calculated on flour weight as a base were used as raw materials. Spiked whole wheat dough was fermented for 4 h, 8 h, 12 h, 24 h, and 48 h at 25 °C, and at each point the fermented dough samples were taken, frozen, lyophilized, grounded, and stored until further analysis. To study the effect of sourdough processing on TeA, AOH and AME content, the validated method of high-performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for these mycotoxins was used. Mathematical models of Alternaria toxins reduction were developed in the form of Four Parameter Logistic Regression function. The maximum reduction of TeA, AOH, and AME levels was archived at 48 h of dough fermentation at 25 °C compared with dough after kneading (0 h). Under these conditions, a reduction of the toxin levels of 60.3 %, 41.5%, and 24.1% was observed for TeA, AOH, and AME, respectively. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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17 pages, 749 KiB

Open AccessArticle

The Role of Selected Lactic Acid Bacteria on Organic Acid Accumulation during Wet and Spray-Dried Fish-Based Silages. Contributions to the Winning Combination of Microbial Food Safety and Environmental Sustainability

by Esmeray Kuley, Gulsun Özyurt, Ilyas Özogul, Mustafa Boga, Ismail Akyol, João M. Rocha and Fatih Özogul

Microorganisms 2020, 8(2), 172; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8020172 - 25 Jan 2020

Cited by 36 | Viewed by 4302

Abstract

Organic acid contents of acidified and fermented fish silages made from gibel carp (Caracius gibelio) and klunzinger’s ponyfish (Equulites klunzingeri) fishes, and from fish processing residues or by-products, were determined and studied. The silages were undertaken in wet and spray-dried fish-based raw-materials for 3 weeks at room temperature (ca. 25 °C). Selected lactic acid bacteria (LAB) of Enterococcus gallinarum, Lactobacillus brevis, Lactobacillus plantarum, Pediococcus acidilactici, and Streptococcus spp. were employed to produce fermented fish-based silages, while acidified silage was prepared resorting to the addition of formic acid (3%, v/v). Lactic and propionic acids were the dominant produced organic acids, while succinic acid was formed at the smallest amounts in fermented silages. In the acidified silage, lactic and formic acids were produced in amounts higher than 800 and 1000 mg _{organic acid}/100 g _sample, respectively. Among the fermented fish-based silages, LAB strains unfolded considerable ability to presumptively produce propionic acid in gibel carp silage (>2370 mg _{organic acid}/100 g _sample). Spray-dried fermented silages displayed significantly higher organic acid content than wet silages. Propionic acid accumulation was found at the highest levels in gibel carp silage fermented with L. plantarum (6335.40 mg _{propionic acid}/100 g _sample). This research effort pointed out the good capability of various selected lactic acid bacteria strains to produce significant amounts of organic acids—especially lactic, acetic, and propionic acids—during the fermentation of fish-based silages. In terms of food safety and quality, such a production of relatively high amounts of organic acids in wet and spray-dried fish-based silages clearly indicated their suitableness to be used for animal feed. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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20 pages, 7810 KiB

Open AccessArticle

Lactic Acid Bacteria Isolation from Spontaneous Sourdough and Their Characterization Including Antimicrobial and Antifungal Properties Evaluation

by Elena Bartkiene, Vita Lele, Modestas Ruzauskas, Konrad J. Domig, Vytaute Starkute, Paulina Zavistanaviciute, Vadims Bartkevics, Iveta Pugajeva, Dovile Klupsaite, Grazina Juodeikiene, Ruta Mickiene and João Miguel Rocha

Microorganisms 2020, 8(1), 64; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8010064 - 30 Dec 2019

Cited by 128 | Viewed by 9448

Abstract

This research effort aimed at isolating and phenotypically characterizing lactic acid bacteria (LAB) isolates from a spontaneous rye sourdough manufactured following traditional protocols, as well as at evaluating their antimicrobial and antifungal properties as key features for future industrial applications. Thirteen LAB strains of potential industrial interest were isolated and identified to species-level via PCR. Most of the sourdough isolates showed versatile carbohydrate metabolisms. The Leuconostoc mesenteroides No. 242 and Lactobacillus brevis No. 173 demonstrated to be gas producers; thus, revealing their heterofermenter or facultative homofermenter features. Viable counts higher than 7.0 log₁₀ (CFU/mL) were observed for Lactobacillus paracasei No. 244, Lactobacillus casei No. 210, L. brevis No. 173, Lactobacillus farraginis No. 206, Pediococcus pentosaceus No. 183, Lactobacillus uvarum No. 245 and Lactobacillus plantarum No. 135 strains, after exposure at pH 2.5 for 2 h. Moreover, L. plantarum No. 122, L. casei No. 210, Lactobacillus curvatus No. 51, L. paracasei No. 244, and L. coryniformins No. 71 showed growth inhibition properties against all the tested fifteen pathogenic strains. Finally, all LAB isolates showed antifungal activities against Aspergillus nidulans, Penicillium funiculosum, and Fusarium poae. These results unveiled the exceptionality of spontaneous sourdough as a source of LAB with effective potential to be considered in the design of novel commercial microbial single/mixed starter cultures, intended for application in a wide range of agri-food industries, where the antimicrobial and antifungal properties are often sought and necessary. In addition, metabolites therefrom may also be considered as important functional and bioactive compounds with high potential to be employed in food and feed, as well as cosmetic and pharmaceutical applications. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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20 pages, 2234 KiB

Open AccessArticle

Use of Autochthonous Lactobacilli to Increase the Safety of Zgougou

by Fabio Minervini, Jihen Missaoui, Giuseppe Celano, Maria Calasso, Lotfi Achour, Dalila Saidane, Marco Gobbetti and Maria De Angelis

Microorganisms 2020, 8(1), 29; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8010029 - 22 Dec 2019

Cited by 13 | Viewed by 2797

Abstract

Seeds of Pinus halepensis are used for preparing zgougou, a spontaneously fermented matrix giving juice and seeds debris, consumed in many Arabian countries, including Tunisia. In the same way as all the food processes based on spontaneous fermentation, zgougou hides health risks due to eventual pathogenic microorganisms and derived toxins. This study aimed at investigating the effect of the use of autochthonous Lactobacillus paraplantarum A1 and Lactobacillus plantarum A2, as fermentation starters, on the microbiological characteristics, profiles of volatile organic compounds (VOC), antibacterial and antioxidant activities of juice and seeds debris from zgougou. The starter lactobacilli inhibited undesired bacteria (e.g., Enterobacter and Aeromonas) and coccus-shaped lactic acid bacteria, as shown by culture-dependent and-independent methods. The inhibitory effect was more evident in juice than in seeds debris. Some VOC (ethanol, acetoin, phenol,2-methoxy and caryophyllene) were present at higher concentrations in juice and seeds obtained upon spontaneous fermentation, compared to the samples deriving from fermentation with lactobacilli. The latter samples were characterized by higher concentrations of acetic acid, decane, 1-nonanol, bornyl acetate and bornyl formate. In addition, they showed a wider spectrum of antibacterial activity than spontaneously fermented juice and seeds. The use of autochthonous lactobacilli did not relevantly affect the antioxidant activity of zgougou. When juice from lactobacilli-driven fermentation was used to prepare a traditional Tunisian pudding (“Assidat-Zgougou”), it improved color and odor with respect to the pudding containing juice from spontaneous fermentation. This study showed that the use, at laboratory scale, of autochthonous lactobacilli is a feasible biotechnological tool to outgrow undesired bacteria, thus improving the safety of zgougou juice. Future studies should be undertaken to confirm the observed benefits at industrial scale. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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23 pages, 3550 KiB

Open AccessArticle

Fermented Seeds (“Zgougou”) from Aleppo Pine as a Novel Source of Potentially Probiotic Lactic Acid Bacteria

by Jihen Missaoui, Dalila Saidane, Ridha Mzoughi and Fabio Minervini

Microorganisms 2019, 7(12), 709; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms7120709 - 17 Dec 2019

Cited by 18 | Viewed by 4045

Abstract

Microorganisms inhabiting fermented foods represent the main link between the consumption of this food and human health. Although some fermented food is a reservoir of potentially probiotic microorganisms, several foods are still unexplored. This study aimed at characterizing the probiotic potential of lactic acid bacteria isolated from zgougou, a fermented matrix consisting of a watery mixture of Aleppo pine′s seeds. In vitro methods were used to characterize the safety, survival ability in typical conditions of the gastrointestinal tract, and adherence capacity to surfaces, antimicrobial, and antioxidant activities. Strains belonged to the Lactobacillus plantarum group and Enterococcus faecalis showed no DNase, hemolytic, and gelatinase activities. In addition, their susceptibility to most of the tested antibiotics, satisfied some of the safety prerequisites for their potential use as probiotics. All the strains tolerated low pH, gastrointestinal enzymes, and bile salts. They displayed a good antibacterial activity and antibiofilm formation against 10 reference bacterial pathogens, especially when used as a cell-free supernatant. Furthermore, the lactic acid bacteria (LAB) strains inhibited the growth of Aspergillus flavus and Aspergillus carbonarius. Finally, they had good antioxidant activity, although depending on the strain. Overall, the results of this work highlight that zgougou represents an important reservoir of potentially probiotic LAB. Obviously, future studies should be addressed to confirm the health benefits of the LAB strains. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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19 pages, 1590 KiB

Open AccessArticle

Meta-Analysis and Meta-Regression Indicate Dynamic Prevalence and Moderators of Foodborne Pathogens in African Indigenous Fermented Milk

by Joseph Wambui, Patrick Murigu Kamau Njage, Taurai Tasara and Elna Maria Buys

Microorganisms 2019, 7(11), 563; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms7110563 - 14 Nov 2019

Cited by 3 | Viewed by 3476

Abstract

As more microbiological data for indigenous fermented milk (IFM) becomes available, concern about their microbial safety becomes eminent. Nonetheless, these data are highly fragmented, and a tool is required to integrate existing data and to provide a basis for data-driven decision making for IFM’s safety. Therefore, meta-analysis and meta-regression were conducted to estimate the prevalence of foodborne pathogens in IFM and to determine factors influencing the estimated values. Using Africa as a case, searches were systematically made for published data and relevant grey literature. Data from 18 studies in 15 countries were analyzed. Staphylococcus aureus (37%), pathogenic Escherichia coli (16%), Listeria monocytogenes (6%), and Salmonella spp. (3%) were the most prevalent pathogens with a pooled prevalence estimate of 12%. Heterogeneity among prevalence estimates was attributed to sampling point and microbial group but could be moderated by publication year, country cluster, and methods for microbial confirmation. The pooled prevalence estimates increased over time as more studies became available, whereby the odds were higher in studies from 2010 onwards than studies before 2010. From the analyses, S. aureus presented the greatest safety concern in African IFM. Future microbiological studies should take into consideration different IFM sampling points and advanced analytical methods to identify pathogens. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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13 pages, 2020 KiB

Open AccessArticle

Effects on Gene Transcription Profile and Fatty Acid Composition by Genetic Modification of Mevalonate Diphosphate Decarboxylase MVD/Erg19 in Aspergillus Oryzae

by Zhihong Hu, Hui Huang, Yunlong Sun, Yali Niu, Wangzishuai Xu, Qicong Liu, Zhe Zhang, Chunmiao Jiang, Yongkai Li and Bin Zeng

Microorganisms 2019, 7(9), 342; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms7090342 - 11 Sep 2019

Cited by 3 | Viewed by 2673

Abstract

Mevalonate diphosphate decarboxylase MVD/Erg19 is required for ergosterol biosynthesis, growth, sporulation, and stress tolerance in Aspergillus oryzae. In this study, RNA-seq was used to analyze the gene transcription profile in AoErg19 overexpression (OE) and RNAi strains. There were 256 and 74 differentially expressed genes (DEGs) in AoErg19 OE and RNAi strains, respectively, compared with the control strain (CK). The most common DEGs were transport- and metabolism-related genes. Only 22 DEGs were obtained that were regulated in both OE and RNAi strains. The transcriptomic comparison between CK and AoErg19 overexpression strain (CK vs. OE), and between CK and AoErg19 RNAi strain (CK vs. RNAi) revealed that the greatest difference existed in the number of genes belonging to the cytochrome P450 family; 12 were found in CK vs. OE, whereas 1 was found in CK vs. RNAi. The expression patterns of lipid biosynthesis and metabolism related genes were altered in OE and RNAi strains, either by gene induction or suppression. Moreover, the total fatty acid content in the RNAi strain was 12.1% greater than the control strain, but no difference in total acid content was found between the overexpression strain and the control strain. Therefore, this study highlights the gene expression regulation within mevalonate (MVA), ergosterol biosynthesis, and fatty acid biosynthesis pathways. Full article

(This article belongs to the Special Issue Microbial Safety of Fermented Products)

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