Studying the dynamics of microbial populations during food fermentation

Exploring the effects of milk-enriched walnut soy sauce: Insights from GC-IMS and metagenomics approach to flavor and microbial shifts

This study investigates the impact of milk addition on the fermentation of walnut soy sauce, using Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) and metagenomics to analyze flavor profiles and microbial dynamics. GC-IMS analysis showed significant increases in volatile compounds such as esters (ethyl acetate), aldehydes (hexanal), and alcohols (isoamyl alcohol), enhancing the aroma and taste. Metagenomic analysis revealed that milk increased microbial diversity, with Weissella and Lactobacillus dominating early fermentation. The milk-enriched soy sauce (SYM) exhibited higher amino acid nitrogen (2.67 g/L), and total nitrogen (7.18 g/L) compared to the control, indicating improved nutritional quality. Protease activity peaked at 2438.5 U/g for neutral protease, supporting efficient protein hydrolysis. Relative Odor Activity Value (ROAV) analysis identified 29 key flavor compounds, including 3-methyl butanol and ethyl 2-methyl butyrate, which contributed fruity and buttery notes to SYM. These results suggest that milk enhances microbial growth and improves both flavor and nutritional quality of walnut soy sauce.

Directed Evolution of Microbial Communities in Fermented Foods: Strategies, Mechanisms, and Challenges

Directed Evolution of Microbial Communities (DEMC) offers a promising approach to enhance the functional attributes of microbial consortia in fermented foods by mimicking natural selection processes. This review details the application of DEMC in fermented foods, focusing on optimizing community traits to improve both fermentation efficiency and the sensory quality of the final products. We outline the core techniques used in DEMC, including the strategic construction of initial microbial communities, the systematic introduction of stress factors to induce desirable traits, and the use of artificial selection to cultivate superior communities. Additionally, we explore the integration of genomic tools and dynamic community analysis to understand and guide the evolutionary trajectories of these communities. While DEMC shows substantial potential for refining fermented food products, it faces challenges such as maintaining genetic diversity and functional stability of the communities. Looking ahead, the integration of advanced omics technologies and computational modeling is anticipated to significantly enhance the predictability and control of microbial community evolution in food fermentation processes. By systematically improving the selection and management of microbial traits, DEMC serves as a crucial tool for enhancing the quality and consistency of fermented foods, directly contributing to more robust and efficient food production systems.

A Review on the Interaction of Acetic Acid Bacteria and Microbes in Food Fermentation: A Microbial Ecology Perspective

In fermented foods, acetic acid bacteria (AAB), kinds of bacteria with a long history of utilization, contribute to safety, nutritional, and sensory properties primarily through acetic acid fermentation. AAB are commonly found in various fermented foods such as vinegar, sour beer, fermented cocoa and coffee beans, kefir beverages, kombucha, and sourdough. They interact and cooperate with a variety of microorganisms, resulting in the formation of diverse metabolites and the production of fermented foods with distinct flavors. Understanding the interactions between AAB and other microbes is crucial for effectively controlling and utilizing AAB in fermentation processes. However, these microbial interactions are influenced by factors such as strain type, nutritional conditions, ecological niches, and fermentation duration. In this review, we examine the relationships and research methodologies of microbial interactions and interaction studies between AAB and yeasts, lactic acid bacteria (LAB), and bacilli in different food fermentation processes involving these microorganisms. The objective of this review is to identify key interaction models involving AAB and other microorganisms. The insights gained will provide scientific guidance for the effective utilization of AAB as functional microorganisms in food fermentation processes.

Soybean fermentation: Microbial ecology and starter culture technology

Fermented soybean products, including Soya sauce, Tempeh, Miso, and Natto have been consumed for decades, mainly in Asian countries. Beans are processed using either solid-state fermentation, submerged fermentation, or a sequential of both methods. Traditional ways are still used to conduct the fermentation processes, which, depending on the fermented products, might take a few days or even years to complete. Diverse microorganisms were detected during fermentation in various processes with Bacillus species or filamentous fungi being the two main dominant functional groups. Microbial activities were essential to increase the bean's digestibility, nutritional value, and sensory quality, as well as lower its antinutritive factors. The scientific understanding of fermentation microbial communities, their enzymes, and their metabolic activities, however, still requires further development. The use of a starter culture is crucial, to control the fermentation process and ensure product consistency. A broad understanding of the spontaneous fermentation ecology, biochemistry, and the current starter culture technology is essential to facilitate further improvement and meet the needs of the current extending and sustainable economy. This review covers what is currently known about these aspects and reveals the limited available information, along with the possible directions for future starter culture design in soybean fermentation.

Estamaran date vinegar: chemical and microbial dynamics during fermentation

Vinegar is a fermented food produced by alcoholic and then acetic acid microbial metabolism. Date palm fruit (Phoenix dactylifera L.) is a valuable source for the production of vinegar. Microbial identification has a major role in the improvement and bio-management of the fermentation process of vinegar. Estamaran and Kabkab two varieties of date palm fruit were selected to study the fermentation process. A culture-dependent approach was used to study bacterial dynamics. 16 S rRNA gene was amplified by Polymerase Chain Reaction (PCR), also restriction enzyme analysis with HinfI and TaqI, and sequencing was done. Assessment of microbial flora of date palm fruit during fermentation showed that Fructobacillus tropaeoli, Bacillus sp., Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, and Weissella paramesenteroides existed in the first phase of fermentation. With fermentation progress, microbial diversity decreased so only one species remained. Komagataeibacter xylinus as an acid acetic producer was present in the third phase of fermentation. Based on chemical analysis, the concentration of reducing sugars decreased during fermentation. With decreasing pH, a simultaneous increase in acidity and total phenolic compounds occurred. The trend of changes during Estamaran fermentation was more severe and a vinegar with desirable properties was produced. Therefore, this date variety is recommended for the production of date vinegar.

Microbial Dynamics during labneh Ambaris Production in Earthenware Jars

The responses of various microbial populations to modifications in the physicochemical properties of a food matrix, as well as interactions between these populations already present, are the main factors that shape microbial dynamics in that matrix. This work focused on the study of microbial dynamics during labneh Ambaris production, a traditional Lebanese concentrated fermented goat milk made in jars during 3 months. This was assessed in two earthenware jars at a production facility. DNA metabarcoding of the ITS2 region as well as the V3-V4 region of the 16S rRNA gene was used to characterize the fungal and bacterial communities, respectively. Viable bacterial isolates were also identified by Sanger sequencing of the V1-V4 region of the 16S rRNA gene. Our results showed that the dominant microorganisms identified within labneh Ambaris (Lactobacillus kefiranofaciens, Lentilactobacillus kefiri, Lactococcus lactis, Geotrichum candidum, Pichia kudriavzevii and Starmerella sp.) settle early in the product and remain until the end of maturation with varying abundances throughout fermentation. Microbial counts increased during early fermentation stage, and remained stable during mid-fermentation, then declined during maturation. While microbial compositions were globally comparable between the two jars during mid-fermentation and maturation stages, differences between the two jars were mainly detected during early fermentation stage (D0 until D10). No significant sensorial differences were observed between the final products made in the two jars. Neither coliforms nor Enterobacteriaceae were detected in their viable state, starting D7 in both jars, suggesting the antimicrobial properties of the product.

Influence of Fermentation Container Type on Chemical and Microbiological Parameters of Spontaneously Fermented Cow and Goat Milk

Fermented goat milk is an artisanal beverage with excellent nutritional properties. There are limited data on its physicochemical properties, fatty acids, phenolic acids, and on any insight on microbiota. The aim of this research was to conduct a pilot study to compare these parameters in raw cow and goat milk before and after spontaneous fermentation in a clay pot and glass container at 37 °C for 24 h. Both types of milk and fermentation containers significantly affected the pH, acidity, proximate composition, viscosity, and whiteness index of fermented milks. A total of 17 fatty acids were identified in fermented milks, where palmitic, stearic, and myristic were the main saturated acids, and oleic and linoleic acids were the main unsaturated ones. These profiles were primarily influenced by the type of raw milk used. Three to five phenolic acids were identified in fermented milks, where quinic acid was the major phenolic compound, and salviolinic acid was identified only in raw goat milk. Preliminary metataxonomic sequencing analysis showed that the genera Escherichia spp. and Streptococcus spp. were part of the microbiota of both fermented milks, with the first genus being the most abundant in fermented goat milk, and Streptococcus in cow's milk. Moreover, Escherichia abundance was negatively correlated with the abundance of many genera, including Lactobacillus. Overall, the results of this pilot study showed significant variations between the physicochemical properties, the fatty and phenolic acids, and the microbial communities of goat and cow fermented milk, showing the opportunity to further investigate the tested parameters in fermented goat milk to promote its production.

Diet Diversification and Priming with Kunu: An Indigenous Probiotic Cereal-Based Non-Alcoholic Beverage in Nigeria

Kunu is a fermented non-alcoholic beverage consumed all over Nigeria. The drink is served as an alternative to alcohol due to its perceived extreme nourishing and therapeutic properties. Varieties of this beverage are determined mostly by the type of grain, the supplements, sensory additives used, and the process employed during its production. Dietary quality is paramount in nutritional well-being and a key factor in human overall health development. The nutritional quality of grains utilised for Kunu production makes the drink more appealing to a large growing population when compared to some other drinks. Some use Kunu drink as an infant weaning drink, thus serving as a priming beverage for infants due to its rich probiotic and nutritional properties. However, this beverage’s short shelf-life has limited its production scale. This review therefore elaborates succinctly on the diverse therapeutic nutritional properties of the Kunu beverage and the effect of additives and fermentation on the microbial dynamics during Kunu production, as well as the prospect of Kunu in diet diversification and priming for weaning infants.

Lactic acid bacteria in cow raw milk for cheese production: Which and how many?

Lactic Acid Bacteria (LAB) exert a fundamental activity in cheese production, as starter LAB in curd acidification, or non-starter LAB (NSLAB) during ripening, in particular in flavor formation. NSLAB originate from the farm and dairy environment, becoming natural contaminants of raw milk where they are present in very low concentrations. Afterward, throughout the different cheesemaking processes, they withstand chemical and physical stresses becoming dominant in ripened cheeses. However, despite a great body of knowledge is available in the literature about NSLAB effect on cheese ripening, the investigations regarding their presence and abundance in raw milk are still poor. With the aim to answer the initial question: "which and how many LAB are present in cow raw milk used for cheese production?," this review has been divided in two main parts. The first one gives an overview of LAB presence in the complex microbiota of raw milk through the meta-analysis of recent taxonomic studies. In the second part, we present a collection of data about LAB quantification in raw milk by culture-dependent analysis, retrieved through a systematic review. Essentially, the revision of data obtained by plate counts on selective agar media showed an average higher concentration of coccoid LAB than lactobacilli, which was found to be consistent with meta-taxonomic analysis. The advantages of the impedometric technique applied to the quantification of LAB in raw milk were also briefly discussed with a focus on the statistical significance of the obtainable data. Furthermore, this approach was also found to be more accurate in highlighting that microorganisms other than LAB are the major component of raw milk. Nevertheless, the variability of the results observed in the studies based on the same counting methodology, highlights that different sampling methods, as well as the "history" of milk before analysis, are variables of great importance that need to be considered in raw milk analysis.

The Impact of Different Inoculation Schemes on the Microbiota, Physicochemical and Sensory Characteristics of Greek Kopanisti Cheese throughout Production and Ripening

Kopanisti is a Greek PDO cheese, which is traditionally produced by the addition of an amount of over-mature Kopanisti, called Mana Kopanisti, to initiate cheese ripening. The aim of this study was the production of four types of Kopanisti cheese (A-D) using pasteurized cow milk, and a combination of the following starters/adjuncts in order to test their ability to be used in Kopanisti cheese production: A: Lactococcus lactis subsp. lactis and Lacticaseibacillus paracasei, B: L. lactis and Lc. paracasei/Mana Kopanisti, C: L. lactis and Lc. paracasei/Ligilactobacillus acidipiscis and Loigolactobacillus rennini, D: Lig. acidipiscis and Loig. rennini. Throughout production and ripening, classical microbiological, metataxonomics and physicochemical analyses were employed, while the final products (Day 35) were subjected to sensory analysis as well. Most interestingly, beta-diversity analysis of the metataxonomics data revealed the clusters constructed among the Kopanisti types based on the different inoculation schemes. On day 35, Kopanisti A-C types clustered together due to their similar 16S microbiota, while Kopanisti D was highly differentiated. On the contrary, ITS data clustered Kopanisti B and C together, while Kopanisti A and D were grouped seperately. Finally, based on the sensory evaluation, Kopanisti C appeared to have the most suitable bacteria cocktail for the Kopanisti cheese production. Therefore, not only were the conventional starters used, but also the Lig. acidipiscis and Loig. rennini strains could be used in a standardized Kopanisti cheese production that could lead to final products of high quality and safety.

The active core microbiota of two high-yielding laying hen breeds fed with different levels of calcium and phosphorus

The nutrient availability and supplementation of dietary phosphorus (P) and calcium (Ca) in avian feed, especially in laying hens, plays a vital role in phytase degradation and mineral utilization during the laying phase. The required concentration of P and Ca peaks during the laying phase, and the direct interaction between Ca and P concentration shrinks the availability of both supplements in the feed. Our goal was to characterize the active microbiota of the entire gastrointestinal tract (GIT) (crop, gizzard, duodenum, ileum, caeca), including digesta- and mucosa-associated communities of two contrasting high-yielding breeds of laying hens (Lohmann Brown Classic, LB; Lohmann LSL-Classic, LSL) under different P and Ca supplementation levels. Statistical significances were observed for breed, GIT section, Ca, and the interaction of GIT section x breed, P x Ca, Ca x breed and P x Ca x breed (p < 0.05). A core microbiota of five species was detected in more than 97% of all samples. They were represented by an uncl. Lactobacillus (average relative abundance (av. abu.) 12.1%), Lactobacillus helveticus (av. abu. 10.8%), Megamonas funiformis (av. abu. 6.8%), Ligilactobacillus salivarius (av. abu. 4.5%), and an uncl. Fusicatenibacter (av. abu. 1.1%). Our findings indicated that Ca and P supplementation levels 20% below the recommendation have a minor effect on the microbiota compared to the strong impact of the bird’s genetic background. Moreover, a core active microbiota across the GIT of two high-yielding laying hen breeds was revealed for the first time.

Fermented foods and cardiometabolic health: Definitions, current evidence, and future perspectives

Unhealthy diets contribute to the increasing burden of non-communicable diseases. Annually, over 11 million deaths worldwide are attributed to dietary risk factors, with the vast majority of deaths resulting from cardiometabolic diseases (CMDs) including cardiovascular disease (∼10 million) and type II diabetes (∼339,000). As such, defining diets and dietary patterns that mitigate CMD risk is of great public health importance. Recently, the consumption of fermented foods has emerged as an important dietary strategy for improving cardiometabolic health. Fermented foods have been present in the human diet for over 10,000 years, but knowledge on whether their consumption benefits human health, and the molecular and microbiological mechanisms underpinning their purported health benefits, is relatively nascent. This review provides an overview of the definitions of fermented foods, types and qualities of fermented foods consumed in Europe and globally, possible mechanisms between the consumption of fermented foods and cardiometabolic health, as well as the current state of the epidemiological evidence on fermented food intake and cardiometabolic health. Finally, we outline future perspectives and opportunities for improving the role of fermented foods in human diets.

Plant-Based Alkaline Fermented Foods as Sustainable Sources of Nutrients and Health-Promoting Bioactive Compounds

Traditional food fermentation is a practice that precedes human history. Acidic products such as yogurts and sourdoughs or alcoholic beverages produced through lactic acid or yeast fermentations, respectively, are widely described and documented. However, a relatively less popular group of fermented products known as alkaline fermented foods are common traditional products in Africa and Asia. These products are so called “alkaline” because the pH tends to increase during fermentation due to the formation of ammonia resulting from protein degradation by Bacillus species. Plant-based alkaline fermented foods (AFFs) are generally produced from legumes including soybean, non-soybean leguminous seeds, and other non-legume plant raw materials. Alkaline fermented food products such as natto, douchi, kinema, doenjang, chongkukjang, thua nao, meitauza, yandou, dawadawa/iru, ugba, kawal, okpehe, otiru, oso, ogiri, bikalga, maari/tayohounta, ntoba mbodi, cabuk, and owoh are produced at small industrial scale or household levels and widely consumed in Asia and Africa where they provide essential nutrients and health-promoting bioactive compounds for the population. Alkaline food fermentation is important for sustainable food security as it contributes to traditional dietary diversity, significantly reduces antinutritional components in raw plant materials thereby improving digestibility, improves health via the production of vitamins, and may confer probiotic and post-biotic effects onto consumers. In this review, we present currently available scientific information on plant-based AFFs and their role as sustainable sources of nutrients and bioactive compounds for improved health. Finally, we provide perspectives on research needs required to harness the full potential of AFFs in contributing to nutrition and health.

Fermented Foods and Their Role in Respiratory Health: A Mini-Review

Fermented foods (FFs) hold global attention because of their huge advantages. Their health benefits, palatability, preserved, tasteful, and aromatic properties impart potential importance in the comprehensive evaluation of FFs. The bioactive components, such as minerals, vitamins, fatty acids, amino acids, and other phytochemicals synthesized during fermentation, provide consumers with several health benefits. Fermentation of food is an ancient process that has met with many remarkable changes owing to the development of scientific technologies over the years. Initially, fermentation relied on back-slapping. Nowadays, starter cultures strains are specifically chosen for the type of fermentation process. Modern biotechnological methods are being implemented in the fermentation process to achieve the desired product in high quality. Respiratory and gastrointestinal tract infections are the most severe health issues affecting human beings of all age groups, especially children and older adults, during this COVID-19 pandemic period. Studies suggest that the consumption of probiotic Lactobacillus strains containing fermented foods protects the subjects from common infectious diseases (CIDs, which is classified as upper respiratory tract infections, lower respiratory tract infections and gastrointestinal infections) by improving the host’s immune system. Further studies are obligatory to develop probiotic-based functional FFs that are effective against CIDs. Presently, we are urged to find alternative, safe, and cost-effective prevention measures against CIDs. The current manuscript briefs the production of FFs, functional properties of FFs, and their beneficial effects against respiratory tract infections. It summarizes the outcomes of clinical trials using human subjects on the effects of supplementation of FFs.

Deciphering the Microbiota and Volatile Profiles of Algerian Smen, a Traditional Fermented Butter

In Algeria, Smen is a fermented butter produced in households using empirical methods. Smen fermentation is driven by autochthonous microorganisms; it improves butter shelf-life and yields highly fragrant products used as ingredients in traditional dishes as well as in traditional medicine. The present study is aimed at investigating microbial diversity and dynamics during Algerian Smen fermentation using both culture-dependent and culture-independent approaches, as well as by monitoring volatile organic compound production. To reach this goal, fifteen Smen samples (final products) produced in households from different regions in Algeria were collected and analyzed. In addition, microbial and volatile compound dynamics at the different stages of Smen manufacturing were investigated for one Smen preparation. The results showed that Smen is a microbiologically safe product, as all hygiene and safety criteria were respected. The dominant microorganisms identified by both techniques were LAB and yeasts. Lactococcus spp. and Streptococcus thermophilus were the main bacterial species involved in spontaneous raw milk fermentation preceding butter-making, while lactobacilli and enterococci were the only bacteria found to be viable during Smen maturation. Regarding fungal diversity, yeast species were only recovered from two mature Smen samples by culturing, while different species (e.g., Geotrichum candidum, Moniliella sp.) were identified in all samples by the culture-independent approach. Using microbial analysis of a single batch, many of these were found viable during manufacturing. Concerning the volatile profiles, they were highly diverse and characterized by a high prevalence of short chain fatty acids, methylketones, and esters. Correlation analysis between microbial diversity and volatile profiles showed that several yeast (Moniliella sp., K. marxianus) and LAB (e.g., Lactococcus spp., S. thermophilus) species were strongly correlated with one or more volatile organic compound families, including several ethyl esters and methyl ketones that can be linked to pleasant, sweetly floral, fruity, buttery, and creamy odors. This study clearly identified key microorganisms involved in Smen fermentation and maturation that could be used in the future for better fermentation control and improvement of quality attributes.

Microbial Quality and Growth Dynamics in Shameta: A Traditional Ethiopian Cereal-Based Fermented Porridge

Shameta is a traditional, Ethiopian, cereal-based fermented porridge exclusively prepared for lactating mothers. The aim of this study was to determine the microbial quality of Shameta samples collected from households of lactating mothers and to determine microbial dynamics and physicochemical changes during laboratory fermentation of Shameta. Isolation and characterization of the dominant microbes and analysis of the physicochemical properties of samples were done following standard microbiological methods and analytical techniques. Results of this study showed that the highest mean count of lactic acid bacteria (8.33 log cfu/g) was recorded in a sample from laboratory-fermented barley-based Shameta, and the lowest (5.88 log cfu/g) in Shameta made from a mixture of barley and maize (BMS). In both barley-based and maize-based laboratory-prepared Shameta, the microflora were dominated by LAB, followed by yeasts. The dominant LAB were the genus Lactobacillus (74.85%), followed by Enterococcus (15.79%). It could be concluded that Shameta collected from households of lactating mothers are fairly safe for consumption, as the stringent physicochemical conditions of the final product could inhibit the growth of pathogens. However, as Shameta is a traditional fermented porridge fed to lactating mothers, we call for a further improvement to the fermentation process by using defined starter cultures.

High-throughput qPCR and 16S rRNA gene amplicon sequencing as complementary methods for the investigation of the cheese microbiota

Background

Next-generation sequencing (NGS) methods and especially 16S rRNA gene amplicon sequencing have become indispensable tools in microbial ecology. While they have opened up new possibilities for studying microbial communities, they also have one drawback, namely providing only relative abundances and thus compositional data. Quantitative PCR (qPCR) has been used for years for the quantification of bacteria. However, this method requires the development of specific primers and has a low throughput. The constraint of low throughput has recently been overcome by the development of high-throughput qPCR (HT-qPCR), which allows for the simultaneous detection of the most prevalent bacteria in moderately complex systems, such as cheese and other fermented dairy foods. In the present study, the performance of the two approaches, NGS and HT-qPCR, was compared by analyzing the same DNA samples from 21 Raclette du Valais protected designation of origin (PDO) cheeses. Based on the results obtained, the differences, accuracy, and usefulness of the two approaches were studied in detail.

Results

The results obtained using NGS (non-targeted) and HT-qPCR (targeted) show considerable agreement in determining the microbial composition of the cheese DNA samples studied, albeit the fundamentally different nature of these two approaches. A few inconsistencies in species detection were observed, particularly for less abundant ones. The detailed comparison of the results for 15 bacterial species/groups measured by both methods revealed a considerable bias for certain bacterial species in the measurements of the amplicon sequencing approach. We identified as probable origin to this PCR bias due to primer mismatches, variations in the number of copies for the 16S rRNA gene, and bias introduced in the bioinformatics analysis.

Conclusion

As the normalized microbial composition results of NGS and HT-qPCR agreed for most of the 21 cheese samples analyzed, both methods can be considered as complementary and reliable for studying the microbial composition of cheese. Their combined application proved to be very helpful in identifying potential biases and overcoming methodological limitations in the quantitative analysis of the cheese microbiota.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02451-y.

Evolution of Food Fermentation Processes and the Use of Multi-Omics in Deciphering the Roles of the Microbiota

Food fermentation has been practised since ancient times to improve sensory properties and food preservation. This review discusses the process of fermentation, which has undergone remarkable improvement over the years, from relying on natural microbes and spontaneous fermentation to back-slopping and the use of starter cultures. Modern biotechnological approaches, including genome editing using CRISPR/Cas9, have been investigated and hold promise for improving the fermentation process. The invention of next-generation sequencing techniques and the rise of meta-omics tools have advanced our knowledge on the characterisation of microbiomes involved in food fermentation and their functional roles. The contribution and potential advantages of meta-omics technologies in understanding the process of fermentation and examples of recent studies utilising multi-omics approaches for studying food-fermentation microbiomes are reviewed. Recent technological advances in studying food fermentation have provided insights into the ancient wisdom in the practice of food fermentation, such as the choice of substrates and fermentation conditions leading to desirable properties. This review aims to stimulate research on the process of fermentation and the associated microbiomes to produce fermented food efficiently and sustainably. Prospects and the usefulness of recent advances in molecular tools and integrated multi-omics approaches are highlighted.

Genotypic and Phenotypic Characterization of Highly Alkaline-Resistant Carnobacterium maltaromaticum V-Type ATPase from the Dairy Product Based on Comparative Genomics

Although Carnobacterium maltaromaticum derived from dairy products has been used as a lactic acid bacterium industrially, several studies have reported potential pathogenicity and disease outbreaks. Because strains derived from diseased fish and dairy products are considered potentially virulent and beneficial, respectively, their genotypic and phenotypic characteristics have attracted considerable attention. A genome-wide comparison of 30 genome sequences (13, 3, and 14 strains from diseased aquatic animals, dairy products, and processed food, respectively) was carried out. Additionally, one dairy and two nondairy strains were incubated in nutrient-rich (diluted liquid media) and nutrient-deficient environments (PBS) at pH 10 to compare their alkaline resistance in accordance with different nutritional environments by measuring their optical density and viable bacterial cell counts. Interestingly, only dairy strains carried 11 shared accessory genes, and 8 genes were strongly involved in the V-type ATPase gene cluster. Given that V-type ATPase contributes to resistance to alkaline pH and salts using proton motive force generated via sodium translocation across the membrane, C. maltaromaticum with a V-type ATPase might use nutrients in food under high pH. Indeed, the dairy strain carrying the V-type ATPase exhibited the highest alkaline resistance only in the nutrient-rich environment with significant upregulation of V-type ATPase expression. These results suggest that the gene cluster of V-type ATPase and increased alkaline resistance of dairy strains facilitate adaptation in the long-term ripening of alkaline dairy products.

The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods

An expert panel was convened in September 2019 by The International Scientific Association for Probiotics and Prebiotics (ISAPP) to develop a definition for fermented foods and to describe their role in the human diet. Although these foods have been consumed for thousands of years, they are receiving increased attention among biologists, nutritionists, technologists, clinicians and consumers. Despite this interest, inconsistencies related to the use of the term 'fermented' led the panel to define fermented foods and beverages as "foods made through desired microbial growth and enzymatic conversions of food components". This definition, encompassing the many varieties of fermented foods, is intended to clarify what is (and is not) a fermented food. The distinction between fermented foods and probiotics is further clarified. The panel also addressed the current state of knowledge on the safety, risks and health benefits, including an assessment of the nutritional attributes and a mechanistic rationale for how fermented foods could improve gastrointestinal and general health. The latest advancements in our understanding of the microbial ecology and systems biology of these foods were discussed. Finally, the panel reviewed how fermented foods are regulated and discussed efforts to include them as a separate category in national dietary guidelines.

Metataxonomic analysis of bacterial communities and mycotoxin reduction during processing of three millet varieties into ogi, a fermented cereal beverage

Ogi is a fermented cereal beverage, made primarily from maize (Zea mays) and rarely from millets. Unlike maize-based ogi, little is known about the bacterial community and mycotoxin profile during the production of millet-based ogi. Therefore, the bacterial community dynamics and mycotoxin reduction during ogi processing from three millet varieties were investigated using next-generation sequencing of the 16S rRNA gene and liquid chromatography-tandem mass spectrometry, respectively. A total of 1163 amplicon sequence variants (ASVs) were obtained, with ASV diversity across time intervals influenced by processing stage and millet variety. ASV distribution among samples suggested that the souring stage was more influenced by millet variety than the steeping stage, and that souring may be crucial for the quality attributes of the ogi. Furthermore, bacterial community structure during steeping and souring was significantly differentiated (PERMANOVA, P < 0.05) between varieties, with close associations observed for closely-related millet varieties. Taxonomically, Firmicutes, followed by Actinobacteria, Bacteroidetes, Cyanobacteria and Proteobacteria phyla were relatively abundant (>1%). Lactic acid bacteria, such as Burkholderia-Caballeronia-Paraburkholderia, Lactobacillus, Lactococcus and Pediococcus, dominated most fermentation stages, suggesting their roles as key fermentative and functional bacteria in relation to mycotoxin reduction. About 52-100%, 58-100% and 100% reductions in mycotoxin (aflatoxins, beauvericin, citrinin, moniliformin, sterigmatocystin and zearalenone) concentrations were recorded after processing of white fonio, brown fonio and finger millet, respectively, into ogi. This study provides new knowledge of the dominant bacterial genera vital for the improvement of millet-based ogi through starter culture development and as well, elucidates the role of processing in reducing mycotoxins in millet ogi.

Ethiopian Indigenous Traditional Fermented Beverage: The Role of the Microorganisms toward Nutritional and Safety Value of Fermented Beverage

Ethiopia is one of the countries where a wide variety of traditional fermented beverages are produced and consumed for a long time. Traditional fermented beverages are those which are indigenous to a particular area and have been developed by the people using age-old techniques from locally available raw materials. Some of Ethiopian indigenous traditional fermented beverages products are Cheka, Keribo, Borde, Areki, Tella, Shamita, Booka, and Korefe, in which fermentation is natural and involves mixed cultures of microbes. The most common fermenting microorganisms, lactic acid bacteria and yeast, are used as probiotics, for improvement of organoleptic properties, for provision of nutritional quality and biopreservative. The nature of beverage preparation in Ethiopia, traditional household processing, associated microorganisms with a fermented beverage, and their contribution toward improving the nutritional value and safety, the extent, and its prospect in supporting the livelihood of people in Ethiopia need concern. Therefore, in the future, to improve its quality, it is important to standardize the methods of beverage fermentation processes.

Development of a High-Throughput Microfluidic qPCR System for the Quantitative Determination of Quality-Relevant Bacteria in Cheese

The composition of the cheese microbiome has an important impact on the sensorial quality and safety of cheese. Therefore, much effort has been made to investigate the microbial community composition of cheese. Quantitative real-time polymerase chain reaction (qPCR) is a well-established method for detecting and quantifying bacteria. High-throughput qPCR (HT-qPCR) using microfluidics brings further advantages by providing fast results and by decreasing the cost per sample. We have developed a HT-qPCR approach for the rapid and cost-efficient quantification of microbial species in cheese by designing qPCR assays targeting 24 species/subspecies commonly found in cheese. Primer pairs were evaluated on the Biomark (Fluidigm) microfluidic HT-qPCR system using DNA from single strains and from artificial mock communities. The qPCR assays worked efficiently under identical PCR conditions, and the validation showed satisfying inclusivity, exclusivity, and amplification efficiencies. Preliminary results obtained from the HT-qPCR analysis of DNA samples of model cheeses made with the addition of adjunct cultures confirmed the potential of the microfluidic HT-qPCR system to screen for selected bacterial species in the cheese microbiome. HT-qPCR data of DNA samples of two downgraded commercial cheeses showed that this approach provides valuable information that can help to identify the microbial origin of quality defects. This newly developed HT-qPCR system is a promising approach that will allow simultaneous monitoring of quality-relevant species in fermented foods with high bacterial diversity, thereby opening up new perspectives for the control and assurance of high product quality.

Fermentative Foods: Microbiology, Biochemistry, Potential Human Health Benefits and Public Health Issues

Fermented foods identify cultures and civilizations. History, climate and the particulars of local production of raw materials have urged humanity to exploit various pathways of fermentation to produce a wide variety of traditional edible products which represent adaptations to specific conditions. Nowadays, industrial-scale production has flooded the markets with ferments. According to recent estimates, the current size of the global market of fermented foods is in the vicinity of USD 30 billion, with increasing trends. Modern challenges include tailor-made fermented foods for people with special dietary needs, such as patients suffering from Crohn's disease or other ailments. Another major challenge concerns the safety of artisan fermented products, an issue that could be tackled with the aid of molecular biology and concerns not only the presence of pathogens but also the foodborne microbial resistance. The basis of all these is, of course, the microbiome, an aggregation of different species of bacteria and yeasts that thrives on the carbohydrates of the raw materials. In this review, the microbiology of fermented foods is discussed with a special reference to groups of products and to specific products indicative of the diversity that a fermentation process can take. Their impact is also discussed with emphasis on health and oral health status. From Hippocrates until modern approaches to disease therapy, diet was thought to be of the most important factors for health stability of the human natural microbiome. After all, to quote Pasteur, "Gentlemen, the microbes will have the last word for human health." In that sense, it is the microbiomes of fermented foods that will acquire a leading role in future nutrition and therapeutics.

Variation of Microbiological and Biochemical Profiles of Laowo Dry-Cured Ham, an Indigenous Fermented Food, during Ripening by GC-TOF-MS and UPLC-QTOF-MS

Fermented foods have unique microbiota and metabolomic profiles that can support dietary diversity, digestion, and gut health of consumers. Laowo ham (LWH) is an example of an indigenous fermented food from Southwestern China that has cultural, ecological, economic, and health significance to local communities. We carried out ethnobiological surveys coupled with metagenomic and metabolomic analyses using GC-TOF-MS and UPLC-QTOF-MS to elucidate the microbiota and metabolic profiles of LWH samples at different ripening stages. The results from high-throughput sequencing showed a total of 502 bacterial genera in LWH samples with 12 genera of bacteria and 6 genera of fungi identified as dominant groups. This is the first study to our knowledge to report the bacteria of Lentibacillus and Mesorhizobium along with fungi Eremascus and Xerochrysium on a fermented meat product. Findings further revealed that the metabolite profiles among LWH samples were significantly different. In total, 27 and 30 metabolites from GC-TOF-MS and UPLC-QTOF-MS analysis, respectively, were annotated as highly discriminative metabolites. Among the differential compounds, the relative contents of most amino acids showed the highest in the LWH sample ripened for two years, while some metabolites with potential therapeutic effects such as levetiracetam were the most abundant in the LWH sample ripened for three years. The correlation analysis indicated that the dominant microbes were closely related to differential metabolites, highlighting the importance of their functional characterization. Findings indicate that the consumption of LWH contributes to microbiological and chemical diversity of human diets as well as suggests efficacy of combining GC-MS and LC-MS to study the metabolites in dry-cured meat products.

A Review on Adventitious Lactic Acid Bacteria from Table Olives

Spontaneous fermentation constitutes the basis of the chief natural method of processing of table olives, where autochthonous strains of lactic acid bacteria (LAB) play a dominant role. A thorough literature search has unfolded 197 reports worldwide, published in the last two decades, that indicate an increasing interest in table olive-borne LAB, especially in Mediterranean countries. This review attempted to extract extra information from such a large body of work, namely, in terms of correlations between LAB strains isolated, manufacture processes, olive types, and geographical regions. Spain produces mostly green olives by Spanish-style treatment, whereas Italy and Greece produce mainly green and black olives, respectively, by both natural and Spanish-style. More than 40 species belonging to nine genera of LAB have been described; the genus most often cited is Lactobacillus, with L. plantarum and L. pentosus as most frequent species—irrespective of country, processing method, or olive type. Certain LAB species are typically associated with cultivar, e.g., Lactobacillus parafarraginis with Spanish Manzanilla, or L. paraplantarum with Greek Kalamata and Conservolea, Portuguese Galega, and Italian Tonda di Cagliari. Despite the potential of native LAB to serve as starter cultures, extensive research and development efforts are still needed before this becomes a commercial reality in table olive fermentation.

Microbiome definition re-visited: old concepts and new challenges

The field of microbiome research has evolved rapidly over the past few decades and has become a topic of great scientific and public interest. As a result of this rapid growth in interest covering different fields, we are lacking a clear commonly agreed definition of the term "microbiome." Moreover, a consensus on best practices in microbiome research is missing. Recently, a panel of international experts discussed the current gaps in the frame of the European-funded MicrobiomeSupport project. The meeting brought together about 40 leaders from diverse microbiome areas, while more than a hundred experts from all over the world took part in an online survey accompanying the workshop. This article excerpts the outcomes of the workshop and the corresponding online survey embedded in a short historical introduction and future outlook. We propose a definition of microbiome based on the compact, clear, and comprehensive description of the term provided by Whipps et al. in 1988, amended with a set of novel recommendations considering the latest technological developments and research findings. We clearly separate the terms microbiome and microbiota and provide a comprehensive discussion considering the composition of microbiota, the heterogeneity and dynamics of microbiomes in time and space, the stability and resilience of microbial networks, the definition of core microbiomes, and functionally relevant keystone species as well as co-evolutionary principles of microbe-host and inter-species interactions within the microbiome. These broad definitions together with the suggested unifying concepts will help to improve standardization of microbiome studies in the future, and could be the starting point for an integrated assessment of data resulting in a more rapid transfer of knowledge from basic science into practice. Furthermore, microbiome standards are important for solving new challenges associated with anthropogenic-driven changes in the field of planetary health, for which the understanding of microbiomes might play a key role. Video Abstract.

Unraveling the Microbiota of Natural Black cv. Kalamata Fermented Olives through 16S and ITS Metataxonomic Analysis

Kalamata natural black olives are one of the most economically important Greek varieties. The microbial ecology of table olives is highly influenced by the co-existence of bacteria and yeasts/fungi, as well as the physicochemical parameters throughout the fermentation. Therefore, the aim of this study was the identification of bacterial and yeast/fungal microbiota of both olives and brines obtained from 29 cv. Kalamata olive samples industrially fermented in the two main producing geographical regions of Greece, namely Aitoloakarnania and Messinia/Lakonia. The potential microbial biogeography association between certain taxa and geographical area was also assessed. The dominant bacterial family identified in olive and brine samples from both regions was Lactobacillaceae, presenting, however, higher average abundances in the samples from Aitoloakarnania compared to Messinia/Lakonia. At the genus level, Lactobacillus, Celerinatantimonas, Propionibacterium and Pseudomonas were the most abundant. In addition, the yeasts/fungal communities were less diverse compared to those of bacteria, with Pichiaceae being the dominant family and Pichia, Ogataea, and Saccharomyces being the most abundant genera. To the best of our knowledge, this is the first report on the microbiota of both olives and brines of cv. Kalamata black olives fermented on an industrial scale between two geographical regions of Greece using metagenomics analysis.

Directional design of a starter to assemble the initial microbial fermentation community of baijiu

Tetramethylpyrazine (TTMP) is an important aroma compound in the sesame-flavored Chinese liquor, baijiu. Similar to other traditional spontaneously fermented foods, it is difficult to directionally increase the key aroma compound in situ fermentation system of baijiu without changing its sensory profile. The assembly of the starting microbial community for fermentation by using a functional starter provides a promising solution which needs careful manipulations. This study aimed to increase TTMP concentration in baijiu using the functional starter inoculated with the indigenous strain B. amyloliquefaciens XJB-104 with high TTMP production ability. After inoculation, the relative abundance of Bacillus in the initial stage of fermentation increased from 82.14% to 88.47%. The TTMP concentration increased by about 26 and 24-fold in the fermented grains (zaopei) and baijiu respectively compared with controls. Moreover, the quality of baijiu was improved according to sensory analyses. In addition, correlation analysis confirmed that the increased TTMP content in baijiu was due to the successful assembly of the initial fermentation microbiota after the inoculation of B. amyloliquefaciens.

Wasted Bread as Substrate for the Cultivation of Starters for the Food Industry

The amount of bread wasted daily worldwide, throughout its entire lifecycle, from production to distribution, is estimated to be hundreds of tons, therefore representing both economic and environmental issues. This work aimed at the valorization of wasted bread, setting-up a protocol for obtaining a growth medium to be used for the cultivation of food industry microbial starters. The optimization of the protocol included the set-up of parameters for the hydrolysis of the bread nutrient compounds with proteolytic and amylolytic enzymes and the supplementation with nitrogen and/or carbon sources. The suitability of the optimized medium for the growth of lactic acid bacteria, yeasts and fungi from dairy, bakery, and wine industries was assessed. Lactic acid bacteria growth was strongly affected by the quantity and quality of nitrogen sources employed, while yeasts and fungi growth exceeded that obtained with the reference media commonly employed for their cultivation. Wasted bread medium (WBM) represents a realistic option for the valorization and re-use of bread waste, responding to the modern vision of circular economy.

Fermented foods in a global age: East meets West

Fermented foods and alcoholic beverages have long been an important part of the human diet in nearly every culture on every continent. These foods are often well-preserved and serve as stable and significant sources of proteins, vitamins, minerals, and other nutrients. Despite these common features, however, many differences exist with respect to substrates and products and the types of microbes involved in the manufacture of fermented foods and beverages produced globally. In this review, we describe these differences and consider the influence of geography and industrialization on fermented foods manufacture. Whereas fermented foods produced in Europe, North America, Australia, and New Zealand usually depend on defined starter cultures, those made in Asia and Africa often rely on spontaneous fermentation. Likewise, in developing countries, fermented foods are not often commercially produced on an industrial scale. Although many fermented products rely on autochthonous microbes present in the raw material, for other products, the introduction of starter culture technology has led to greater consistency, safety, and quality. The diversity and function of microbes present in a wide range of fermented foods can now be examined in detail using molecular and other omic approaches. The nutritional value of fermented foods is now well-appreciated, especially in resource-poor regions where yoghurt and other fermented foods can improve public health and provide opportunities for economic development. Manufacturers of fermented foods, whether small or large, should follow Good Manufacturing Practices and have sustainable development goals. Ultimately, preferences for fermented foods and beverages depend on dietary habits of consumers, as well as regional agricultural conditions and availability of resources.

Raw Material Regulates Flavor Formation via Driving Microbiota in Chinese Liquor Fermentation

Raw material is important for flavors in fermented foods. Here, the effect of hulless barley on the microbiota in Chinese liquor was studied using two main cultivars (heilaoya and dulihuang). Six genera (Lactobacillus, Saccharomyces, Komagataella, Aspergillus, Pichia, and Weissella) were identified as flavor producers. Komagataella, mainly correlated with esters, dominated in heilaoya, and Pichia, mainly correlated with carbonyls, dominated in dulihuang. The Mantel test indicated reducing sugar drove the succession of microbiota (heilaoya: P = 0.001; dulihuang: P = 0.006). Especially, glucose (P = 0.0226) and fructose (P = 0.0168) presented the most significant correlations with Pichia and Komagataella, respectively. The simulative fermentation confirmed Komagataella phaffii QK2 grew better in heilaoya with more fructose, whereas Pichia fermentans PF grew better in dulihuang with more glucose. This work highlighted the effect of raw material on microbiota, which would be beneficial for regulating the quality of fermented foods.

Construction of Synthetic Microbiota for Reproducible Flavor Compound Metabolism in Chinese Light-Aroma-Type Liquor Produced by Solid-State Fermentation

Natural microbiota plays an essential role in flavor compounds used in traditional food fermentation; however, the fluctuation in natural microbiota results in inconsistency in food quality. Thus, it is critical to reveal the core microbiota for flavor compound production and to construct a synthetic core microbiota for use in constant food fermentation. Here, we reveal the core microbiota based on their flavor production and cooccurrence performance, using Chinese light-aroma-type liquor as a model system. Five genera, Lactobacillus, Saccharomyces, Pichia, Geotrichum, and Candida, were identified to be the core microbiota. The synthetic core microbiota of these five genera presented a reproducible dynamic profile similar to that in the natural microbiota. A Monte Carlo test showed that the effects of five environmental factors (lactic acid, ethanol, and acetic acid contents, moisture, and pH) on the synthetic microbiota distribution were highly significant (P < 0.01), similar to those effects on a natural fermentation system. In addition, 77.27% of the flavor compounds produced by the synthetic core microbiota showed a similar dynamic profile (ρ > 0) with that in the natural liquor fermentation process, and the flavor profile presented a similar composition. It indicated that the synthetic core microbiota is efficient for reproducible flavor metabolism. This work established a method for identifying core microbiota and constructing a synthetic microbiota for reproducible flavor compounds. This work is of great significance for the tractable and constant production of various fermented foods.IMPORTANCE The transformation from natural fermentation to synthetic fermentation is essential in constructing a constant food fermentation process, which is the premise for stably making high-quality food. According to flavor-producing and cooccurring functions in dominant microbes, we provided a system-level approach to identify the core microbiota in Chinese light-aroma-type liquor fermentation. In addition, we successfully constructed a synthetic core microbiota to simulate the microbial community succession and flavor compound production in the in vitro system. The constructed synthetic core microbiota could not only facilitate a mechanistic understanding of the structure and function of the microbiota but also be beneficial for constructing a tractable and reproducible food fermentation process.

Influence of Pickling Process on Allium cepa and Citrus limon Metabolome as Determined via Mass Spectrometry-Based Metabolomics

Brine, the historically known food additive salt solution, has been widely used as a pickling media to preserve flavor or enhance food aroma, appearance, or other qualities. The influence of pickling, using brine, on the aroma compounds and the primary and secondary metabolite profile in onion bulb Allium cepa red cv. and lemon fruit Citrus limon was evaluated using multiplex metabolomics technologies. In lemon, pickling negatively affected its key odor compound “citral”, whereas monoterpene hydrocarbons limonene and γ-terpinene increased in the pickled product. Meanwhile, in onion sulphur rearrangement products appeared upon storage, i.e., 3,5-diethyl-1,2,4-trithiolane. Profiling of the polar secondary metabolites in lemon fruit via ultra-performance liquid chromatography coupled to MS annotated 37 metabolites including 18 flavonoids, nine coumarins, five limonoids, and two organic acids. With regard to pickling impact, notable and clear separation among specimens was observed with an orthogonal projections to least squares-discriminant analysis (OPLS-DA) score plot for the lemon fruit model showing an enrichment of limonoids and organic acids and that for fresh onion bulb showing an abundance of flavonols and saponins. In general, the pickling process appeared to negatively impact the abundance of secondary metabolites in both onion and lemon, suggesting a decrease in their food health benefits.

Draft genome sequence data of Lactobacillus paracasei strain DTA83 isolated from infant stools

Here the draft genome sequence of Lactobacillus paracasei strain DTA83, isolated from stools of healthy infants in Rio de Janeiro (Brazil), is reported. The 2.8-Mb genome possesses 2825 protein-coding sequences distributed on 330 SEED subsystems. This strain belongs to a set of potentially probiotic Lactobacillus spp. strains used to study genetic factors related to antibiotic resistance after stress conditions, such as simulated gastrointestinal conditions. The complete genome data have been deposited in GenBank under the accession number QRBH00000000, https://www.ncbi.nlm.nih.gov/nuccore/QRBH00000000.

High-Throughput Sequence Analyses of Bacterial Communities and Multi-Mycotoxin Profiling During Processing of Different Formulations of Kunu, a Traditional Fermented Beverage

Kunu is a traditional fermented single or mixed cereals-based beverage popularly consumed in many parts of West Africa. Presently, the bacterial community and mycotoxin contamination profiles during processing of various kunu formulations have never been comprehensively studied. This study, therefore, investigated the bacterial community and multi-mycotoxin dynamics during the processing of three kunu formulations using high-throughput sequence analysis of partial 16S rRNA gene (hypervariable V3-V4 region) and liquid chromatography tandem mass spectrometry (LC-MS/MS), respectively. A total of 2,303 operational taxonomic units (OTUs) were obtained across six processing stages in all three kunu formulations. Principal coordinate analysis biplots of the Bray-Curtis dissimilarity between bacterial communities revealed the combined influences of formulations and processing steps. Taxonomically, OTUs spanned 13 phyla and 486 genera. Firmicutes (phylum) dominated (relative abundance) most of the processing stages, while Proteobacteria dominated the rest of the stages. Lactobacillus (genus taxa level) dominated most processing stages and the final product (kunu) of two formulations, whereas Clostridium sensu stricto (cluster 1) dominated kunu of one formulation, constituting a novel observation. We further identified Acetobacter, Propionibacterium, Gluconacetobacter, and Gluconobacter previously not associated with kunu processing. Shared phylotypes between all communities were dominated by lactic acid bacteria including species of Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, and Weissella. Other shared phylotypes included notable acetic acid bacteria and potential human enteric pathogens. Ten mycotoxins [3-Nitropropionic acid, aflatoxicol, aflatoxin B1 (AFB1), AFB2, AFM1, alternariol (AOH), alternariolmethylether (AME), beauvericin (BEAU), citrinin, and moniliformin] were quantified at varying concentrations in ingredients for kunu processing. Except for AOH, AME, and BEAU that were retained at minimal levels of < 2 μg/kg in the final product, most mycotoxins in the ingredients were not detectable after processing. In particular, mycotoxin levels were substantially reduced by fermentation, although simple dilution and sieving also contributed to mycotoxin reduction. This study reinforces the perception of kunu as a rich source of bacteria with beneficial attributes to consumer health, and provides in-depth understanding of the microbiology of kunu processing, as well as information on mycotoxin contamination and reduction during this process. These findings may aid the development of starter culture technology for safe and quality kunu production.

Purification and characterization of alkaline phosphatase from lactic acid bacteria

Alkaline phosphatase (ALP) excreted from lactic acid bacteria (LAB) showed the ability to degrade organophosphorus pesticides. This study reported the first purification and characterization of ALP from LAB. The molecular weight of ALP was estimated to be 43 kDa measured by SDS-PAGE. The activity of purified enzyme was determined with the binding of p-nitrophenyl phosphate as the substrate. The results showed that the optimal temperature for ALP activity was 37 °C, and the optimal pH was 8.5. But ALP was stable at temperatures below 32 °C. The ALP activity remained at 80% when the pH was 8-9.5. The enzyme activity could be activated by Mg2+, Ca2+, and inhibited by Cu2+, Zn2+, and EDTA. The Michaelis-Menten constant was 6.05 mg kg-1 with dimethoate as the substrate according to the Lineweaver-Burk plots. These results highlight an important potential use of ALP from LAB for the cleanup of pesticide pollution in raw materials for the food industry.

Monitoring of assertive Lactobacillus sakei and Lactobacillus curvatus strains using an industrial ring trial experiment

AIMS

In a previous study, we used a 5-day fermenting sausage model to characterize assertiveness of Lactobacillus curvatus and Lactobacillus sakei starter strains towards employ autochthonous contaminants. In this work, we probed those findings and their transferability to real sausage fermentation including the drying process in an industrial ring trial experiment.

METHODS AND RESULTS

Raw fermented sausages ('salami') were produced with three L. curvatus and four L. sakei strains as starter cultures in cooperation with three manufacturers from Germany. We monitored pH, water activity and microbiota dynamics at strain level over a total fermentation and ripening time of 21 days by MALDI-TOF-MS identification of isolates. The principal behaviour of the strains in real sausage fermentations was the same as that one observed in the 5-day model system delineating single strain assertiveness of a bacteriocin producer from co-dominance of strains.

CONCLUSIONS

The water activity decrease, which is concomitant with the sausage ripening process has only limited impact on the assertiveness and survival of the starter strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results of a 5-day model can provide insight in the assertiveness of a specific starter strain in sausage fermentation.

Bacterial community analysis in three types of the fermented seafood, jeotgal, produced in South Korea

Jeotgal is a traditional Korean seafood fermented by indigenous microbes. The bacterial community in five myeolchi-jeot (Engraulis japonica), five meongge-jeot (Halocynthia roretzi), and six saeu-jeot (Acetes japonicas) produced in South Korea was analyzed by barcoded pyrosequencing targeting the V1/V2 hyper-variable regions of the 16S rRNA gene. All samples were dominated by the phyla Firmicutes, which represented 67.7% (SD = 27.2%) of the population. Tetragenococcus halophilus and Tetragenococcus muriaticus were the predominant species in myeolchi-jeot. The LABs, Lactobacillus sakei, Lactobacillus curvatus, and Weissella koreensis were the predominant species in meongge-jeot. In myeolchi-jeot and meongge-jeot, the bacterial communities within samples were consistent in their predominance, however each of saeu-jeot samples had inter-individual variety in the bacterial community leading to the difficulties of standardization for the commercial production of saeu-jeot. The results of this study will conclusively help to expand our basic knowledge of jeotgal and the related microorganisms involved in food fermentation.

Enhancement of anti-tubercular activity and biomass of fermented food associated Staphylococcus hominis strain MANF2 using Taguchi orthogonal array and Box-Behnken design

The prime focus of the present investigation was to optimize statistically the anti-tubercular activity and biomass of fermented food associated Staphylococcus hominis strain MANF2 using Taguchi orthogonal array (OA) and Box-Behnken design (BBD). The anti-tubercular activity of strain MANF2 was determined against Mycobacterium tuberculosis H37Rv using luciferase reporter phase assay. Among varied media examined, the isolate exhibited impressive anti-tubercular activity with paramount relative light unit reduction of >90% in de Man Rogose Sharpe (MRS) broth. Primarily, the anti-tubercular activity and biomass of strain MANF2 were estimated in MRS broth by optimizing eight diversified parameters using one factor at a time (OFAT) method after working out a series of experiments. The most significant contributing factors selected through OFAT tool were optimized using Taguchi approach with a standard OA layout of L18 (2² × 3⁶). Results demonstrated the significant (P ≤ 0.05) influence of pH, temperature, yeast extract, magnesium sulphate, and glycerol on response variables. These controlled variables were further optimized using BBD matrix at N = 46 by second-order polynomial equation. The fermentation medium of pH 6.5 constituting yeast extract (0.5% w/v), magnesium sulphate (0.1% w/v), and glycerol (1.5% v/v), being further incubated at 30 °C showed enhanced anti-tubercular activity (98.7%) and approximately 4 fold increment in the bacterial biomass yield (8.3 mg/mL) with respect to traditional OFAT method. Three-dimensional response plots of the quadratic model showed interdependent interaction between the significant variables. In conclusion, the present study revealed the first report on the optimization of anti-tubercular activity and biomass of S. hominis via Taguchi OA as well as BBD design, and thus, paved a path for its proficient applications in pharmaceutical industries as dynamic mycobactericidal agent in future.

Biofilm formation by Staphylococcus aureus and Salmonella spp. under mono and dual-species conditions and their sensitivity to cetrimonium bromide, peracetic acid and sodium hypochlorite

The aim of this study was evaluated the biofilm formation by Staphylococcus aureus 4E and Salmonella spp. under mono and dual-species biofilms, onto stainless steel 316 (SS) and polypropylene B (PP), and their sensitivity to cetrimonium bromide, peracetic acid and sodium hypochlorite. The biofilms were developed by immersion of the surfaces in TSB by 10 d at 37°C. The results showed that in monospecies biofilms the type of surface not affected the cellular density (p>0.05). However, in dual-species biofilms on PP the adhesion of Salmonella spp. was favored, 7.61±0.13Log10CFU/cm2, compared with monospecies biofilms onto the same surface, 5.91±0.44Log10CFU/cm2 (p<0.05). The mono and dual-species biofilms were subjected to disinfection treatments; and the most effective disinfectant was peracetic acid (3500ppm), reducing by more than 5Log10CFU/cm2, while the least effective was cetrimonium bromide. In addition, S. aureus 4E and Salmonella spp. were more resistant to the disinfectants in mono than in dual-species biofilms (p<0.05). Therefore, the interspecies interactions between S. aureus 4E and Salmonella spp. had a negative effect on the antimicrobial resistance of each microorganism, compared with the monospecies biofilms.

Silver nanoparticles stimulate the proliferation of sulfate reducing bacterium Desulfovibrio vulgaris

The intensive use of silver nanoparticles (AgNPs) in cosmetics and textiles causes their release into sewer networks of urban water systems. Although a few studies have investigated antimicrobial activities of nanoparticles against environmental bacteria, little is known about potential impacts of the released AgNPs on sulfate reducing bacteria in sewers. Here, we investigated the effect of AgNPs on Desulfovibrio vulgaris Hidenborough (D. vulgaris), a typical sulfate-reducing bacterium (SRB) in sewer systems. We found AgNPs stimulated the proliferation of D. vulgaris, rather than exerting inhibitory or biocidal effects. Based on flow cytometer detections, both the cell growth rate and the viable cell ratio of D. vulgaris increased during exposure to AgNPs at concentrations of up to 100 mg/L. The growth stimulation was dependent on the AgNP concentration. These results imply that the presence of AgNPs in sewage may affect SRB abundance in sewer networks. Our findings also shed new lights on the interactions of nanoparticles and bacteria.