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Fermentation, Volume 4, Issue 1 (March 2018)

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Cover Story (view full-size image) 3-hydroxypropionic acid is a building block chemical with a wide range of application and currently [...] Read more.
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Open AccessFeature PaperReview The Impact of Simple Phenolic Compounds on Beer Aroma and Flavor
Fermentation 2018, 4(1), 20; https://doi.org/10.3390/fermentation4010020
Received: 2 February 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 19 March 2018
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Abstract
Beer is a complex beverage containing a myriad of flavor- and aroma-active compounds. Brewers strive to achieve an appropriate balance of desired characters, while avoiding off-aromas and flavors. Phenolic compounds are always present in finished beer, as they are extracted from grains and
[...] Read more.
Beer is a complex beverage containing a myriad of flavor- and aroma-active compounds. Brewers strive to achieve an appropriate balance of desired characters, while avoiding off-aromas and flavors. Phenolic compounds are always present in finished beer, as they are extracted from grains and hops during the mashing and brewing process. Some of these compounds have little impact on finished beer, while others may contribute either desirable or undesirable aromas, flavors, and mouthfeel characteristics. They may also contribute to beer stability. The role of simple phenolic compounds on the attributes of wort and beer are discussed. Full article
(This article belongs to the Special Issue Brewing & Distilling)
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Open AccessReview The Microbial Diversity of Sherry Wines
Fermentation 2018, 4(1), 19; https://doi.org/10.3390/fermentation4010019
Received: 15 February 2018 / Revised: 13 March 2018 / Accepted: 16 March 2018 / Published: 19 March 2018
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Abstract
The principal role of wine yeast is to transform efficiently the grape-berries’ sugars to ethanol, carbon dioxide, and other metabolites, without the production of off-flavors. Wine yeast strains are able to ferment musts, while other commercial or laboratory strains fail to do so.
[...] Read more.
The principal role of wine yeast is to transform efficiently the grape-berries’ sugars to ethanol, carbon dioxide, and other metabolites, without the production of off-flavors. Wine yeast strains are able to ferment musts, while other commercial or laboratory strains fail to do so. The genetic differences that characterize wine yeast strains in contrast to the biological ageing of the veil-forming yeasts in Sherry wines are poorly understood. Saccharomyces cerevisiae strains frequently exhibit rather specific phenotypic features needed for adaptation to a special environment, like fortified wines with ethanol up to 15% (v/v), known as Sherry wines. Factors that affect the correct development of the veil of flor during ageing are also reviewed, along with the related aspects of wine composition, biofilm formation processes, and yeast autolysis. This review highlights the importance of yeast ecology and yeast metabolic reactions in determining Sherry wine quality and the wealth of untapped indigenous microorganisms co-existing with the veil-forming yeast strains. It covers the complexity of the veil forming wine yeasts’ genetic features, and the genetic techniques often used in strain selection and monitoring during fermentation or biological ageing. Finally, the outlook for new insights to protect and to maintain the microbiota of the Sherry wines will be discussed. Full article
(This article belongs to the Special Issue Microbiota of Fermented Beverages)
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Open AccessReview The Use of UV-Vis Spectroscopy in Bioprocess and Fermentation Monitoring
Fermentation 2018, 4(1), 18; https://doi.org/10.3390/fermentation4010018
Received: 11 February 2018 / Revised: 1 March 2018 / Accepted: 7 March 2018 / Published: 13 March 2018
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Abstract
Real-time analytical tools to monitor bioprocess and fermentation in biological and food applications are becoming increasingly important. Traditional laboratory-based analyses need to be adapted to comply with new safety and environmental guidelines and reduce costs. Many methods for bioprocess fermentation monitoring are spectroscopy-based
[...] Read more.
Real-time analytical tools to monitor bioprocess and fermentation in biological and food applications are becoming increasingly important. Traditional laboratory-based analyses need to be adapted to comply with new safety and environmental guidelines and reduce costs. Many methods for bioprocess fermentation monitoring are spectroscopy-based and include visible (Vis), infrared (IR) and Raman. This paper describes the main principles and recent developments in UV-Vis spectroscopy to monitor bioprocess and fermentation in different food production applications. Full article
(This article belongs to the Special Issue Bioprocess and Fermentation Monitoring)
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Open AccessFeature PaperArticle The Effect of pH and Temperature on Arachidonic Acid Production by Glycerol-Grown Mortierella alpina NRRL-A-10995
Fermentation 2018, 4(1), 17; https://doi.org/10.3390/fermentation4010017
Received: 9 February 2018 / Revised: 2 March 2018 / Accepted: 4 March 2018 / Published: 12 March 2018
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Abstract
Arachidonic acid (AA) has a wide range of applications in medicine, pharmacology, diet, infant nutrition, and agriculture, due to its unique biological properties. The microbiological processes involved in AA production usually require carbohydrate substrates. In this paper, we propose a method for AA
[...] Read more.
Arachidonic acid (AA) has a wide range of applications in medicine, pharmacology, diet, infant nutrition, and agriculture, due to its unique biological properties. The microbiological processes involved in AA production usually require carbohydrate substrates. In this paper, we propose a method for AA production from glycerol, an inexpensive and renewable carbon substrate that is produced by the fungal strain, Mortierella alpina NRRL-A-10995. Our experimental results showed that the optimum pH values required for fungal growth and the production of lipids and AA were different and depended on the growth phase of the fungus. The AA production was shown to be extremely sensitive to acidic pH values and was completely inhibited at a pH of 3.0. The optimum temperature for AA production was 20–22 °C. Continuous cultivation of M. alpina occurred in a glycerol-containing medium, and growth limitations were implemented through the addition of nitrogen and the selection of optimal conditions (pH 6.0, 20 °C). This ensured that active AA production occurred (25.2% of lipids and 3.1% of biomass), with the product yield from the consumed glycerol being 1.6% by mass and 3.4% by energy. Full article
(This article belongs to the Special Issue Microbial Production of Added-value Products from Renewable Resources)
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Open AccessFeature PaperReview Bioethanol a Microbial Biofuel Metabolite; New Insights of Yeasts Metabolic Engineering
Fermentation 2018, 4(1), 16; https://doi.org/10.3390/fermentation4010016
Received: 7 January 2018 / Revised: 17 February 2018 / Accepted: 23 February 2018 / Published: 8 March 2018
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Abstract
Scarcity of the non-renewable energy sources, global warming, environmental pollution, and raising the cost of petroleum are the motive for the development of renewable, eco-friendly fuels production with low costs. Bioethanol production is one of the promising materials that can subrogate the petroleum
[...] Read more.
Scarcity of the non-renewable energy sources, global warming, environmental pollution, and raising the cost of petroleum are the motive for the development of renewable, eco-friendly fuels production with low costs. Bioethanol production is one of the promising materials that can subrogate the petroleum oil, and it is considered recently as a clean liquid fuel or a neutral carbon. Diverse microorganisms such as yeasts and bacteria are able to produce bioethanol on a large scale, which can satisfy our daily needs with cheap and applicable methods. Saccharomyces cerevisiae and Pichia stipitis are two of the pioneer yeasts in ethanol production due to their abilities to produce a high amount of ethanol. The recent focus is directed towards lignocellulosic biomass that contains 30–50% cellulose and 20–40% hemicellulose, and can be transformed into glucose and fundamentally xylose after enzymatic hydrolysis. For this purpose, a number of various approaches have been used to engineer different pathways for improving the bioethanol production with simultaneous fermentation of pentose and hexoses sugars in the yeasts. These approaches include metabolic and flux analysis, modeling and expression analysis, followed by targeted deletions or the overexpression of key genes. In this review, we highlight and discuss the current status of yeasts genetic engineering for enhancing bioethanol production, and the conditions that influence bioethanol production. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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Open AccessArticle Adding Flavor to Beverages with Non-Conventional Yeasts
Fermentation 2018, 4(1), 15; https://doi.org/10.3390/fermentation4010015
Received: 21 January 2018 / Revised: 13 February 2018 / Accepted: 21 February 2018 / Published: 26 February 2018
Cited by 1 | PDF Full-text (2535 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Fungi produce a variety of volatile organic compounds (VOCs) during their primary and secondary metabolism. In the beverage industry, these volatiles contribute to the the flavor and aroma profile of the final products. We evaluated the fermentation ability and aroma profiles of non-conventional
[...] Read more.
Fungi produce a variety of volatile organic compounds (VOCs) during their primary and secondary metabolism. In the beverage industry, these volatiles contribute to the the flavor and aroma profile of the final products. We evaluated the fermentation ability and aroma profiles of non-conventional yeasts that have been associated with various food sources. A total of 60 strains were analyzed with regard to their fermentation and flavor profile. Species belonging to the genera Candida, Pichia and Wickerhamomyces separated best from lager yeast strains according to a principal component analysis taking alcohol and ester production into account. The speed of fermentation and sugar utilization were analysed for these strains. Volatile aroma-compound formation was assayed via gas chromatography. Several strains produced substantially higher amounts of aroma alcohols and esters compared to the lager yeast strain Weihenstephan 34/70. Consequently, co-fermentation of this lager yeast strain with a Wickerhamomyces anomalus strain generated an increased fruity-flavour profile. This demonstrates that mixed fermentations utilizing non-Saccharomyces cerevisiae biodiversity can enhance the flavour profiles of fermented beverages. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessFeature PaperArticle Schizosaccharomyces japonicus: A Polysaccharide-Overproducing Yeast to Be Used in Winemaking
Fermentation 2018, 4(1), 14; https://doi.org/10.3390/fermentation4010014
Received: 23 January 2018 / Revised: 8 February 2018 / Accepted: 9 February 2018 / Published: 23 February 2018
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Abstract
Mixed starter cultures made of Saccharomyces cerevisiae EC1118 and Schizosaccharomyces japonicus #13 were inoculated in commercial grape must, and the impact of different inoculum ratios (1:1; 1:100; 1:10,000) on growth and fermentation kinetics and on the analytical profiles of the experimental wines was
[...] Read more.
Mixed starter cultures made of Saccharomyces cerevisiae EC1118 and Schizosaccharomyces japonicus #13 were inoculated in commercial grape must, and the impact of different inoculum ratios (1:1; 1:100; 1:10,000) on growth and fermentation kinetics and on the analytical profiles of the experimental wines was here evaluated. Results obtained showed that S. japonicus #13 affects S. cerevisiae growth and fermentative capability only for S. cerevisiae/S. japonicus inoculum ratio 1:10,000. The analytical profiles of the wines produced by mixed starter cultures indicated that this non-Saccharomyces yeast modulates the concentration of malic and acetic acids and of some of the most important volatile compounds, such as β-phenyl ethanol, in an inoculum-ratio-dependent fashion. Moreover, all experimental wines obtained with S. japonicus #13 in mixed cultures reached concentrations of total polysaccharides significantly higher than those obtained with pure cultures of S. cerevisiae EC1118, and total polysaccharides increased with the increase of S. japonicus #13 cell concentration. Based on these results, S. japonicus #13 might be profitably inoculated in combination with S. cerevisiae EC1118 to enhance wine complexity and aroma and to improve wine stability by increasing the final concentration of polysaccharides. Full article
(This article belongs to the Special Issue Microbiota of Fermented Beverages)
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Open AccessFeature PaperReview Biological Production of 3-Hydroxypropionic Acid: An Update on the Current Status
Fermentation 2018, 4(1), 13; https://doi.org/10.3390/fermentation4010013
Received: 22 January 2018 / Revised: 5 February 2018 / Accepted: 9 February 2018 / Published: 13 February 2018
Cited by 1 | PDF Full-text (2028 KB) | HTML Full-text | XML Full-text
Abstract
The production of high added-value chemicals from renewable resources is a necessity in our attempts to switch to a more sustainable society. 3-Hydroxypropionic acid (3HP) is a promising molecule that can be used for the production of an important array of high added-value
[...] Read more.
The production of high added-value chemicals from renewable resources is a necessity in our attempts to switch to a more sustainable society. 3-Hydroxypropionic acid (3HP) is a promising molecule that can be used for the production of an important array of high added-value chemicals, such as 1,3-propanediol, acrylic acid, acrylamide, and bioplastics. Biological production of 3HP has been studied extensively, mainly from glycerol and glucose, which are both renewable resources. To enable conversion of these carbon sources to 3HP, extensive work has been performed to identify appropriate biochemical pathways and the enzymes that are involved in them. Novel enzymes have also been identified and expressed in host microorganisms to improve the production yields of 3HP. Various process configurations have also been proposed, resulting in improved conversion yields. The intense research efforts have resulted in the production of as much as 83.8 g/L 3HP from renewable carbon resources, and a system whereby 3-hydroxypropionitrile was converted to 3HP through whole-cell catalysis which resulted in 184.7 g/L 3HP. Although there are still challenges and difficulties that need to be addressed, the research results from the past four years have been an important step towards biological production of 3HP at the industrial level. Full article
(This article belongs to the Special Issue Bioconversion Processes) Printed Edition available
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Open AccessFeature PaperArticle Integrated Process for Extraction of Wax as a Value-Added Co-Product and Improved Ethanol Production by Converting Both Starch and Cellulosic Components in Sorghum Grains
Fermentation 2018, 4(1), 12; https://doi.org/10.3390/fermentation4010012
Received: 18 January 2018 / Revised: 5 February 2018 / Accepted: 11 February 2018 / Published: 13 February 2018
Cited by 1 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text
Abstract
Grain sorghum is a potential feedstock for fuel ethanol production due to its high starch content, which is equivalent to that of corn, and has been successfully used in several commercial corn ethanol plants in the United States. Some sorghum grain varieties contain
[...] Read more.
Grain sorghum is a potential feedstock for fuel ethanol production due to its high starch content, which is equivalent to that of corn, and has been successfully used in several commercial corn ethanol plants in the United States. Some sorghum grain varieties contain significant levels of surface wax, which may interact with enzymes and make them less efficient toward starch hydrolysis. On the other hand, wax can be recovered as a valuable co-product and as such may help improve the overall process economics. Sorghum grains also contain lignocellulosic materials in the hulls, which can be converted to additional ethanol. An integrated process was developed, consisting of the following steps: 1. Extraction of wax with boiling ethanol, which is the final product of the proposed process; 2. Pretreatment of the dewaxed grains with dilute sulfuric acid; 3. Mashing and fermenting of the pretreated grains to produce ethanol. During the fermentation, commercial cellulase was also added to release fermentable sugars from the hulls, which then were converted to additional ethanol. The advantages of the developed process were illustrated with the following results: (1) Wax extracted (determined by weight loss): ~0.3 wt % of total mass. (2) Final ethanol concentration at 25 wt % solid using raw grains: 86.1 g/L. (3) Final ethanol concentration at 25 wt % solid using dewaxed grains: 106.2 g/L (23.3% improvement). (4) Final ethanol concentration at 25 wt % solid using dewaxed and acid-treated grains (1 wt % H2SO4) plus cellulase (CTec2): 117.8 g/L (36.8% improvement). Full article
(This article belongs to the Special Issue Bioconversion Processes) Printed Edition available
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Open AccessFeature PaperArticle Pigment Production by the Edible Filamentous Fungus Neurospora Intermedia
Fermentation 2018, 4(1), 11; https://doi.org/10.3390/fermentation4010011
Received: 23 January 2018 / Revised: 7 February 2018 / Accepted: 9 February 2018 / Published: 13 February 2018
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Abstract
The production of pigments by edible filamentous fungi is gaining attention as a result of the increased interest in natural sources with added functionality in the food, feed, cosmetic, pharmaceutical and textile industries. The filamentous fungus Neurospora intermedia, used for production of
[...] Read more.
The production of pigments by edible filamentous fungi is gaining attention as a result of the increased interest in natural sources with added functionality in the food, feed, cosmetic, pharmaceutical and textile industries. The filamentous fungus Neurospora intermedia, used for production of the Indonesian food “oncom”, is one potential source of pigments. The objective of the study was to evaluate the fungus’ pigment production. The joint effect from different factors (carbon and nitrogen source, ZnCl2, MgCl2 and MnCl2) on pigment production by N. intermedia is reported for the first time. The scale-up to 4.5 L bubble column bioreactors was also performed to investigate the effect of pH and aeration. Pigment production of the fungus was successfully manipulated by varying several factors. The results showed that the formation of pigments was strongly influenced by light, carbon, pH, the co-factor Zn2+ and first- to fourth-order interactions between factors. The highest pigmentation (1.19 ± 0.08 mg carotenoids/g dry weight biomass) was achieved in a bubble column reactor. This study provides important insights into pigmentation of this biotechnologically important fungus and lays a foundation for future utilizations of N. intermedia for pigment production. Full article
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Open AccessArticle Novel Wine Yeast for Improved Utilisation of Proline during Fermentation
Fermentation 2018, 4(1), 10; https://doi.org/10.3390/fermentation4010010
Received: 24 December 2017 / Revised: 30 January 2018 / Accepted: 2 February 2018 / Published: 6 February 2018
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Abstract
Proline is the predominant amino acid in grape juice, but it is poorly assimilated by wine yeast under the anaerobic conditions typical of most fermentations. Exploiting the abundance of this naturally occurring nitrogen source to overcome the need for nitrogen supplementation and/or the
[...] Read more.
Proline is the predominant amino acid in grape juice, but it is poorly assimilated by wine yeast under the anaerobic conditions typical of most fermentations. Exploiting the abundance of this naturally occurring nitrogen source to overcome the need for nitrogen supplementation and/or the risk of stuck or sluggish fermentations would be most beneficial. This study describes the isolation and evaluation of a novel wine yeast isolate, Q7, obtained through ethyl methanesulfonate (EMS) mutagenesis. The utilisation of proline by the EMS isolate was markedly higher than by the QA23 wild type strain, with approximately 700 and 300 mg/L more consumed under aerobic and self-anaerobic fermentation conditions, respectively, in the presence of preferred nitrogen sources. Higher intracellular proline contents in the wild type strain implied a lesser rate of proline catabolism or incorporation by this strain, but with higher cell viability after freezing treatment. The expression of key genes (PUT1, PUT2, PUT3, PUT4, GAP1 and URE2) involved in proline degradation, transport and repression were compared between the parent strain and the isolate, revealing key differences. The application of these strains for efficient conduct for nitrogen-limited fermentations is a possibility. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessFeature PaperReview Strategies to Extend Bread and GF Bread Shelf-Life: From Sourdough to Antimicrobial Active Packaging and Nanotechnology
Received: 30 December 2017 / Revised: 28 January 2018 / Accepted: 29 January 2018 / Published: 2 February 2018
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Abstract
Bread is a staple food worldwide. It commonly undergoes physico-chemical and microbiological changes which impair its quality and shelf-life. Staling determines organoleptic impairment, whereas microbiological spoilage causes visible mould growth and invisible production of mycotoxins. To tackle this economic and safety issue, the
[...] Read more.
Bread is a staple food worldwide. It commonly undergoes physico-chemical and microbiological changes which impair its quality and shelf-life. Staling determines organoleptic impairment, whereas microbiological spoilage causes visible mould growth and invisible production of mycotoxins. To tackle this economic and safety issue, the bakery industry has been working to identify treatments which allow bread safety and extended shelf-life. Physical methods and chemical preservatives have long been used. However, new frontiers have been recently explored. Sourdough turned out an ancient but novel technology to preserve standard and gluten-free bread. Promising results have also been obtained by application of alternative bio-preservation techniques, including antifungal peptides and plant extracts. Active packaging, with absorbing and/or releasing compounds effective against bread staling and/or with antimicrobials preventing growth of undesirable microorganisms, showed up an emerging area of food technology which can confer many preservation benefits. Nanotechnologies are also opening up a whole universe of new possibilities for the food industry and the consumers. This work thus aims to provide an overview of opportunities and challenges that traditional and innovative anti-staling and anti-spoilage methods can offer to extend bread shelf-life and to provide a basis for driving further research on nanotechnology applications into the bakery industry. Full article
(This article belongs to the Special Issue Microbial Control)
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Open AccessFeature PaperArticle Molecular and Phenotypic Characterization of Metschnikowia pulcherrima Strains from Douro Wine Region
Received: 22 December 2017 / Revised: 22 January 2018 / Accepted: 24 January 2018 / Published: 29 January 2018
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Abstract
Some non-Saccharomyces yeasts, including Metschnikowia pulcherrima, have been proposed as selected starters due to their contribution for the overall aroma and chemical profiles of wines. In this work, we aimed to evaluate the genetic and phenotypic diversity of Metschnikowia pulcherrima strains
[...] Read more.
Some non-Saccharomyces yeasts, including Metschnikowia pulcherrima, have been proposed as selected starters due to their contribution for the overall aroma and chemical profiles of wines. In this work, we aimed to evaluate the genetic and phenotypic diversity of Metschnikowia pulcherrima strains isolated from different locations of Douro Wine Region, and to explore their potential as co-adjuncts of S. cerevisiae in alcoholic fermentation. For that purpose, a set of 64 M. pulcherrima isolates were used. Polymerase chain reaction (PCR) fingerprinting with M13 primers demonstrated to be an efficient tool in intraspecific discrimination of M. pulcherrima strains. No significant associations were found between genotypic profiles and either geographical origin or winery. The isolates were screened for their stress resistance ability (ethanol, SO2, chitosan, copper, H2O2, and Grape Juice Medium), aroma-related activities (resistance to 5, 5′, 5′′-trifluor-d, l-leucine and cerulenin and β-glycosidase, β-lyase and sulfite-reductase activities) as well as other relevant technological proprieties (protease activity and biogenic amines production). M. pulcherrima response to the different enological traits evaluated was greatly strain-dependent. The most discriminant features were the ability of the strains to grow in Grape-Juice Medium (GJM) and sulfite-reductase, and their β-lyase and protease activities. The enological potential of a selected M. pulcherrima strain in mixed-culture with S. cerevisiae was also assessed in natural grape-juice of a local variety, under two nitrogen regimes. M. pulcherrima proved to be promising for future industrial application as a co-starter, lowering ethanol, acetic acid and, reported here for the first time, lowering hydrogen sulfide levels in the wines. Full article
(This article belongs to the Special Issue Microbiota of Fermented Beverages)
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Open AccessFeature PaperReview Massive Sequencing: A New Tool for the Control of Alcoholic Fermentation in Wine?
Received: 23 December 2017 / Revised: 19 January 2018 / Accepted: 24 January 2018 / Published: 26 January 2018
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Abstract
In wine industry, there is a prevalent use of starter cultures to promote a controlled and efficient alcoholic fermentation preventing the growth of spoilage microbes. However, current trends in enology aim to combine the guaranteed success of monitored process and the complexity of
[...] Read more.
In wine industry, there is a prevalent use of starter cultures to promote a controlled and efficient alcoholic fermentation preventing the growth of spoilage microbes. However, current trends in enology aim to combine the guaranteed success of monitored process and the complexity of fermentations either by inoculating autochthonous starters or by performing spontaneously to produce distinctive wines. To understand the complex roles of microorganisms on wine fermentation, we must understand their population dynamics and their relationships with wine quality and metabolome. Current metagenomics techniques based on massive sequencing are gaining relevance to study the diversity and evolution of microbial population on every stage of the wine making process. This new tool and technique increases the throughput and sensitivity to study microbial communities. This review focuses on the current knowledge about wine alcoholic fermentation, the contribution of massive sequencing techniques and the possibility of using this tool for microbial control. Full article
(This article belongs to the Special Issue Microbial Control)
Open AccessReview Accumulation of Biogenic Amines in Wine: Role of Alcoholic and Malolactic Fermentation
Received: 5 December 2017 / Revised: 20 January 2018 / Accepted: 23 January 2018 / Published: 25 January 2018
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Abstract
Biogenic amines (BAs) are detrimental to health and originate in foods mainly from decarboxylation of the corresponding amino acid by the activity of exogenous enzymes released by various microorganisms. BAs can be generated at different stages of the wine production. Some of them
[...] Read more.
Biogenic amines (BAs) are detrimental to health and originate in foods mainly from decarboxylation of the corresponding amino acid by the activity of exogenous enzymes released by various microorganisms. BAs can be generated at different stages of the wine production. Some of them are formed in the vineyard and are normal constituents of grapes with amounts varying with variety, soil type and composition, fertilization and climatic conditions during growth and degree of maturation. BAs can be also formed by the yeasts during the alcoholic fermentation (AF), as well as by the action of bacteria involved in the malolactic fermentation (MLF). As aminogenesis is a complex and multifactorial phenomenon, the studies carried out to identify the main vinification stage of BAs production yielded contradictory results. In particular, there is not a general consensus yet on which fermentation supports mostly the accumulation of BAs in wine. In this context, the aim of the present paper deals with the most recent results related with the influence of alcoholic and malolactic fermentation parameters on BAs-producer microorganism in wine. Full article
(This article belongs to the Special Issue Microbial Control)
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Open AccessArticle Influence of Lysozyme Addition on Hydroxycinnamic Acids and Volatile Phenols during Wine Fermentation
Received: 10 December 2017 / Revised: 15 January 2018 / Accepted: 19 January 2018 / Published: 21 January 2018
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Abstract
Most yeast and bacteria in wine are able to metabolize hydroxycinnamic acids into volatile phenols via enzyme-mediated decarboxylation. Our trials performed in wine and model systems suggest that lysozyme addition prior to fermentation affects both bacterial activity and the release of hydroxycinnamic acids
[...] Read more.
Most yeast and bacteria in wine are able to metabolize hydroxycinnamic acids into volatile phenols via enzyme-mediated decarboxylation. Our trials performed in wine and model systems suggest that lysozyme addition prior to fermentation affects both bacterial activity and the release of hydroxycinnamic acids from their tartrate esters. This increases the potential for volatile phenol formation, as microorganisms can only metabolize free hydroxycinnamates. Wines with delayed malolactic fermentation due to lysozyme addition contained significantly higher concentrations of free hydroxycinnamic acids and elevated levels of volatile phenols in some cases. The reason for this is likely related to the side activity of lysozyme in combination with a detoxification mechanism that only occurs under stressful conditions for the yeast. Experiments in model systems indicate that lysozyme can affect the yeast at a pH higher than usually found in wine by attacking chitin in the bud scars of the cell walls and therefore weakening the cell structure. Free hydroxycinnamates can also affect yeast viability, making an increased release during fermentation problematic for a successful fermentation. Full article
(This article belongs to the Special Issue Microbial Foods—The Science of Fermented Foods)
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Open AccessEditorial Acknowledgement to Reviewers of Fermentation in 2017
Received: 9 January 2018 / Revised: 9 January 2018 / Accepted: 9 January 2018 / Published: 10 January 2018
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Peer review is an essential part in the publication process, ensuring that Fermentation maintains high quality standards for its published papers[...] Full article
Open AccessReview Malting and Brewing Industries Encounter Fusarium spp. Related Problems
Received: 30 November 2017 / Revised: 28 December 2017 / Accepted: 4 January 2018 / Published: 9 January 2018
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Abstract
Versatile microbiota are inevitably naturally present on cereals. Fungi, yeasts and bacteria and their metabolites all contribute to the quality and safety of the final products derived from most common beer cereals—barley and wheat. The microorganisms that are most often associated with the
[...] Read more.
Versatile microbiota are inevitably naturally present on cereals. Fungi, yeasts and bacteria and their metabolites all contribute to the quality and safety of the final products derived from most common beer cereals—barley and wheat. The microorganisms that are most often associated with the safety and quality of cereals for beer production belong to the Fusarium spp. They greatly influence yields from the field, and can modify and diminish economic success for farmers. However, the real problem is their harmful metabolites—mycotoxins—that affect the health of humans and animals. In the era of emerging analytical methodologies, the spectrum of known toxins originating from microorganisms that can pose a threat to humans has grown tremendously. Therefore, it is necessary to monitor microflora throughout the productive “barley to beer” chain and to act suppressive on the proliferation of unwanted microorganisms, before and during malting, preventing the occurrence of mycotoxins in final products and by-products. Multi-mycotoxin analyses are very advanced and useful tools for the assessment of product safety, and legislation should follow up and make some important changes to regulate as yet unregulated, but highly occurring, microbial toxins in malt and beer. Full article
(This article belongs to the Special Issue Microbiota of Fermented Beverages)
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Open AccessArticle Mitigation of Volatile Fatty Acid Build-Up by the Use of Soft Carbon Felt Electrodes: Evaluation of Anaerobic Digestion in Acidic Conditions
Received: 15 December 2017 / Revised: 26 December 2017 / Accepted: 3 January 2018 / Published: 4 January 2018
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Abstract
Anaerobic digestion and bioelectrochemical systems have great potential to recover energy from waste streams and help overcome common hurdles associated with this process, as integrated technologies. In this study, the benefit of integrating an electrogen-enriched bioanode in a batch anaerobic digester was explored
[...] Read more.
Anaerobic digestion and bioelectrochemical systems have great potential to recover energy from waste streams and help overcome common hurdles associated with this process, as integrated technologies. In this study, the benefit of integrating an electrogen-enriched bioanode in a batch anaerobic digester was explored under ambient temperature conditions associated with organic overloading and reactor acidity. An increase in CH4 production was observed in the electrode-containing reactors (0.56 L CH4 kgVS−1 h−1) in comparison with the conventional anaerobic digester (0.14 L CH4 kgVS−1 h−1) during the initial stages of operation. In addition, the mere presence of electrodes operating in open circuit mode resulted in a delay in volatile fatty acid (VFA) build-up. This seems to be associated with the enhancement in VFA consumption due to biomass proliferation on the electrode surface, rather than on electrochemical activity. Full article
(This article belongs to the Special Issue Microbial Production of Added-value Products from Renewable Resources)
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Open AccessReview Fermentation Assisted by Pulsed Electric Field and Ultrasound: A Review
Received: 15 October 2017 / Revised: 29 November 2017 / Accepted: 22 December 2017 / Published: 4 January 2018
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Abstract
Various novel techniques are proposed to improve process efficiency, quality, and safety of fermented food products. Ultrasound and pulsed electric field (PEF) are versatile technologies that can be employed in conjunction with fermentation processes to enhance process efficiency and production rates by improving
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Various novel techniques are proposed to improve process efficiency, quality, and safety of fermented food products. Ultrasound and pulsed electric field (PEF) are versatile technologies that can be employed in conjunction with fermentation processes to enhance process efficiency and production rates by improving mass transfer and cell permeability. The aim of this review is to highlight current and potential applications of ultrasound and PEF techniques in food fermentation processes. Their effects on microbial enzymes, along with mechanisms of action, are also discussed. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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