Special Issue "Yeast Biotechnology 2.0"

A special issue of Fermentation (ISSN 2311-5637).

Deadline for manuscript submissions: closed (30 September 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Ronnie G. Willaert

Structural Biology Brussels Lab, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Website | E-Mail
Interests: yeast biotechnology; cell immobilization; beer brewing biochemistry and fermentation; mini- and microbioreactors; Saccharomyces cerevisiae; Candida; yeast space biology (bioreactors for microgravity research); yeast adhesins; yeast systems biology; glycobiology; nanobiotechnology; Atomic Force Microscopy; protein crystallization; yeast protein structural biology

Special Issue Information

Dear Colleagues,

Yeasts are truly fascinating microorganisms. Due to their diverse and dynamic activities, they have been used for the production of many interesting products, such as beer, wine, bread, biofuels and biopharmaceuticals. Saccharomyces cerevisiae (bakers’ yeast) is the yeast species that is surely the most exploited by man. Saccharomyces is a top choice organism for industrial applications, although its use for producing beer dates back to at least the 6th millennium BC. Bakers’ yeast has been a cornerstone of modern biotechnology, enabling the development of efficient production processes for antibiotics, biopharmaceuticals, technical enzymes, and ethanol and biofuels. Today, diverse yeast species are explored for industrial applications, such as, e.g., Saccharomyces species, Pichia pastoris and other Pichia species, Kluyveromyces marxianus, Hansenula polymorpha, Yarrowia lipolytica, Candida species, Phaffia rhodozyma, wild yeasts for beer brewing, etc.

The Special Issue is focused on recent developments of yeast biotechnology with topics including recent techniques for characterizing yeast and their physiology (including omics and nanobiotechnology techniques), methods to adapt industrial strains (including metabolic, synthetic and evolutionary engineering) and the use of yeasts as microbial cell factories to produce biopharmaceuticals, enzymes, alcohols, organic acids, flavours and fine chemicals, and advances in yeast fermentation technology and industrial fermentation processes.

This Special Issue, “Yeast Biotechnology 2.0”, is a second issue on this topic. The first Special Issue was published last year and included 11 published papers: https://www.mdpi.com/journal/fermentation/special_issues/saccharomyce

Topics including but not limited to:

 

Yeast characterization and analysis

Brewing yeasts (including wild yeasts), wine yeasts, baker’s yeasts.
Evolution and variation of genomes of industrial yeasts.
Yeast systems biology: genomics, proteomics, fluxomics, metabolomics, omics integration.
Yeast nanobiotechnology (nanoanalysis techniques, construction of nanostructures, etc.).

Yeast strain engineering

Yeast metabolic engineering: production of biofuels, secondary metabolites, commodity chemicals, proteins, biopharmaceuticals, material precursors.
Yeast synthetic biology: yeasts as cell factories, tools for controlling enzyme expression levels, strategies for regulating spatial localization of enzymes in yeast, regulatory networks, biomolecular logic gates.
Strain improvement via evolutionary engineering.

Fermentation technology

Industrial bioreactors.
Mini- and microbioreactors: single-cell analysis, high-throughput screening, microfluidic bioreactors.
Process intensification: high-density fermentations, high-gravity fermentation.
Fermentative stress adaptation.

Industrial fermentation processes

Production of food (bread, etc.) and beverages (beer, wine, cider, etc.).
Production of baker’s yeast.
Production of biofuels (bioethanol, 1-butanol, biodiesel, jetfuels), commodity chemicals, pharmaceuticals, material precursors, secondary metabolites.

Prof. Dr. Ronnie G. Willaert
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fermentation is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • systems biology
  • genomics
  • proteomics
  • fluxomics
  • metabolomics
  • synthetic yeast biology
  • metabolic engineering
  • evolutionary engineering
  • industrial yeast products
  • beer
  • wine
  • bread
  • biofuels
  • commodity chemical
  • biopharmaceuticals
  • material precursors
  • yeast fermentation technology
  • industrial bioreactors
  • mini- and microbioreactors
  • high-density fermentations
  • yeast stress adaptation

Related Special Issue

Published Papers (13 papers)

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Research

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Open AccessArticle Recombinant Diploid Saccharomyces cerevisiae Strain Development for Rapid Glucose and Xylose Co-Fermentation
Fermentation 2018, 4(3), 59; https://doi.org/10.3390/fermentation4030059
Received: 25 June 2018 / Revised: 23 July 2018 / Accepted: 25 July 2018 / Published: 30 July 2018
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Abstract
Cost-effective production of cellulosic ethanol requires robust microorganisms for rapid co-fermentation of glucose and xylose. This study aims to develop a recombinant diploid xylose-fermenting Saccharomyces cerevisiae strain for efficient conversion of lignocellulosic biomass sugars to ethanol. Episomal plasmids harboring codon-optimized Piromyces sp. E2
[...] Read more.
Cost-effective production of cellulosic ethanol requires robust microorganisms for rapid co-fermentation of glucose and xylose. This study aims to develop a recombinant diploid xylose-fermenting Saccharomyces cerevisiae strain for efficient conversion of lignocellulosic biomass sugars to ethanol. Episomal plasmids harboring codon-optimized Piromyces sp. E2 xylose isomerase (PirXylA) and Orpinomyces sp. ukk1 xylose (OrpXylA) genes were constructed and transformed into S. cerevisiae. The strain harboring plasmids with tandem PirXylA was favorable for xylose utilization when xylose was used as the sole carbon source, while the strain harboring plasmids with tandem OrpXylA was beneficial for glucose and xylose cofermentation. PirXylA and OrpXylA genes were also individually integrated into the genome of yeast strains in multiple copies. Such integration was beneficial for xylose alcoholic fermentation. The respiration-deficient strain carrying episomal or integrated OrpXylA genes exhibited the best performance for glucose and xylose co-fermentation. This was partly attributed to the high expression levels and activities of xylose isomerase. Mating a respiration-efficient strain carrying the integrated PirXylA gene with a respiration-deficient strain harboring integrated OrpXylA generated a diploid recombinant xylose-fermenting yeast strain STXQ with enhanced cell growth and xylose fermentation. Co-fermentation of 162 g L−1 glucose and 95 g L−1 xylose generated 120.6 g L−1 ethanol in 23 h, with sugar conversion higher than 99%, ethanol yield of 0.47 g g−1, and ethanol productivity of 5.26 g L−1·h−1. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessArticle Fluorinated Phenylalanine Precursor Resistance in Yeast
Fermentation 2018, 4(2), 41; https://doi.org/10.3390/fermentation4020041
Received: 27 April 2018 / Revised: 2 June 2018 / Accepted: 4 June 2018 / Published: 9 June 2018
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Abstract
Development of a counter-selection method for phenylalanine auxotrophy could be a useful tool in the repertoire of yeast genetics. Fluorinated and sulfurated precursors of phenylalanine were tested for toxicity in Saccharomyces cerevisiae. One such precursor, 4-fluorophenylpyruvate (FPP), was found to be toxic
[...] Read more.
Development of a counter-selection method for phenylalanine auxotrophy could be a useful tool in the repertoire of yeast genetics. Fluorinated and sulfurated precursors of phenylalanine were tested for toxicity in Saccharomyces cerevisiae. One such precursor, 4-fluorophenylpyruvate (FPP), was found to be toxic to several strains from the Saccharomyces and Candida genera. Toxicity was partially dependent on ARO8 and ARO9, and correlated with a strain’s ability to convert FPP into 4-fluorophenylalanine (FPA). Thus, strains with deletions in ARO8 and ARO9, having a mild phenylalanine auxotrophy, could be separated from a culture of wild-type strains using FPP. Tetrad analysis suggests FPP resistance in one strain is due to two genes. Strains resistant to FPA have previously been shown to exhibit increased phenylethanol production. However, FPP resistant isolates did not follow this trend. These results suggest that FPP could effectively be used for counter-selection but not for enhanced phenylethanol production. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessCommunication Citric Acid Production by Yarrowia lipolytica Yeast on Different Renewable Raw Materials
Fermentation 2018, 4(2), 36; https://doi.org/10.3390/fermentation4020036
Received: 28 April 2018 / Revised: 11 May 2018 / Accepted: 15 May 2018 / Published: 17 May 2018
Cited by 1 | PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
The world market of citric acid (CA) is one of the largest and fastest growing markets in the biotechnological industry. Microbiological processes for CA production have usually used the mycelial fungi Aspergillus niger as a producer and molasses as a carbon source. In
[...] Read more.
The world market of citric acid (CA) is one of the largest and fastest growing markets in the biotechnological industry. Microbiological processes for CA production have usually used the mycelial fungi Aspergillus niger as a producer and molasses as a carbon source. In this paper, we propose methods for CA production from renewable carbon substrates (rapeseed oil, glucose, glycerol, ethanol, glycerol-containing waste of biodiesel industry and glucose-containing aspen waste) by the mutant strain Yarrowia lipolytica NG40/UV5. It was revealed that Y. lipolytica grew and synthesized CA using all tested raw materials. The obtained results are sufficient for industrial use of most of the raw materials studied for CA production. Using rapeseed oil, ethanol and raw glycerol (which is an important feedstock of biodiesel production), a high CA production (100–140 g L−1) was achieved. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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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 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
Cited by 1 | PDF Full-text (3068 KB) | HTML Full-text | XML Full-text | Supplementary Files
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 AccessArticle Cytosolic Redox Status of Wine Yeast (Saccharomyces Cerevisiae) under Hyperosmotic Stress during Icewine Fermentation
Fermentation 2017, 3(4), 61; https://doi.org/10.3390/fermentation3040061
Received: 30 October 2017 / Revised: 10 November 2017 / Accepted: 13 November 2017 / Published: 18 November 2017
Cited by 2 | PDF Full-text (1109 KB) | HTML Full-text | XML Full-text
Abstract
Acetic acid is undesired in Icewine. It is unclear whether its production by fermenting yeast is linked to the nicotinamide adenine dinucleotide (NAD+/NADH) system or the nicotinamide adenine dinucleotide phosphate (NADP+/NADPH) system. To answer this question, the redox status
[...] Read more.
Acetic acid is undesired in Icewine. It is unclear whether its production by fermenting yeast is linked to the nicotinamide adenine dinucleotide (NAD+/NADH) system or the nicotinamide adenine dinucleotide phosphate (NADP+/NADPH) system. To answer this question, the redox status of yeast cytosolic NAD(H) and NADP(H) were analyzed along with yeast metabolites to determine how redox status differs under Icewine versus table wine fermentation. Icewine juice and dilute Icewine juice were inoculated with commercial wine yeast Saccharomyces cerevisiae K1-V1116. Acetic acid was 14.3-fold higher in Icewine fermentation than the dilute juice condition. The ratio of NAD+ to total NAD(H) was 24-fold higher in cells in Icewine fermentation than the ratio from the dilute juice condition. Conversely, the ratio of NADP+ to total NADP(H) from the dilute fermentation was 2.9-fold higher than that in the Icewine condition. These results support the hypothesis that in Icewine, increased NAD+ triggered the catalysis of NAD+-dependent aldehyde dehydrogenase(s) (Aldp(s)), which led to the elevated level of acetic acid in Icewine, whereas, in the dilute condition, NADP+ triggered NADP+-dependent Aldp(s), resulting in a lower level of acetic acid. This work, for the first time, analyzed the yeast cytosolic redox status and its correlation to acetic acid production, providing a more comprehensive understanding of the mechanism of acetic acid production in Icewine. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessArticle A Microtiter Plate Assay as a Reliable Method to Assure the Identification and Classification of the Veil-Forming Yeasts during Sherry Wines Ageing
Fermentation 2017, 3(4), 58; https://doi.org/10.3390/fermentation3040058
Received: 10 October 2017 / Revised: 27 October 2017 / Accepted: 31 October 2017 / Published: 3 November 2017
Cited by 1 | PDF Full-text (1679 KB) | HTML Full-text | XML Full-text
Abstract
Yeasts involved in veil formation during biological ageing of Sherry wines are mainly Saccharomyces cerevisiae, and they have traditionally been divided into four races or varieties: beticus, cheresiensis, montuliensis and rouxii. Recent progress in molecular biology has led to the development of
[...] Read more.
Yeasts involved in veil formation during biological ageing of Sherry wines are mainly Saccharomyces cerevisiae, and they have traditionally been divided into four races or varieties: beticus, cheresiensis, montuliensis and rouxii. Recent progress in molecular biology has led to the development of several techniques for yeast identification, based on similarity or dissimilarity of DNA, RNA or proteins. In view of the latest yeast taxonomy, there are no more races. However, molecular techniques are not enough to understand the real veil-forming yeast diversity and dynamics in Sherry wines. We propose a reliable method, using a microtiter reader, to evaluate the fermentation and assimilation of carbon and nitrogen sources, the osmotolerance and the antibiotic resistance, using 18 S. cerevisiae and 5 non-Saccharomyces yeast strains, to allow correct identification and classification of the yeast strains present in the velum of flor complex. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessArticle Impact of Glucose Concentration and NaCl Osmotic Stress on Yeast Cell Wall β-d-Glucan Formation during Anaerobic Fermentation Process
Fermentation 2017, 3(3), 44; https://doi.org/10.3390/fermentation3030044
Received: 13 July 2017 / Revised: 1 September 2017 / Accepted: 7 September 2017 / Published: 13 September 2017
Cited by 1 | PDF Full-text (2742 KB) | HTML Full-text | XML Full-text
Abstract
Yeast β-glucan polysaccharide is a proven immunostimulant molecule for human and animal health. In recent years, interest in β-glucan industrial production has been increasing. The yeast cell wall is modified during the fermentation process for biomass production. The impact of environmental conditions on
[...] Read more.
Yeast β-glucan polysaccharide is a proven immunostimulant molecule for human and animal health. In recent years, interest in β-glucan industrial production has been increasing. The yeast cell wall is modified during the fermentation process for biomass production. The impact of environmental conditions on cell wall remodelling has not been extensively investigated. The aim of this research work was to study the impact of glucose and NaCl stress on β-glucan formation in the yeast cell wall during alcoholic fermentation and the assessment of the optimum fermentation phase at which the highest β-glucan yield is obtained. VIN 13 Saccharomyces cerevisiae (S. cerevisiae) strain was pre-cultured for 24 h with 0% and 6% NaCl and inoculated in a medium consisting of 200, 300, or 400 g/L glucose. During fermentation, 50 mL of fermented medium were taken periodically for the determination of Optical Density (OD), cell count, cell viability, cell dry weight, β-glucan concentration and β-glucan yield. Next, dry yeast cell biomass was treated with lytic enzyme and sonication. At the early stationary phase, the highest β-glucan concentration and yield was observed for non-NaCl pre-cultured cells grown in a medium containing 200 g/L glucose; these cells, when treated with enzyme and sonication, appeared to be the most resistant. Stationary is the optimum phase for cell harvesting for β-glucan isolation. NaCl and glucose stress impact negatively on β-glucan formation during alcoholic fermentation. The results of this work could comprise a model study for yeast β-glucan production on an industrial scale and offer new perspectives on yeast physiology for the development of antifungal drugs. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessArticle A Pichia anomala Strain (P. anomala M1) Isolated from Traditional Greek Sausage is an Effective Producer of Extracellular Lipolytic Enzyme in Submerged Fermentation
Fermentation 2017, 3(3), 43; https://doi.org/10.3390/fermentation3030043
Received: 4 August 2017 / Revised: 18 August 2017 / Accepted: 22 August 2017 / Published: 30 August 2017
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Abstract
Ayeast isolate, selected for its lipolytic activity from a meat product, was characterized as Pichia anomala. Lipolytic activity, determined on p-NPA as esterase, was maximum at 28 °C, pH 6.5, and induced by the short chain triglyceride tributyrin. Fermentations in 2
[...] Read more.
Ayeast isolate, selected for its lipolytic activity from a meat product, was characterized as Pichia anomala. Lipolytic activity, determined on p-NPA as esterase, was maximum at 28 °C, pH 6.5, and induced by the short chain triglyceride tributyrin. Fermentations in 2 L and 10 L stirred tank bioreactors, with 20 and 60 g/L glucose respectively, showed that in the second case lipolytic activity increased 1.74-fold, while the biomass increased 1.57-fold. Under otherwise identical aeration conditions, improved mixing in the 10 L reactor maintained higher dissolved oxygen levels which, along with the elevated glucose concentration, resulted in significant increase of specific rates of lipolytic activity (51 vs. 7 U/g/L), while specific rates of growth and glucose consumption maintained lower. The Crabtree-negative yeast (glucose insensitive growth) exhibited a Pasteur effect at lower dissolved oxygen concentrations while elevated glucose prevented ethanol formation under oxygen saturation. The particular physiological traits can be exploited to obtain significant lipolytic activity in a scalable aerobic process. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessFeature PaperArticle Combinatorial Engineering of Yarrowia lipolytica as a Promising Cell Biorefinery Platform for the de novo Production of Multi-Purpose Long Chain Dicarboxylic Acids
Fermentation 2017, 3(3), 40; https://doi.org/10.3390/fermentation3030040
Received: 22 July 2017 / Revised: 7 August 2017 / Accepted: 8 August 2017 / Published: 18 August 2017
Cited by 4 | PDF Full-text (6034 KB) | HTML Full-text | XML Full-text
Abstract
This proof-of-concept study establishes Yarrowia lipolytica (Y. lipolytica) as a whole cell factory for the de novo production of long chain dicarboxylic acid (LCDCA-16 and 18) using glycerol as the sole source of carbon. Modification of the fatty acid metabolism pathway
[...] Read more.
This proof-of-concept study establishes Yarrowia lipolytica (Y. lipolytica) as a whole cell factory for the de novo production of long chain dicarboxylic acid (LCDCA-16 and 18) using glycerol as the sole source of carbon. Modification of the fatty acid metabolism pathway enabled creating a pool of fatty acids in a β-oxidation deficient strain. We then selectively upregulated the native fatty acid ω-oxidation pathway for the enhanced terminal oxidation of the endogenous fatty acid precursors. Nitrogen-limiting conditions and leucine supplementation were employed to induce fatty acid biosynthesis in an engineered Leu modified strain. Our genetic engineering strategy allowed a minimum production of 330 mg/L LCDCAs in shake flask. Scale up to a 1-L bioreactor increased the titer to 3.49 g/L. Our engineered yeast also produced citric acid as a major by-product at a titer of 39.2 g/L. These results provide basis for developing Y. lipolytica as a safe biorefinery platform for the sustainable production of high-value LCDCAs from non-oily feedstock. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Review

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Open AccessFeature PaperReview The Smell of Synthetic Biology: Engineering Strategies for Aroma Compound Production in Yeast
Fermentation 2018, 4(3), 54; https://doi.org/10.3390/fermentation4030054
Received: 27 June 2018 / Revised: 13 July 2018 / Accepted: 13 July 2018 / Published: 16 July 2018
Cited by 1 | PDF Full-text (2367 KB) | HTML Full-text | XML Full-text
Abstract
Yeast—especially Saccharomyces cerevisiae—have long been a preferred workhorse for the production of numerous recombinant proteins and other metabolites. S. cerevisiae is a noteworthy aroma compound producer and has also been exploited to produce foreign bioflavour compounds. In the past few years, important
[...] Read more.
Yeast—especially Saccharomyces cerevisiae—have long been a preferred workhorse for the production of numerous recombinant proteins and other metabolites. S. cerevisiae is a noteworthy aroma compound producer and has also been exploited to produce foreign bioflavour compounds. In the past few years, important strides have been made in unlocking the key elements in the biochemical pathways involved in the production of many aroma compounds. The expression of these biochemical pathways in yeast often involves the manipulation of the host strain to direct the flux towards certain precursors needed for the production of the given aroma compound. This review highlights recent advances in the bioengineering of yeast—including S. cerevisiae—to produce aroma compounds and bioflavours. To capitalise on recent advances in synthetic yeast genomics, this review presents yeast as a significant producer of bioflavours in a fresh context and proposes new directions for combining engineering and biology principles to improve the yield of targeted aroma compounds. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Open AccessReview Micro- and Nanoscale Approaches in Antifungal Drug Discovery
Fermentation 2018, 4(2), 43; https://doi.org/10.3390/fermentation4020043
Received: 7 May 2018 / Revised: 4 June 2018 / Accepted: 5 June 2018 / Published: 11 June 2018
PDF Full-text (1371 KB) | HTML Full-text | XML Full-text
Abstract
Clinical needs for novel antifungal agents have increased due to the increase of people with a compromised immune system, the appearance of resistant fungi, and infections by unusual yeasts. The search for new molecular targets for antifungals has generated considerable research, especially using
[...] Read more.
Clinical needs for novel antifungal agents have increased due to the increase of people with a compromised immune system, the appearance of resistant fungi, and infections by unusual yeasts. The search for new molecular targets for antifungals has generated considerable research, especially using modern omics methods (genomics, genome-wide collections of mutants, and proteomics) and bioinformatics approaches. Recently, micro- and nanoscale approaches have been introduced in antifungal drug discovery. Microfluidic platforms have been developed, since they have a number of advantages compared to traditional multiwell-plate screening, such as low reagent consumption, the manipulation of a large number of cells simultaneously and independently, and ease of integrating numerous analytical standard operations and large-scale integration. Automated high-throughput antifungal drug screening is achievable by massive parallel processing. Various microfluidic antimicrobial susceptibility testing (AST) methods have been developed, since they can provide the result in a short time-frame, which is necessary for personalized medicine in the clinic. New nanosensors, based on detecting the nanomotions of cells, have been developed to further decrease the time to test antifungal susceptibility to a few minutes. Finally, nanoparticles (especially, silver nanoparticles) that demonstrated antifungal activity are reviewed. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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Other

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Open AccessBrief Report Two Novel Strains of Torulaspora delbrueckii Isolated from the Honey Bee Microbiome and Their Use in Honey Fermentation
Fermentation 2018, 4(2), 22; https://doi.org/10.3390/fermentation4020022
Received: 9 February 2018 / Revised: 8 March 2018 / Accepted: 13 March 2018 / Published: 26 March 2018
PDF Full-text (1923 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Yeasts are ubiquitous microbes found in virtually all environments. Many yeast species can ferment sugar into ethanol and CO2, and humans have taken advantage of these characteristics to produce fermented beverages for thousands of years. As a naturally abundant source of
[...] Read more.
Yeasts are ubiquitous microbes found in virtually all environments. Many yeast species can ferment sugar into ethanol and CO2, and humans have taken advantage of these characteristics to produce fermented beverages for thousands of years. As a naturally abundant source of fermentable sugar, honey has had a central role in such fermentations since Neolithic times. However, as beverage fermentation has become industrialized, the processes have been streamlined, including the narrow and almost exclusive usage of yeasts in the genus Saccharomyces for fermentation. We set out to identify wild honey- or honey-bee-related yeasts that can be used in honey fermentation. Here, we isolated two strains of Torulaspora delbrueckii from the gut of a locally collected honey bee. Both strains were able to ferment honey sugar into mead but failed to metabolize more than a modest amount of wort sugar in trial beer fermentations. Further, the meads fermented by the T. delbrueckii strains displayed better sensory characteristics than mead fermented by a champagne yeast. The combination of T. delbrueckii and champagne yeast strains was also able to rapidly ferment honey at an industrial scale. Thus, wild yeasts represent a largely untapped reservoir for the introduction of desirable sensory characteristics in fermented beverages such as mead. Full article
(This article belongs to the Special Issue Yeast Biotechnology 2.0)
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