Fermentation and Bioactive Metabolites

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Microbial Metabolism, Physiology & Genetics".

Deadline for manuscript submissions: closed (31 October 2018) | Viewed by 139586

Special Issue Editors


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Guest Editor
Department of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Via R. Balzarini 1, 64100 Teramo, Italy
Interests: microbial ecology; molds; mycotoxin; biofilms; antimicrobial compounds; fermented food
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, 64100 Teramo, Italy
Interests: milk; dairy; food analysis; food microbiology and technology; food preservation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microorganisms are known to produce secondary metabolites, being exploited as useful bioactive molecules. In addition, they are very diverse both phylogenetically and functionally, being able to carry out complex metabolic transformations. This metabolic versatility leads to a pool of biomolecules that are highly diverse in chemical structure and biological function which have potential application in medicine, pharmaceutical and food industry fields. In addition, several microorganisms have been exploited to obtain biologically active compounds like peptides, carbohydrates, polyphenols, carotenoids, phytosterols, and fatty acids, that offers health benefits like prevention of diseases, utilizing different plant and animal derived products as substrates. In fact, nowadays, the use of fermented foods is considered as a promising alternative to satisfy the growing consumer demands for healthy foods. To increase the production of biomolecules, many strategies, such as the use of specialized single-strain microbial origin cultures, co- cultures exhibiting high diversity allowing complementarity of functions or that can be able to modulate their physiology to produce new bioactive molecules, have been used. To this purpose, the design of bioreactor and bioprocesses are also exploited. This Special Issue aims to publish technological developments (in the form of original research articles, short communications, reviews, mini-reviews, methods articles, perspectives and opinions that make a considerable and efficient contribution to the scientific community) used to investigate different aspects of the impact of fermentation on the production of bioactive metabolites. Topics that are considered include the production of biomolecules in relation to foods, agriculture, industry, biotechnology and public health.

Prof. Dr. Clemencia Chaves-López
Prof. Dr. Annalisa Serio
Guest Editor

Manuscript Submission Information

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Keywords

  • Peptides
  • Fatty acids
  • Phenolic compounds
  • Organic Volatile compounds
  • Antimicrobial compounds
  • Secondary metabolites

Published Papers (15 papers)

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Research

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9 pages, 754 KiB  
Article
Enhanced Production and Quantitative Evaluation of Nigericin from the Algerian Soil-Living Streptomyces youssoufiensis SF10 Strain
by Nassima Leulmi, Denise Sighel, Andrea Defant, Karima Khenaka, Abderrahmane Boulahrouf and Ines Mancini
Fermentation 2019, 5(1), 13; https://doi.org/10.3390/fermentation5010013 - 26 Jan 2019
Cited by 10 | Viewed by 3698
Abstract
Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated [...] Read more.
Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated from a semi-arid soil sample collected at Chélia Mountain, in Khenchela (Northeastern Algeria) and identified as Streptomyces youssoufiensis. The extracts from the strain, cultured in a solid state or submerged fermentation conditions, using several carbon sources at different pH values, in the presence or absence of iron (II) sulfate and in co-culture with other Streptomyces species, were analyzed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). The best culture conditions provided a concentration of nigericin of 0.490 ± 0.001 mg/mL in the extract. The HPLC-ELSD method, optimized here for the quantitative detection of nigericin, can find wider applications in the analysis of several other metabolites characterized by a similar polycyclic polyether structure or, more generally, by the lack of significant chromophores in their molecular structure. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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9 pages, 2024 KiB  
Article
Bioconversion of Kaempferol and Quercetin Glucosides from Plant Sources Using Rhizopus spp.
by Nguyen Thai Huynh, Guy Smagghe, Gerard Bryan Gonzales, John Van Camp and Katleen Raes
Fermentation 2018, 4(4), 102; https://doi.org/10.3390/fermentation4040102 - 07 Dec 2018
Cited by 17 | Viewed by 4687
Abstract
Fermentation with filamentous fungi is known for the ability to convert bioactive compounds. The aim of this research was to investigate the metabolism of glycosidic derivatives of kaempferol and quercetin during fungal fermentation of extracts from cauliflower outer leaves and onion by Rhizopus [...] Read more.
Fermentation with filamentous fungi is known for the ability to convert bioactive compounds. The aim of this research was to investigate the metabolism of glycosidic derivatives of kaempferol and quercetin during fungal fermentation of extracts from cauliflower outer leaves and onion by Rhizopus oryzae and R. azygosporus. The highest release of kaempferol and quercetin was observed after 2 days and 1 day of fermentation with R. oryzae, respectively. It was proposed that glycosidic compounds were initially deglycosylated to form kaempferol-3-glucoside and quercetin-3-glucoside and then further metabolized into their aglycones. Clear differences in conversion efficiency towards the aglycones were observed between the two Rhizopus strains. Although both flavonoids only differ in one hydroxyl group, the metabolism of the glycosides towards their respective aglycones, kaempferol or quercetin, was different. It is concluded that the fermentation with R. oryzae and R. azygosporus could be considered as a way to produce kaempferol and quercetin aglycone from their glycosidic derivatives. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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8 pages, 1227 KiB  
Communication
Biotransformation of Ganoderic Acid A to 3-O-Acetyl Ganoderic Acid A by Soil-isolated Streptomyces sp.
by Te-Sheng Chang, Horng-Huey Ko, Tzi-Yuan Wang, Chun-Hsien Lee and Jiumn-Yih Wu
Fermentation 2018, 4(4), 101; https://doi.org/10.3390/fermentation4040101 - 01 Dec 2018
Cited by 2 | Viewed by 3886
Abstract
The medicinal fungus Ganoderma lucidum contains many bioactive triterpenoids, ganoderic acid A (GAA) being one of the major ones. The present study explored the microbial biotransformation of GAA, isolating 283 strains of soil actinomycetes and determining their abilities to biotransform GAA with ultra-performance [...] Read more.
The medicinal fungus Ganoderma lucidum contains many bioactive triterpenoids, ganoderic acid A (GAA) being one of the major ones. The present study explored the microbial biotransformation of GAA, isolating 283 strains of soil actinomycetes and determining their abilities to biotransform GAA with ultra-performance liquid chromatography analysis. One positive strain, AI 045, was selected to validate the biotransformation activity. The strain was identified as Streptomyces sp. based on the sequenced 16S rRNA gene. The produced compound obtained from the biotransformation of GAA was purified with the preparative high-performance liquid chromatography method and identified as 3-O-acetyl GAA based on mass and nuclear magnetic resonance spectral data. The present study is the first report that bacteria have the novel ability to biotransform the triterpenoids of fungus G. lucidum. Moreover, the identified 3-O-acetyl GAA is a new triterpenoid product discovered in microbes. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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12 pages, 1125 KiB  
Article
Enhanced Production and in situ Product Recovery of Fusicocca-2,10(14)-Diene from Yeast
by Lisa Halka and Rolf Wichmann
Fermentation 2018, 4(3), 65; https://doi.org/10.3390/fermentation4030065 - 17 Aug 2018
Cited by 7 | Viewed by 3818
Abstract
Fusicocca-2,10(14)-diene (FCdiene) is a tricyclic diterpene which has many pharmaceutical applications, for example, it is a precursor for different anticancer drugs, including fusicoccin A. Chemical synthesis of this diterpene is not economical as it requires 14 steps with several stereospecific reactions. FCdiene is [...] Read more.
Fusicocca-2,10(14)-diene (FCdiene) is a tricyclic diterpene which has many pharmaceutical applications, for example, it is a precursor for different anticancer drugs, including fusicoccin A. Chemical synthesis of this diterpene is not economical as it requires 14 steps with several stereospecific reactions. FCdiene is naturally produced at low titers in phytopathogenic filamentous fungi. However, production of FCdiene can be achieved via expression of fusicoccadiene synthase in yeast. The objective of this study is to increase FCdiene production by optimizing the yeast fermentation process. Our preliminary fermentations showed influences of carbon sources, buffer agents, and oxygen supply on FCdiene production. Buffer agents as well as oxygen supply were investigated in detail at 0.2 and 1.8 L cultivation volumes. Using glucose as the carbon source, FCdiene concentrations were increased to 240 mgFCdiene/L by optimizing pH and oxygen conditions. In situ extraction and adsorption techniques were examined at the 0.2 L scale to determine if these techniques could improve FCdiene yields. Different adsorbents and solvents were tested with in situ product recovery and 4-fold increases in FCdiene productivity could be shown. The results generated in this work provide a proof-of-concept for the fermentative production of FCdiene from S. cerevisiae as a practical alternative to chemical synthesis. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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11 pages, 1865 KiB  
Article
Antiviral and Antioxidant Potential of Fungal Endophytes of Egyptian Medicinal Plants
by Khaled A. Selim, Waill A. Elkhateeb, Ahmed M. Tawila, Ahmed A. El-Beih, Tahany M. Abdel-Rahman, Ahmed I. El-Diwany and Eman F. Ahmed
Fermentation 2018, 4(3), 49; https://doi.org/10.3390/fermentation4030049 - 25 Jun 2018
Cited by 47 | Viewed by 6993
Abstract
This study aimed to explore the antioxidant potential and antiviral activity of endophytic fungi which were isolated from healthy living tissues of medicinal plants. Endophytic strains (29 different taxa) were isolated from 18 Egyptian medicinal plants collected from Saint Katherine Protectorate, Egypt. The [...] Read more.
This study aimed to explore the antioxidant potential and antiviral activity of endophytic fungi which were isolated from healthy living tissues of medicinal plants. Endophytic strains (29 different taxa) were isolated from 18 Egyptian medicinal plants collected from Saint Katherine Protectorate, Egypt. The fungal endophytes were identified based on morphological characters. All isolates were identified as ascomycetes, except two Zygomycetes strains (Absidia corymbifera and Mucor fuscus). Isolated endophytes were cultivated on potato dextrose media. The fungal metabolites were extracted by ethyl acetate and examined for their biological activities. Among 99 total extracts, only Chaetomium globosum, which was isolated from Adiantum capillus, showed a promising DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity (99% at 100 µg/mL). Fifteen extracts prohibited the reproduction of HSV-2 virus. On the other hand, the reproduction of VSV-virus was inhibited by sixteen endophytic extracts. The promising anti-(HSV-2 and VSV) extract of endophytic Pleospora tarda strain; that was originally isolated from the medicinal plant Ephedra aphylla, showed viral inhibitory activity of 40.7% and 15.2%, respectively. Two compounds, for which antiviral activates could be attributed, were isolated and identified as alternariol and alternariol-(9)-methyl ether using different NMR techniques from P. tarda extract. For the first time, we report here the ability of the endophytic fungus P. tarda to produce alternariol and alternariol-(9)-methyl ether. The results indicate that the endophytic fungi from medicinal plants are promising sources of bioactive compounds. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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993 KiB  
Article
Inhibition of Growth and Ammonia Production of Ruminal Hyper Ammonia-Producing Bacteria by Chinook or Galena Hops after Long-Term Storage
by Michael D. Flythe, Brittany E. Harlow, Glen E. Aiken, Gloria L. Gellin, Isabelle A. Kagan and Jesse Pappas
Fermentation 2017, 3(4), 68; https://doi.org/10.3390/fermentation3040068 - 19 Dec 2017
Cited by 5 | Viewed by 4532
Abstract
Surplus hops (Humulus lupulus L.) that are not needed by the brewing industry could be used as a feed supplement for cattle and other ruminants. Previous research indicates that antimicrobial hops plant secondary metabolites (i.e., α- and β-acids) inhibit methane and ammonia [...] Read more.
Surplus hops (Humulus lupulus L.) that are not needed by the brewing industry could be used as a feed supplement for cattle and other ruminants. Previous research indicates that antimicrobial hops plant secondary metabolites (i.e., α- and β-acids) inhibit methane and ammonia production and promote the growth of ruminant animals. The goal was to determine that hop pellets produced for brewing still possessed the requisite antimicrobial activity after 5-year storage. HPLC (high performance liquid chromatography) analysis indicated that the α- and β-acid concentrations in two varieties of hops were relatively stable after 5 years of storage under N2. Either hop variety inhibited the growth of the ruminal hyper ammonia-producing bacterium, Clostridium sticklandii SR, in broth culture and Petri plate bioassays. Either hop variety inhibited ammonia production from amino acids or peptides by mixed rumen microorganisms from Holstein steers. These results are similar to those previously obtained with fresh hops, hops extracts, other antimicrobial phytochemicals and typical feed ionophores, such as monensin. The rumen-active antimicrobial phytochemicals in hops can still be present and active after years under certain storage conditions. Further investigation is warranted to determine how surplus and older hops can be used to benefit ruminant nutrition and ruminant industries. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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1800 KiB  
Article
Interaction between Galactomyces geotrichum KL20B, Lactobacillus plantarum LAT3 and Enterococcus faecalis KE06 during Milk Fermentation
by Clemencia Chaves-López, Annalisa Serio, Chiara Rossi, Alessia Pepe, Elisabetta Compagnone and Antonello Paparella
Fermentation 2017, 3(4), 52; https://doi.org/10.3390/fermentation3040052 - 09 Oct 2017
Cited by 11 | Viewed by 5784
Abstract
Microbial interactions are fundamental during milk fermentation, determining the product final characteristics. Galactomyces geotrichum, Lactobacillus plantarum and Enterococcus faecalis are among the most common microorganisms in the Colombian Kumis. The aim of the research was to evaluate the yeast–bacteria interactions [...] Read more.
Microbial interactions are fundamental during milk fermentation, determining the product final characteristics. Galactomyces geotrichum, Lactobacillus plantarum and Enterococcus faecalis are among the most common microorganisms in the Colombian Kumis. The aim of the research was to evaluate the yeast–bacteria interactions in milk fermentation at 28 °C. UHT (Ultra-High Temperature) milk was inoculated with single- or multiple-strains associations and analysed periodically to determine the microbial counts, organic acids and total free amino acids (FAA). The results evidenced different growth performance of the strains in single or co-culture, with a positive effect of G. geotrichum KL20B on the lactic acid bacteria (LAB) growth performance. All the strains consumed citric acid after 6 h of incubation with E. faecalis KE06 as the major consumer; however, all the co-cultures showed an early metabolism of citrate but with a low intake rate. In addition, the interaction between G. geotrichum KL20B and E. faecalis KE06 led to a low accumulation of acetic acid. Formic acid fluctuated during fermentation. The strains interaction also led to an increase in ethanol content and a lower accumulation of FAA. In conclusion, the three strains co-culture enhances the LAB viability, with high production of lactic acid and ethanol, as a consequence of adaptation to the environment and substrate exploitation. To our knowledge, this is the first time in which it is showed that G. geotrichum KL20B could be used to compensate for the slow acid-producing ability of Lb. plantarum and E. faecalis in milk, underlining that this consortium applies some mechanisms to regulate the growth and milk composition in acids and ethanol content. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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3065 KiB  
Article
Time-Dependent Production of the Bioactive Peptides Endolides A and B and the Polyketide Mariline A from the Sponge-Derived Fungus Stachylidium bicolor 293K04
by Celso Almeida, Gerald Bills, Víctor González-Menéndez, Jesús Martin, José R. Tormo and Olga Genilloud
Fermentation 2017, 3(3), 45; https://doi.org/10.3390/fermentation3030045 - 05 Sep 2017
Cited by 6 | Viewed by 4020
Abstract
Previous investigations of the sponge-derived fungus Stachylidium bicolor (S. bicolor) 293K04 led to the isolation of the biosynthetically unusual polyketides marilines A-C and the bioactive tetrapeptides endolides A-B, identified as potential neuropathic drug leads. Furthermore, prior extended solid cultivation of S. bicolor 293K04 [...] Read more.
Previous investigations of the sponge-derived fungus Stachylidium bicolor (S. bicolor) 293K04 led to the isolation of the biosynthetically unusual polyketides marilines A-C and the bioactive tetrapeptides endolides A-B, identified as potential neuropathic drug leads. Furthermore, prior extended solid cultivation of S. bicolor 293K04 for 60 days resulted in a significant increase of polyketide yield, and the isolation of seven new polyketides. Due to the interest in endolide activity, unusual biosynthetic diversity, and the late stage polyketide production, we studied the cultivation conditions for determining the production time distribution and yields of these secondary metabolites. Results indicated a first production phase of secondary metabolite dominated by peptides, after 21–23 days. Polyketide mariline A1/A2 only started at day 35 of growth, an unusually late period for secondary metabolite expression. This unusual bimodal sequential expression of different families of secondary metabolites suggests value in exploring extended cultivation times to identify novel bioactive fungal compounds. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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4020 KiB  
Article
The Importance of a Comparative Characterization of Saccharomyces Cerevisiae and Saccharomyces Pastorianus Strains for Brewing
by Tim Meier-Dörnberg, Mathias Hutzler, Maximilian Michel, Frank-Jürgen Methner and Fritz Jacob
Fermentation 2017, 3(3), 41; https://doi.org/10.3390/fermentation3030041 - 21 Aug 2017
Cited by 31 | Viewed by 11137
Abstract
The volume and market share loss for classical beer types such as pils beer and wheat beer has been declining for several years, but the overall beer market remains almost unchanged as a result of the increasing interest in beer specialties Due to [...] Read more.
The volume and market share loss for classical beer types such as pils beer and wheat beer has been declining for several years, but the overall beer market remains almost unchanged as a result of the increasing interest in beer specialties Due to high biodiversity, the diversity of the strains, and the different flavor profiles, reliable and practical information regarding the characteristics of individual brewing strains is required to help brewers to find the right strain for their brewing purposes. This paper presents a comparison of 10 commercially available Technical University of Munich (TUM) brewing yeast strains. The strains were screened for genetic and phenotypic characteristics. After confirming the genetic distinctiveness by using species-specific real-time polymerase chain reaction (RT-PCR) systems and a strain typing method based on PCR-capillary electrophoresis of the partial intergenic spacer 2 (IGS2) fragment (IGS2-314 PCR-capillary electrophoresis), the strains were tested regarding phenotypic characteristics under controlled and identical fermentation conditions in small-scale brewing trials. Besides the fermentation performance, flocculation behavior, sugar metabolism and other phenotypic characteristics, the main focus was on the flavor and aroma profile of each investigated TUM yeast strain. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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579 KiB  
Article
Fortification and Elevated Alcohol Concentration Affect the Concentration of Rotundone and Volatiles in Vitis vinifera cv. Shiraz Wine
by Pangzhen Zhang, Fangping Luo and Kate Howell
Fermentation 2017, 3(3), 29; https://doi.org/10.3390/fermentation3030029 - 27 Jun 2017
Cited by 6 | Viewed by 5491
Abstract
Rotundone is a key aromatic compound for cool-climate Shiraz. This compound is produced in the skin of grape berries and extracted into wine during fermentation. This project investigated the influence of fermentation techniques on the concentration of rotundone in the resultant wine. Wine [...] Read more.
Rotundone is a key aromatic compound for cool-climate Shiraz. This compound is produced in the skin of grape berries and extracted into wine during fermentation. This project investigated the influence of fermentation techniques on the concentration of rotundone in the resultant wine. Wine was fortified with ethanol and sucrose on the 1st and 5th days of fermentation and rotundone, volatile aroma compounds and colour were assessed in the resultant wine. The relationship between the concentration of rotundone and alcoholic strength during fermentation process was also investigated. Wine alcoholic strength and skin–wine contact time were two factors affecting rotundone extraction rate from grapes into wine. Fortification significantly enhanced rotundone extraction rate, and improved wine colour and phenolics and affects the concentration of ethyl acetate, 3-methylbutyl acetate, ethyl butanoate, ethyl hexanoate, ethyl octanoate, methyl nonanoate, isopentanol and phenylethyl alcohol in the resultant wine. Understanding how ethanol produced during fermentation can change the extraction of skin-bound aroma compounds and the colour and flavour of wine allows greater control of fermentation parameters to produce quality wine. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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1767 KiB  
Article
Amylase Production from Thermophilic Bacillus sp. BCC 021-50 Isolated from a Marine Environment
by Altaf Ahmed Simair, Imrana Khushk, Abdul Sattar Qureshi, Muhammad Aqeel Bhutto, Haider Ali Chaudhry, Khalil Ahmed Ansari and Changrui Lu
Fermentation 2017, 3(2), 25; https://doi.org/10.3390/fermentation3020025 - 01 Jun 2017
Cited by 19 | Viewed by 17859
Abstract
The high cost of fermentation media is one of the technical barriers in amylase production from microbial sources. Amylase is used in several industrial processes or industries, for example, in the food industry, the saccharification of starchy materials, and in the detergent and [...] Read more.
The high cost of fermentation media is one of the technical barriers in amylase production from microbial sources. Amylase is used in several industrial processes or industries, for example, in the food industry, the saccharification of starchy materials, and in the detergent and textile industry. In this study, marine microorganisms were isolated to identify unique amylase-producing microbes in starch agar medium. More than 50 bacterial strains with positive amylase activity, isolated from marine water and soil, were screened for amylase production in starch agar medium. Bacillus sp. BCC 021-50 was found to be the best amylase-producing strain in starch agar medium and under submerged fermentation conditions. Next, fermentation conditions were optimized for bacterial growth and enzyme production. The highest amylase concentration of 5211 U/mL was obtained after 36 h of incubation at 50 °C, pH 8.0, using 20 g/L molasses as an energy source and 10 g/L peptone as a nitrogen source. From an application perspective, crude amylase was characterized in terms of temperature and pH. Maximum amylase activity was noted at 70 °C and pH 7.50. However, our results show clear advantages for enzyme stability in alkaline pH, high-temperature, and stability in the presence of surfactant, oxidizing, and bleaching agents. This research contributes towards the development of an economical amylase production process using agro-industrial residues. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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Review

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27 pages, 2454 KiB  
Review
Bioethanol a Microbial Biofuel Metabolite; New Insights of Yeasts Metabolic Engineering
by Khaled A. Selim, Dina E. El-Ghwas, Saadia M. Easa and Mohamed I. Abdelwahab Hassan
Fermentation 2018, 4(1), 16; https://doi.org/10.3390/fermentation4010016 - 08 Mar 2018
Cited by 45 | Viewed by 15620
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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12 pages, 1132 KiB  
Review
Fermentation Assisted by Pulsed Electric Field and Ultrasound: A Review
by Leandro Galván-D’Alessandro and Ramiro Ariel Carciochi
Fermentation 2018, 4(1), 1; https://doi.org/10.3390/fermentation4010001 - 04 Jan 2018
Cited by 29 | Viewed by 7954
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 [...] Read more.
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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16018 KiB  
Review
The Production of Secondary Metabolites with Flavour Potential during Brewing and Distilling Wort Fermentations
by Graham G. Stewart
Fermentation 2017, 3(4), 63; https://doi.org/10.3390/fermentation3040063 - 27 Nov 2017
Cited by 52 | Viewed by 29295
Abstract
Ethanol, carbon dioxide and glycerol are the major products produced by yeast during wort fermentation but they have little impact on beer and spirit flavour. It is the type and concentration of secondary metabolites that can determine overall beer flavour. These compounds are [...] Read more.
Ethanol, carbon dioxide and glycerol are the major products produced by yeast during wort fermentation but they have little impact on beer and spirit flavour. It is the type and concentration of secondary metabolites that can determine overall beer flavour. These compounds are (but not only) primarily: higher alcohols, esters, carbonyls and sulphur compounds—inorganic and organic. There are a number of factors that can modify the balance of these compounds most of which are discussed in this review paper. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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681 KiB  
Review
Why Are Weissella spp. Not Used as Commercial Starter Cultures for Food Fermentation?
by Amandine Fessard and Fabienne Remize
Fermentation 2017, 3(3), 38; https://doi.org/10.3390/fermentation3030038 - 03 Aug 2017
Cited by 93 | Viewed by 12693
Abstract
Among other fermentation processes, lactic acid fermentation is a valuable process which enhances the safety, nutritional and sensory properties of food. The use of starters is recommended compared to spontaneous fermentation, from a safety point of view but also to ensure a better [...] Read more.
Among other fermentation processes, lactic acid fermentation is a valuable process which enhances the safety, nutritional and sensory properties of food. The use of starters is recommended compared to spontaneous fermentation, from a safety point of view but also to ensure a better control of product functional and sensory properties. Starters are used for dairy products, sourdough, wine, meat, sauerkraut and homemade foods and beverages from dairy or vegetal origin. Among lactic acid bacteria, Lactobacillus, Lactococcus, Leuconostoc, Streptococcus and Pediococcus are the majors genera used as starters whereas Weissella is not. Weissella spp. are frequently isolated from spontaneous fermented foods and participate to the characteristics of the fermented product. They possess a large set of functional and technological properties, which can enhance safety, nutritional and sensory characteristics of food. Particularly, Weissella cibaria and Weissella confusa have been described as high producers of exo-polysaccharides, which exhibit texturizing properties. Numerous bacteriocins have been purified from Weissella hellenica strains and may be used as bio-preservative. Some Weissella strains are able to decarboxylate polymeric phenolic compounds resulting in a better bioavailability. Other Weissella strains showed resistance to low pH and bile salts and were isolated from healthy human feces, suggesting their potential as probiotics. Despite all these features, the use of Weissella spp. as commercial starters remained non-investigated. Potential biogenic amine production, antibiotic resistance pattern or infection hazard partly explains this neglecting. Besides, Weissella spp. are not recognized as GRAS (Generally Recognized As Safe). However, Weissella spp. are potential powerful starters for food fermentation as well as Lactococcus, Leuconostoc or Lactobacillus species. Full article
(This article belongs to the Special Issue Fermentation and Bioactive Metabolites)
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