10th Anniversary of Fermentation: Feature Papers in the “Fermentation Process Design” Section

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Fermentation Process Design".

Deadline for manuscript submissions: 31 December 2025 | Viewed by 2125

Special Issue Editors


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Guest Editor
Department of Animal Sciences and Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, 305 Gerlaugh Hall, 1680 Madison Avenue, Wooster, OH 44691, USA
Interests: microbial physiology; biofuel (butanol, ethanol, methane) and biochemical (2,3-butanediol, acetone, isopropanol) production; downstream processing; biomass pretreatment technologies; lignocellulose-derived microbial inhibitory compounds and mitigations; metabolic engineering; bioreactor design; alcoholic fermentation and anaerobic digestion
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Guest Editor
Department of Chemical Engineering and Materials, College of Chemical Sciences, Complutense University of Madrid, 28040 Madrid, Spain
Interests: glycerol; biodiesel; valorization; catalysts; carbonates; ketals; monomers; ethers; esters; lactic acid; hydrogen; diols; refining; oxidation; dehydration; biorefinery; biomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

As we celebrate the 10th anniversary of Fermentation, it is with great excitement that we announce the upcoming Special Issue titled “10th Anniversary of Fermentation: Feature Papers in the 'Fermentation Process Design' Section”. This Special Issue aims to publish high-quality original research and review articles spanning all aspects of fermentation process design. We invite researchers from related fields to contribute and highlight the latest developments in this area. Topics of interest for this Special Issue include, but are not limited to, novel bioreactor and bioprocess designs; the production of macromolecules (e.g., enzymes, proteins, antibodies, and lipids); the production of small molecules (e.g., amino acids, peptides, and vitamins); the bioremediation of pollutants; improved separation methods for the recovery of fermentation products; advanced tools for monitoring and controlling bioreactors; and analyses of bioreactor performance. We eagerly anticipate your innovative and impactful contributions to this special celebration of a decade of progress in fermentation science!

Prof. Dr. Thaddeus Ezeji
Prof. Dr. Miguel Ladero
Guest Editors

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 submissions that pass pre-check are 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 monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). 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

  • process design
  • bioreactor performance
  • scale-up
  • scale-down
  • microbial kinetics
  • fed-batch
  • purification methods
  • bioprocess monitoring

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Published Papers (3 papers)

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Research

18 pages, 2970 KiB  
Article
Synthetic Biofilm Reactor with Independent Supply of Gas and Liquid Phase for Studying Chain Elongation with Immobilized Clostridium kluyveri at Defined Reaction Conditions
by Josha Herzog, Karlis Blums, Simon Gregg, Lukas Gröninger, Johannes Poppe, Verena Uhlig, Qifei Wang and Dirk Weuster-Botz
Fermentation 2025, 11(4), 200; https://doi.org/10.3390/fermentation11040200 - 9 Apr 2025
Viewed by 359
Abstract
In this study, we explore the use of C. kluyveri in synthetic biofilms for the production of 1-butyrate and 1-hexanoate, investigating the impact of inoculation temperature during biofilm formation and the presence of yeast extract. Therefore, a novel synthetic biofilm reactor has been [...] Read more.
In this study, we explore the use of C. kluyveri in synthetic biofilms for the production of 1-butyrate and 1-hexanoate, investigating the impact of inoculation temperature during biofilm formation and the presence of yeast extract. Therefore, a novel synthetic biofilm reactor has been designed and constructed. Prior to investigating synthetic biofilms in this reactor, we carried out preliminary batch experiments in anaerobic flasks containing an inoculated agar hydrogel fixed at the bottom and overlaid medium. For the operation of the novel synthetic biofilm reactor, specific volumes of inoculated agar hydrogel were dispensed into a cylindrical mold with a diameter of 102 mm, forming the synthetic biofilm with a height of 4 mm, which was then transferred into the biofilm reaction chamber onto the support grid. The biofilm support grid separates the gas phase (CO2, N2) above the synthetic biofilm from the aqueous phase (medium) below. Our results show that C. kluyveri remains metabolically active at biofilm preparation temperatures of up to 45 °C, with extended lag phases observed at 70 °C. The synthetic biofilm demonstrated efficient chain elongation in batch processes, converting ethanol and acetate into 1-butyrate and 1-hexanoate, with final concentrations of 2.7 g L−1 and 10.1 g L−1, respectively, with yeast extract in the circulating liquid medium of the synthetic biofilm reactor setup. The maximum estimated space-time yields for 1-butyrate and 1-hexanoate, referenced to the biofilm volume, were 1.331 g L−1 h−1 and 4.947 g L−1 h−1, respectively. Experiments without yeast extract lead to final concentrations of 2.0 g L−1 1-butyrate, and 7.3 g L−1 1-hexanoate and maximum estimated space-time yields, referenced to the biofilm volume, were 0.332 g L−1 h−1 and 1.123 g L−1 h−1, respectively. The use of synthetic biofilms, even without yeast extract, eliminates the need for significant cell growth during chain elongation. However, product concentrations were lower without yeast extract. Full article
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20 pages, 1971 KiB  
Article
Enhanced Sugar Yield from Enzymatic Hydrolysis of Cellulignin from Sugarcane Bagasse Using a Biosurfactant and Soybean Protein in Powdered and Cavitated Forms
by Alain Monsalve Mera, Salvador Sánchez Muñoz, Felipe A. Fernandes Antunes, Júlio C. dos Santos and Silvio Silvério da Silva
Fermentation 2025, 11(3), 114; https://doi.org/10.3390/fermentation11030114 - 28 Feb 2025
Viewed by 579
Abstract
The enzymatic hydrolysis of lignocellulosic biomass is often hindered by lignin, which acts as a physical barrier and promotes non-productive enzyme adsorption. This study evaluated the potential of soybean protein in powdered and cavitated forms, along with lactonic sophorolipid biosurfactant (LSLB), to enhance [...] Read more.
The enzymatic hydrolysis of lignocellulosic biomass is often hindered by lignin, which acts as a physical barrier and promotes non-productive enzyme adsorption. This study evaluated the potential of soybean protein in powdered and cavitated forms, along with lactonic sophorolipid biosurfactant (LSLB), to enhance sugar yields from cellulignin derived from sugarcane bagasse, a residue with a high lignin content. A Box–Behnken design was used to investigate the effects of enzyme loading (10–20 FPU/g cellulignin), soybean protein powder (10–30% w/w of dried cellulignin), and LSLB concentration (25–250 mg/L) on glucose and xylose yields. Hydrodynamic cavitation was employed to produce soluble soybean protein, achieving a solubility yield of 44.4% w/w in 10 min. The cavitated protein was compared with powdered protein to assess its impact on enzymatic hydrolysis efficiency. The results showed that hydrodynamic cavitation reduced the required SBP dosage while maintaining sugar yields, allowing 10% w/w of dried cellulignin cavitated SBP to achieve glucose and xylose yields comparable to 25% w/w of dried cellulignin non-cavitated SBP. Specifically, glucose yield increased by 24.92% (from 34.1% ± 1.01 to 42.6% ± 1.4), and xylose yield by 30.86% (from 32.4% ± 0.53 to 42.4% ± 2.21) compared to the no-additive condition. These improvements were linked to enhanced solubility, increased surface area, and reduced particle size in the cavitated protein. This study highlights hydrodynamic cavitation as a novel approach for modifying soybean protein structure to optimize enzymatic hydrolysis in lignocellulosic bioconversion. Full article
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18 pages, 4037 KiB  
Article
Bioenergetic Modeling of the Relationship Between Voltage and Electroactive Microbial Biomass Yield for Bioelectrochemical Carbon Dioxide Reduction to Methane
by Vafa Ahmadi and Nabin Aryal
Fermentation 2025, 11(1), 40; https://doi.org/10.3390/fermentation11010040 - 17 Jan 2025
Cited by 1 | Viewed by 945
Abstract
Optimal product synthesis in bioelectrochemical systems (BESs) requires a comprehensive understanding of the relationship between external voltage and microbial yield. While most studies assume constant growth yields or rely on empirical estimates, this study presents a novel thermodynamic model, linking anodic oxidation and [...] Read more.
Optimal product synthesis in bioelectrochemical systems (BESs) requires a comprehensive understanding of the relationship between external voltage and microbial yield. While most studies assume constant growth yields or rely on empirical estimates, this study presents a novel thermodynamic model, linking anodic oxidation and cathodic carbon dioxide (CO2) reduction to methane (CH4) by growing microbial biofilm. Through integrating theoretical Gibbs free energy calculations, the model predicts electron and proton transfers for autotrophic methanogen and anode-respiring bacteria (ARB) growth, accounting for varying applied voltages and substrate concentrations. The findings identify an optimal applied cathodic potential of −0.3 V vs. the standard hydrogen electrode (SHE) for maximizing CH4 production under standard conditions (pH 7, 25 °C, 1 atm) regardless of ohmic losses. The model bridges the stoichiometry of anodic and cathodic biofilms, addressing research gaps in simulating anodic and cathodic biofilm growth simultaneously. Additionally, sensitivity analyses reveal that lower substrate concentrations require more negative voltages than standard condition to stimulate microbial growth. The model was validated using experimental data, demonstrating reasonable predictions of biomass growth and CH4 yield under different operating voltages in a multi substrate system. The results show that higher voltage inputs increase biomass yield while reducing CH4 output due to non-optimal voltage. This validated model provides a tool for optimizing BES performance to enhance CH4 recovery and biofilm stability. These insights contribute to finding optimum voltage for the highest CH4 production for energy efficient CO2 reduction for scaling up BES technology. Full article
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