Search Results (84)

Simultaneous conversion of syngas and sugars is a promising approach to overcome limitations of syngas fermentation. Clostridium autoethanogenum LAbrini, obtained by adaptive laboratory evolution, is known to show improved autotrophic process performance. Under purely autotrophic conditions, C. autoethanogenum LAbrini exhibits substantially faster growth and biomass formation compared to the wild-type in fully controlled, stirred-tank bioreactors with a continuous gas supply. In mixotrophic processes, the pre-culture strategy has a significant impact on the growth and metabolic activity of C. autoethanogenum LAbrini. C. autoethanogenum LAbrini can metabolize sugars (D-fructose, D-xylose, or L-arabinose) and CO simultaneously. All mixotrophic batch processes showed increased growth and product formation compared to the autotrophic process. The mixotrophic batch process with D-fructose enabled superior production of alcohols (10.7 g L⁻¹ ethanol and 3.2 g L⁻¹ D-2,3-butanediol) with a heterotrophic pre-culture. Using an autotrophic pre-culture and L-arabinose resulted in a total alcohol formation of more than 13 g L⁻¹. The formation of meso-2,3-butanediol (>0.50 g L⁻¹) occurred exclusively under mixotrophic conditions. Thus, C. autoethanogenum LAbrini, clearly representing notable improvements over the wild-type strain in mixotrophic batch processes, offers a good basis for further strain improvements to shift the product range even further towards more reduced products. Full article

Continuous ethanol fermentation is crucial for renewable bio-manufacturing, but delay-induced ethanol inhibition triggers self-oscillations via Hopf bifurcations, undermining productivity and stability. This study investigates instability mechanisms and proposes a washout-filter-aided control strategy. Using Hopf bifurcation theory, the critical delay time τ_c (20.97 h) was quantified, and it confirmed that τ > τ_c (intrinsic τ = 21.72 h) induces oscillations. Closed-loop analysis reveals that the filter extends τ_c to 25.57 h (e.g., K = 2, d = 0.5), expanding the stability margin by modulating ethanol dynamics through phase-shifted feedback. Numerical simulations and experimental validation demonstrate effective oscillation suppression, maintaining steady-state substrate (S* = 84.32 g/L), biomass (X* = 6.92 g/L), and ethanol (P* = 22.02 g/L) concentrations without sacrificing productivity. Unlike conventional methods, the strategy retains the system’s equilibrium structure, resists noise, and requires no additional hardware. This work bridges bifurcation analysis with practical control, offering a robust, scalable solution for industrial continuous ethanol production to mitigate delay-induced instabilities. Full article

The global sparkling wine market continues to grow steadily, reaching approximately 24 million hectoliters in 2023, with an annual increase of around 4% despite a general decline in overall alcoholic beverage consumption. This growth highlights the importance of employing diverse yeast strains to improve product variety and quality. Flor yeasts are specialized strains of Saccharomyces cerevisiae that develop a biofilm on the surface of certain wines during biological ageing. They possess unique physiological properties, including high ethanol tolerance and the capacity to adhere, which supports wine clarification. They also have the ability to contribute unique volatile compounds and aroma profiles, making them promising candidates for sparkling wine production. This study evaluated two flor yeast strains (G1 and N62), which were isolated from the Pérez Barquero winery during the second fermentation process using the traditional method. Sparkling wines were produced by inoculating base wine (BW) with each strain, and the wines were monitored at 3 bar CO₂ pressure and after 9 months of ageing on lees. Comprehensive metabolomic analysis was performed using GC-MS for volatile compounds and HPLC for nitrogen compounds, with statistical analysis including PCA, ANOVA, Fisher’s LSD, and correction FDR tests. Strain N62 demonstrated faster fermentation kinetics and higher cellular concentration, reaching 3 bar pressure in 27 days compared to 52 days for strain G1. Both strains achieved similar final pressures, 5.1–5.4 bars. Metabolomic profiling revealed significant differences in the profiles of volatile and nitrogen compounds between the two strains. G1 produced higher concentrations of 3-methyl-1-butanol, 2-methyl-1-butanol, and acetaldehyde, while N62 generated elevated levels of glycerol, ethyl esters, and amino acids, including glutamic acid, aspartic acid, and alanine. These findings demonstrate that both flor yeast strains successfully complete sparkling wine fermentation while producing distinct metabolic signatures that could contribute to unique sensory characteristics. This supports their potential as alternatives to conventional sparkling wine yeasts for enhanced product diversification. Full article

In this study, to enhance the concentration of caproic acid generated from maize straw fermentation and clarify the structures of bacterial and fungal communities within the serially subcultured rumen microbial fermentation system, maize straw was used as the substrate. In a continuous subculture system, the impacts of ethanol addition on pH and gas production were explored, with a focus on the caproic acid yield in the final (eighth generation) generation and alterations in bacterial and fungal communities. The results showed that the relative abundances of unidentified_Clostridiales, Shuttleworthia, and Syntrophococcus in ethanol-driven caproic acid production were enriched by 5.36-fold, 2.61-fold, and 2.25-fold, respectively. This consequently increased the concentration of caproic acid in the fermentation broth to 1492 mg/L, representing a 3.7-fold increase. These findings are highly significant for the high-value utilization of maize straw waste to produce caproic acid via the carboxylic acid platform using rumen microorganisms in industrial processing. Full article

Saccharomyces cerevisiae often undergoes strain degeneration during industrial serial subculturing, though this phenomenon remains understudied. This study first conducted strain screening and biological characterization through TTC (2,3,5-triphenyltetrazolium chloride) colorimetric assays, Durham tube fermentation gas production tests, and WL medium (Wallerstein Laboratory medium) cultivation. Subsequently, the changes in intergenerational biological traits after serial subculturing were investigated. Finally, transcriptomic analysis was employed to examine differential gene expression under high-glucose stress during continuous subculturing. The experimental results demonstrated that: (1) The S. cerevisiae QDSK310-Z-07 (GenBank: PP663884), isolated from farm soil, exhibited robust growth within a temperature range of 24–36 °C, with optimal growth observed at 28 °C. It thrived in a pH range of 4–5.5 and efficiently utilized various carbon and nitrogen sources; (2) After serial subculturing, the strain’s ethanol production capacity and fermentation rate partially declined and then stabilized, while maintaining strong tolerance to high ethanol concentrations and hyperosmotic stress; (3) Transcriptomic analysis revealed significant differential expression of genes related to lipid metabolism, amino acid metabolism, and other pathways under high-glucose stress following continuous subculturing. These findings elucidate the biological trait variations in S. cerevisiae during serial subculturing and provide key metabolic regulation candidate targets for its long-term adaptive evolution under high-glucose stress. Full article

This study presents a non-invasive approach to monitoring post-harvest fruit quality by applying CO₂ laser photoacoustic spectroscopy (CO₂LPAS) to study the respiration of “Conference” pears from local and commercially stored (supermarket) sources. Concentrations of ethylene (C₂H₄), ethanol (C₂H₆O), and ammonia (NH₃) were continuously monitored under shelf-life conditions. Our results reveal that ethylene emission peaks earlier in supermarket pears, likely due to post-harvest treatments, while ethanol accumulates over time, indicating fermentation-related deterioration. Significantly, ammonia levels increased during the late stages of senescence, suggesting its potential role as a novel biomarker for fruit degradation. The application of CO₂LPAS enabled highly sensitive, real-time detection of trace gases without damaging the fruit, offering a powerful alternative to traditional monitoring methods. Additionally, artificial intelligence (AI) models, particularly convolutional neural networks (CNNs), were explored to enhance data interpretation, enabling early detection of ripening and spoilage patterns through volatile compound profiling. This study advances our understanding of post-harvest physiological processes and proposes new strategies for improving storage and distribution practices for climacteric fruits. Full article

This research investigated the interaction between the labile and stable fractions of soil organic carbon (SOC) during the cultivation of organic cassava in sandy soil in northeastern Thailand over a period of five years. We collected surface soil samples (0–30 cm) from this sandy region, utilizing a combination of cow and chicken manure along with dried distilled grains (DDGs) from cassava fermentation for ethanol production, to monitor and compare the effects of continuous mixed organic fertilization on SOC, carbon fractions, soil pH, and nitrogen and phosphorus levels throughout a five-year period of varying land use ages (LUA) to the pre-fertilization state. This study proposed that the use of a combination of organic fertilizers could increase soil organic carbon levels. This study indicates that the continuous application of organic fertilizers over five years does not lead to a significant increase in soil carbon; however, it may result in temporary alterations in different organic carbon fractions. The study showed that the mixed organic fertilization could the increase carbon fractions. Labile carbon (LBC) fraction was at its lowest before fertilization, peaking at LUA 3 and increasing by 5.44–25.50% after organic fertilizer addition. The first year revealed high non labile carbon (NLBC) levels, exceeding 60%, in comparison to the pre-fertilizer period. In the second year, NLBC levels declined to LUA 5, a change that was not statistically significant. After pre-fertilization, the concentration of recalcitrant carbon (REC) did not significantly decrease. Nitrate (NO₃⁻-N) concentrations exhibited no significant fluctuation pre-and post-fertilization. Furthermore, the Bray II-extractable phosphorus (P(B)) decreased (i.e., LUA 1 and 4). The pH levels dropped after the addition of organic fertilizer, particularly in the second year. We found strong positive links between SOC and carbon fractions such as NLBC (r = 0.54 ***) and POXC (r = 0.49 ***). However, neither LBC nor less labile carbon fraction (LLBC) showed any significant correlations with SOC. The negative correlations were observed between ammonium (NH₄⁺-N) and NO₃⁻-N with labile carbon types, such as LBC, LLBC, and POXC, while positive correlations were noted with stable carbon fractions, such as NLBC, and REC. From the application of this organic fertilizer, there are various amounts of organic carbon which cause the following effects: The inclusion of LBC from mixed organic fertilization seems to enhance SOC decomposition rather than accumulation. NLCB may persist in sandy soil for a longer duration than LBC, resulting in the retention of SOC in sandy soil. Our results suggested the implementation of a systematic soil testing strategy to monitor temporal variations in carbon fractions and nutrient levels. Using the right amounts of both LBC and NLBC would improve soil health and help store carbon through organic fertilizers. Full article

A mathematical model was developed for the dynamic and static simulation of a continuous ethanol production process in a tower bioreactor packed with yeast cells immobilized in citrus pectin gel. To avoid accumulation of CO₂ gas during the bioprocess, a vertical fixed bed bioreactor with a working volume of 0.245 L, divided into four stages and equipped with external gas–liquid separators was used. The performance of the bioreactor was evaluated through continuous fermentations using feed medium (sugarcane juice) with substrate concentrations of 161.4 and 312.5 g/L, temperature of 30 °C, pH 4.0 and hydraulic residence times of 5 and 6 h. The developed mathematical model takes into account mass flow by convection and dispersion axial, external and internal mass transfer to/within particle, Contois kinetics for cell growth with inhibition terms, cell death, and substrate consumption for cell maintenance. The partial differential equations regarding cell, substrate and product mass balances in the solid and fluid phase were solved by numerical methods. The calculated profiles of state variables in the fluid phase agreed satisfactorily with the experimental data. The diffusional resistances within particles concerning the substrate consumption rate were not significant, resulting in calculated values of the effectiveness factor close to one. Full article

This study investigated the physiological and biochemical responses of Styrax japonica Sieb. et Zucc. seedlings to normal water and nutrient management (control group, CK), waterlogging (root submerged, T1), and partial submergence (partial stem submergence, T2) over a period of 25 days. Measurements of root activity, malondialdehyde (MDA) content, hydrogen peroxide (H₂O₂) content, antioxidant enzyme (SOD, POD, and CAT), and anaerobic respiratory enzyme (LDH, ADH, and PDC) activities were conducted every 5 days. The results showed the following: the seedlings of the control group maintained high root activity and low oxidative damage levels throughout the experiment; under T1 treatment, root activity initially increased but declined, while MDA and H₂O₂ content gradually increased; T2 seedlings showed little change initially, but root activity briefly increased at Day 20 before rapidly declining. Regarding the antioxidant system, the control group had the highest SOD activity, while seedlings under T1 and T2 treatments exhibited compensatory upregulation of CAT and POD activities (from Day 15 to 20). Additionally, under waterlogging stress, LDH and ADH activities significantly increased, reflecting the activation of anaerobic metabolic pathways, while PDC content continuously decreased, indicating that low-oxygen stress induced the accumulation of LDH and ADH but reduced ethanol fermentation. PCA revealed that the first two principal components explained 61.53% of the total variation, with PC1 (45.76%) reflecting the contrasting relationship between the activation of anaerobic metabolism (increased ADH and LDH activity) and decreased root activity under waterlogging stress, while PC2 (15.77%) primarily captured the responses of oxidative damage (increased MDA) and corresponding antioxidant defense (upregulated CAT and POD activities). Overall, S. japonica seedlings adapt to short-term waterlogging stress by regulating anaerobic respiration and antioxidant systems, but prolonged stress leads to a continued increase in H₂O₂ and a decline in antioxidant enzyme activities. This study provides experimental evidence and theoretical support for understanding the waterlogging tolerance mechanisms of S. japonica. This experiment provides important information on the adaptive mechanisms of plants under waterlogging stress. Full article

The bioethanol produced from biomass fermentation is characterised by its renewable nature, as expressed in its life cycle. The Amazonian taro, with 72% starch content, can be an alternative to traditional raw materials such as corn and sugarcane. The objective of this study was to evaluate taro (Colocasia esculenta) as a raw material for bioethanol production through ultrasound-assisted enzymatic hydrolysis. For the enzymatic hydrolysis process, α-amylase and glucoamylase enzymes were used. Active dry yeast Saccharomyces cerevisiae was employed for fermentation. The chemical characterisation analysis of the flour with peel (WP) revealed high levels of protein (8.71%), crude fibre (4.21%) and total ash (5.56%). However, taro flour without peel (NP) revealed higher starch results (27.5%). The evaluation of reducing sugars during enzymatic hydrolysis showed better results in the samples with ultrasonic pretreatment, specifically in the sample with peel (WP-US) (1017.8 mg/L). The ethanol yield was significantly higher in the ultrasound-treated samples, achieving an approximately 35% increase in ethanol yield for both peeled and unpeeled samples compared to untreated samples. These findings open up new perspectives for using this tuber in the biofuel industry. Furthermore, they emphasise the need for continued research on biomass conversion processes. Full article

Beer is one of the most popular alcoholic beverages globally, leading to continuous efforts to enhance its production methods. Raw materials and the production process are crucial in the brewing industry, with fermentation being a vital stage that significantly impacts beer quality. The aim of this study is to optimize the beer fermentation process by maximizing the ethanol concentration while minimizing species that adversely affect the organoleptic properties of beer. A novel optimization approach has been developed to derive an optimal, smooth, and continuous temperature profile that can be directly applied in real-world processes. This method integrates Fourier series and orthogonal polynomials for control action parameterization, in combination with evolutionary algorithms for parameter optimization. A key advantage of this methodology lies in its ability to handle a reduced parameter set efficiently, resulting in temperature profiles that are continuous and differentiable. This feature eliminates the need for post-smoothing and is particularly advantageous in biotechnological applications, where abrupt changes in temperature could negatively affect the viability of microorganisms. The optimized profiles not only enhance fermentation efficiency, but also improve the ethanol yield and reduce undesirable flavor compounds, providing a substantial improvement over current industrial practices. These advancements present significant potential for improving both the quality and consistency of beer production. Full article

Ethanol production by fermentation results in obtaining, in addition to the main product, ethyl alcohol, by-products and secondary products, which include carbon dioxide, fusel oil, and ester–aldehyde cut. Fusel oil, despite its low yield and the large volume of ethanol production, accumulates at distilleries, which ultimately raises the question of its disposal or the rational use of this by-product. Fusel oil, being a complex mixture, can serve as a source of technical alcohols used in various sectors of the economy, including the food industry, pharmaceuticals, organic synthesis, perfume, and cosmetics industries, as well as the production of paints and varnishes. However, the complexity of using fusel oil lies in its difficult separation. The reason for this is the presence of water, which forms low-boiling azeotropes with aliphatic alcohols. Our study aimed to develop a process flow diagram (PFD) that allows individual components from fusel oil to be obtained without extraneous separating agents (not inherent in fusel oil). This condition is necessary to obtain products labeled as natural for further use in the food, perfume, cosmetic, and pharmaceutical industries. The distinctive feature of this work is that the target product is not only isoamyl alcohol but also all other alcohols present in the composition of fusel oil. To achieve this goal and create a mathematical model, the Aspen Plus V14 application, the Non-Random Two Liquid (NRTL) thermodynamic model, and the Vap-Liq/Liq-Liq phase equilibrium were used. Fusel oil separation was modeled using a continuous separation PFD to obtain ethanol, water, isoamyl alcohol, and raw propanol and butanol cuts. The Sorel and Barbet distillation technique was used to isolate ethanol. The isolation of isopropanol and 1-propanol, as well as isobutanol and 1-butanol, was modeled using the batch distillation method. The isolation of fusel oil components was based on their thermodynamic properties and the selection of appropriate techniques for their separation, such as extraction, distillation, pressure swing distillation, and decantation. The simulation of fusel oil separation PFD showed the possibility of obtaining the components of a complex mixture without separating agents, as discussed earlier. Ethanol corresponds to the quality of rectified ethyl alcohol, and 1-butanol and isoamyl alcohols to anhydrous alcohols, whereas isopropanol (which contains an admixture of ethanol), 1-propanol, and isobutanol are obtained as aqueous solutions of different concentrations of alcohols. However, due to a distillation boundary in the raw propanol and butanol cuts, these mixtures cannot be separated completely, which leads to the production of intermediate fractions. To eliminate intermediate fractions and obtain anhydrous isopropanol, 1-propanol, and isobutanol in the future, it is necessary to solve the dehydration problem of either fusel oil or the propanol–butanol mixture. Full article

Computational modeling and the theory of nonlinear dynamical systems allow us not only to simply describe the events of biochemical oscillators in the ethanol fermentation process but also to understand why these events occur. This article reviews results of experimental and theoretical studies about the behavior of fermentation systems for bio-ethanol production so as to understand the self-oscillatory phenomena that could affect productivity in industry. In general, Hopf bifurcation and limit cycles are the theoretical basis for the oscillations observed in continuous ethanol fermentation processes, but the underline mechanisms and causes might be different because the studied system is a collection of multi-scale oscillators. To characterize the oscillatory dynamics quantitatively, negative feedback laws are implemented. However, the stimulated oscillation through linear feedback is not adequate in describing such complex dynamics. Hence, elements of nonlinearity, auto-catalysis, and time delay are sorted out and added into the feedback loops to formulate biochemical oscillators. Then, we discuss specific examples of the various models and classify them according to the three kinds of mechanisms: nonlinear feedback, positive feedback, and delay feedback. These mechanisms and modeling work might be used as a guide for process design/operation to eliminate possible oscillations and to develop out advanced configurations that could produce bio-ethanol in a continuous, cost-effective manner. Full article

The cell immobilization technique, which restricts living cells to a certain space, has received widespread attention as an emerging biotechnology. In this study, a yeast (Saccharomyces cerevisiae)-loaded highly open-cell emulsion-templated polyethylene glycol (PEG-polyHIPE) was synthesized to be a reusable enzymatic catalyst. An emulsion was prepared with polyethylene glycol diacrylate (PEGDA) aqueous solution, cyclohexane, and polyethylene-polypropylene glycol (F127) as the continuous phase, dispersed phase, and surfactant, respectively. Then PEG-polyHIPE was obtained by polymerization of the PEGDA in emulsion. The highly porous materials obtained by the emulsion-templating method are suitable for use as carrier materials for yeast immobilization, due to their favorable structural designability. During the activation process, the yeast S. cerevisiae can readily gain access to the interior of the material via the interconnected pores and immobilize itself inside the voids. The yeast-loaded polyHIPE was then used to ferment glucose for ethanol production. The yeast immobilized inside the polyHIPE has high fermentation efficiency, good recoverability, and storage stability. After seven cycles, the yeast maintained 70% initial fermentation efficiency. The S. cerevisiae kept more than 90% of the initial cellular activity after one week of storage both in the dry state and in yeast extract peptone dextrose medium (YPD) at 4 °C. This study strongly demonstrates the feasibility of using high-throughput porous materials as cell immobilization carriers to efficiently osmotically immobilize cells in polyHIPEs for high-performance fermentation. Full article

Biofuel has received worldwide attention as one of the most promising renewable energy sources. Particularly, in many countries such as the U.S. and Brazil, first-generation ethanol from corn and sugar cane has been used as automobile fuel after blending with gasoline. Nevertheless, in order to continuously increase the use of biofuels, efforts are needed to reduce the cost of biofuel production and increase its profitability. This can be achieved by increasing the efficiency of a sequential biofuel production process consisting of multiple operations such as feedstock supply, pretreatment, fermentation, distillation, and biofuel transportation. This study aims at investigating methodologies for predicting feedstock yields, which is the earliest step for stable and sustainable biofuel production. Particularly, this study reviews feedstock yield estimation approaches using machine learning technologies that focus on gradually improving estimation accuracy by using big data and computer algorithms from traditional statistical approaches. Given that it is becoming increasingly difficult to stably produce biofuel feedstocks as climate change worsens, research on developing predictive modeling for raw material supply using the latest ML techniques is very important. As a result, this study will help researchers and engineers predict feedstock yields using various machine learning techniques, and contribute to efficient and stable biofuel production and supply chain design based on accurate predictions of feedstocks. Full article