Ethanol Production Research Articles

Assessment for industrial production of poplar ethanol after analysis of influencing factors and predicted yield

Assessment for industrial production of poplar ethanol after analysis of influencing factors and predicted yield

Energizing the future: Unleashing the potential of innovative waste-to-energy technologies for energy development and sustainability within Zimbabwe's tourism sector.

Zimbabwe's tourism industry, renowned for its natural wonders and cultural heritage, faces a looming energy crisis rooted in the detrimental over-reliance on fossil fuels and the underutilization of substantial waste resources that lie dormant. The article investigates multifaceted relationship between six independent variables: landfill gas recovery and anaerobic digestion, pyrolysis and gasification, incineration, biogas production, biodiesel production, ethanol production and syngas fermentation and one dependent variable: energy development and sustainability. In this study, a quantitative methodology was adopted, involving the gathering of data from 519 stakeholders in the tourism supply chain through a simple random sampling technique, with the sample size determined using the Krejcie and Morgan table. The distribution of questionnaires was facilitated through Google Forms, and the data analysis was conducted using Smart PLS. Statistical findings indicate direct significant relationship between variables, and t-statistic values all hypotheses were all greater than the threshold of 1.96, ranging from a minimum of 2.911 to a maximum of 9.431. These findings underscore the robustness of the relationships between the waste-to-energy technologies and energy development and sustainability within Zimbabwe's tourism sector. This empirical evidence highlights the substantial potential for these innovative technologies to play a pivotal role in mitigating the energy crisis and fostering sustainable energy development.

Distinct effects of dilute acid prehydrolysate inhibitors on enzymatic hydrolysis and yeast fermentation.

The effects of dilute acid prehydrolysate from poplar were investigated and compared in the enzymatic hydrolysis, fermentation, and simultaneous saccharification fermentation (SSF) in this study. The improvement of enzymatic hydrolysis and fermentation with resin adsorption and surfactant addition has also been represented. A total of 16 phenolic alcohols, aldehydes, acids and 3 furan derivatives in the prehydrolysates were identified and quantified by gas chromatography/mass spectrometry (GC/MS). The degree of inhibition from the phenolic compounds (26.55%) in prehydrolysate on the enzymatic hydrolysis was much higher than carbohydrates-derived inhibitors (0.52-4.64%). Around 40% degree of inhibition was eliminated in Avicel enzymatic hydrolysis when 75% of prehydrolysates phenolic compounds were removed by resin adsorption. This showed distinguishing inhibition degrees of various prehydrolysate phenolic compounds. Inhibition of prehydrolysate on enzymatic hydrolysis was more dosage-dependent, while their suppression on the fermentation showed a more complicated mode: fermentation could be terminated by the untreated prehydrolysate, while a small number of prehydrolysate inhibitors even improved the glucose consumption and ethanol production in the fermentation. Correlated with this distinct inhibition modes of prehydrolysate, the improvement of Tween 80 addition in SSF was around 7.10% for the final ethanol yield when the glucose accumulation was promoted by 76.6%.

Valorization of Residual Fractions from Defatted Rice Bran Protein Extraction: A Carbohydrate-Rich Source for Bioprocess Applications

Defatted rice bran (DRB) is the by-product of rice bran oil extraction and presents approximately 66% carbohydrates and 15% proteins, a composition with the potential to integrate biorefinery systems. This study aimed to investigate the feasibility of residual fractions from ultrasound-assisted protein extraction from DRB as sources of carbohydrates in bioprocesses. First, DRB was exposed to protein extraction in an alkaline medium assisted by ultrasound. The residual fractions, including the precipitate from the extraction process (P1) and the supernatant from protein precipitation (S2), were combined and autoclaved to gelatinize the starch. Enzyme activity tests showed that a temperature of 70 °C was optimal for the simultaneous application of α-amylase and amyloglucosidase (AMG). To study enzymatic hydrolysis, a Full Factorial Design (FFD) 22 was employed, with α-amylase and AMG concentrations ranging from 0.12 to 0.18 mL∙L−1 and a substrate concentration (P1/S2 ratio) between 30 and 70 g∙L−1, resulting in a maximum of 18 g∙L−1 of reducing sugars (RS). Fermentation assays with Saccharomyces cerevisiae demonstrated that the hydrolysate of the residual fractions was effective for ethanol production (8.84 g∙L−1 of ethanol; YP/S: 0.614 gethanol∙gRS−1; η: 120.24%), achieving results comparable to control media (with sucrose as the substrate), indicating its potential for application in bioprocesses. These outcomes highlight a promising technological approach for utilizing DRB in integrated biorefineries.

Scale sensitivity of ethanol production via consolidated bioprocessing with consideration of feedstock cost

AbstractWe examine feedstock cost and minimum selling price for ethanol production from corn stover as a function of scale, stover yield, participation rate, and price incentives for two conversion technologies: a conventional base case featuring thermochemical pretreatment with added cellulase, and an advanced case featuring consolidated bioprocessing with cotreatment (C‐CBP). Delivered feedstock cost ranged from $85 Mg−1 at small (10 million gallons year−1 or ~38 million L year−1) scale with high yield and participation rates to $124 Mg−1 at large scale (60 million gallons year−1 or 227 million L year−1) and low yield and participation rates. The minimum ethanol selling price (MESP) was approximately twofold lower for the advanced case compared with the base case. The payback period was several times lower for the advanced case compared with the base case, with increasing disparity at smaller scales, and was highly sensitive to ethanol price supports. For both C‐CBP and the conventional processing paradigm, MESP decreased with increasing scale, indicating that the cost penalty due to higher feedstock transport distances was more than outweighed by lower capital costs. However, the cost penalty for operation at small scale, expressed in $ gallon−1 ethanol, is lower for C‐CBP than for the conventional paradigm by roughly twofold. Particularly for initial applications of C‐CBP, we speculate that this cost penalty will likely be modest compared with the anticipated benefits of small‐scale operation such as increased opportunity to use existing infrastructure, easier plant siting and supply chain establishment, and lower total investment required.

Evaluation of the Physico-chemical and Biological Properties of Fermented Nipa (Nypa fruticans) Sap Under Closed and Open Vessel Fermentation System for Bioethanol Production

Background The potential of Nipa (Nypa fruticans) sap in the Cagayan Region, Philippines, for bioethanol production remains largely underexplored despite its vast expanse. Methods This study investigates the key physico-chemical properties of Nipa sap from Aparri, Cagayan, with a focus on fermentation dynamics and storage conditions to optimize ethanol production. Two fermentation treatments closed and open vessel conditions, were compared to determine the optimal conditions for maximum ethanol yield. Over a 7-day fermentation period, the acetic acid production, yeast activity, sugar content, and ethanol concentration of closed vessel fermented sap (CVFS) and open vessel fermented sap (OVFS) were monitored. Results CVFS demonstrated a higher ethanol yield (7.56%v/v at peak day), characterized by minimized acetic acid accumulation and stable yeast activity. In contrast, OVFS exhibited significant fluctuations in acetic acid and ethanol levels, indicating a lower fermentation efficiency. Conclusion The presence of methanol and high acetic acid content in open-vessel fermentation systems highlights the importance of fermentation conditions to prevent impurities. This study provides valuable insights into optimizing ethanol production from fermenting Nipa sap by employing closed vessel fermentation, which is crucial for sustainable bioethanol production in the Cagayan region.

Optimized spacing of active sites in Ni-Mo catalysts enhances ethanol production in syngas conversion

The direct conversion of syngas to ethanol is highly attractive but remains challenging due to low CO conversion and poor EtOH/ROH. We investigated the conversion of syngas over a KNiMo2C catalyst modified with carbon dots (CDs) derived from Ligustrum lucidum leaves. On the Ni0.54Mo-A catalyst, a CO conversion of 43.4 % was achieved, with oxygenates selectivity and EtOH/ROH，reaching 48.2 % and 63.7 %, the space-time yield of ethanol was 132.5 mg/gcat/h. Comprehensive characterization revealed that CDs regulate the distance between Ni-Mo active sites, preventing excessive proximity and maintaining an optimal separation. This adjustment significantly enhances EtOH/ROH by modulating the probability of carbon chain growth. A potential new reaction pathway for directly converting syngas to ethanol is proposed, The C-C coupling of CHx* with *COOH or *CO2 is identified as a key step in carbon chain growth. This work provides a new catalytic pathway for the syngas to ethanol industry.

Nutrient Consumption Patterns of Saccharomyces cerevisiae and Their Application in Fruit Wine Fermentation

This study aimed to evaluate the nutritional requirements of Saccharomyces cerevisiae to improve low ethanol production in some fruit wines. The growth kinetics, ethanol production and nutrient requirements of S. cerevisiae were analyzed in chemically defined media. The results revealed that Ca2⁺, Fe2⁺, Co2⁺, Mo2⁺, Cu2⁺ and BO₃3− were predominantly utilized during the late lag phase, whereas free amino acids, nicotinic acid, calcium pantothenate, Na⁺ and Mg2⁺ were mainly consumed during the logarithmic phase. Compared with the control medium, supplementation with threonine, inositol, calcium pantothenate, thiamine hydrochloride, riboflavin, biotin, MgSO4 or KH2PO4 significantly increased the ethanol content by 1.10-fold (p < 0.05). Furthermore, adding key nutrients to noni-, guava- and mango juice significantly shortened the fermentation time and increased the final alcohol content of the fruit wines (p < 0.05). This study provides scientific insights and effective methods for shortening fermentation time and increasing alcohol content with S. cerevisiae in some fruit wines.

Enhanced bioethanol production from Compositae plant stalks: Integrating dry acid pretreatment and fungal mediated biodetoxification

Compositae is an important economic plant with relatively high contents of water-soluble sugars in stalk section. The pretreatment of Compositae plant stalks quickly converts the water-soluble sugars into high titers of furan aldehydes, which inhibits the viability of consequent fermentation strains. This study used the typical Compositae plant stalks of sunflower, Jerusalem artichoke, and stevia as feedstocks for dry acid pretreatment under high solids loading, then a unique solid-state biodetoxification method was applied to degrade these high-titer inhibitors. The results showed that temperature and sulfuric acid concentration were two key parameters for enhancing pretreatment efficiency. Enzymatic hydrolysis yield of the above pretreated stalks reached up to 79.68%, 66.75% and 74.05%, respectively. For pretreated Jerusalem artichoke stalk, it contained 37.36% of cellulose, 2.72% of xylan, 3.04% of glucose, 11.64% of xylose, 20.54% of lignin, and some inhibitors (3.80% of acetate, 0.24% of HMF and 0.23% of furfural). After biodetoxification, 100% of furfural, 40% of HMF, and 36% of acetate were quickly removed by Amorphotheca resinae ZN1, which resulted in 55.57 g/L ethanol production (equivalent to 7.1% by volumetric percentage) with the yield of 55.54% from 73.59 g/L of glucose and 40.69 g/L of xylose by simultaneous saccharification and co-fermentation (SSCF). This study provides a combinational approach of dry acid pretreatment and biodetoxification for Compositae plant stalks biorefinery.

Differences in microbial communities among different types of zaopei and their effects on quality and flavor of baijiu

Three types of zaopei (fermented grain) of xiaoqu light-flavor baijiu (XQZP), daqu light-flavor baijiu (DQZP), and strong-flavor baijiu (SFZP) at the end of fermentation and their dominant lactic acid bacteria were systematically compared and analyzed in this study. The results showed that these three types of zaopei differed significantly in acidity, reducing sugar content, and ethanol content, and that the main factors influencing their microbial community were acidity and lactic acid. The diversity and contents of flavor substances were significantly higher in SFZP than in DQZP and XQZP. Additionally, there was a strong correlation between dominant lactic acid bacteria and flavor substances in all three zaopei, but the correlation between fungi and flavor substances was higher than that between bacteria and flavor substances. Differential gene analysis revealed that the microbial activities followed the order of SFZP > DQZP > XQZP. The KEGG enrichment analysis indicated that the differential genes from different zaopei were enriched in different metabolic pathways. Furthermore, various microorganisms in 3 types of zaopei contained different functional genes, of which fungi mainly contained genes responsible for the synthesis of ethanol and acetic acid, while lactic acid bacteria mainly contained genes responsible for the synthesis of lactic acid. In XQZP, L. helveticus was dominant lactic acid bacteria prominent in acetic acid tolerance and lactic acid production; in DQZP, L. acetotolerans was remarkable in its tolerance to lactic acid, acetic acid, ethanol and lactic acid production; and in SFZP, A. jinshanensis was superior in acetic acid tolerance and production. Taken together, this study reveals the mechanism underlying flavor differences among three types of baijiu and provides valuable references for the development and utilization of baijiu microbial resources.

Enhancing CO2 Electroreduction Precision to Ethylene and Ethanol: The Role of Additional Boron Catalytic Sites in Cu-Based Tandem Catalysts.

The electrocatalytic conversion of carbon dioxide (CO2) into valuable multicarbon (C2+) compounds offers a promising approach to mitigate CO2 emissions and harness renewable energy. However, achieving precise selectivity for specific C2+ products, such as ethylene and ethanol, remains a formidable challenge. This study shows that incorporating elemental boron (B) into copper (Cu) catalysts provides additional adsorption sites for *CO intermediates, enhancing the selectivity of desirable C2+ products. Additionally, using a nickel single-atom catalyst (Ni-SAC) as a *CO source increases local *CO concentration and reduces the hydrogen evolution reaction. In situ experiments and density functional theory (DFT) calculations reveal that surface-bound boron units adsorb and convert *CO more efficiently, promoting ethylene production, while boron within the bulk phase of copper influences charge transfer, facilitating ethanol generation. In a neutral electrolyte, the bias current density for ethylene production using the B-O-Cu2@Ni-SAC0.05 hybrid catalyst exceeded 300 mA cm-2, and that for ethanol production with B-O-Cu5@Ni-SAC0.2 surpassed 250 mA cm-2. This study underscores that elemental doping in Cu-based catalysts not only alters charge and crystalline phase arrangements at Cu sites but also provides additional reduction sites for coupling reactions, enabling the efficient synthesis of distinct C2+ products.

Steering the Selectivity of CORR from Acetate to Ethanol via Tailoring the Thermodynamic Activity of Water

AbstractThe electrochemical conversion of carbon monoxide (CO) into oxygenated C2+ products at high rates and selectivity offers a promising approach for the two‐step conversion of carbon dioxide (CO2). However, a major drawback of the CO electrochemical reduction in alkaline electrolyte is the preference for the acetate pathway over the more valuable ethanol pathway. Recent research has shed light on the significant impact of thermodynamic water activity on the electrochemical CO2 reduction reaction pathways, but less is understood for the electrochemical reduction of CO. In this study, we investigated how the water activity at the electrified interface can be enhanced to adjust the selectivity between acetate and ethanol. We employed an ionomer modifier to lower the local concentration of alkali ions (via Donnan exclusion), successfully enhancing ethanol production while suppressing acetate formation. We observed a remarkable improvement in the Faradaic efficiency of ethanol and alcohol (i. e. ethanol, propanol etc), which reached 42.5 % and 55.1 %, respectively, at a current density of 700 mA cm−2. The partial current densities of ethanol and alcohol reached 698 and 942 mA cm−2 at 2000 mA cm−2. Furthermore, we achieved a 3.7‐fold increase in the ethanol/acetate ratio, providing clear evidence of our successful modulation of product selectivity.

Waste Bread as Raw Material for Ethanol Production: Effect of Mash Preparation Methods on Fermentation Efficiency

The issue of managing waste bread is a global concern, with significant environmental and the economic implications. The utilisation of waste bread for bioethanol production, employing energy-saving technology, could prevent these consequences and reduce the consumption of traditionally used fossil fuels. The objective of this study was to evaluate the influence of the type of waste bread (wheat and wheat–rye sourdough) and the mash preparation method on the results of alcoholic fermentation and the concentration of selected congeners in the distillates. The highest fermentation efficiency (96% of theoretical) was achieved for both types of bread through the utilisation of the pressureless starch liberation method combined with simultaneous saccharification and fermentation. The separate saccharification of starch resulted in lower process efficiencies (from 85.75 to 88.60% of theoretical). The application of the native starch hydrolysis method (without starch activation) for the fermentation of wheat bread-based mashes exhibited a higher efficiency (87.85% of the theoretical) than that observed for the wheat–rye bread-based mash sample (83.74% of theoretical). All of the obtained spirit distillates exhibited a low concentration of methanol (≤300 mg/L alcohol 100% v/v) and comply with the requirements of the EU regulation for ethyl alcohol of agricultural origin (rectified spirit).

Isolation and identification of epiphytic Pichia kudriavzevii from loquat peels and investigation of its fermentation characteristics for liquor production.

During the process of fruit wine production, yeast plays a crucial role in influencing the taste, flavor, and overall quality of the wine. This study aims to enhance the flavor and quality of loquat wine by isolating strains of Pichia kudriavzevii (P. kudriavzevii) with desirable winemaking characteristics from loquat fruit fermentation broth. A total of 12 strains of P. kudriavzevii were isolated and subjected to morphological and molecular biological identification. Their fermentation performance, ethanol production, ester production, hydrogen sulfide production, killer activity, and tolerance were evaluated. The results revealed that strains Q-2, Q-9, Q-10, Q-12, Q-20, and Q-42 exhibited robust growth and strong tolerance under conditions of 40°C temperature, 12% ethanol concentration, 350g/L glucose concentration, and pH 2.8. Strain Q-42 demonstrated the strongest gas production capacity, killer activity, and good ester and ethanol production. As a highly active fermentation strain with excellent wine making characteristics, P. kudriavzevii Q-42 provides a valuable yeast resource for the industrial production of loquat wine and offers technical support for improving the overall quality of loquat wine.

Prompting CO2 Electroreduction to Ethanolby Iron Group Metal Ion Dopants Induced Multi-sites at the Interface of SnSe/SnSe2 p-n Heterojunction.

The development of non-copper-based materials for CO2 electroreduction to ethanol with high selectivity at large current density is highly desirable, but still a great challenge. Herein, we report iron group metal ions of M2+ (M = Fe, Co, or Ni)-doped amorphous/crystalline SnSe/SnSe2nanorod/nanosheet hierarchical structures (a/c-SnSe/SnSe2) for selective CO2 electroreduction to ethanol. Iron group metal ions doping induces multiple active sites at the interface of M2+-doped SnSe/SnSe2 p-n heterojunction, which strengthens *CO intermediate binding for further C-C coupling to eventual ethanol generation. As a representative, Fe9.0%-a/c-SnSe/SnSe2 exhibits an ethanol Faradaic efficiency of 62.7% and a partial current density of 239.0 mA cm-2 at -0.6 V in a flow cell. Moreover, it can output an ethanol Faradaic efficiency of 63.5% and a partial current density of 201.2 mA cm-2 with a full-cell energy efficiency of 24.1% at 3.0 V in a membrane electrode assembly (MEA) electrolyzer. This work provides insight into non-Cu based catalyst design for stabilizing the key intermediates for selective ethanol production from CO2 electroreduction.

Evaluation of a phenolic-tolerant Wickerhamomyces anomalus strain for efficient ethanol production based on omics analysis

Lignocellulosic biomass is a highly economically viable substrate for ethanol fermentation, but the presence of phenolic compounds (PCs) in lignocellulosic hydrolysates severely hinders the growth of ethanologenic strains. This study aims to investigate the ethanol fermentation capabilities and PC tolerance of the newly isolated Wickerhamomyces anomalus CAP5. The strain demonstrated remarkable ethanol production, achieving 87.1 g/L with a yield of 0.47 g/g, exceeding 90 % of the theoretical maximum. To elucidate the mechanisms responsible for this high ethanol yield, comprehensive genome and transcriptome analyses were performed. These analyses identified key metabolic pathways, including acetate reabsorption and an incomplete glycerol synthesis pathway, as crucial factors contributing to the strain's superior performance. Moreover, W. anomalus CAP5 demonstrated notable resistance to PCs, particularly phenolic acids. In fermenting with coffee husk hydrolysate (CHH), which is rich in PCs, W. anomalus CAP5 achieved noteworthy ethanol production of 60.5 g/L, marking a record for ethanol production from CHH. Hence, W. anomalus CAP5 emerges as a promising strain for effective ethanol production from lignocellulosic hydrolysates enriched with PCs.

Yeast Solutions and Hyperpolarization Enable Real-Time Observation of Metabolized Substrates Even at Natural Abundance.

Metabolic changes in an organism often occur much earlier than macroscopic manifestations of disease, such as invasive tumors. Therefore, noninvasive tools to monitor metabolism are fundamental as they provide insights into in vivo biochemistry. NMR represents one of the gold standards for such insights by observing metabolites. Using nuclear spin hyperpolarization greatly increases the NMR sensitivity, enabling μmol/L sensitivity with a time resolution of about one second. However, a metabolic phantom with reproducible, rapid, and human-like metabolism is needed to progress research in this area. Using baker's yeast as a convenient metabolic factory, we demonstrated in a single study that yeast cells provide a robust and rapidly metabolizing phantom for pyruvate and fumarate, including substrates with a natural abundance of 13C: we observed the production of ethanol, carbon dioxide, bicarbonate, lactate, alanine from pyruvate, malate, and oxaloacetate from fumarate. For observation, we hyperpolarized pyruvate and fumarate via the dissolution dynamic nuclear polarization (dDNP) technique to about 30% 13C polarization that is equivalent to 360,000 signal enhancement at 1 T and 310 K. Major metabolic pathways were observed using tracers at a natural abundance of 13C, demonstrating that isotope labeling is not always essential in vitro. Enriched [1-13C]pyruvate revealed minor lactate production, presumably via the D-lactate dehydrogenase (DLD) enzyme pathway, demonstrating the sensitivity gain using a dense yeast solution. We foresee that yeast as a metabolic factory can find application as an abundant MRI phantom standard to calibrate and optimize molecular MRI protocols. Our study highlights the potential of using hyperpolarization to probe the metabolism of yeast and other microorganisms even with naturally abundant substrates, offering valuable insights into their response to various stimuli such as drugs, treatment, nourishment, and genetic modification, thereby advancing drug development and our understanding of biochemical processes.

Boosting selectivity for multi-carbon products in electrochemical CO2 reduction via enhanced hydroxide adsorption in ultrafine CuOx/CeOx nanoparticles

The electricity-driven reduction of CO2 presents a unique prospect of mitigating atmospheric CO2 levels and converting renewable energy into chemical fuels. However, the lack of an efficient catalyst that can transform CO2 into desired products with appreciable selectivity at commercially relevant current densities (ID) impedes the practical implications of this technology. This work describes a scalable approach for producing ultrafine nanoparticles of CuOx-CeOx (CuCe) composites via rapid coprecipitation under oxygen-deprived conditions. In this process, Ce(OH)3 acts as a reducing agent converting Cu(OH)2 into ultrafine Cu2O nanoparticles. Thus, the Ce: Cu ratio in composite effectively controls the particle size and bulk structural fixture of the CuCe composites. Despite having lower ECSA, The CuCe composites exhibit superior catalytic performance compared to CuO, with significantly higher selectivity for ethanol production and lower selectivity for CO and H2. The Cu1.5Ce prepared using a Cu: Ce ratio of 1.5:1, demonstrated remarkable catalytic activity with Faradaic efficiencies (F. E.) of 34.2 % for ethanol, 44.1 % for ethylene, and 81.08 % for multi-carbon (C2+) products. Moreover, while operating at the ID of 500 mA cm−2, Cu1.5Ce achieves a single pass CO2 conversion (SPCC) of 19.9 %, and a half-cell energy efficiency (E. E. half-cell) of 31.5 % for the C2+ products. It produces the C2+ products at the partial current density (pID) of 405.4 mA cm−2. The superior performance of Cu1.5Ce can be attributed to the improved hydroxide adsorption and partial retention of oxidized copper species under cathodic bias.

Production of Sugars and Ethanol from Acid–Alkaline-Pretreated Agave sisalana Residue

Drylands in Brazil have been exploring sisal (Agave sisalana) as an essential source of income. However, the solid residues generated because of this activity still need suitable destinations; therefore, research has been carried out to transform them into added-value products. Therefore, the present study evaluated the potential of sisal or agave solid residue as a precursor feedstock for second-generation ethanol production. Acid and acid–alkaline pretreatments were carried out on sisal residues to enrich the biomass with cellulose and maximize enzymatic digestibility. Second-generation ethanol production was carried out using Semi-simultaneous saccharification and fermentation (SSSF). Regardless of catalyst dosage and incubation time, oxalic acid pretreatments generated samples with a similar chemical composition to those pretreated with sulfuric acid. However, samples pretreated with oxalic acid showed lower enzymatic digestibility. Samples pretreated with oxalic acid and sodium hydroxide obtained 14.28 g/L of glucose and cellulose conversion of 79.1% (at 5% solids), while 21.49 g/L glucose and 91.2% of cellulose conversion were obtained in the hydrolysis of pretreated samples with sulfuric acid and sodium hydroxide combined pretreatments. The pretreatment sequence efficiently reduced cellulase dosage from 20 to 10 FPU/g without compromising sugar release. SSSF achieved maximum production of 40 g/L ethanol and 43% ethanol conversion using 30% solids and gradually adding biomass and cellulases.

Ethanol Production Using Zymomonas mobilis and In Situ Extraction in a Capillary Microreactor

The bacterium Zymomonas mobilis is investigated as a model organism for the cultivation and separation of ethanol as a product by in situ extraction in continuous flow microreactors. The considered microreactor is the Coiled Flow Inverter (CFI), which consists of a capillary coiled onto a support structure. Like other microreactors, the CFI benefits from a high surface-to-volume ratio, which enhances mass and heat transfer. Compared to many other microreactors, the CFI offers the advantage of operating without internal structures, which are often used to ensure good mixing. The simplicity of the design makes the CFI particularly suitable for biochemical applications as cells do not get stuck or damaged by internal structures. Despite this simplicity, good mixing is achieved through flow vortices caused by Taylor and Dean vortices. The reaction system consists of two phases, in which the aqueous phase carries the bacterium and an oleyl alcohol phase is used to extract the ethanol produced. Key parameters for evaluation are bacteria growth and the amount of ethanol produced by the microorganism. The results show the suitability of the CFI for microbial production of valuable compounds. A maximum ethanol concentration of 1.26 g L−1 was achieved for the experiment in the CFI. Overall, the cultivation in the CFI led to faster growth of Z. mobilis, resulting in 25% higher ethanol production than in conducted batch experiments.