Simultaneous Production Of Ethanol Research Articles

Sequential fed batch extractive fermentation for enhanced bioethanol production using recycled Spathaspora passalidarum and mixed sugar composition

The simultaneous ethanol production and removal during sequential cell recycle fed batch fermentation provides a complementary route to produce this biofuel from sugar mixtures, which may greatly improve yields and productivity from lignocellulosic hydrolysates. Spathaspora passalidarum is a wild-type strain able to naturally convert glucose, fructose, xylose and arabinose into ethanol. Therefore, the present work has focused on 2G bioethanol production by S. passalidarum aiming at the consumption of all sugars released after pre-treatment and enzymatic hydrolysis of sugarcane bagasse in a single fermentation step. The fermentation strategy with sequential cell recycle, fed-batch mode and ethanol removal in situ was performed on a hemicellulosic hydrolysate medium supplemented with molasses. This strategy gave improved fermentation performance and enabled the co-fermention of all sugars under microaerobic conditions. The maximum ethanol yield and productivity was 0.482 g.g−1 and 9.5 g·L-1·h−1, respectively, showing a process efficiency of 94.3%. The selective ethanol removal enables the operation of the bioreactor at low levels of ethanol (20–30 g·L-1), even with high sugar concentration inputs, accelerating the fermentation performance and avoiding inhibitory effects on yeast metabolism. Applying the cell recycle strategy, S. passalidarum was able to increase its robustness, as shown by a 10-fold increase in ethanol productivity, and it was also able to tolerate a high acetic acid concentration (4.5 g·L-1) during long-term fermentations. These results demonstrate that the bioprocess strategy has a strong potential to improve bioethanol production of rich mixed sugar from lignocellulosic hydrolysates in a single fermentation step.

Improving bioethanol production by Scheffersomyces stipitis using retentostat extractive fermentation at high xylose concentration

The improvement of yields and productivity for second-generation ethanol (2G) production as well as a better understanding of industrial yeasts and processes are required. Nevertheless, a process to produce 2G ethanol efficiently from lignocellulosic C5-sugars has not yet been proposed. Scheffersomyces stipitis presents good fermentation performance, promising to be a potential biocatalyst for converting C5-sugars to ethanol. In order to evaluate yeast performance, experiments were carried out in a retentostatic extractive vacuum system (REV) with total cell retention, controlled substrate feeding (at different xylose concentrations 100–200gL−1) and simultaneous ethanol production and extraction. During REV at 100gL−1, it was possible to achieve an efficient ethanol production. The optimum dilution rate was 0.025h−1. To avoid stress effects to the yeast metabolism, the ethanol was continuously extracted. Low ethanol concentrations were kept inside the fermenter (25–35gL‐1), resulting in higher yields and productivity when compared with batch, fed-batch and continuous cultures.

New generation biofuel: continuous acidogenesis of sucrose-raffinose mixture simulating vinasse is promoted by γ-alumina pellets.

BackgroundThis investigation comprises a contribution on the production of a new generation biofuel using the industrial liquid waste of bioethanol distilleries, known as vinasse. This study focuses on the exploitation of vinasse as an acidogenesis substrate for volatile fatty acids and simultaneous ethanol production. These products can be used for ester production, which is the new generation biofuel. Therefore, the aims of the present study are (i) to examine any promotional effect of γ-alumina on acidogenesis of a sucrose-raffinose mixture simulating vinasse, (ii) to study the operational stability of the continuous acidogenesis of sucrose and raffinose and subsequently of vinasse, and (iii) to determine the volatile fatty acid chemical composition and ethanol formation.ResultsBatch acidogenesis of sucrose and raffinose mixtures showed that γ-alumina promoted fermentation leading to an increase in the volatile fatty acid yield factor from 40% to 95% compared to free cells. The application of the system in continuous mode for more than 3 months showed that the continuous volatile fatty acid productivity obtained was higher than 7 g/L/day. Lactic acid was the predominant acid when sucrose and raffinose were used while butyric acid in the case of vinasse. The highest volatile fatty acid concentration reached was 19 g/L for vinasse.ConclusionsA promoting effect of γ-alumina in acidogenic fermentation of sucrose-raffinose and vinasse is reported. Continuous acidogenesis of sucrose-raffinose mixtures and vinasse using γ-alumina with immobilized cells showed high operational stability (more than 3 months). These findings result in easy scale up of the process that will produce a high annual added value of $11,000,000 in a daily bioethanol production plant of 50,000 L.

Co-production of bioethanol and biodiesel from corn stover pretreated with nitric acid

This research explores the application of glucose and xylose from corn stover pretreated with nitric acid (HNO3) for the co-production of bioethanol and biodiesel. Response surface methodology was employed to optimize HNO3 pretreatment condition including HNO3 concentration (0.2–1.0%), temperature (140–160°C), and reaction time (1–10min). The optimal reaction condition was 151.9°C, 0.68% HNO3 and 2.5min, which resulted in the highest xylose yield of 77.8% and glucan content of 57.1%. Quasi-simultaneous saccharification and fermentation (Q-SSF) of pretreated corn stover with Saccharomyces cerevisiae gave an ethanol concentration of 22.4g/L, corresponding to 69.1% theoretical ethanol yield based on initial cellulose weight. In addition, Cryptococcus curvatus in hydrolysate medium showed the lipid yield (final cell weight×lipid content) of 1.04g/L, which was higher than those in defined medium using pure xylose. Our work demonstrates that the simultaneous production of ethanol and lipid can be one potentially promising option for lignocellulose-derived fuel production.

Simultaneous Optimization and Heat Integration for the Coproduction of Diesel Substitutes: Biodiesel (FAME and FAEE) and Glycerol Ethers from Algae Oil

In this paper, an optimal process for the simultaneous production of biodiesel (using methanol or bioethanol) and ethers of glycerol is proposed to increase the yield to diesel substitutes in current biodiesel production facilities. The problem is formulated as an optimization model including algae oil production, production of ethanol from starch, transesterification of the oil with bioethanol or methanol, etherification of glycerol with i-butene, which depends on a dynamic model to compute the complex chemical kinetics, and the purification of the ethers. Simultaneous optimization and heat integration are carried out and finally the water consumption of the integrated processes is optimized. Several comparisons are presented. First, the use of glycerol to produce ethers or as a byproduct. Second, the use of different alcohols for biodiesel synthesis in an integrated process. The production of glycerol ethers increases the yield of diesel substitutes by 20%. Furthermore, the energy and water consumptions are competitive with those processes when glycerol is the byproduct. For the integration of glycerol ethers with current biodiesel plants, the use of methanol instead of ethanol is cheaper. However, the current price of i-butene results in high production costs. Simultaneous production of ethanol, biodiesel and glyerol ethers reaches the target of $1/gal for biofuels production cost.

Hydrogen production potentials and fermentative characteristics of various substrates with different heat-pretreated natural microflora

Batch tests were carried out to investigate the effects of heat-pretreated inocula on the fermentative hydrogen production characteristics of various types of substrates. A total of 8 different inocula and 4 different substrates (starch, glycerol, oil and peptone) were used. Heat pretreatment of the inocula was conducted in order to harvest spore-forming clostridial bacteria. Significant hydrogen production potentials were observed from starch (20.5–174.4 ml H2/g-CODstarch) and glycerol (11.5–38.1 ml H2/g-CODglycerol); however, almost no hydrogen was produced from oil and peptone. When starch was used as a substrate, two different fermentation patterns were observed, according to the inocula: butyric acid-type and ethanol-type fermentation. Polymerase chain reaction combined with denaturing gradient gel electrophoresis (PCR-DGGE) analysis was conducted to compare the bacterial structures cultivated on the starch medium. Different species of clostridial bacteria were observed between the butyric acid-type and ethanol-type fermentation cultures. When glycerol was used as a substrate, 1,3-propanediol was the main by-product with each inoculum. The results of the present study suggest that simultaneous production of ethanol or 1,3-propanediol in addition to hydrogen is a more promising strategy than conventional hydrogen production in acidogenesis.

Fructan Biosynthesis by Intra‐ and Extracellular Zymomonas mobilis Levansucrase after Simultaneous Production of Ethanol and Levan

AbstractThe chemical composition of the Zymomonas mobilis biomass and the culture liquid after ethanol and levan synthesis were studied. The activities of intra‐ and extracellular levansucrase produced by the Z. mobilis strain 113 “S” under optimum conditions both for levan and fructooligosaccharide (FOS) synthesis were also determined. It was shown that levan production relates to the reduction of the carbohydrate and lipid content in the biomass by increasing the nucleic acid and protein content. The levan producing activity of cellular levansucrase after ethanol and levan synthesis was approximately 30–40% of the total activity in the second fermentation stage. It was established that the cell free culture liquid, containing ethanol, levan, gluconic acid and sucrose (15%) at 25 °C, did not show any additional levan synthesising activity. At optimum FOS synthesis conditions (45 °C and 70% sucrose), the cell‐free culture liquid exhibited a high FOS synthesising activity (31% from total carbohydrates), with slightly reduced biomass activity. It was concluded that as a result of the simultaneous ethanol and levan production, the remaining biomass as well as the cell‐free culture liquid could be used for FOS production.

Construction of a flocculating yeast for fructose production from inulin

Construction of flocculating yeast lacking for fructose utilisation was realised by integration of the FLO1 flocculation gene in the ribosomal DNA of an hexokinase deficient (hxk1, hxk2) Saccharomyces cerevisiae strain (ATCC36859). Simultaneous production of ethanol and fructose was obtained from glucose/fructose mixtures or from hydrolysed Jerusalem artichoke extracts using the transformed yeast in batch fermentations and in a continuous reactor with internal biomass recycle. This allowed the production of 5 g ethanol/L and 48 g sugars/L containing up to 99 % fructose from diluted hydrolysed Jerusalem artichoke extracts containing 60 g sugars/L. © Rapid Science Ltd. 1998

96/01723 Simultaneous production of ethanol and kraft pulp from pine ( Pinus radiata) using steam explosion

96/01723 Simultaneous production of ethanol and kraft pulp from pine ( Pinus radiata) using steam explosion

Inulin enrichment by fermentation in a flocculating yeast reactor

Simultaneous production of ethanol and fructose enriched syrups was obtained from Jerusalem artichoke extract using a Saccharomyces diastaticus flocculating yeast in a continuous gas-lift reactor with internal biomass recycle. This allowed the production of 42 g/L of ethanol and 70 g/L of inulin containing up to 92% fructose (fructose/glucose ratio of 11). These results can be compared to the batch and chemostat fermentations which gave a higher ethanol concentration but a lower fructose enrichment. Mass transfert limitations can explain both the productivity decrease and the selectivity improvement in the gas-lift reactor.

Simultaneous production of sugars and ethanol from inulin rich-extracts in a chemostat

Incomplete fermentation of inulin-containing extracts by Saccharomyces diastaticus allows the simultaneous production of ethanol and syrups with increased fructose content. The yeast strain used ferments sucrose and inulin small polymers but does not easily ferment inulin large polymers. After batch fermentation a production of 62.5 g/L ethanol and 75 g/L of sugars containing up to 94 % fructose can be obtained. A continuous fermentation was performed in a chemostat permitting the adjustment of both productions according to the dilution rate with a maximal ethanol productivity of 3.9 g/L.h.