Application of solvent extraction to ethanol fermentation

Summary The basic problems of applying solvent extraction to ethanol fermentation were investigated. The selection of solvents was based on the selectivity ratio, which was expressed as the ratio of the ethanol distribution coefficient to the water distribution coefficient. Solvents with high selectivity ratios of more than 50 were found mainly among the alcohols and esters. However, most of these solvents were toxic to ethanol-producing microorganisms. We tried to make a barrier to solvent molecules beneath the surface of gel beads immobilizing the cells as a protection against solvent toxicity. Porapack Q was found to be an effective barrier, and the ethanol production rate of immobilized cells protected with Porapack Q did not change event after the production of eight batches in medium saturated with sec-octanol, which was the most toxic solvent used in our experiments.     

Estimation of ethanol in fermentation broth by solvent extraction and gas chromatography

Ethanol from fermentation is usually estimated by gas chromatography after centrifuging or distilling the broth. In this paper a more efficient and rapid method is described in which ethanol is extracted by an organic solvent such as n-butanol and the extract is analysed by gas chromatography. The distribution factor determined has a value close to unity and is dependent on ethanol concentration, but independent of sugar concentration.     

Sugaring-out extraction of acetoin from fermentation broth by coupling with fermentation

Bioprocess and Biosystems Engineering - Acetoin is a natural flavor and an important bio-based chemical which could be separated from fermentation broth by solvent extraction, salting-out...     

Production of fuel ethanol from bamboo by concentrated sulfuric acid hydrolysis followed by continuous ethanol fermentation

An efficient process for the production of fuel ethanol from bamboo that consisted of hydrolysis with concentrated sulfuric acid, removal of color compounds, separation of acid and sugar, hydrolysis of oligosaccharides and subsequent continuous ethanol fermentation was developed. The highest sugar recovery efficiency was 81.6% when concentrated sulfuric acid hydrolysis was carried out under the optimum conditions. Continuous separation of acid from the saccharified liquid after removal of color compounds with activated carbon was conducted using an improved simulated moving bed (ISMB) system, and 98.4% of sugar and 90.5% of acid were recovered. After oligosaccharide hydrolysis and pH adjustment, the unsterilized saccharified liquid was subjected to continuous ethanol fermentation using Saccharomycescerevisiae strain KF-7. The ethanol concentration, the fermentation yield based on glucose and the ethanol productivity were approximately 27.2 g/l, 92.0% and 8.2 g/l/h, respectively. These results suggest that the process is effective for production of fuel ethanol from bamboo.     

Production of ethanol from raw cassava starch by a nonconventional fermentation method

Raw cassava root starch was transformed into ethanol in a one-step process of fermentation, in which are combined the conventional processes of liquefaction, saccharification, and fermentation to alcohol. Aspergillus awamori NRRL 3112 and Aspergillus niger were cultivated on wheat bran and used as Koji enzymes. Commercial A. niger amyloglucosidase was also used in this experiment. A raw cassava root homogenate–enzymes–yeast mixture fermented optimally at pH 3.5 and 30°C, for five days and produced ethanol. Alcohol yields from raw cassava roots were between 82.3 and 99.6%. Fungal Koji enzymes effectively decreased the viscosity of cassava root fermentation mashes during incubation. Commercial A. niger amyloglucosidase decreased the viscosity slightly. Reduction of viscosity of fermentation mashes was 40, 84, and 93% by commercial amyloglucosidase, A. awamori, and A. niger enzymes, respectively. The reduction of viscosity of fermentation mashes is probably due to the hydrolysis of pentosans by Koji enzymes.     

Production of fungal chitosan by solid substrate fermentation followed by enzymatic extraction

An improved method is described for the production of chitosan from mycelia of the fungus Gongronella butleri, grown by solid substrate fermentation on sweet potato. The chitosan was extracted subsequently by 11 M NaOH at 45 °C, and 0.35 M acetic acid at 95 °C. The resulting extract was clarified using a heat-stable, commercial -amylase. The yield (4–6 g/100 g mycelia) and relative number average molecular weight (44–54 kDa) of the chitosan increased with increasing duration of fungal growth up to the sixth day.     

Production of ethanol from extruded corn starch by a nonconvencional fermentation method

Summary In single-step 48-hour fermentations of extruded, liquefied and raw corn starch, the yields of ethanol from extruded starch were similar to those from liquefied starch, whereas the yields of ethanol from raw starch were lower.     

Mixed solvent systems for recovery of ethanol from dilute aqueous solution by liquid-liquid extraction

Distribution coefficients and selectivities of a number of mixed solvent systems have been determined in order to assess their suitability in preferentially extracting ethanol from aqueous solution. The measured values of distribution coefficients and selectivities differ substantially from the values estimated by interpolating between the pure solvents.     

Production of ethanol by immobilized Saccharomyces bayanus in an extractive fermentation system

An extractive fermentation system using immobilized yeast cells was developed to study the ethanol production at high sugar concentrations. Organic acids were used as extracting solvents of ethanol and their toxicity was tested in free and k-carrageenan entrapped cell preparations. Immobilization seems to protect cells against solvent toxicity, when long-chain organic acids, e.g., oleic acid, were used, probably due to steric and diffusional limitations, the free cells not being viable at high oleic acid concentrations. The entrapped cells also present a higher metabolic activity than their free counterparts at high glucose concentrations. A solution of 300 g/L of glucose was totally fermented by the immobilized yeast cells, which when free cannot normally convert more than 200 g/L. In situ recovery of ethanol by oleic acid in a batch immobilized cell system led to higher ethanol productivities and to the fermentation of 400 g/L, when an oleic acid/medium ratio of 5 was used.     

Production of ethanol in repeated-batch fermentation with membrane-type bioreactor

The average ethanol content in sake is 14 wt%; continuous production of such a high ethanol content was found not to be stably maintained in a packed-bed bioreactor with immobilized yeast cells, used normally for production of an ethanol content of up to 10 wt%. However, use of repeated-batch ethanol fermentation incorporating a membrane filter for product separation enabled a high ethanol content and improved productivity to be achieved. In this bioreactor, the yeast cells were retained within the bioreactor and a high yeast concentration was possible. A filtrate containing 14 wt% ethanol was obtained steadily after each batchwise operation. At a yeast concentration of 110 g/l, an ethanol productivity of 3.5 g/l/h was attained, which is 9 times higher than that in conventional batch fermentation. A mathematical model is proposed for assessment of the repeated-batch fermentation process. The estimated results agreed well with the observed ones. With a view to the application of this system to sake production, the aroma components of the filtrate were assayed and compared with those of a commercial-grade sake.     

Efficient extraction of intracellular reduced glutathione from fermentation broth of Saccharomyces cerevisiae by ethanol

Reduced glutathione (GSH) from fermentation broth of Saccharomyces cerevisiae was extracted with ethanol without disruption of the cells. The effects of ethanol concentration, extraction temperature and extraction time were assessed by using 2(3) full factorial designs (FFD). Preliminary studies showed that ethanol concentration had the most influence on GSH yield by ethanol extraction, based on the first order regression coefficients derived using MINITAB software, and an optimal ethanol concentration (25%, v/v) was obtained. However, compared to the conventional extraction technique (hot water extraction), there was no significant advantage in yield of GSH from yeast cells using ethanol extraction under these optimized conditions. But ethanol extraction has several advantages, such as lower energy consumption and lower protein concentration of extraction broth, which may reduce the complexity and cost of the purification process. Hence, ethanol extraction which does not disrupt yeast cells could be an inexpensive, simple and efficient alternative to conventional extraction techniques in the GSH industry.     

Production of ethanol from extruded degermed corn grits by a nonconventional fermentation method

Degermed corn grits (DCG) were extruded at 150°C, with a compression rate of 1 : 2, and the materials were fermented by a nonconventional fermentation method. Yields of ethanol from various concentrations (12–30 g/200 ml) of extruded DCG were 0.37–0.38. It was found that the mold brad enzyme was superior to the glucoamylase preparations for ethanol fermentation, but combinedenzyme systems such as a mixture of glucoamylase, acid protease, and cellulolytic enzymes are as efficient in converting the extruded DCG to ethanol as the mold bran enzyme alone.     

Optimal process/solvent design for ethanol extractive fermentation with cell recycling

In this study, the computer-aided process/solvent design is introduced to find an optimal biocompatible solvent and to maximize the ethanol production rate simultaneously for the single- or double-stage extractive fermentation process with cell recycling. Such a process/solvent design problem is formulated as a mixed-integer nonlinear programming problem that is solved by mixed-integer hybrid differential evolution in order to obtain a global design. The double-stage process can use a smaller amount of fresh solvent to increase ethanol productivity compared with that of the single-stage process, but it will also decrease overall conversion. Comparing the case studies, the simultaneous process/solvent design could yield higher overall ethanol productivity than that of the process design. The maximum ethanol production rate for the double-stage extractive fermentation with cell recycling was about 10-fold higher than that of continuous fermentation and about twofold higher than that of continuous fermentation with cell recycling.     

Production of acetone,butanol and ethanol (ABE) from potato wastes: fermentation with integrated membrane extraction

The technical possibilities of the microbial production of acetone, butanol and ethanol (ABE) from potato waste using in-line solvent recovery, are evaluated. Clostridium acetobutylicum DSM 1731 produces up to 20 g·l^–1 of solvents when grown on a medium containing 14% (w/v) potato powder. Using a polypropylene perstraction system and a oleyl alcohol/decane mixture as the extractant, the product yield (based on total solvents and potato dry weight) increased from 0.13 g·g^–1 to 0.23 g·g^–1. The recovery system worked well for 50 h, after which membrane fouling frustrated proper operation. In the second system a microfiltration step was incorporated whereas the solvents were extracted through a hydrophilic membrane using fatty acid methyl esters from sunflower oil as an extractant. This process configuration resulted in a comparable increase of ABE production. Correspondence to: G. Eggink     

Production of ethanol by raw starch hydrolysis and fermentation of damaged grains of wheat and sorghum

The simultaneous saccharification and fermentation was used to produce ethanol from raw starch of damaged quality wheat and sorghum grains by utilising crude amylase preparation from B. subtilis VB2 and an amylolytic yeast strain S. cerevisiae VSJ4. Various concentrations of damaged wheat and sorghum starch from 10% to 30%W/V were used and 25% was found to be optimum for damaged wheat and sorghum starch yielding 4.40%V/V and 3.50%V/V ethanol respectively. Whereas 25% raw starch of fine quality wheat and sorghum grains gave an yield of 5.60%V/V and 5.00%V/V respectively. The process was carried out at 35v°C, 5.8 pH and 200 rpm for 4 days.     

Inhibition of alcoholic fermentation by substrate and ethanol

The effect of ethanol and sugars on rates of fermentation was studied. We used a strain of Canadida pseudotropicalis. The specific rate of fermentation was determined by using the Warburg manometer. The effect of ethanol was formulated as an exponential function of ethanol concentration, but the empirical constant was different when glucose or lactose was used as a substrate. The effects of both ethanol and substrate were formulated. It was demonstrate that when lactose and glucose were present in the medium with a small amount of alcohol, a synergistic effect on the rate of fermentation appeard. This phenomenon considerably limits the rate of fermentation.     

Acetonobutylic fermentation: improvement of performances by coupling continuous fermentation and ultrafiltration

The technology of coupling ultrafiltration and fermentation has been tested with the acetonobutylic fermentation in continuous mode. The device developed was sterilizable by steam and permitted drastic cleaning of the ultrafiltration (UF) membrane without interrupting the continuous fermentation. It has been shown to be an easily operated and reliable experimental tool for studying high-cell-density cultures and inhibition phenomena. With total recycle of biomass, a dry weight concentration of 125 g/L was attained, which greatly enhanced the volumetric solvent productivity of acetonobutylic fermentation in averaging 4. 5 g/L h for significant periods of time (>70 h) and maintaining solvent concentration and yield at acceptable levels.     

发酵法生产D-核糖

Ｄ－核糖是一种重要的生理物质,可用于合成维生素Ｂ２,风味提高剂以及多种核酸药物等,具有广泛的应用前景,由于化学合成法存在污染公害,故近年来各国相继研究微生物发酵法生产Ｄ－核糖,并致力于工业化生产。本文对国内外Ｄ－核糖的研究进展作了综述,并对Ｄ－核糖的提取方法进行了探讨。