Production of bioethanol from corn meal hydrolyzates

The two-step enzymatic hydrolysis of corn meal by commercially available α-amylase and glucoamylase and further ethanol fermentation of the obtained hydrolyzates by Saccharomyces cerevisiae yeast was studied. The conditions of starch hydrolysis such as substrate and enzyme concentration and the time required for enzymatic action were optimized taking into account both the effects of hydrolysis and ethanol fermentation. The corn meal hydrolyzates obtained were good substrates for ethanol fermentation by S. cerevisiae. The yield of ethanol of more than 80% (w/w) of the theoretical was achieved with a satisfactory volumetric productivity P (g/l h). No shortage of fermentable sugars was observed during simultaneous hydrolysis and fermentation. In this process, the savings in energy by carrying out the saccharification step at lower temperature (32 °C) could be realized, as well as a reduction of the process time for 4 h.     

Studies on the Interaction of Arabic (Acacia senegal) and Mesquite (Prosopis juliflora) Cum as Emulsion Stabilizing Agents for Spray-Dried Encapsulated Orange Peel Oil

ABSTRACT

The encapsulation properties of pure mesquite and arabic gum powders and mixtures thereof with orange peel oil were measured. The highest rate of encapsulated oil was found to be 93.5 % for a ratio of 60.40% of arabic to mesquite gums. Pure arabic gum preparations were able to encapsulate similar amounts of the oil. Sensory evaluvation of the microencapsulates showed no significant differences (a≤.05) in flavor intensity beween orange peel oil encapsulated with pure arabic gum and mixtures containing mesquite gum.     

Kinetics of Bioethanol Production Employing Mono‐ and Co‐Cultures of Saccharomyces cerevisiae and Pichia stipitis

The kinetics of bioethanol production using mono‐ and co‐cultures of Saccharomyces cerevisiae and Pichia stipitis with glucose, xylose, and glucose‐xylose sugar mixtures were investigated. A MATLAB® program was formulated for simulation of experimental results in order to get predicted values of ethanol production and sugar consumption and for kinetic parameter estimation. Kinetic parameters implied less extent of substrate and/or product inhibition when the co‐culture scheme of immobilized S. cerevisiae and free P. stipitis was employed for fermentation of mixed sugars. In addition, a high ethanol yield was achieved by applying this co‐culture strategy to wheat straw hydrolysates.     

Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.     

Simultaneous saccharification and fermentation of alkaline-pretreated corn stover to ethanol using a recombinant yeast strain

Bio-ethanol converted from cheap and abundant lignocellulosic materials is a potential renewable resource to replace depleting fossil fuels. Simultaneous saccharification and fermentation (SSF) of alkaline-pretreated corn stover for the production of ethanol was investigated using a recombinant yeast strain Saccharomyces cerevisiae ZU-10. Low cellobiase activity in Trichoderma reesei cellulase resulted in cellobiose accumulation. Supplementing the simultaneous saccharification and fermentation system with cellobiase greatly reduced feedback inhibition caused by cellobiose to the cellulase reaction, thereby increased the ethanol yield. 12 h of enzymatic prehydrolysis at 50 °C prior to simultaneous saccharification and fermentation was found to have a negative effect on the overall ethanol yield. Glucose and xylose produced from alkaline-pretreated corn stover could be co-fermented to ethanol effectively by S. cerevisiae ZU-10. An ethanol concentration of 27.8 g/L and the corresponding ethanol yield on carbohydrate in substrate of 0.350 g/g were achieved within 72 h at 33 °C with 80 g/L of substrate and enzyme loadings of 20 filter paper activity units (FPU)/g substrate and 10 cellobiase units (CBU)/g substrate. The results are meaningful in co-conversion of cellulose and hemicellulose fraction of lignocellulosic materials to fuel ethanol.     

Effect of different fermentation parameters on bioethanol production from corn meal hydrolyzates by free and immobilized cells of Saccharomyces cerevisiae var. ellipsoideus

BACKGROUND: Bioethanol produced from renewable biomass, such as corn meal, is a biofuel that is both renewable and environmentally friendly. Significant scientific and technological investments will be needed to achieve substitution of conventional fossil fuels with alternative fuels. The ethanol fermentation of enzymatically obtained corn meal hydrolyzates by free and immobilized cells of Saccharomyces cerevisiae var. ellipsoideus yeast in a batch system was studied. The initial glucose and inoculum concentration and the time required for the efficient ethanol production were optimized taking into account parameters such as ethanol concentration, ethanol yield, percentage of the theoretical yield of ethanol and volumetric productivity in both immobilized and free cell systems. RESULTS: The yeast cells were immobilized in Ca–alginate by an electrostatic droplet generation method. An optimal initial inoculum concentration of 2% (v/v) and optimal fermentation time of 38 h for both immobilized and free yeasts were determined. An optimal initial glucose concentration of 150 g L^?1 for free system was achieved. At the initial glucose concentration of 176 g L no substrate or product inhibition were achieved with immobilized yeast. CONCLUSION: By immobilization of the yeast into Ca–alginate using the method of electrostatic droplet generation a superior system was realized, which exhibited lower substrate inhibition and higher tolerance to ethanol. The cells of S. cerevisiae var. ellipsoideus yeast entrapped in Ca–alginate showed good physical and chemical stability, and no substrate and product diffusion restrictions were noticed. Copyright © 2008 Society of Chemical Industry     

冰糖橙皮渣发酵产燃料乙醇的工艺优化

采用纤维素酶、果胶酶和β-葡萄糖苷酶对冰糖橙皮渣进行水解,所得还原糖液接种异常毕赤酵母进行发酵,考察了酵母接种量、发酵时间、pH和发酵温度等单因素对乙醇得率的影响。单因素结果表明:接种量为12%、发酵时间72 h、pH 4.5、发酵温度33℃时乙醇得率最高。在此基础上设计L9(34)正交实验。结果表明,最佳工艺条件为pH 4.5,接种量12%,发酵时间72 h,发酵温度30℃。在此条件下乙醇产率为0.2451 g/g,显著高于单因素实验(0.2263 g/g)和正交实验结果(0.2329 g/g)。     

Ethanol production by co-fermentation of hexose and pentose from food wastes using Saccharomyces coreanus and Pichia stipitis

To improve the conversion rate of a saccharification liquid from food wastes containing pentoses and hexoses into bioethanol, after selecting Saccharomyces coreanus and Pichia stipitis, the respective fermentation and co-fermentation properties were investigated. In the fermentation using S. coreanus, the result under anaerobic condition was better than under aerobic conditions. In the anaerobic fermentation, the concentration of the reducing sugar and glucose remaining after 24 hrs was 9.09 and 1.88 g/L, respectively, with 40.59 g/L of ethanol produced; the ethanol productivity was 1.69 g/L-h. Also, even with the fermentation using P. stipitis, the reducing sugars and glucose were rapidly reduced, with a marked production of ethanol, but the ethanol produced was lower than those under anaerobic and aerobic conditions with the use of S. coreanus. Therefore, for the production of a high concentration of bioethanol from food wastes, ethanol fermentation was induced using S. coreanus until the middle of the fermentation, with P. stipitis used during the latter stage of the fermentation, where the circumstance favored its use, and thus, the carbon source not converted by S. coreanus was later converted to ethanol. As a result, both ethanol production of 48.63 g/L and productivity of 2.03 g/L-h increased over those of the anaerobic fermentation using S. coreanus.     

Increased tolerance and conversion of inhibitors in lignocellulosic hydrolysates by Saccharomyces cerevisiae

During hydrolysis of lignocellulosic biomass, monomeric sugars and a broad range of inhibitory compounds are formed and released. These inhibitors, which can be organized around three main groups, furans, weak acids and phenolics, reduce ethanol yield and productivity by affecting the microorganism performance during the fermentation step. Among the microorganisms that have been evaluated for lignocellulosic hydrolysate ethanol fermentation, the yeast Saccharomyces cerevisiae appears to be the least sensitive. In order to overcome the effect of inhibitors, strategies that include improvement of natural tolerance of microorganism and use of fermentation control strategies have been developed. An overview of the origin, effects and mechanisms of action of known inhibitors on S. cerevisiae is given. Fermentation control strategies as well as metabolic, genetic and evolutionary engineering strategies to obtain S. cerevisiae strains with improved tolerance are discussed. Copyright © 2007 Society of Chemical Industry     

A comprehensive ligninolytic pre-treatment approach from lignocellulose green biotechnology to produce bio-ethanol

In the present study, we developed a novel ligninolytic enzymes based pre-treatment method for lignocellulosic wheat straw to depolymerize lignin and expose the cellulose polymers to produce bio-ethanol. Wheat straw was pre-treated with ligninolytic enzymes extract produced from Ganoderma lucidum under optimum solid state fermentation conditions. The pre-treated biomass was further subjected to the enzymatic hydrolysis by the crude unprocessed cellulases (β-1,4 endoglucanase, 53.5 ± 1.24 U/mL; β-1,4 exoglucanase, 41.3 ± 1.31 U/mL; β-1,4 glucosidase, 46.8 ± 1.43 U/mL; and xylanase 39 ± 2.2 U/mL) produced by Trichoderma harzaianum. Under optimal conditions for enzymatic saccharification, 10% (w/v) of pre-treated biomass was hydrolyzed completely and converted to 72.5 and 2.4 g/L of glucose and xylose, respectively. Initial time screening Sequential Saccharification and Fermentation (SSF) of the concentrated enzymatic hydrolyzate (10%, w/v) by Saccharomyces cerevisiae produced 22.6 g/L ethanol in a fermented medium after 72 h of temperature controlled incubation at 37 °C. For maximum ethanol production, different physical and nutritional parameters like pH, temperature, substrate level and inoculum sizes were optimized. Under optimal conditions ethanol production of 33.5 g/L was obtained from ligninolytic treated residual (wheat straw) biomass.     

橘皮柠檬烯的研究与应用进展

综述了柑橘皮中的柠檬烯在制备和应用方面的研究进展。介绍了柑橘皮柠檬烯曲提取分离技术、分析方法、生理与生物活性及其应用的研究进展,并对柠檬烯的应用前景进行了展望。     

Bioethanol production from micro-algae, Schizocytrium sp., using hydrothermal treatment and biological conversion

Hydrothermal fractionation for micro-algae, Schizocytrium sp., was investigated to separate sugars, lipids, and proteins. This fractionation process produced protein-rich solid cake and liquid hydrolysates, which contained oligomeric sugars and lipids. Oligomeric sugars and lipids were easily separated by liquid-liquid separation. Sugars in the separated hydrolyzate were determined to be mainly D-glucose and L-galactose. Fractionation conditions were optimized by response surface methodology (RSM). Optimal conditions were found to be 115.5 °C of reaction temperature, 46.7 min of reaction time, and 25% (w/w) of solid loading. The model predicted that maximum oligomeric sugar yield (based on untreated micro-algae weight), which can be recovered by hydrothermal fractionation at the optimum conditions, was 19.4 wt% (based on the total biomass weight). Experimental results were in agreement with the model prediction of 16.6 wt%. Production of bioethanol using micro-algae-induced glucan and E. coli KO11 was tested with SSF (simultaneous saccharification and fermentation), which resulted in 11.8 g-ethanol/l was produced from 25.7 g/l of glucose; i.e. the theoretical maximum ethanol yield based on glucan in hydrolyzate was 89.8%.     

Bioactive Compounds,Antioxidant Activities and Heat Stability of Corn Oil Enriched with Tunisian Citrus aurantium L. Peel Extract

This study was designed to examine physicochemical composition, antioxidant activities and heat stability of corn oil enriched with bitter orange peel. Volatile compounds composition of corn oil flavored with Citrus aurantium peel was investigated. Flavored oil total aroma content (2.6 mg/mg oil) was mainly represented by monoterpene hydrocarbons and limonene was the major one (2.49 mg/mg oil). Flavored oil methanolic extract was characterized by total phenol content of 1.22 mg GAE/kg. Chlorogenic, ferulic and p-coumaric acids were the major phenolic components of the flavored oil extract (34.33, 30.24 and 19.39 %, respectively). It was also characterized by a higher chlorophylls and carotenoids contents than the refined one. Antioxidant activities of methanolic extracts of both samples were determined using four assays: DPPH, reducing power, β-carotene bleaching and metal chelating tests. In β-carotene bleaching and DPPH radical scavenging assays, flavored oil methanolic extract showed higher activities than the control. It was characterized by a total antioxidant activity of 4.08 mg GAE/kg and an EC₅₀ value of 3.14 mg/mg oil. Its concentration providing 50 % inhibition (IC₅₀) was 0.53 mg/mg oil in the DPPH test and 4.08 mg/mg oil in the β-carotene bleaching test. However, refined corn extract showed significantly lower antioxidant activities (p < 0.05). Results of the oxidative stability index showed bitter orange peel effectiveness against thermal oxidation based on the increased induction time observed in flavored oil (5.95).     

Evaluation of process conditions in the performance of yeast on alcoholic fermentation

This work studied the resistance of Saccharomyces cerevisiae Y904 to ethanol on an alcoholic fermentation process operated in fed-batch. The effect of temperature, inoculum size and substrate concentration on fermentation yield, productivity and residual sugars concentration was studied by a central composite design (CCD). Based on the CCD study, it was determined the optimum values of 240, 35?g/L, and 26°C for total reducing sugars, inoculum concentration and temperature, respectively. This set of conditions experimentally enabled a productivity of 6.0?g/L?h, a yield of 93% and an alcohol content of 113.6?g/L, after 10?h of fermentation. When yeast cells were adapted at 4°C, the inoculum pH adjusted to 2.5 and sugarcane broth used as substrate, a 94% yield and a 10.1?g/L.?h productivity were achieved.     

Conversion of Extracted Oil Cake Fibers into Bioethanol Including DDGS,Canola, Sunflower,Sesame, Soy,and Peanut for Integrated Biodiesel Processing

We have come up with a novel, integrated approach for making biodiesel by in-house producion of ethanol after fermentation of hexane extracted edible oil cake fiber. In addition, we have demonstrated how ethanol could be manufactured from commonly available oil cakes (such as canola, sunflower, sesame, soy, peanut) and dried distiller’s grains with solubles (DDGS). The edible oil cakes and DDGS were hexane extracted, ammonia fiber expansion pretreated, enzymatically hydrolysed and fermented to produce ethanol. From all the oil cakes tested in this work, DDGS and peanut oil cake showed the most promising results giving more than 180 g of glucose/kg of oil cake. These two feedstock’s were hydrolyzed at 15% solids loading and fermented by a native strain of Pichia stipitis. Most sugars were consumed during the first 24 h, with no pronounced inhibition of P. stipitis by the degradation products in the hydrolysate. Xylose consumption was more effective for peanut cake hydrolyzate compared to DDGS.     

Productivity enhancement of S‐adenosylmethionine in Saccharomyces cerevisiae using n‐hexadecane as oxygen vector

BACKGROUND: Saccharomyces cerevisiae is one of the main microorganisms that can produce S‐adenosylmethionine (SAM) from L‐methionine and ATP with high productivity. To satisfy the ATP requirement for SAM synthesis, sufficient oxygen should be supplied to the medium to improve aerobic metabolism in S. cerevisiae. In this study, n‐hexadecane used as oxygen vector for enhancement of SAM production by this yeast was investigated. RESULTS: N‐hexadecane was most favorable for cell growth and SAM synthesis in S. cerevisiae when added at the time of inoculation. It could increase glucose consumption, reduce ethanol accumulation, and ultimately improve biomass and SAM productivity in a fermentation process. In a bioreactor, the highest yield of SAM (2.27 g L^?1) was achieved in the presence of 4% (v/v) n‐hexadecane after 24 h of inoculation, which was 23.37% higher than the control (1.84 g L^?1). CONCLUSION: The addition of n‐hexadecane to cultures of S. cerevisiae significantly enhanced SAM production without increasing energy consumption, and has the potential for use in large‐scale fermentation processes to increase oxygen supply. Copyright © 2012 Society of Chemical Industry     

Enzymatic hydrolysis and fermentation of lime pretreated wheat straw to ethanol

BACKGROUND: The objective of this work is to develop an efficient pretreatment method that can help enzymes break down the complex carbohydrates present in wheat straw to sugars, and to then ferment of all these sugars to ethanol. RESULTS: The yield of sugars from wheat straw (8.6%, w/v) by lime pretreatment (100 mg g^?1 straw, 121 °C, 1 h) and enzymatic hydrolysis (45 °C, pH 5.0, 120 h) using a cocktail of three commercial enzyme preparations (cellulase, β‐glucosidase, and xylanase) at the dose level of 0.15 mL of each enzyme preparation g^?1 straw was 568 ± 13 mg g^?1 (82% yield). The concentration of ethanol from lime pretreated enzyme saccharified wheat straw (78 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 35 °C in 24 h was 22.5 ± 0.6 g L^?1 with a yield of 0.50 g g^?1 available sugars (0.29 g g^?1 straw). The ethanol concentration was 20.6 ± 0.4 g L^?1 with a yield of 0.26 g g^?1 straw in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 35 °C in 72 h. CONCLUSION: The results are important in choosing a suitable pretreatment option for developing bioprocess technologies for conversion of wheat straw to fuel ethanol. Copyright © 2007 Society of Chemical Industry     

Alternating current electrophoretic deposition of Saccharomyces cerevisiae cells and the viability of the deposited biofilm in ethanol production

In this work, we have explored the possibility of using asymmetrical alternating current electrophoretic deposition (AC-EPD) process, which we have previously reported for enzyme deposition, to immobilize Saccharomyces cerevisiae (S. cerevisiae) cells onto stainless steel substrates. The deposition of S. cerevisiae cells at 30 Hz and 200 V_p-p permits the formation of 89 ± 16 μm thick cell layers in 30 min. The mass of the deposited cells is shown to increase quasi-linearly with the deposition time and the applied amplitude. In order to increase the mechanical stability of the immobilized cells, a thin layer of polyurethane was applied after the AC-EPD of S. cerevisiae cells. The viability of the immobilized cells was tested in the production of ethanol. The results showed that the fermentation process with the immobilized S. cerevisiae cells is more efficient than the fermentation carried out with similarly treated free cells.     

Evaluation of different kinetics for bioethanol production with emphasis to analytical solution of substrate equation

Fermentation is typically modelled by kinetic equations giving the time evolutions for biomass, substrate, and product concentrations. In the present study, production of bioethanol from glucose, substrate and Saccharomyces cerevisiae (S. cerevisiae) as a biomass was investigated through a batch fermentation process. Time variation of the S. cerevisiae growth, glucose utilization and ethanol productivity was described using different kinetic models and analytically solution. The kinetic constants were determined through the fitting of experimental data with the kinetic model equations. The results demonstrated that the Monod, Logistic, and Luedeking-Piret served as the best describing models for S. cerevisiae growth, glucose, and ethanol concentrations, respectively. Moreover, determination of substrate concentration in according to time via analytical solution of equation was hallmark result of this research.     

Simultaneous hydrolysis and fermentation of pulp mill primary clarifier sludge

Bioconversion of sludge from the primary clarifier of a sulphite pulping operation to ethanol offers a number of advantages over conventional disposal options. The amount of material which must be disposed of is reduced while, at the same time, salable and environmentally friendly fuel-ethanol is produced. In this study, primary clarifier sludge (PCS) was shown to be hydrolysed to produce fermentable sugars at a rate proportional to enzyme loading. Initial (1 hour) hydrolysis rates as high as 12.6 g reducing sugar/L · h were observed at an initial enzyme loading of 10 filter paper units (FPU)/g. Hydrolysis was inhibited by spent sulphite liquor (SSL), an inhibition which could be completely overcome by fermenting the SSL to remove sugars. Surfactants were found to only marginally improve the production of sugars. To reduce the deleterious effects of end product inhibition, single stage simultaneous hydrolysis and fermentation (SHF) was carried out using cellulase enzymes and Saccharomyces cerevisiae.