Xylitol production from DEO hydrolysate of corn stover by Pichia stipitis YS-30

Corn stover that had been treated with vapor-phase diethyl oxalate released a mixture of mono- and oligosaccharides consisting mainly of xylose and glucose. Following overliming and neutralization, a d-xylulokinase mutant of Pichia stipitis, FPL-YS30 (xyl3-a dagger 1), converted the stover hydrolysate into xylitol. This research examined the effects of phosphoric or gluconic acids used for neutralization and urea or ammonium sulfate used as nitrogen sources. Phosphoric acid improved color and removal of phenolic compounds. d-Gluconic acid enhanced cell growth. Ammonium sulfate increased cell yield and maximum specific cell growth rate independently of the acid used for neutralization. The highest xylitol yield (0.61 g(xylitol)/g(xylose)) and volumetric productivity (0.18 g(xylitol)/g(xylose) l) were obtained in hydrolysate neutralized with phosphoric acid. However, when urea was the nitrogen source the cell yield was less than half of that obtained with ammonium sulfate.

Comparative study of the biochemical changes and volatile compound formations during the production of novel whey-based kefir beverages and traditional milk kefir

Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8-8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir. (C) 2010 Elsevier Ltd. All rights reserved.

ETHANOL PRODUCTION FROM XYLOSE BY Pichia stipitis NRRL Y-7124 IN A STIRRED TANK BIOREACTOR

The ethanol production by Pichia stipitis was evaluated in a stirred tank bioreactor using semi-defined medium containing xylose (90.0 g/l) as the main carbon source. Experimental assays were performed according to a 2(2) full factorial design to evaluate the influence of aeration (0.25 to 0.75 vvm) and agitation (150 to 250 rpm) conditions on ethanol production. In the studied range of values, the agitation increase and aeration decrease favored ethanol production, which was maximum (26.7 g/l) using 250 rpm and 0.25 vvm, conditions that gave a volumetric oxygen transfer coefficient (k(L)a value) of 4.9 h(-1). Under these conditions, the ethanol yield factor, ethanol productivity, and the process efficiency were 0.32 g/g, 0.32 g/l.h, and 63%, respectively. These results are promising and contribute to the development of a suitable process for ethanol production from xylose by Pichia stipitis.

Contribution of Tris Buffer on Xylitol Enzymatic Production

Xylitol enzymatic production can be an alternative to chemical and microbial processes, because of advantages like higher conversion efficiency. However, for an adequate conversion, it is necessary to investigate the effect of many parameters, such as buffer initial concentration, pH, temperature, agitation, etc. In this context, the objective of this work was to evaluate xylitol enzymatic production under different Tris buffer initial concentrations in order to determine the best condition for this parameter to begin the reaction. The best results were obtained when Tris buffer initial concentration was 0.22 M, reaching 0.31 g L(-1) h(-1) xylitol volumetric productivity with 99% xylose-xylitol conversion efficiency. Although the increase in buffer concentration allowed better pH maintenance, it hindered the catalysis. The results demonstrate that this bioreaction is greatly influenced by involved ions concentrations.

Xylooligosaccharides Production from Alkali-Pretreated Sugarcane Bagasse Using Xylanases from Thermoascus aurantiacus

Sugarcane bagasse hemicellulose was isolated in a one-step chemical extraction using hydrogen peroxide in alkaline media. The polysaccharide containing 80.9% xylose and small amounts of L-arabinose, 4-O-methyl-D-glucuronic acid and glucose, was hydrolyzed by crude enzymatic extracts from Thermoascus aurantiacus at 50 degrees C. Conditions of enzymatic hydrolysis leading to the best yields of xylose and xylooligosaccharides (DP 2-5) were investigated using substrate concentration in the range 0.5-3.5% (w/v), enzyme load 40-80 U/g of the substrate, and reaction time from 3 to 96 h, applying a 22 factorial design. The maximum conversion to xylooligosaccharides (37.1%) was obtained with 2.6% of substrate and xylanase load of 60 U/g. The predicted maximum yield of xylobiose by a polynomial model was 41.6%. Crude enzymatic extract of T. aurantiacus generate from sugarcane bagasse hemicellulose 39% of xylose, 59% of xylobiose, and 2% of other xylooligosaccharides.

Ethanol Production from Sugarcane Bagasse Hydrolysate Using Pichia stipitis

The objective of this study was to evaluate the ethanol production from the sugars contained in the sugarcane bagasse hemicellulosic hydrolysate with the yeast Pichia stipitis DSM 3651. The fermentations were carried out in 250-mL Erlenmeyers with 100 mL of medium incubated at 200 rpm and 30 A degrees C for 120 h. The medium was composed by raw (non-detoxified) hydrolysate or by hydrolysates detoxified by pH alteration followed by active charcoal adsorption or by adsorption into ion-exchange resins, all of them supplemented with yeast extract (3 g/L), malt extract (3 g/L), and peptone (5 g/L). The initial concentration of cells was 3 g/L. According to the results, the detoxification procedures removed inhibitory compounds from the hemicellulosic hydrolysate and, thus, improved the bioconversion of the sugars into ethanol. The fermentation using the non-detoxified hydrolysate led to 4.9 g/L ethanol in 120 h, with a yield of 0.20 g/g and a productivity of 0.04 g L(-1) h(-1). The detoxification by pH alteration and active charcoal adsorption led to 6.1 g/L ethanol in 48 h, with a yield of 0.30 g/g and a productivity of 0.13 g L(-1) h(-1). The detoxification by adsorption into ion-exchange resins, in turn, provided 7.5 g/L ethanol in 48 h, with a yield of 0.30 g/g and a productivity of 0.16 g L(-1) h(-1).

Production, characterization and application of activated carbon from brewer`s spent grain lignin

Different types of activated carbon were prepared by chemical activation of brewer`s spent grain (BSG) lignin using H(3)PO(4) at various acid/lignin ratios (1, 2, or 3 g/g) and carbonization temperatures (300, 450, or 600 degrees C), according to a 2(2) full-factorial design. The resulting materials were characterized with regard to their surface area, pore volume, and pore size distribution, and used for detoxification of BSG hemicellulosic hydrolysate (a mixture of sugars, phenolic compounds, metallic ions, among other compounds). BSG carbons presented BET surface areas between 33 and 692 m(2)/g, and micro- and mesopores with volumes between 0.058 and 0.453 cm(3)/g. The carbons showed high capacity for adsorption of metallic ions, mainly nickel, iron, chromium, and silicon. The concentration of phenolic compounds and color were also reduced by these sorbents. These results suggest that activated carbons with characteristics similar to those commercially found and high adsorption capacity can be produced from BSG lignin. (C) 2009 Elsevier Ltd. All rights reserved.

Improved xylitol production in media containing phenolic aldehydes: application of response surface methodology for optimization and modeling of bioprocess

BACKGROUND: The combined effects of vanillin and syringaldehyde on xylitol production by Candida guilliermondii using response surface methodology (RSM) have been studied. A 2(2) full-factorial central composite design was employed for experimental design and analysis of the results. RESULTS: Maximum xylitol productivities (Q(p) = 0.74 g L(-1) h(-1)) and yields (Y(P/S) = 0.81 g g(-1)) can be attained by adding only vanillin at 2.0 g L(-1) to the fermentation medium. These data were closely correlated with the experimental results obtained (0.69 +/- 0.04 g L(-1) h(-1) and 0.77 +/- 0.01 g g(-1)) indicating a good agreement with the predicted value. C. guilliermondii was able to convert vanillin completely after 24 h of fermentation with 94% yield of vanillyl alcohol. CONCLUSIONS: The bioconversion of xylose into xylitol by C. guilliermondii is strongly dependent on the combination of aldehydes and phenolics in the fermentation medium. Vanillin is a source of phenolic compound able to improve xylitol production by yeast. The conversion of vanillin to alcohol vanilyl reveals the potential of this yeast for medium detoxification. (C) 2009 Society of Chemical Industry

An integrated approach to produce biodiesel and monoglycerides by enzymatic interestification of babassu oil (Orbinya sp)

Two screenings of commercial lipases were performed to find a lipase with superior performance for the integrated production of biodiesel and monoglycerides. The first screening was carried out under alcoholysis conditions using ethanol as acyl acceptor to convert triglycerides to their corresponding ethyl esters (biodiesel). The second screening was performed under glycerolysis conditions to yield monoglycerides (MG). All lipases were immobilized on silica-PVA composite by covalent immobilization. The assays were performed using babassu oil and alcohols (ethanol or glycerol) in solvent free systems. For both substrates, lipase from Burkholderia cepacia (lipase PS) was found to be the most suitable enzyme to attain satisfactory yields. To further improve the process, the Response Surface Methodology (RSM) was used to determine the optima operating conditions for each biotransformation. For biodiesel production, the highest transesterification yield (>98%) was achieved within 48 h reaction at 39 degrees C using an oil-to-ethanol molar ratio of 1:7. For MG production, optima conditions corresponded to oil-to-glycerol molar ratio of 1: 15 at 55 degrees C, yielding 25 wt.% MG in 6 h reaction. These results show the potential of B. cepacia lipase to catalyze both reactions and the feasibility to consider an integrated approach for biodiesel and MG production. (C) 2009 Elsevier Ltd. All rights reserved.

PVA-Hydrogel Entrapped Candida Guilliermondii for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing-thawing method. Entrapment experiments were planned according to a 2(3) full factorial design, using the PVA concentration (80, 100, and 120 g L(-1)), the freezing temperature (-10, -15, and -20 degrees C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 degrees C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L(-1), a xylitol yield on consumed xylose of 0.49 g g(-1) and a xylitol volumetric productivity of 0.24 g L(-1) h(-1) were obtained.

Banana as Adjunct in Beer Production: Applicability and Performance of Fermentative Parameters

Traditionally, the raw materials for beer production are barley, hops, water, and yeast, but most brewers use also different adjuncts. During the alcoholic fermentation, the contribution of aroma compounds from other ingredients to the final beer flavor depends on the wort composition, on the yeast strain, and mainly on the process conditions. In this context, banana can also be a raw material favorable to alcoholic fermentation being rich in carbohydrates and minerals and providing low acidity. In this work, the objective was to evaluate the performance of wort adjusted with banana juice in different concentrations. For this, static fermentations were conducted at 15 degrees C at pilot scale (140 L of medium). The addition of banana that changed the concentration of all-malt wort from 10 degrees P to 12 and 15 degrees P were evaluated (degrees P is the weight of the extract or the sugar equivalent in 100 g solution, at 20 degrees C). The results showed an increase in ethanol production, with approximately 0.4 g/g ethanol yield and 0.6 g/L h volumetric productivity after 84 h of processing when concentrated wort was used. Thus, it was concluded that banana can be used as an adjunct in brewing methods, helping in the development of new products as well as in obtaining concentrated worts.

Use of sugarcane bagasse as biomaterial for cell immobilization for xylitol production

This study provides a preliminary contribution to the development of a bioprocess for the contintious production of xylitol from hemicellulosic hydrolyzate utilizing Candida guilliermondii cells immobilized onto natural sugarcane bagasse fibers. To this purpose, cells of this yeast were submitted to batch tests of ""in situ"" adsorption onto crushed and powdered sugarcane bagasse after treatment with 0.5 M NaOH. The results obtained on a xylose-based semi-synthetic medium were evaluated in terms of immobilization efficiency, cell retention and specific growth rates of suspended, immobilized and total cells. The first two parameters were shown to increase along the immobilization process, reached maximum values of 50.5% and 0.31 g immobilized cells/g bagasse after 21 h and then sharply decreased. The specific growth rate of suspended cells continuously increased during the immobilization tests, while that of the immobilized ones, after an initial growth, exhibited decreasing values. Under the conditions selected for cell immobilization, fermentation also took place with promising results. The yields of xylitol and biomass on consumed xylose were 0.65 and 0.18 g/g, respectively, xylitol and biomass productivities 0.66 and 0.13 g L-1 h(-1), and the efficiency of xylose-to-xylitol bioconversion was 70.8%. (C) 2007 Elsevier Ltd. All rights reserved.

Glulam beams reinforced with FRP externally-bonded: theoretical and experimental evaluation

The glued- laminated lumber (glulam) technique is an efficient process for the rational use of wood. Fiber-reinforced polymer (FRPs) associated with glulam beams provide significant improvements in strength and stiffness and alter the failure mode of these structural elements. In this context, this paper presents guidance for glulam beam production, an experimental analysis of glulam beams made of Pinus caribea var. hondurensis species without and with externally-bonded FRP and theoretical models to evaluate reinforced glulam beams (bending strength and stiffness). Concerning the bending strength of the beams, this paper aims only to analyze the limit state of ultimate strength in compression and tension. A specific disposal was used in order to avoid lateral buckling, once the tested beams have a higher ratio height-to-width. The results indicate the need of production control so as to guarantee a higher efficiency of the glulam beams. The FRP introduced in the tensile section of glulam beams resulted in improvements on their bending strength and stiffness due to the reinforcement thickness increase. During the beams testing, two failure stages were observed. The first was a tensile failure on the sheet positioned under the reinforcement layer, while the second occurred as a result of a preliminary compression yielding on the upper side of the lumber, followed by both a shear failure on the fiber-lumber interface and a tensile failure in wood. The model shows a good correlation between the experimental and estimated results.

Influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars

Mortar is the material responsible for the distribution of stresses in masonry structures. The knowledge about the fresh and hardened properties of mortar is fundamental to ensure a good performance of masonry walls. Water/cement ratio and aggregates grading are among several variables that influence physical and mechanical behaviour of mortars. An experimental program is presented in order to evaluate the influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars. Eighteen compositions of mortar are prepared using three relations cement:lime:sand, two types of sand and three water/cement ratios. Specimens are analyzed through flow table test, compressive and flexural strength tests. Results indicate that the increase of water/cement ratio reduces the values of hardened properties and increases the workability. Besides, sands grading has no influence in compressive strength. On the other hand, significant differences in deformation capacity of mortars were verified with the variation of the type of sand. Finally, some correlations are presented among hardened properties and the compressive strength. (C) 2010 Elsevier Ltd. All rights reserved.