Inês Conceição Roberto

Technological trends, global market, and challenges of bio-ethanol production

Ethanol use as a fuel additive or directly as a fuel source has grown in popularity due to governmental regulations and in some cases economic incentives based on environmental concerns as well as a desire to reduce oil dependency. As a consequence, several countries are interested in developing their internal market for use of this biofuel. Currently, almost all bio-ethanol is produced from grain or sugarcane. However, as this kind of feedstock is essentially food, other efficient and economically viable technologies for ethanol production have been evaluated. This article reviews some current and promising technologies for ethanol production considering aspects related to the raw materials, processes, and engineered strains development. The main producer and consumer nations and future perspectives for the ethanol market are also presented. Finally, technological trends to expand this market are discussed focusing on promising strategies like the use of microalgae and continuous systems with immobilized cells.

Optimization of xylitol production by Candida guilliermondii FTI 20037 using response surface methodology

Abstract The combined effects of initial xylose concentration and inoculum level on xylitol production by Candida guilliermondii from rice straw hydrolysate were studied using response surface methodology. A 2 2 full-factorial central composite design was employed for experimental design and analysis of the results. The optimum xylose concentration and inoculum level were found to be 82 and 3 g/l, respectively. In these conditions, xylitol concentration of 52 g/l with a production rate of 0.54 g/l and a yield factor of 0.65 g/g was attained. These results are in close agreement with the model predictions.

Utilization of sugar cane bagasse hemicellulosic hydrolyzate by Candida guilliermondii for xylitol production

Abstract Sugar cane bagasse hemicellulosic hydrolyzate from steam explosion was treated by seven different methods in which the pH was altered by bases (including Ca(OH) 2 , CaO and KOH) and H 2 SO 4 . The effectiveness of the treatment was judged by measuring the conversion of the hydrolyzate to xylitol by Candida guilliermondii . The best treatment was found to be the alteration of pH to 10 with Ca(OH) 2 and its subsequent decrease to 6·5 with H 2 SO 4 , since 95% of the original 70 g/liter xylose contained in the hydrolyzate was converted to xylitol with a yield of 0·48 g/g (53% of the theoretical maximum).

Optimal experimental condition for hemicellulosic hydrolyzate treatment with activated charcoal for xylitol production

Rice straw was hydrolyzed into a mixture of sugars using diluted H2SO4. During hydrolysis, a variety of inhibitors was also produced, including acetic acid, furfural, hydroxymethylfurfural, and lignin degradation products (several aromatic and phenolic compounds). To reduce the toxic compounds concentration in the hydrolyzate and to improve the xylitol yield and volumetric productivity, rice straw hemicellulosic hydrolyzate was treated with activated charcoal under different pH values, stirring rates, contact times, and temperatures, employing a 24 full‐factorial design. Fermentative assays were conducted with treated hydrolyzates containing 90 g/L xylose. The results indicated that temperature, pH, and stirring rate strongly influenced the hydrolyzate treatment, temperature and pH interfering with all of the responses analyzed (removal of color and lignin degradation products, xylitol yield factor, and volumetric productivity). The combination of pH 2.0, 150 rpm, 45 °C, and 60 min was considered an optimal condition, providing significant removal rates of color (48.9%) and lignin degradation products (25.8%), as well as a xylitol production of 66 g/L, a volumetric productivity of 0.57 g/L·h, and a yield factor of 0.72 g/g.

Xylitol production by Candida guillermondii as an approach for the utilization of agroindustrial residues

Abstract Different substrates based on hydrolyzed hemicellulosic fractions of agroindustrial residues were used for xylitol production by Candida guilliermondii FTI 20037 under semi-aerobic conditions. Batch fermentation performances were characterized and compared with those attained in a synthetic medium using d -xylose as a major carbon source. For all media tested, simultaneous utilization of hemicellulosic sugars (glucose and xylose) was observed and the highest substrate uptake rate was attained in sugar cane bagasse medium. Increased xylitol concentrations (40 g/litre) were achieved in synthetic and rice straw-media, although the highest xylitol production rate was obtained in sugar cane bagasse hydrolysate. These results show that both hydrolysates can be converted into xylitol with satisfactory yields and productivities.

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

Different types of activated carbon were prepared by chemical activation of brewers spent grain (BSG) lignin using H(3)PO(4) at various acid/lignin ratios (1, 2, or 3g/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.

Perspectives on Bioenergy and Biotechnology in Brazil

Brazil is one of the world’s largest producers of alcohol from biomass at low cost and is responsible for more than 1 million direct jobs. In 1973, the Brazilian Program of Alcohol (Proalcool) stimulated the creation of a bioethanol industry that has led to large economic, social, and scientific improvements. In the year 1984, 94.5% of Brazil’s cars used bioethanol as fuel. In 2003/2004, 350.3 million of sugarcane produced 24.2 million t of sugar and 14.4 billion L of ethanol for an average 4.3 million cars using ethanol. Since its inception, cumulative investment in Proalcool totals US

Evaluation of rice straw hemicellulose hydrolysate in the production of xylitol byCandida guilliermondii

11 billion, and Brazil has saved US

Xylitol production from rice straw hemicellulose hydrolysate using different yeast strains

27 billion in oil imports. The ethanol production industry from sugarcane generates 152 times more jobs than would have been the case if the same amount of fuel was produced from petroleum, and the use of ethanol as a fuel is advantageous for environmental reasons. In 2003, one of the biggest Brazilian ethanol industries started consuming 50% of the residual sugarcane bagasse to produce electrical energy (60 MW), a new alternative use of bioenergy for the Brazilian market. Other technologies for commercial uses of bagasse are in development, such as in the production of natural fibers, sweeteners (glucose and xylitol), single-cell proteins, lactic acid, microbial enzymes, and many other products based on fermentations (submerged and semisolid). Furthermore, studies aimed at the increase in the biosynthesis of sucrose and, consequently, ethanol productivity are being conducted to understand the genetics of sugarcane. Although, at present, there remain technical obstacles to the economic use of some ethanol industry residues, several research projects have been carried out and useful data generated. Efficient utilization of ethanol industry residues has created new opportunities for new value-added products, especially in Brazil, where they are produced in high quantities.

Techno-economic analysis for brewer's spent grains use on a biorefinery concept: the Brazilian case.

SummaryRice straw was used as a lignocellulosic source to provide rich pentose media. By using a well characterized yeast strain,Candida guilliermondii FTI 20037, the hydrolysate obtained was converted to xylitol with an efficiency of 75% and production of 27 g of xylitol per liter in 48 hours. The satisfactory results reported here can be attributed to the low concentrations of toxic components generated throughout the chemical depolymerization of this raw material.