Larissa Canilha

Bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification, and ethanol fermentation.

Depleted supplies of fossil fuel, regular price hikes of gasoline, and environmental damage have necessitated the search for economic and eco-benign alternative of gasoline. Ethanol is produced from food/feed-based substrates (grains, sugars, and molasses), and its application as an energy source does not seem fit for long term due to the increasing fuel, food, feed, and other needs. These concerns have enforced to explore the alternative means of cost competitive and sustainable supply of biofuel. Sugarcane residues, sugarcane bagasse (SB), and straw (SS) could be the ideal feedstock for the second-generation (2G) ethanol production. These raw materials are rich in carbohydrates and renewable and do not compete with food/feed demands. However, the efficient bioconversion of SB/SS (efficient pretreatment technology, depolymerization of cellulose, and fermentation of released sugars) remains challenging to commercialize the cellulosic ethanol. Among the technological challenges, robust pretreatment and development of efficient bioconversion process (implicating suitable ethanol producing strains converting pentose and hexose sugars) have a key role to play. This paper aims to review the compositional profile of SB and SS, pretreatment methods of cane biomass, detoxification methods for the purification of hydrolysates, enzymatic hydrolysis, and the fermentation of released sugars for ethanol production.

A study on the pretreatment of a sugarcane bagasse sample with dilute sulfuric acid.

Experiments based on a 23 central composite full factorial design were carried out in 200-ml stainless-steel containers to study the pretreatment, with dilute sulfuric acid, of a sugarcane bagasse sample obtained from a local sugar–alcohol mill. The independent variables selected for study were temperature, varied from 112.5°C to 157.5°C, residence time, varied from 5.0 to 35.0 min, and sulfuric acid concentration, varied from 0.0% to 3.0% (w/v). Bagasse loading of 15% (w/w) was used in all experiments. Statistical analysis of the experimental results showed that all three independent variables significantly influenced the response variables, namely the bagasse solubilization, efficiency of xylose recovery in the hemicellulosic hydrolysate, efficiency of cellulose enzymatic saccharification, and percentages of cellulose, hemicellulose, and lignin in the pretreated solids. Temperature was the factor that influenced the response variables the most, followed by acid concentration and residence time, in that order. Although harsher pretreatment conditions promoted almost complete removal of the hemicellulosic fraction, the amount of xylose recovered in the hemicellulosic hydrolysate did not exceed 61.8% of the maximum theoretical value. Cellulose enzymatic saccharification was favored by more efficient removal of hemicellulose during the pretreatment. However, detoxification of the hemicellulosic hydrolysate was necessary for better bioconversion of the sugars to ethanol.

Xylitol production from wheat straw hemicellulosic hydrolysate: hydrolysate detoxification and carbon source used for inoculum preparation

Wheat straw hemicellulosic hydrolysate was used for xylitol bioproduction. The use of a xylose-containing medium to grow the inoculum did not favor the production of xylitol in the hydrolysate, which was submitted to a previous detoxification treatment with 2.5% activated charcoal for optimized removal of inhibitory compounds.

Uma visão sobre a estrutura, composição e biodegradação da madeira

Wood is the main raw material used in the pulp and paper industry. It is a material that presents heterogeneous structure and complex composition, which results in a relatively resistant material to the biodegradation process. In the present review, we attempted to summarize the structural characteristics of wood and describe the chemical nature of its major components to, afterwards, comment about its biodegradation. The role of the enzyme manganese peroxidase in the lignin degradation by a selective white-rot fungus, Ceriporiopsis subvermispora, was highlighted.

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

During the processing of sugarcane, the sugarcane straw (SS) is remained on field and do not presents suitable use. After the juice extraction from sugarcane stem, the fraction that is left over is called sugarcane bagasse (SB) [3]. Both residues (SB and SS) represent a sizeable fraction of agro-residues collected annually. The annual world production of sugarcane is ∼1.6 billion tons, which yields approximately 279 million metric tons (MMT) of SB and SS [1, 4].

Statistical Approaches for the Optimization of Parameters for Biotechnological Production of Xylitol

Statistics is a fundamental tool in the analysis of any process data where there is variability. There are many ways to approach the problem of optimization and design of a process, which can be handled quickly using a number of statistical techniques. Statistical design of experiments is a mechanism of data collection appropriate to study the biotechnological process, like xylitol production. Several fermentation processes have been optimized using response surface methodology. However, one of the major problems to the researcher is identifying the independent variables that influence the study in order to explain the model which best represents the process. The upstream independent variables studied in the statistical design for fermentation processes are aeration rate, temperature, phosphate level, back pressure, carbon source, pH, power input, agitation rate, carbon/nitrogen ratio, nitrogen source and dissolved oxygen level. The statistical approach for biotechnological production of xylitol from lignocellulosic materials also could be helpful to optimize pretreatment of lignocellulosic biomass, conditioning of hemicellulosic hydrolysates and xylitol recovery from fermented hydrolysates. This chapter will provide an overview on the state of knowledge in these areas focus on statistical approaches.

USO DE DIFERENTES MATERIAS PRIMAS PARA LA PRODUCCIÓN BIOTECNOLÓGICA DE XILITOL USE OF DIFFERENT RAW MATERIALS FOR BIOTECHNOLOGICAL XYLITOL PRODUCTION USO DE DIFERENTES MATERIAS PRIMAS PARA Á PRODUCCIÓN BIOTECNOLÓXICA DE XILITOL

Abstract This work deals with the biotechnological production of xylitol from xylose of hemicellulosic hydrolysates of sugarcane bagasse, eucalyptus, rice straw and wheat straw, by the yeast Candida guilliermondii FTI 20037. The hydrolysates were evaporated under vacuum in order to achieve a xylose concentration about 100 g/L and then treated with CaO until pH 7.0 and H3PO4 until pH 5.5, followed by activated charcoal (2.4%). The fermentations of hydrolysates were carried out in 125 mL Erlenmeyer flasks, in shaker at 300 rpm, during 80 h. By the kinetic study it was possible to observe the behavior of the yeast under the different characteristics of hydrolysates and the consequences on the fermentation parameters. It was obtained a volumetric productivity of 0.50 g/Lh for the hydrolysate from sugarcane bagasse, 0.35 g/Lh for rice straw, 0.34 g/Lh for eucalyptus and 0.24 g/Lh for wheat straw.

Utilização de Membrana de Fibras Ocas na Destoxificação de Hidrolisado Hemicelulósico de Bagaço de Cana-de açúcar visando à Produção de Etanol

Foi avaliado o desempenho fermentativo da levedura Sheffersomyces stipitis em hidrolisado hemicelulosico de bagaco de cana-de-acucar (HHBCA), tratado com membrana de fibras ocas. A fase orgânica foi composta por uma mistura dos solventes alamina 336 TM e octanol em diferentes proporcoes. Foi empregada a levedura S. stipitis como inoculo, obtido do cultivo em meio semi sintetico enquanto as fermentacoes ocorreram em frascos Erlenmeyer com HHBCA tratado por membrana de fibras ocas e suplementado com nutrientes. A maxima remocao de acido acetico, furfural, hidroximetilfurfural e fenois foi de 56,90; 83,33; 50; 22,78 (%), respectivamente. Apesar dos otimos resultados quanto a destoxificacao, nao verificou-se a producao de etanol pela levedura durante a fermentacao de HHBCA destoxificado com membrana de fibras ocas, nas condicoes operacionais empregadas.