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Ethanol production from sugar-cane-bagasse: enzymatic pre-treatments, microbiological assays to evaluate toxicity and tolerance to hydrolysates at increasing temperatures


The hydrolysis of cellulolytic materials with diluted acids is well known, but this process generates toxic products of hydrolysis. Other negative factors related to the acid hydrolysis are the corrosion and the high amounts of salts resulting from the acid neutralization. The production of enzymatic preparations at lower cost showing activity at lower pHs and resistance to its reuse are needed. In addition, the fermentation of cellulolytic hydrolysates depends on the yeast strain and the levels of toxic compounds present in the hydrolysates. Physicochemical methods reported in literature for the pretreatment and hydrolysis of bagasse as well as the use of crude preparations of cellulolytic enzymes produced by fungi will be evaluated and improved. The identification and quantification of the activity of each enzyme of the enzymatic complex able to hydrolyze the sugar-cane bagasse will be another target of this investigation. The production of ethanol by simultaneous saccharification and fermentation (SSF) of sugar-cane bagasse will be also studied. There is a great need for the development of fast and reliable microbiological methods to assay yeasts strains and levels of the toxicity of the hydrolysates. Frequently, the circumstances preceding the arrest of the fermentation and types of changes of the fermentation profiles can provide valuable information. Assays have to be developed to predict how the fermentation will proceed. A synthetic medium will be optimized and used as a reference medium to study the effects of inhibitors produced during the bagasse hydrolysis and their interactions with respect to growth and fermentation using statistical methods. This medium will be used as a tool in fast diagnostic assays to evaluate the toxicity of the hydrolysates and the tolerance of the yeast strains to acidity and levels of inhibitors prior to the fermentation process. Solid media will be developed for the qualitative evaluation the toxic inhibitors of hydrolysis on the yeast growth capacity. As temperatures greater than 30°C-34°C are observed in industrial reactors operating in tropical countries, the search for yeasts strains tolerant to acidity and high temperatures are required for hydrolysates fermentation. Strains tolerant to acidity and temperature will be used in the present study. Temperature usually aggravates the effects of other stress determinant factors. Assays in bioreactors will allow the optimization of the entire process for maximal efficiency of the ethanol production. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
LALUCE, CECILIA; IGBOJIONU, LONGINUS I.; SILVA, JOSE L.; RIBEIRO, CLOVIS A. Statistical prediction of interactions between low concentrations of inhibitors on yeast cells responses added to the SD-medium at low pH values. BIOTECHNOLOGY FOR BIOFUELS, v. 12, MAY 9 2019. Web of Science Citations: 0.
GRIMALDI, MAIRA PREARO; MARQUES, MARINA PAGANINI; LALUCE, CECILIA; CILLI, EDUARDO MAFFUD; POMBEIRO SPONCHIADO, SANDRA REGINA. Evaluation of lime and hydrothermal pretreatments for efficient enzymatic hydrolysis of raw sugarcane bagasse. BIOTECHNOLOGY FOR BIOFUELS, v. 8, DEC 2 2015. Web of Science Citations: 17.
GALLARDO, J. C. M.; SOUZA, C. S.; CICARELLI, R. M. B.; OLIVEIRA, K. F.; MORAIS, M. R.; LALUCE, C. Enrichment of a continuous culture of Saccharomyces cerevisiae with the yeast Issatchenkia orientalis in the production of ethanol at increasing temperatures. Journal of Industrial Microbiology & Biotechnology, v. 38, n. 3, p. 405-414, MAR 2011. Web of Science Citations: 19.

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Filed patent(s) as a result of this research project

PROCESSO DE PRODUÇÃO DE ETANOL BR1020130282391 - Universidade Estadual Paulista (UNESP) . Cecilia Laluce; Jéssica Carolina Medina Gallardo; Maria Olivia Campos Masiero; Eduardo Maffud Cilli - November 2013, 01