Fuel ethanol production: effect of nitrogen supplementation in the fermentation of must of sugarcane juice with high concentrations of sugar

Author(s)

Bruno Miguel dos Santos Monteiro

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2015-11-30

Examining board members

Sandra Helena da Cruz; Sandra Regina Ceccato Antonini; Mario Lucio Lopes; Cândida Manuel Ribeiro Simões Lucas; Sarita Cândida Rabelo

• Advisor: Sandra Helena da Cruz

Abstract

Nitrogen plays an essential role in the physiology of yeast and fermentation of high concentration sugars. It provides higher yield, efficiency and productivity, as well as protects yeast cells from osmotic stress caused by high concentrations of sugar and ethanol. To evaluate the influence of nitrogen supplementation on fermentative parameters, must containing concentrated sugarcane juice to 25, 30 or 35°Brix and supplemented or not with 16 mM urea or 24 mM ammonium phosphate were fermented at 30°C by PE-2 or CAT-1 yeast strains of Saccharomyces cerevisiae into 6 consecutive cycles of 24h. At the end of each cycle, cell viability by staining with erythrosine method, wet mass (biomass) by weighing; and the ethanol concentration in digital densitometer, after samples distillation were analyzed. The concentration of total usable nitrogen was determined by the ninhydrin using glycine as standard. In 30°Brix wort, CAT-1 strain produced averaged 12.9, 17.1 and 14.4% (v/v) of ethanol concentration, respectively, in the (T1) control or with (T2) urea or (T3) phosphate supplemented treatments. In this condition, the PE-2 strain produced 14.9 (T1), 15.8 (T2) and T3 15.8% (v / v) and the wet weight of CAT-1 increased from 7% to 16%, in the presence of phosphate. In the fermentation of the must 35°Brix by the two strains, supplementation with phosphate (T3) led to increased ethanol production, increased wet weight and maintenance of cell viability. CAT-1 strain, in 30°Brix, produced more glycerol upon treatment with ammonium phosphate being about 1 g glycerol per 1 g of biomass produced. Supplementation with urea had beneficial effects on VHG fermentation enabling increased production of ethanol, and a lower production of glycerol against other nitrogen supplementation. (AU)

• FAPESP's process: 11/12185-0 - Título em Inglês Production of fuel ethanol: effects of free nitrogen on the fermentation of very high gravity sugar cane juice
• Grantee: Bruno Miguel dos Santos Monteiro
• Support Opportunities: Scholarships in Brazil - Doctorate