Processo biotecnológico de produção de edulcorantes a partir do hidrolisado do sisal (Agave sisalana)

Abstract

Concern about the amount of waste generated by industries and the commitments made to the environment has aroused a growing interest in the use of alternative energy sources for the generation of sweeteners, such as arabitol and xylitol. In this context, sisal bagasse has been considered promising biomass to meet demand sustainably. Therefore, the objective of this research was to study the biotechnological production of sweeteners using sisal bagasse hydrolyzed liquor (Agave sisalana) as substrate and as fermentation agents Candida guilliermondii and Debaryomyces hansenii yeasts, species capable of metabolizing arabinose and xylose. The sisal bagasse was washed, dried, ground and characterized. Then, a 23 + 3 central points factorial design was performed to verify the influence of the variables: temperature, bagasse/dilute acid ratio and acid concentration on the release of pentoses from hydrolysed liquors. After hydrolysis the liquor in the best concentration (0.001 gL-1 glucose, 2.86 gL-1 xylose and 1.14 gL-1 arabinose) was subjected to fermentation prepared in erlenmeyer flasks with 400 ml of hydrolyzed liquor medium, stirred at 200 rpm, 30 °C from 0 to 120 h using D. hansenii CCT 2371 yeast. Characterization of the lignocellulosic composition showed the presence of 18.28% cellulose, 14.80% hemicellulose and 29.42% lignin. It has been found that the acid treatment liquor should operate under conditions of temperature, acid concentration and bagasse/dilute acid ratio at level -1 (110 °C, 1.5% and 1:12 respectively). The fermentation of sisal bagasse hydrolyzate obtained 100% substrate consumption (arabinose and xylose), 0.9913 g.g-1 of theoretical yield of conversion of arabinose to arabitol and 0.0387 g.g-1 of xylose to xylitol and volumetric productivity. 0.0095 g·L-1·h-1 for arabitol and 0.0009 g·L-1·h-1 for xylitol. The maximum production of arabitol was obtained with 96 h of fermentation, while for xylitol with 120 hours. Thus, sisal bagasse presented considerable quantities of lignocellulosic compounds, demonstrating its potential as raw material in obtaining fermentable sugars. Structural chemical analyzes performed demonstrated the efficiency of the hydrolysis process. Debaryomyces hansenii yeast was able to obtain high values of arabitol production in sisal bagasse hydrolyzed medium, adding economic value to sisal bagasse and reducing the environmental impact