Optimization of ethanol fermentation from discarded carrots using immobilized Saccharomyces cerevisiae

CLEMENTZ ADRIANA; AIMARETTI NORA; MANUALE DEBORA; CODEVILLA AGUSTÍN; YORI JUAN CARLOS

International Journal of Energy and Environmental Engineering

Springer Berlin Heidelberg

Año: 2015 vol. 6 p. 129 - 135

2008-9163

Discarded carrots are a valuable source ofbiomass amenable for valorization. Their use as rawmaterial for ethanol production by fermentation, usingyeasts immobilized in Calcium alginate, was proposed. Thebiocatalyst immobilization method, the existence of internaland external mass transfer limitations, the effect of theinitial pH and the reuse of immobilized yeasts were particularlyevaluated. Results indicate that beads made with a2 % solution of Sodium alginate and a 30 % solution ofSaccharomyces cerevisiae were strong enough to allow anefficient nutrient transfer into the matrix and to prevent cellleaking. A stirring rate of 200 rpm was needed to avoidexternal mass transfer limitations. These beads were usedin three successive fermentations. An initial pH of 5.5reached the best fermentation parameters. Non-enriched,non-sterile carrot must was fermented through immobilizedyeasts; and values of ethanol concentration (29.9 g L-1),Yp/s (0.409 g g-1), and productivity (7.45 g L-1 h-1) wereobtained. These values were similar to those registeredwhen free cells were used.