M Saska, S Zossi, M Coronel and RM Ruiz
Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Av. William Cross 3150, Las Talitas, Tucumán, Argentina, CP: T4101XAC; drmsaska@gmail.com
Colorants and especially melanoidins, which are the products of Maillard reaction between reducing sugars and amino acids, are reported to affect sugarcane molasses fermentation and reduce ethanol yield. To quantify these effects, a batch micro-fermentation technique was adapted from the literature and used in a series of laboratory tests. Ethanol production was followed by periodically measuring weight loss from CO2 release during incubation at 30°C. Feedstocks were final molasses whose color was prior to the fermentation tests increased either by adding synthetic Maillard reaction products obtained by reacting glucose with glycine, or by heating. In some tests, up to four fermentation cycles with full yeast recycle were carried out. With fresh baker’s yeast, the kinetics of fermentation or final fermentation yield were unaffected by the molasses color. However, in yeast recycle tests, yeast biomass production rate using molasses with high color was reduced by 15–25%. In fermentation of high color molasses, ethanol yield after 7 hours of incubation was lower but more so only in the two initial cycles of fermentation when the overall cell count was low and the effect of color on yeast growth, therefore, significant. At the 20-hour retention time, with fermentation completed, there was no discernible effect of molasses color on fermentation yield.