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In the present work, we evaluated the mineral composition of three sugarcane varieties from different areas in northeast Brazil and their influence on the fermentation performance of Saccharomyces cerevisiae. The mineral composition was homogeneous in the different areas investigated. However, large variation coefficients were observed for concentrations of copper, magnesium, zinc and phosphorus. Regarding the fermentation performances, the sugarcane juices with the highest magnesium concentration showed the highest ethanol yield. Synthetic media supplemented with magnesium also showed the highest yield (0.45 g g(-1)) while the excess of copper led to the lowest yield (0.35 g g(-1)). According to our results, the magnesium is the principal responsible for the increase on the ethanol yield, and it also seems to be able to disguise the inhibitory effects of the toxic minerals present in the sugarcane juice.

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The aim of this study was to evaluate the influence of recycling the liquid fraction of pretreatment with alkaline hydrogen peroxide (AHP) on the hydrolysis of corn stover. Corn stover was pretreated in the traditional condition with 7.5% v/v HO. After pretreatment, the solids were separated from the liquid fraction and five successive reuse cycles of the liquid fraction were tested. The solid fraction from pretreatment in each recycle was submitted to enzymatic hydrolysis. The number of recycles had a linear negative effect (R=0.98) on biomass delignification efficiency and also affected negatively the enzymatic conversion efficiency. Despite the decrease in efficiency after each recycling step, reuse of the liquid fraction leads to reduction in water, HO and NaOH consumption of up to 57.6%, 59.6% and 57.6%, respectively. These findings point to an efficient recycling technology, which may reduce costs and save water.

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