Evaluation of the conversion potential of maize stover from soil phytoremediation to bioethanol

This work aimed to evaluate the conversion potential of maize stover (MS) from phytoremediation of heavy metals contaminated soil to bioethanol. Thus, MS was submitted to an acid pretreatment with 3% (v/v) H2SO4, HCl, HNO3 or CH3COOH at 85 °C for 48 hours. An enzymatic hydrolysis step with Accellerase or Ultraflo was applied at 50 °C for 13 hours. Finally, Saccharomyces cerevisiae was used to ferment the glucose at 37 °C, followed by distillation to recover ethanol. The average yield in ethanol for the MS produced in the two contaminated soils was 0.51 and 0.32 gethanol/gMS for the MS treated with HCl and Accellerase and 0.39 and 0.27 gethanol/gMS for the MS treated with HNO3 and Ultraflo, respectively. For the MS produced in the control soil, the yield was 0.37 and 0.44 gethanol/gMS for the treatment with HNO3 and Ultraflo and HCl and Accellerase, respectively, being the differences in ethanol yield assigned to the dif-ferent cellulose/ hemicellulose content of the MS samples. No metals were detected in the ethanol recovered. This research demonstrated the feasibility of val-orization of MS from heavy metals contaminated soil phytoremediation through ethanol production, contributing to a more sustainable process of soil phytoreme-diation.