Screening and optimization of trace elements supplement in sweet sorghum juice for ethanol production

► Efficiency of ethanol yield of sweet sorghum juice was increased by trace elements. ► MnCl2·4H2O, CoCl2·6H2O and biotin as the significant variables were screened. ► The optimal values of MnCl2·4H2O,CoCl2·6H2O and biotin were obtained. ► The experimental efficiency of ethanol yield at optimal conditions was 89.30 ± 0.10%. ► The efficiency of ethanol yield was enhanced by 5.63% compared to the control.