Efficient production of ethanol by engineered Pichia pastoris using simultaneous saccharification and fermentation of rice straw. A method to produce ethanol from rice straw was developed. The rice straw was treated with dilute sulphuric acid and hydrolyzed with cellulase. After saccharification, ethanol production was carried out by simultaneous saccharification and fermentation (SSF). The rice straw was firstly pretreated by dilute sulphuric acid to hydrolyze cellulose and hemicellulose into simple sugars, and the pretreated solid residue containing residual cellulose was hydrolyzed into glucose by fungal cellulase. Ethanol production was then carried out by SSF using the produced sugar. The ethanol yield was significantly increased by the dilute acid pretreatment in comparison with the raw material (11.8-fold in 72 h of SSF). Moreover, it was possible to produce ethanol directly from the pretreated rice straw for SSF without pre-pretreatment for the glucose production. The process can be used for the ethanol production from any other agricultural biomass.