Yeast cells were cultured aerobically in YPS medium at 30 ◦C for 72 h. Yeast cells were harvested by centrifugation at 3000 × g for 5 min, washed twice with water,and re-suspended in 50 mL of medium containing the carbon source supplemented with nutrients. Raw corn starch or high-yielding rice was used as a carbon source. The initial cell concentration was adjusted to 50 g of wet cells/L, and wet cell weight was determined by weighing cells that had been pelleted by centrifuging at 3000 × g for 5 min. The estimated dry cell weight was approximately 0.15-fold the wet cell weight. For the low-cost fermentation, yeast cells were also cultured
aerobically in YPS medium at 30 ◦C for 72 h. The culture broth was inoculated into the fermentation medium containing only a carbon source. The inoculated volume ranged between 5, 10, 20% of the volume of the fermentation medium. The total volume of the fermentation medium was adjusted to same volume in each inoculum size. Ethanol fermentation proceeded in a working volume of 50 mL incubated at 30 ◦C with mild agitation in 100 mL bottles equipped with a bubbling CO2 outlet, or in a working volume of 1 L agitated at 500 rpm in 2 L jar fermenters.