The transesterification efficiency fell from 98.4 ± 1.0% to 87.3 ± 3.4% as the hexane-to-methanol ratio was increased from 2:1 to 10:1 (Fig. 4). The optimal ratio was set at, 6:1, because the transesterification efficiency at the ratio of 8:1 was below 95% (92.1 ± 2.5%).