Optimization of enzymatic pretreatment for n-hexane extraction of oil from Silybum marianum seeds using response surface methodology

An investigation on enzymatic pretreatment for n-hexane extraction of oil from the Silybum marianum seeds was conducted. The optimum combination of extraction parameters was obtained with the response surface methodology (RSM) at a four-variable and five-level central composite design (CCD). The optimum parameters of enzymatic pretreatment were as follows: enzyme concentration of 2.0% (w/w), temperature of 42.8 °C, reaction time of 5.6 h, and pH of 4.8. After enzymatic pretreatment, the oil was extracted by n-hexane for 1.5 h, and the oil yield on a dry basis was 45.70%, which well matched with the predicted value (45.86%). The results of the effects of the enzymatic pretreatment for n-hexane extraction of oil from the aspects of oil yield, microstructure and the fatty acid compositions showed that the enzymatic pretreatment had not affected on the fatty acid compositions, but could cause structure breakage of the S. marianum seeds and accelerate releasing extra oil, which increased the oil yield by 10.46% compared with n-hexane extraction for 1.5 h without enzymatic pretreatment, and confirmed the efficacy of enzymatic pretreatment for n-hexane extraction of oil from the S. marianum seeds.

The effect of enzymatic pretreatment on the microstructure of the Silybum marianum seed powders was analyzed with Scanning electron microscopy. Scanning electron microscopy images of Silybum marianum seed powders. (a) The seed powders untreated, (b) the remained solids obtained by n-hexane extraction for 1.5 h, and (c) the remained solids obtained by the procedures of enzymatic pretreatment under the optimum condition for n-hexane extraction for 1.5 h.Figure optionsDownload high-quality image (162 K)Download as PowerPoint slideHighlights
► The optimum combination of extraction parameters was obtained with RSM.
► Increase in yield of oil on enzymatic pretreatment was important for oil industry.
► The fatty acid compositions were scarcely affected by the enzymatic pretreatment.
► The effect of enzymatic pretreatment on the microstructure of seeds was analyzed.