Sorghum bran, containing high-value lipids and phenolic compounds, is an underutilized food processing byproduct. This study developed and optimized a green method based on a sequential pure supercritical carbon dioxide (SC−CO 2 ) and ethanol/water-modified SC−CO 2 extraction to extract wax-rich lipids and phenolic compounds from sorghum bran in a single step. The extraction conditions, namely, temperature (20−100 °C), pressure (20−40 MPa), extraction time (0.5−5 h), and cosolvent type (ethanol or ethanol−water), were optimized for the highest wax-rich lipids and phenolics extraction yields. In the first part, neat SC−CO 2 at 40 MPa and 60 °C resulted in the highest lipid yield (6.2%, w/w dry basis), which contained ∼5% (w/w) high-melting point waxes. The purified wax fractions containing phytosterols showed high melting points of 57−87 °C. In the second part, the highest total phenolics and flavonoids yields were achieved at 40 MPa and 40 °C via 15% (w/w) ethanol−water (1:1, v/v) modified SC−CO 2 by 150 ± 3 mg of gallic acid equivalent (GAE)/100 g of bran (dry basis) and 99.6 ± 4 mg of catechin equivalent (CAE)/ 100 g of bran (dry basis), respectively. Overall, this study provides a novel single-step extraction approach based on SC−CO 2 to extract and fractionate lipids and phenolic compounds from sorghum bran.
The purpose of this study is to evaluate the effect of high hydrostatic pressure (HHP) as a novel approach for yeast cell disruption and lipid extraction from Lipomyces starkeyi DSM 70295 grown in glucose medium (40 g/L and C/N:55/1) at initial pH of 5.0, 25 • C, and 130 rpm for 8 days. HHP extraction conditions including pressure, time, and temperature were optimized by response surface methodology. The high speed homogenizer-assisted extraction (HSH) was also used for comparison. The biomass subjected to HHP was examined under scanning electron microscopy and light microscope. A maximal lipid yield of 45.8 ± 2.1% in dry cell basis (w/w) was achieved at 200 MPa, 40 • C, and 15 min, while a minimum yield of 15.2 ± 0.9% was observed at 300 MPa, 40 • C, and 10 min (p < 0.05). The lipid yield decreased with increasing pressure. It was demonstrated that low pressure (200 MPa) collapsed the cells, while high pressure (400 MPa) created protrusions on the cell wall and cell fragments spread in the environment. This study favors HHP as a promising method for Lipomyces oil extraction.
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