Optimization of low-abundance protein extraction and abundant protein removal from defatted soybean meal

Abstract

The aim of this study was to optimize the conditions for the extraction of low-abundance proteins (LAPs) and the removal of abundant proteins (APs; β-conglycinin and glycinin) from soybean meal. Single factor and orthogonal experiments were designed to determine the effects of four factors (isopropanol concentration, total extraction time, ultrasonic power, and ultrasonic time) on protein concentration in isopropanol extracts. Proteins in the isopropanol supernatant and the cold acetone precipitate of isopropanol were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). The results showed that the optimal conditions were 50% isopropanol, ultrasonic pretreatment for 15 min at 350 W, and a total extraction time of 1 h. Under these conditions, the protein concentration in the isopropanol extracts reached 0.8081 g/L. Many LAPs were detected, including β-amylase, soybean agglutinin, soybean trypsin inhibitor, fumarylacetoacetase-like, phospholipase D alpha 1-like, oleosin, and even some unknown soybean proteins. The soybean APs (β-conglycinin and glycinin) were not found. The method may be useful for discovering new soybean proteins and extracting enough LAPs of soybean to allow further studies of their physiological effects on animals without the influence of APs.

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“…Similarly, in another investigation, the authors reported the optimization of conditions for the extraction of LAPs and removal of APs from defatted soybean meal. 59 The optimal conditions were marginally different (50% isopropanol, ultrasonic pretreatment for 15 min at 350 W and total extraction time of 1 h) but depleted APs ( -conglycinin and glycinin) significantly. Li et al 60 used physical-enzymatic modification methods to improve the emulsifying properties of SPI under acidic conditions.…”

“…The authors reported that 50% isopropanol concentration was efficient for removal of APs using ultrasonic treatment at 400 W for 10 min with a total extraction time of 1 h. Under these conditions, the protein concentration increased by 26.4% when compared with the control (no ultrasonic treatment). Similarly, in another investigation, the authors reported the optimization of conditions for the extraction of LAPs and removal of APs from defatted soybean meal . The optimal conditions were marginally different (50% isopropanol, ultrasonic pretreatment for 15 min at 350 W and total extraction time of 1 h) but depleted APs ( β ‐conglycinin and glycinin) significantly.…”