豆粕(SBM)是一种优质的植物蛋白,由于其高分子量和抗营养特性,其应用受到极大限制。本研究的目的是通过枯草芽孢杆菌固态发酵对豆粕中的蛋白质进行修饰。发酵条件优化为,最后,获得最佳工艺参数,即发酵温度为37°C,接种量12%,时间47小时,料液比为1:0.58,提高了酸溶蛋白的含量。探讨改性SBM作为食品原料的应用,研究了蛋白质的结构和性质。与SBM相比,最佳工艺发酵豆粕(FSBM)的蛋白质二级结构α-螺旋含量下降8.3%,β-折叠增加了3.08%,β转角增加2.71%,随机卷曲增加了2.51%。SDS-PAGE图谱显示其25-250KDa条带明显减弱,具有多个小于25KDa的新生肽带。颗粒尺寸和zeta电位分析表明,发酵降低了平均颗粒尺寸,增加了zeta电位的绝对值。通过SEM和CLSM图可以看出,FSBM中的大分子蛋白被分解成具有折叠和多孔表面结构的碎片。发酵增加了溶解度,降低了疏水性,增加了游离巯基含量,降低了抗原性,改善了SBM的蛋白质性质,并促进了FSBM作为食品原料的进一步加工和生产。
Soybean meal (SBM) is a high-quality vegetable protein, whose application is greatly limited due to its high molecular weight and anti-nutritional properties. The aim of this study was to modify the protein of soybean meal via solid-state fermentation of Bacillus subtilis. The fermentation conditions were optimized as, finally, the best process parameters were obtained, namely fermentation temperature of 37 °C, inoculum amount of 12%, time of 47 h, and material-liquid ratio of 1:0.58, which improved the content of acid-soluble protein. To explore the utilization of modified SBM as a food ingredient, the protein structure and properties were investigated. Compared to SBM, the protein secondary structure of fermented soybean meal (FSBM) from the optimal process decreased by 8.3% for α-helix content, increased by 3.08% for β-sheet, increased by 2.71% for β-turn, and increased by 2.51% for random coil. SDS-PAGE patterns showed that its 25-250 KDa bands appeared to be significantly attenuated, with multiple newborn peptide bands smaller than 25 KDa. The analysis of particle size and zeta potential showed that fermentation reduced the average particle size and increased the absolute value of zeta potential. It was visualized by SEM and CLSM maps that the macromolecular proteins in FSBM were broken down into fragmented pieces with a folded and porous surface structure. Fermentation increased the solubility, decreased the hydrophobicity, increased the free sulfhydryl content, decreased the antigenicity, improved the protein properties of SBM, and promoted further processing and production of FSBM as a food ingredient.