Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China.
Appl Microbiol Biotechnol. 2017 Oct;101(19):7129-7140. doi: 10.1007/s00253-017-8431-1. Epub 2017 Aug 11.
Okara (soybean residue) is a highly perishable food processing by-product from soymilk and tofu manufacture. It contains a large proportion of insoluble dietary fibre (40-60% on a dry basis), as well as digestion-resistant proteins, trypsin inhibitors and phytic acid. These factors contribute lead to the under-utilisation of okara. To improve the overall nutritional quality of okara, sequential saccharification of okara by Celluclast® 1.5L (cellulase) or Viscozyme® L (cellulase and hemicellulase) and fermentation by the yeast Yarrowia lipolytica were performed. The changes in the antioxidant capacity, amino acids, phenolic acids, isoflavones, phytic acid and dietary fibre during biotransformation were studied. Carbohydrase pre-treatment increased the amounts of monosaccharides, trans-cinnamic acid and aglycone isoflavones in okara. After fermentation, the okara had higher antioxidant activity and greater amounts of total amino acids and ferulic acid. Some positive interactions between the carbohydrase and Y. lipolytica were hypothesised: the carbohydrase and Y. lipolytica proteases could have synergised with each other to break down the okara secondary cell wall more efficiently. After 52 h, Celluclast® 1.5 L and Viscozyme® L significantly reduced the insoluble dietary fibre content from 61.9 ± 0.6 to 45.6 ± 3.0% and 24.7 ± 0.3%, respectively (all w/w, dry basis), while increasing the soluble dietary fibre content by about onefold. Both carbohydrases also increased the amounts of monosaccharides, trans-cinnamic acid, and aglycone isoflavones in okara. The addition of Y. lipolytica led to a higher antioxidant capacity and greater amounts of total amino acids and ferulic acid in okara. The overall improvements in the digestibility and potential health benefits of okara highlight the promising applicability of biotransformation in okara valorisation.
豆渣是豆浆和豆腐加工过程中的一种极易腐坏的副产物。它含有大量不可溶性膳食纤维（干基含量为 40-60%），以及抗消化蛋白、胰蛋白酶抑制剂和植酸。这些因素导致豆渣的利用率较低。为了提高豆渣的整体营养价值，采用纤维素酶 Celluclast® 1.5L 和半纤维素酶 Viscozyme® L 对豆渣进行顺序糖化，然后用酵母解脂耶罗维亚酵母进行发酵。研究了生物转化过程中豆渣抗氧化能力、氨基酸、酚酸、异黄酮、植酸和膳食纤维的变化。碳水化合物酶预处理增加了豆渣中单糖、反式肉桂酸和糖苷异黄酮的含量。发酵后，豆渣具有更高的抗氧化活性和更多的总氨基酸和阿魏酸。假设碳水化合物酶和解脂耶罗维亚酵母之间存在一些积极的相互作用：碳水化合物酶和解脂耶罗维亚酵母蛋白酶可能协同作用，更有效地破坏豆渣的次生细胞壁。52 小时后，Celluclast® 1.5L 和 Viscozyme® L 显著降低了豆渣中不溶性膳食纤维的含量，分别从 61.9±0.6%和 24.7±0.3%（均为 w/w，干基）降至 45.6±3.0%，同时使可溶性膳食纤维的含量增加了约一倍。两种碳水化合物酶还增加了豆渣中单糖、反式肉桂酸和糖苷异黄酮的含量。添加解脂耶罗维亚酵母可提高豆渣的抗氧化能力和总氨基酸及阿魏酸的含量。豆渣消化率和潜在健康益处的整体提高，突出了生物转化在豆渣增值方面的应用前景。
