Department of Food Science and Technology, National University of Singapore, 2 Science Drive 2, Singapore 117542, Singapore.
Department of Food Science and Technology, National University of Singapore, 2 Science Drive 2, Singapore 117542, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Jiangsu 215213, China.
Food Res Int. 2021 Feb;140:109901. doi: 10.1016/j.foodres.2020.109901. Epub 2020 Nov 10.
Soy (tofu) whey is a liquid side stream generated from tofu production and is often discarded as waste after it is generated. Direct disposal of soy whey can result in environmental issue in the long run. Soy whey has been previously successfully fermented using different types of wine yeasts, but the yeast available nitrogen (YAN) was found to be deficient. In this study, the soy whey YAN was estimated to be approximately 45.9 mg N/L. A mixture of four amino acids (valine, leucine, isoleucine and phenylalanine) was added into soy whey at a total concentration of +40, +80, +120 and +160 mg N/L and fermented with Torulaspora delbrueckii Biodiva for a period of 10 days. Increasing amino acid supplementation did not affect the yeast cell growth, but it sped up the sugar utilization proportionally. Increasing amino acid supplementation resulted in lower organic acid production and higher glycerol production. Amino acid supplementation also enhances the production rate of higher alcohols; increasing amount of higher alcohols and their respective esters were obtained with increasing amount of amino acid supplementation. However, higher levels of amino acid supplementation (particularly at +160 mg N/L sample) resulted in higher residual nitrogen contents which may lead to microbial instability. Supplementation of 120 mg N/L of amino acids was found to be the optimum concentration to enhance the metabolism of the yeast without leaving a high residual amino acid content. Therefore, with proper control of the amino acid addition dosage, the usage of mixed amino acid supplementation may be a strategy to regulate the fermentation kinetics and volatile compound modulation in soy whey alcohol fermentation.
豆浆乳清是豆腐生产过程中的一种液体副产物，通常在产生后被丢弃作为废物。从长远来看，直接处理豆浆乳清可能会导致环境问题。此前，已经成功使用不同类型的葡萄酒酵母发酵豆浆乳清，但发现酵母可用氮 (YAN) 不足。在这项研究中，估计豆浆乳清的 YAN 约为 45.9 mg N/L。将四种氨基酸（缬氨酸、亮氨酸、异亮氨酸和苯丙氨酸）混合物以总浓度+40、+80、+120 和+160 mg N/L 添加到豆浆乳清中，并使用德巴利酵母属 Biodiva 发酵 10 天。增加氨基酸补充并没有影响酵母细胞的生长，但它使糖利用率成比例加快。增加氨基酸补充会导致有机酸产量降低，甘油产量增加。氨基酸补充还可以提高高级醇的产量；随着氨基酸补充量的增加，获得了更多种类的高级醇及其相应的酯。然而，更高水平的氨基酸补充（特别是在+160 mg N/L 样品中）会导致残留氮含量升高，这可能导致微生物不稳定。发现添加 120 mg N/L 的氨基酸是增强酵母代谢而不留下高残留氨基酸含量的最佳浓度。因此，通过适当控制氨基酸添加剂量，混合氨基酸补充的使用可能是一种调节豆浆乳清酒精发酵动力学和挥发性化合物调节的策略。
