Soy (tofu) whey is a liquid by-product generated from tofu (soybean curd) production and it is often discarded off as a waste liquid by the tofu manufacturers. Previous studies have demonstrated that soy whey can be biotransformed into a soy alcoholic beverage by using Saccharomyces and non-Saccharomyces yeasts even though soy whey is low in yeast assimilable nitrogen (YAN) content. In this study, the initial YAN of the soy whey was estimated to be 46.6 mg N/L and Torulaspora delbrueckii Biodiva was used to ferment soy whey supplemented with either isoleucine only or isoleucine paired with valine, leucine or phenylalanine (each amino acid supplemented at a dosage of 30 mg N/L). Amino acid supplementation was found to enhance sugar utilization by the yeast, which led to higher ethanol production (7.49% v/v in control versus 8.35–8.80% v/v in supplemented samples). Samples supplemented with isoleucine only experienced slower sugar utilization during the fermentation as compared to the paired amino acid samples, but the yeast was still able to utilize the sugar to low levels at the end of the fermentation. The presence of leucine supplementation counteracted the “inhibition” induced by the presence of isoleucine at the first day of the fermentation. Amino acid supplementation slowed down glutamic acid utilization and resulted in higher levels of residual glutamic acid and alanine. Amino acid supplementation increased the corresponding fusel alcohol production and the presence of other amino acids reduced the active amyl alcohol production. Therefore, interactions between amino acids can impact the metabolism of the yeast as well as the flavor modulation during soy whey fermentation.

大豆（豆腐）乳清是由豆腐（豆腐）生产产生的液态副产品，通常被豆腐制造商作为废液丢弃。以前的研究已经表明，大豆乳清可以通过使用生物转化成大豆酒精饮料酿酒和非酿酒酵母即使大豆乳清是在酵母同化的氮（YAN）含量低。在这项研究中，大豆乳清的初始YAN估计为46.6 mg N / L，而Torulaspora delbrueckiiBiodiva用于发酵仅添加异亮氨酸或异亮氨酸与缬氨酸，亮氨酸或苯丙氨酸配对的大豆乳清（每种氨基酸以30 mg N / L的剂量补充）。发现添加氨基酸可以提高酵母对糖的利用，从而提高乙醇的产量（对照中的酒精含量为7.49％v / v，而补充样品中的酒精含量为8.35–8.80％v / v）。与配对的氨基酸样品相比，补充有异亮氨酸的样品在发酵过程中仅经历了较慢的糖利用，但是酵母在发酵结束时仍能够将糖利用至低水平。亮氨酸补充剂的存在抵消了发酵第一天异亮氨酸的存在引起的“抑制”。氨基酸补充减慢了谷氨酸的利用并导致更高水平的残留谷氨酸和丙氨酸。氨基酸补充增加了相应的杂醇产量，而其他氨基酸的存在降低了活性戊醇的产量。因此，氨基酸之间的相互作用会影响酵母的代谢以及大豆乳清发酵过程中的风味调节。