Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources , Nanjing Forestry University , Nanjing 210037 , People's Republic of China.
College of Chemical Engineering , Nanjing Forestry University , Nanjing 210037 , People's Republic of China.
J Agric Food Chem. 2019 Jan 23;67(3):829-835. doi: 10.1021/acs.jafc.8b05150. Epub 2019 Jan 14.
In this study, the dual production of valuable d-tagatose and bioethanol from lactose and cheese whey powder is presented. First, a one-pot biosynthesis involving lactose hydrolysis and d-galactose isomerization for d-tagatose production was established using crude enzymes of recombinant Escherichia coli with l-arabinose isomerase (L-AI) at 50 °C. Compared to the current enzymatic system, only L-AI was overexpressed, because of the unexpectedly thermotolerant β-galactosidase in E. coli BL21(DE3). Moreover, this high temperature rendered the d-glucose catabolism of E. coli inactive, while retaining all fermentable sugars for bioethanol fermentation. Thereafter, the mixed sugar syrup was fermented by Saccharomyces cerevisiae NL22. A total of 23.5 g/L d-tagatose and 26.9 g/L bioethanol was achieved from cheese whey powder containing 100 g/L lactose. This bioprocess not only provides an efficient method for the functionalization of byproduct whey, but also offsets the high production cost of d-tagatose and bioethanol.
本研究提出了从乳糖和奶酪乳清粉中同时生产有价值的 d-塔格糖和生物乙醇的双效生产方法。首先，在 50°C 下，使用含有 L-阿拉伯糖异构酶（L-AI）的重组大肠杆菌的粗酶，建立了一锅法生物合成，包括乳糖水解和 d-半乳糖异构化生产 d-塔格糖。与目前的酶系统相比，仅过量表达了 L-AI，因为大肠杆菌 BL21(DE3)中的β-半乳糖苷酶出人意料地具有耐热性。此外，这种高温使大肠杆菌的 d-葡萄糖分解代谢失活，同时保留了所有可发酵糖用于生物乙醇发酵。然后，利用酿酒酵母 NL22 发酵混合糖糖浆。从含有 100 g/L 乳糖的奶酪乳清粉中，共获得 23.5 g/L 的 d-塔格糖和 26.9 g/L 的生物乙醇。该生物工艺不仅为副产物乳清的功能化提供了一种有效方法，而且还降低了 d-塔格糖和生物乙醇的高生产成本。
