Whey is a liquid residue generated during the production of cheese and yogurt. It has a pH between 3.9 and 5.6, and a high chemical oxygen demand (COD), from 60 to 80 g/L. Whey contains lactose, proteins, and minerals. Globally, approximately 50% of the whey generated is untreated and is released directly into the environment, which represents an environmental risk. To overcome whey management problems, conventional thermo-physical valorization treatments have been explored, which are complex, costly and energy-intensive. As an alternative, whey fermentation processes employing bacteria, fungi and yeast are economical and promising methods. Among them, yeast fermentation creates value-added products such as antimicrobials, biofuels, aromas, flavors, and antioxidants with no need for previous conditioning of the whey, such as hydrolysis of the lactose, prior to whey biorefining. The biorefining concept applied to whey is discussed using chemical and biological transformation pathways, showing their pluses and minuses, such as technical drawbacks. The main challenges and solutions for the production of fusel alcohols, specifically for 2-phenylethanol, are also discussed in this review.

乳清是奶酪和酸奶生产过程中产生的液体残留物。它的pH在3.9至5.6之间，化学需氧量（COD）高，为60至80 g / L。乳清含有乳糖，蛋白质和矿物质。在全球范围内，大约50％产生的乳清未经处理并直接释放到环境中，这代表了环境风险。为了克服乳清管理问题，已经研究了常规的热物理价衡方法，其复杂，昂贵且耗能大。作为替代，利用细菌，真菌和酵母的乳清发酵方法是经济且有前途的方法。其中，酵母发酵可产生增值产品，例如抗微生物剂，生物燃料，香气，风味剂和抗氧化剂，而无需事先调理乳清，例如在乳清生物精制之前将乳糖水解。使用化学和生物转化途径讨论了应用于乳清的生物精炼概念，显示了它们的优缺点，例如技术缺陷。这篇综述还讨论了生产杂醇，特别是2-苯基乙醇的主要挑战和解决方案。