Bio-utilization of cheese manufacturing wastes (cheese whey powder) for bioethanol and specific product (galactonic acid) production via a two-step bioprocess

Cheese whey, produced from coagulation of milk during cheese manufacture, is a major environmental pollutant. The most abundant component in cheese whey is lactose, which is a potential resource for various value-added chemicals. Here, a two-step bioprocess using Saccharomyces cerevisiae and Gluconobacter oxydans to bioconvert cheese whey into ethanol and galactonic acid was first proposed. First, the lactose in cheese whey powder was pretreated with beta-galactosidase to obtain glucose and galactose. Subsequently, the glucose was selectively fermented to ethanol by S. cerevisiae to enable G. oxydans-mediated biooxidation of galactose to galactonic acid. Finally, approximately 110 g ethanol, 320 g galactonate, and 150 g mixed protein (residual cheese whey protein and cell protein) was produced from 1 kg CWP. These results are suggestive of alternative methods for management of cheese whey, which may reduce its impact on the environment and result in production of value-added biochemicals.