Valorization of Cheese whey powder by two-step fermentation for gluconic acid and ethanol preparation

Whey from cheesemaking is an environmental contaminant with a high BOD, containing an abundance of lactose. Hence, it has the potential to be utilized in the manufacturing of bio-based chemicals that have increased worth. A designed sequential fermentation approach was employed in this research to convert enzymatic hydrolysate of cheese whey (which primarily consists of glucose and galactose) into gluconic acid and bio-ethanol. This conversion was achieved by utilizing Gluconobacter oxydans and Saccharomyces cerevisiae .Glucose in the enzyme hydrolysate will undergo preferential oxidation to gluconic acid as a result of the glucose effect from Gluconobacter oxydans . Subsequently, Saccharomyces cerevisiae will utilize the remaining galactose exclusively for ethanol fermentation, while the gluconic acid in the fermentation broth will be retained. As a result, approximately 293 g gluconic acid and 103 g ethanol could be produced from 1 kg of cheese whey powder. Simultaneously, it was feasible to collect a total of 140 g of blended protein, encompassing cheese whey protein and cellular protein. Two-step fermentation has proven to be an effective method for utilizing cheese whey in a sustainable manner and reducing the environmental impact.