Enrichment of whey with Rhizopus sp. biomass aiming at functional food

Abstract

Whey is a byproduct that can be used in food products due to its nutritional properties; however, improper disposal results in a highly polluting waste stream. Consequently, it is necessary to develop products and processes that allow for the valorization of whey in human nutrition while avoiding its disposal. Filamentous fungal biomass contains essential amino acids and fatty acids, minerals, vitamins, and polysaccharides with prebiotic potential. The aim of this study was to cultivate Rhizopus sp. in sweet whey to achieve nutritional enrichment and develop a functional food. Experiments were conducted using either whole whey or whey diluted to 50% (both pasteurized), inoculated with 1 mL of spore suspension (10⁸ spores/mL), and incubated at 180 rpm and 30°C. Cultures using whole whey yielded twice as much biomass (7 g/L) as those using diluted whey (over 24 hours). With whole whey, the specific growth rate was 0.0137 g/h. Across all cultures, the following occurred within 24 hours: 1) consumption of 92% of the initial glucose concentration, with no decrease in total reducing sugars, indicating that lactose was not consumed; and 2) visible signs of autolysis under microscopic analysis and a reduction in mycelium thickness, which contributes to the biomass's digestibility. The mineral composition of the biomass meets daily intake recommendations for potassium (55%), phosphorus and copper (100%), sodium (35%), magnesium (28%), and zinc (17%). There was no protein loss in the fermented whey. It can be concluded that using sweet whey as a substrate for fungal biomass production represents a promising strategy for nutrient production and the development of functional foods.