*3.4. Technological Consideration of the Study*

The principal target of this study was the development of a holistic exploitation approach for cheese whey, that will engage with sustainability and generate value-added products via the aligned food waste reduction and by-product streams treatment, as cornerstones of the circular economy concept. Likewise, an efficient fungal-based, two-stage bioprocess was employed to produce a nutrient rich feedstock for subsequent upstream bacterial bioconversions. Cost effective production of crude enzymes, without further purification steps was undertaken using food industry by-products, specifically cheese whey. The significant hydrolytic activity of this novel biocatalyst was demonstrated, leading to the formulation of a suitable feedstock for bacterial cellulose (BC) production. The results of our study confer an insight for the fermentative production of BC using whey

lactose hydrolysates, which effectively sustained the nutrient requirements of *A. xylinum*, displaying high production yields. Evidently, enhanced feasibility could be established through the development of suitable bioprocesses to mediate BC production costs via the replacement of conventional fermentation media. The consolidated bioprocess presented hereof is currently further extended within the concept of holistic refining of cheese whey streams (lactose and protein). In particular, in our forthcoming research, novel probiotic starter cultures will be developed, and BC generated in this study will be implemented as a carrier for lactic acid bacteria starter to be reintroduced into dairy products, thereby closing the loop. Ultimately, the combined proposed approach conforms to the pillars of circular bioeconomy, encompassing environmentally benign processes, zero waste generation in parallel with novel food product development and potential health benefits.
