Expanding the Valorization Routes of Cheese Whey: Lactose Hydrolysis Using <em>A. awamori</em>-derived β-Galactosidase for the Subsequent Production of Bacterial Cellulose

Cheese whey constitutes one of the most polluting by-products of food industry. Regardless the numerous bioprocessing approaches that have been proposed for whey lactose utilization, still, valorization options are restricted by the fact that the majority of strains do not express the gene that encodes β-galactosidase. As a result, the formulation of several high value-added products is hindered, entailing at the same time definite end applications. The aim of this work was to undertake the cost-effective production of crude enzymes, including β-galactosidase, and the subsequent exploitation of whey hydrolysate in an upstream bioconversion process resulting in bacterial cellulose (BC) production. The ability of Aspergillus awamori to secrete β-galactosidase was evaluated via SSF using wheat bran as substrate. Specifically β-galactosidase was assessed at 60-75 % initial moisture content. Crude enzyme extracts produced, were employed in whey hydrolysis at different temperatures (50-70°C) to estimate the effect of temperature in lactose hydrolysis. Subsequently, hydrolyzed whey was used for BC production by Acetobacter xylinum. Results demonstrate that β-galactosidase production was notably affected by moisture content and fermentation time, whereas the maximum activity of 148 U/g was observed at 70% initial moisture content after 79h of SSF. Hydrolysis kinetics showed a 93% lactose hydrolysis at 48h. The produced crude hydrolyzate was subsequently utilized in BC fermentations, leading to the production of up to 5.5 g/L of BC. Evidently, the above findings exhibit a novel and promising approach with respect to cheese whey hydrolysis, thereby expanding the output potential for end products.