Assessment of the lactose-converting ability of yeast Kluyveromyces lactis, depending on the concentration of zinc in the cultivation medium

The constantly increasing volumes of lactose-containing waste from the food industry, up to half of which ends up in wastewater, necessitate the development of biotechnologies for the fermentation of lactose from this raw material. Several such modifications use the possibility of increasing the activity of key lactose conversion enzymes by adding some biogenic trace elements to the culture medium. The article considers the effects of zinc on the efficiency of cheese whey fermentation by three commercial cultures of Kluyveromyces lactis . The efficiency of lactose utilization was assessed by its content in the culture medium before and after 5 days of fermentation. The K. lactis strain of the MicroMilk KF KL culture utilized 80.2-84.2% lactose. After the addition of zinc ions, these indicators ranged from 74.5 to 85.7%. The strain of the Zdoroteevo culture demonstrated the utilization of lactose in the control series in the range of 78.7-82.0%. After the addition of zinc ions at 2 MPC concentrations, utilization increased slightly, and after the addition of 5 MPC concentrations, we see values lower than the control ones. The lactose content in STANDA KL D cultures in the control series ranged from 41.5 to 59.0%; after addition of zinc ions at 2 MPC concentrations, it was from 50.5 to 69.0%; and after addition of 5 MPC, it was from 38.7 to 57.4%. Thus, the addition of zinc ions to K. lactis culture increases its lactose-converting ability at a concentration of 2 MPC and inhibits this ability if we use a concentration of 5 MPC. It is advisable to use the obtained data in developing a strategy for cleaning lactose-containing waste in the food industry