Apple squeeze and sugar beet molasses application for yeast invertase production

Biomass obtained from sugar and apple juice production is rich in nutrients therefore could be reused for microbial fermentation and biologically active compounds production. The aim of research was to apply by-products obtained from food processing, such as sugar beet molasses and apple squeeze for invertase production using yeast strains belonging to Kluyveromyces genus and to evaluate the influence of various factors (temperature, pH and metal ions) on extracellular invertase production and stability. Invertase production increased by 5.33 and 9.99 times, respectively, using Kluyveromyces marxianus DSM 5422 and Kluyveromyces lactis var. lactis DSM 70799 in molasses medium in comparison with traditional yeast propagation medium (YPD medium made by 10 g of yeast extract, 20 g of peptone and 20 g of glucose). Whereas invertase production increased by 5.91 and 4.40 times, respectively, using K. marxianus DSM 5422 and K. lactis var. lactis DSM 70799 in apple squeeze comparing with traditional YPD medium. The highest activity of invertase was observed at 55 °C and pH 4.5. Effectors such as Mg, Ca, Cu, Zn, Na ions significantly decreased invertase activity. The results confirmed that sugar beet molasses and apple squeeze are suitable as nutrients source for invertase producing yeast propagation and invertase production.