Valorization of fruit and vegetable byproducts for the beta-glucan production from Euglena gracilis

Five fruit and vegetable byproducts were evaluated as carbon sources and media for beta-glucan production from Euglena gracilis. Orange peel showed the highest beta-glucan concentration (6.5 g/L) and productivity (1.9 g/L/day) when used as a medium. However, when employed as carbon sources, apple pomace showed the highest beta-glucan concentration (10.6 g/L) and productivity (3.5 g/L/day). The appropriate chemical oxygen demand/nitrogen ratio (71.1) and favorable carbon sources of apple contributed to beta-glucan production. Increasing sugar concentrations in apple pomace and orange peel from 10 to 30 g/L raised the beta-glucan concentration to 11.6 g/L. Using apple pomace and orange peel individually proved more effective than mixing them for beta-glucan production. Therefore, apple as a carbon source is the most effective fruit and vegetables byproduct for beta-glucan production. This is expected to reduce the cost of E. gracilis cultivation on a large-scale and contribute to the circular economy.