Ethanol production by immobilized Saccharomyces cerevisiae cells on 3D spheres designed by different lattice structure types

Natural or synthesized materials can be used for cell immobilization to enhance cell viability and productivity in fermentation processes (batch, fed-batch or continuous fermentations). 3D printing is one of the newest technologies to produce unique immobilization support materials. In this research, the selection strategy of 3D lattice structure type for unique immobilization materials, effect of different lattice structure types on cell immobilization in a shake flask experiments and optimization of ethanol production in a laboratory scale bioreactor with 3D spheres were studied. Firstly, 3D designs were compared to determine the best type of 3D spheres with a higher area:volume ratio for cell immobilization. Then shake flask experiments were performed and showed that W, 20 mm is the best 3D sphere combination for ethanol fermentation. Finally, over 37 g/L ethanol (ethanol yield ranged from 41.91% to 46.36%) was produced at all repeated batch cycles by using 100 g/L initial sugar with at least 82% sugar utilization capacity in a lab-scale bioreactor successfully. All results showed that 3D-printed materials could be used as immobilization agents for microorganisms by selecting the proper geometry, size and printing technology.