Polylactic acid (PLA) is a biodegradable thermoplastic derived from renewable resources such as corn starch, sugar cane and cassava root. This environmentally friendly material is popular in the 3D printing industry due to its low environmental impact, ease of use and compatibility with various 3D printers. Polylactic acid has a variety of desirable properties that make it a popular choice for 3D printing applications.
Milk contains essential micronutrients for the human body and is essential for people to have a balanced diet. However, after consuming milk containing lactose, lactose-intolerant patients will experience bloating, diarrhea and gastrointestinal cramps due to the lack of lactase in the intestines to hydrolyze lactose. Although the food industry has now achieved the production of low-lactose and lactose-free milk through methods such as membrane separation, ultrafiltration and addition of free β-galactosidase, the complex production process and waste of resources in the production process have led to its low cost effectiveness. Therefore, an efficient, stable and safe β-galactosidase immobilization method for the production of low-lactose and lactose-free milk is of great significance. To achieve this goal, researchers have developed a 3D printed β-galactosidase flow reactor for the production of low-lactose and lactose-free milk. The 3D printed polylactic acid scaffold was quickly modified by layer-by-layer self-assembly of polyethyleneimine and sodium hyaluronate layers to simplify the modification process of enzyme immobilization carriers, and the cross-linker covalently fixed β-Gal to ensure efficient and stable enzyme fixation. In addition, the 3D printed scaffold integrated into the flow reactor disturbed the fluids in different reactors through directional channels, improved internal mass transfer, and thus achieved efficient milk lactose hydrolysis. The reactor has high enzyme immobilization efficiency and stable catalytic activity, and has broad application prospects in the production of low-lactose and lactose-free milk and other biocatalytic fields.
In the study, the researchers made a 3D printed polylactic acid scaffold with directional channels and pores inside. Compared with traditional enzyme immobilization carriers such as micro-nanoparticles and hydrogels, 3D printed scaffolds can be more easily combined with flow reactors without considering the problems of pipeline blockage and compaction. In addition, the 3D printed scaffold was modified by layer-by-layer self-assembly of polyethyleneimine and sodium hyaluronate to simplify the modification process of enzyme immobilization carriers.
At the same time, the researchers combined the 3D printed β-galactosidase scaffold with the flow reactor, and studied the effect of fluid disturbance on the mass transfer of enzyme and substrate by designing different internal structures of the scaffold. In addition, the distribution of fluid inside the reactor was further studied by COMSOL simulation. The 3D printed scaffold integrated into the flow reactor disturbed the fluid in different reactors through directional channels, improved internal mass transfer, and thus achieved high catalytic activity.
In addition, traditional carrier modification uses chemical methods to graft functional groups. Once the functional groups are occupied, re-modification is a complicated process. The layer-by-layer self-assembly modification can rely on hydrogen bonds or ionic interactions on the surface of the carrier to conveniently and quickly repeatedly graft functional groups for enzyme immobilization. The layer-by-layer self-assembled modified 3D printed polylactic acid scaffold can be reused to fix β-galactosidase. It only needs to collect the immobilized enzyme after it loses its enzymatic activity and re-self-assemble and modify the fixed enzyme.
