Synthesis of β-Cyclodextrin by immobilized recombinant <i>Escherichia coli</i> on hollow fiber membrane

Abstract Cyclodextrin (CD) is produced through an enzymatic reaction between cyclodextrin glucanotransferase (CGTase) and starch. CD has numerous applications across various industries, including pharmaceuticals, agriculture, and food. Generally, the CGTase is produced by Bacillus sp. but is held back by low production and high downstream cost. Since these issues largely stem from the use of free cells, the recombinant DNA technology is one of the strategies being considered to address them. In this study, the recombinant Escherichia coli ( E. coli ) is used for the β-CGTase production. However, plasmid stability and cell lysis are significant challenges that obstruct recombinant β-CGTase production in E. coli . Hence, the technique of cell immobilization is employed to overcome these bottlenecks, while simultaneously enhancing β-CGTase production for β-CD synthesis. The β-CD synthesis by immobilized recombinant E. coli on hollow fiber membrane was investigated in this study by manipulating the reaction parameters such as agitation rate (50, 100, 150, 200, and 250 rpm), pH (5, 6, 7, 8, and 9) and substrate concentration (3, 4, 5, 6, and 7%, w/v). The optimal agitation rate for the highest synthesis of β-CD was 200 rpm (7.1 mg/mL). Meanwhile, the best pH and substrate concentration for the highest β-CD production was pH 6 (7.8 mg/mL) and 6% substrate concentration (7.9 mg/mL), respectively. The immobilized cells also demonstrated excellent reusability, achieving a cumulative β-CD production of 32.2 mg/mL over six fermentation cycles, an approximately 519% increase compared to free cells (5.2 mg/mL). In conclusion, the results supported the industrial application of immobilized recombinant E. coli using a hollow fiber membrane as a support for β-CD synthesis.