Combine strategy of treated activated charcoal and cell surface protein curli induction for enhanced performance in Escherichia coli immobilization

Abstract

Immobilization of Escherichia coli (E. coli) on commercial activated charcoal was enhanced by mild chemical treatment coupled with curli production from E. coli. The chemical used to treat the activated charcoal were sodium hydroxide, hydrochloric acid, ammonium hydroxide, and acetic acid while nickel (II) chloride was used to promote the production of curli. Characteristics of the activated charcoal before and after chemical treatments were analyzed including its surface properties, pore size, and crystalline structure. The immobilization of E. coli was enhanced greatly after sodium hydroxide treatment which gave rise to more than 120 % cell immobilized compared to the untreated activated charcoal which was mainly attributed to the larger size of macropore, surface area, and pore volume. Curli were produced by the induction of nickel (II) chloride and further enhanced the cell immobilization by at least 50 %. Overall, the combine strategy enhanced cell immobilization by more than 160 %. The resulting biocatalyst from the enhanced cell immobilization managed to be reused up to 10 cycles for the enzyme cyclodextrin glucanotransferase expression while retaining up to 60 % of the enzyme’s initial activity.