Alginate immobilization of recombinant Escherichia coli whole cells harboring l-arabinose isomerase for l-ribulose production

Abstract

Recombinant Escherichia coli whole cells harboring Bacillus licheniformis L-arabinose isomerase (BLAI) were immobilized with alginate. The operational conditions for immobilization were optimized with response surface methodology. Optimal alginate concentration, Ca(2+) concentration, and cell mass loading were 1.8% (w/v), 0.1 M, and 44.5 g L(-1), respectively. The interactions between Ca(2+) concentration, alginate concentration, and initial cell mass were significant. After immobilization of BLAI, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The half-life of immobilized whole cells was 150 days, which was 50-fold longer than that of free cells. In seven repeated batches for L-ribulose production, the productivity was as high as 56.7 g L(-1) h(-1) at 400 g L(-1) substrate concentration. The immobilized cells retained 89% of the initial yield after 33 days of reaction. Immobilization of whole cells harboring BLAI, therefore, makes a suitable biocatalyst for the production of L-ribulose, particularly because of its high stability and low cost.

Immobilization of thermoalkalophilic recombinant esterase enzyme by entrapment in silicate coated Ca-alginate beads and its hydrolytic properties

“…Meanwhile, immobilized esterase in non-coated alginate beads displayed a minor possibility of reuse with significant loss of original enzymatic activity after three subsequent cycles. Similar results was observed with other immobilized enzymes and reported that soft surface of non-coated beads compare to silicate coated alginate beads may be the reason for leakage of enzyme from the beads that results in loss of enzymatic activity after subsequent cycle in noncoated Ca-alginate beads [16,17]. The results prove that coating alginate beads with silicate is important for utilization of esterase in continuous processes.…”

“…In contrast, non-coated alginate beads surface have had some pores which may be the reason of enzyme leakage displaying lower enzymatic activity. Other researchers have also reported that surface modification of immobilized enzyme may prevent the leakage and keep the activity of enzyme by forming a physical barrier [16,17,20].…”

“…The structural changes in the enzyme and/or steric limitations introduced by the immobilization may be attributed to this change in the enzyme affinity for its substrate. A decrease in the kcat value during the immobilization process is commonly observed because of limitations on diffusion [16].…”

“…In the case of entrapment of enzymes, optimization of the immobilization conditions improves their utilization [16], therefore different experimental conditions were studied for determining the optimum parameters for esterase immobilization. Since sodium alginate and CaCl 2 concentration are major parameters for enzyme entrapment in gel beads due to gelation formation by cross-linking between alginate and Ca 2+ ions, the immobilization process of purified thermoalkalophilic esterase enzyme was carried out varying concentration of alginate solution 1-4% (w/v) using 0.01-1 mg/ml esterase and 0.1-1.1 M CaCl 2 solution.…”

Response Surface Methodology Optimization of Dibenzothiophene Biodesulfurization in Model Oil by Nanomagnet Immobilized Rhodococcus Erythropolis R1

“…Clearly, immobilization has inherent advantages compared to the free cells including enhanced stability of the system, easy separation of cells, minimizing or eliminating the cell contaminations in the products, convenient recovery and re-use of cells which enable their frequent use in the process [5]. Magnetic separation is a promising technology in the support systems for immobilization, since the rapid separation and easy recovery of immobilized cells could be reached in an external magnetic field, and the capital and operation costs could also be reduced [6].…”