Bioprocess Scale-up for Acetohydroxamic Acid Production by Hyperactive Acyltransferase of Immobilized Rhodococcus Pyridinivorans

In this study, Rhodococcus pyridinivorans cells containing hyperactive acyltransferase was immobilized on various macromolecules based-polymeric matrices and used to improve acetohydroxamic acid production. The calcium-alginate-based matrix retained the maximum residual activity up to 97.8% as compared to free cells (576 U/mg of dry cell weight). After immobilization, cells exhibited a significant improvement in their tolerance towards pH, temperature, and metal ions as potent enzyme inhibitors. Immobilized cells showed 25.5-fold higher thermal stability at 60 °C to control (free cells). Compared to free cells, immobilized cells exhibited a high bioconversion of acetamide and hydroxylamine-HCl to acetohydroxamic acid up to 96% molar conversion. Repeated bench-scale production at 3-L culture, immobilized cells showed 9.5-fold higher residual conversion as compared to control (100%), after five cycles of reuses. The product characterization achieved high purity (97%) of acetohydroxamic acid. This finding showed high feasibility to achieve efficient conversion that can be scaled up to the industrial level for biotechnological application. Graphical Abstract