Enhanced production of cell-bound cholesterol oxidase from Rhodococcus sp. NCIM 2891 by the statistical method

Classical (one-variable-at-a-time) and statistical methods (Plackett-Burman and Central composite design) were used to optimise growth medium for the production of cholesterol oxidase (COX) from Rhodococcus sp. NCIM 2891. COX activities from the classically and statistically optimised media were 0.75 and 3.25 U/ml, respectively. The statistically optimised medium had 4.33- and 9.7-fold higher enzymatic activity than the classically optimised and un-optimised basal medium, respectively. The ratio of enzyme production to cell growth rate was 29-fold higher in our statistically optimised medium than in the basal medium, indicating that the enzyme production could be classified as mixed type of growth. Cell-bound COX accounted for 90.68?±?2 % of the total enzymatic activity of the growth medium. Interactions between the COX-inducing substrate cholesterol and medium growth substrates yeast extract and (NH₄)₂HPO₄ significantly enhanced the production of cell-bound COX. Our results validate the statistical approach as a potential technique for achieving the large-scale production of cell-bound COX from Rhodococcus sp. NCIM 2891.