Effect of some additives on gentamicin production by free and immobilized cells of micromonospora purpurea

ABSTRACT

The effect of magnesium, calcium, cetrimide, ampicillin and cefotaxime on the production of gentamicin by free and immobilized cells of Micromonospora purpurea was studied. Addition of magnesium to fermentation media resulted in an increase in gentamicin production by the free cells which was directly proportional to the added magnesium. On the other hand, addition of magnesium to immobilized cells decreased the production of gentamicin. Calcium and cetrimide reduced gentamicin productivity in fermentation media of both free and immobilized cells. Addition of a sub-bacteriostatic concentration of either ampicillin or cefotaxime to free cells resulted in an increase in gentamicin production from 52.48 to 83.2 and 150 ug/ml when using both concentrations of cefotaxime. Ampicillin and cefotaxime at 0.25 and 0.5 MIC increased production of gentamicin by using immobilized cells from 83.2 to 150 and 260 ug/ml, respectively. However, the period of peak production was substantially delayed up to 9 days