Overproduction and purification of an agarase of bacterial origin

The agarase gene from Streptomyces coelicolor has been cloned in the non-producer bacterium Streptomyces lividans under the control of its own set of promoters and under the control of a heterologous promoter that is functional only during exponential growth. The best level of overproduction was obtained when the strain containing the natural gene was cultivated in fed batch with mannitol as carbon source. The protein, with a relative molecular mass of 32 kDa, has been purified following an affinity purification method. Contaminating activities seem to be absent from the purified enzyme preparation that can be used to purify DNA from agarose gels.