The viability of mutant strains of Streptomyces aureofaciens (10(6) spores/
0.2 ml) and tetracycline production remained stable for stored lyophilized
spores. The same mutant produced (9375 +/- 1584) and (12336 +/- 1023) mu g/
g of tetracycline (p < 0.01), respectively for spores lyophilized in the me
dia: (i) control skim milk with added sucrose and sodium glutamate, and (ii
) synthetic polyvinylpyrrolidone plus sucrose, peptone and sodium glutamate
.