The United States of America As Represented by the Secretary of

Dennis H Steinberg

George A Somkuti

Mutant strains of Streptococcus thermophilus having defective lactose transport systems having a phenotype, sucS.sup.+ and gluS.sup.-, lacS.sup.- .beta.gal.sup.+ are effective for use in processes where the hydrolysis of lactose is sought. Thermostability of these strains as well as the .beta.-galactosidase produced allows lactose hydrolysis prior to and during pasteurization. These organisms provide the food industry with improved methods of making reduced lactose dairy products.

Lactose hydrolysis by mutant Streptococcus thermophilus

Mutant strains of Streptococcus thermophilus having defective lactose transport systems having a phenotype gluS.sup.31, lacS.sup.-, sucS.sup.+ and .beta.gal.sup.+ are effective for use in processes where the hydrolysis of lactose is sought. Thermostability of these strains as well as the .beta.-galactosidase produced allows lactose hydrolysis prior to and during pasteurization. These organisms provide the food industry with improved methods of making reduced lactose dairy products.

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Dennis H Steinberg