The strategies appropriate for increasing the yield of a commercially important enzyme are all four: (1) A, B, C and D.

Assessing each strategy

(A) Genome was selectively modified to increase yield – Appropriate

• Rational or targeted genetic modifications (e.g., promoter strengthening, gene copy-number increase, removal of negative regulators) directly enhance synthesis of the enzyme.

• This is a core approach in strain improvement programs.

(B) Reappraisal of culture requirements of the modified organism – Appropriate

• Even a genetically improved strain may not perform optimally unless medium composition, pH, temperature, aeration, and inducers are re-optimized.

• Process optimization routinely yields substantial additional increases in enzyme titer.

(C) Screening induced mutants for higher enzyme synthesis – Appropriate

• Classical mutagenesis followed by screening/selection for overproducers is a proven method in industrial microbiology to find strains with deregulated or amplified pathways.

• This can be combined with or precede targeted genetic engineering.

(D) Engineering the organism to produce a factor that enhances enzyme stability – Appropriate

• Higher product yield in a fermenter depends not only on synthesis rate but also on stability in the broth.

• Engineering secretion of chaperones, protease inhibitors, or modifying the environment to prevent degradation effectively increases recoverable enzyme yield.

Why option (1) is correct

• All four strategies—genome modification (A), process optimization (B), mutant selection (C), and stability engineering (D)—are standard and complementary methods to raise the yield of a commercially important enzyme from a natural isolate.

• Therefore, the combination that includes all of them, A, B, C and D, is the most appropriate choice.