A method for producing a heterologous non-catabolic compound, the method comprising: (a) culturing a population of a genetically modified yeast host cell in a culture medium comprising an essential compound, the essential compound being essential for cell growth, wherein the genetically modified yeast host cell comprises: (i) a heterologous nucleic acid encoding an enzyme of a biosynthetic pathway for producing the heterologous non-catabolic compound, wherein the heterologous nucleic acid is operably linked to a first promoter; (ii) a heterologous nucleic acid encoding a conditional essential gene product of a biosynthetic pathway for producing the essential compound, the conditional essential gene product being necessary for cell growth when yeast host cells are grown in a culture medium lacking the essential compound, wherein the nucleic acid is operably linked to a second promoter; and (iii) a nucleic acid encoding a transcriptional regulator operably linked to a maltose-responsive promoter, wherein the first promoter and the second promoter are both regulated by the transcriptional regulator, and wherein expression of the heterologous nucleic acid encoding the non-catabolic compound and expression of the nucleic acid encoding the conditional essential gene product are limited, and wherein the first promoter and second promoter are selected from the group consisting of pGAL1, pGAL2, pGAL3, pGAL7, pGAL10, pGCY1, pGAL80, and pGAL synthetic promoters, and (b) culturing the population or a subpopulation thereof in a culture medium comprising a sufficiently low amount of or none of the essential compound under a culture condition which promotes expression of the nucleic acid encoding the conditional essential gene product resulting in production of the essential compound necessary for cell growth, and which culture condition promotes expression of the heterologous nucleic acid encoding the enzyme of a biosynthetic pathway for producing the non-catabolic compound, resulting in increased production of the heterologous non-catabolic compound compared to step (a), wherein the transcriptional regulator is transcriptional repressor Gal80p and the culture medium in step (a) comprises a maltose based inducer to induce transcription of the heterologous nucleic acid encoding the transcriptional repressor, or the transcriptional regulator is transcriptional activator Gal4p and the culture medium in step (b) comprises a maltose based inducer to induce transcription of the heterologous nucleic acid encoding the transcriptional activator. (a) culturing a population of a genetically modified yeast host cell in a culture medium comprising an essential compound, the essential compound being essential for cell growth, wherein the genetically modified yeast host cell comprises: (i) a heterologous nucleic acid encoding an enzyme of a biosynthetic pathway for producing the heterologous non-catabolic compound, wherein the heterologous nucleic acid is operably linked to a first promoter; (ii) a heterologous nucleic acid encoding a conditional essential gene product of a biosynthetic pathway for producing the essential compound, the conditional essential gene product being necessary for cell growth when yeast host cells are grown in a culture medium lacking the essential compound, wherein the nucleic acid is operably linked to a second promoter; and (iii) a nucleic acid encoding a transcriptional regulator operably linked to a maltose-responsive promoter, wherein the first promoter and the second promoter are both regulated by the transcriptional regulator, and wherein expression of the heterologous nucleic acid encoding the non-catabolic compound and expression of the nucleic acid encoding the conditional essential gene product are limited, and wherein the first promoter and second promoter are selected from the group consisting of pGAL1, pGAL2, pGAL3, pGAL7, pGAL10, pGCY1, pGAL80, and pGAL synthetic promoters, and (i) a heterologous nucleic acid encoding an enzyme of a biosynthetic pathway for producing the heterologous non-catabolic compound, wherein the heterologous nucleic acid is operably linked to a first promoter; (ii) a heterologous nucleic acid encoding a conditional essential gene product of a biosynthetic pathway for producing the essential compound, the conditional essential gene product being necessary for cell growth when yeast host cells are grown in a culture medium lacking the essential compound, wherein the nucleic acid is operably linked to a second promoter; and (iii) a nucleic acid encoding a transcriptional regulator operably linked to a maltose-responsive promoter, (b) culturing the population or a subpopulation thereof in a culture medium comprising a sufficiently low amount of or none of the essential compound under a culture condition which promotes expression of the nucleic acid encoding the conditional essential gene product resulting in production of the essential compound necessary for cell growth, and which culture condition promotes expression of the heterologous nucleic acid encoding the enzyme of a biosynthetic pathway for producing the non-catabolic compound, resulting in increased production of the heterologous non-catabolic compound compared to step (a),