NOVELTY - A metabolically-engineered yeast capable of metabolizing a carbon source to produce n-butanol, a pathway configured for producing an increased amount of cytosolic acetyl-coenzyme A (CoA) relative to another amount of cytosolic acetyl-CoA produced by a wild-type yeast, and a heterologous gene to encode and express an enzyme for a metabolic pathway capable of utilizing NADH to convert acetyl-CoA to the n-butanol, is new.    USE - The yeast and methods are useful for producing n-butanol and increasing metabolic activity of yeast (all claimed).    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a method of producing n-butanol comprises: (a) providing metabolically-engineered yeast capable of metabolizing a carbon source to produce n-butanol, a pathway configured for producing an increased amount of cytosolic acetyl-CoA relative to another amount of cytosolic acetyl-CoA produced by a wild-type yeast, and at least one heterologous gene to encode and express at least one enzyme for a metabolic pathway capable of utilizing nicotinamide adenine dehydrogenase (NADH) to convert acetyl-CoA to the n-butanol; (b) culturing the metabolically-engineered yeast for a period of time and under conditions to produce the n-butanol; (c) metabolically engineering the yeast to increase cytosolic acetyl-CoA production; (d) metabolically engineering the yeast to express a metabolic pathway that converts a carbon source to n-butanol, where the pathway requires a non-native enzyme of the yeast, where (a) and (b) can be performed in either order; (e) culturing the yeast for a period of time and under conditions to produce a recoverable amount of n-butanol; (f) culturing a metabolically-engineered yeast for a period of time and under conditions to produce a yeast-cell biomass without activating n-butanol production; and (g) altering the culture conditions for another period of time and under conditions to produce a recoverable amount of n-butanol; and    (2) a method of increasing metabolic activity of yeast comprises producing an increased amount of cytosolic acetyl-CoA of the yeast relative to another amount of cytosolic acetyl-CoA produced by a wild-type yeast.