(3S)-3-hydroxybutanoyl-CoA + NADP(+) = acetoacetyl-CoA + H(+) + NADPH Lipid metabolism; butanoate metabolism. Expressed in the mother cell at intermediate stages of sporulation under the control of the sigma-E factor. Subject to catabolite repression. Belongs to the 3-hydroxyacyl-CoA dehydrogenase family.