Abstract: The present invention provides genetically engineered expression vectors, and recombinant cells comprising those vectors, or portions of those vectors. The vectors comprise a mutant form of a gene encoding an aldose reductase (AR) enzyme in which only a portion of the gene is present on the vector. The mutated aldose reductase sequence serves as a site for homologous crossing over of vector-encoded sequences and a host cell genome. Recombinant cells made using the vector of the invention lack an aldose reductase gene and are capable of fermenting lignocellulose hydrolysates to ethanol in high quantities. The invention also provides recombinant vectors and cells with multiple copies of genes encoding enzymes involved in the conversion of lignocellulose or lignocellulose hydrolysates to ethanol. Accordingly, the invention provides methods of making recombinant cells and methods of efficiently producing ethanol from lignocellulose-containing compositions.