Isoprenoids are a diverse group of compounds that have received considerable interest as pharmaceuticals, food/feed ingredients, as well as nutritional supplements. There has been intensive interest in developing strategies to make large quantities of specific isoprene-compounds by fermentation, including linear and cyclic terpenes, carotenoids, CoQ10, as well as a variety of compounds useful as fragrances and flavors. To this end a number of microbial platforms, including Saccharomyces cerevisiae, E. coli, and Rhodobacter sphaeroides, have been developed. Each platform can be modified to produce a variety of desired individual target compounds. Work at BTR has focused on producing large amounts of the isoprenoid pathway alcohol intermediate, farnesol, in S. cerevisiae. Introduction of additional genes/pathways can lead to production of specific isoprenoid compounds of interest from farnesol. While much of this work can be rational recombinant pathway engineering, strain improvement can often benefit from mutations introduced by classical mutagenesis. The original BTR concept was to overexpress and de-regulate specific critical isoprenoid pathway genes in a strain blocked at the ERG9 (squalene synthase) gene to eliminate carbon flow to sterols, a lethal mutation under aerobic conditions in S. cerevisiae. Blocked strains were modified by introducing aerobic sterol uptake genes, e.g., SUT1, UPC2, or HEM1. Alcohol production was inadequate. A new aerobic sterol uptake mutation, sue, was generated by classical mutagenesis. Production of farnesol by aerobic fermentation using strains with the UPC2 and sue mutation backgrounds will be compared and contrasted.