Pichia stipitis Shi21
Mutational profiling of Scheffersomyces stipitis (previously known as Pichia stipitis Shi21)
<i>Scheffersomyces stipitis</i> (synonym: <i>Pichia stipitis</i>) strain Shi21 is derived from reference strain CBS 6054. Shi21 has been subjected to chemical  mutagenesis, phenotypic selection, genetic engineering and adaptive evolution in order to develop strains improved for ethanol production. Chemical mutagenesis and selection resulted in small improvements in ethanol production attributable in part to carbon  catabolite derepression. Disruption of CYC1 (Cyctochrome c, isoform 1) to create strain Shi21 increased the specific ethanol production rate by 50% and the ethanol yield by 10%