A genetic transformation protocol for the xylose‐fermenting yeast Spathaspora passalidarum

Abstract

Spathaspora passalidarum, a recently isolated native xylose‐fermenting yeast, can ferment xylose faster than glucose, and can co‐ferment glucose, xylose, and cellobiose. Studies on S. passalidarum have been reported in terms of fermentation conditions. However, to the best of our knowledge, the molecular modification of S. passalidarum has not been achieved. The lack of successful transformants may be attributed to the absence of an effective transformation method. In the current work, a genetic transformation protocol for S. passalidarum was established. Spathaspora passalidarum was transformed via the lithium acetate method with a plasmid containing the KmR as a selectable marker and the Saccharomyces cerevisiae 2 μ replicon as a replication origin. Several important parameters affecting transformation efficiency were optimized; these parameters included the strain growth period, heat shock time, lithium acetate concentration, and the amount of plasmid DNA. The transformation efficiency reached 170 ± 30 transformants/μg plasmid DNA with the optimized method. This novel transformation system will allow for the genetic analysis and metabolic engineering of S. passalidarum for industrial bioethanol production.