Yeast with surface displayed xylanase as a new dual purpose delivery vehicle of xylanase and yeast

• A xylanase from rumen microbiome was successfully surface displayed on yeast.
• Yeast surface displayed xylanase had great xylanolytic ability producing xylose and xylobiose.
• Yeast surface displayed xylanase improved corn stover digestion and fermentation.

This study aimed to develop a yeast strain that surface displays a xylanase that was found from a rumen fosmid library and optimized by directed evolution (Orf6-unm). The Orf6-unm enzyme was successfully surface-displayed using Saccharomyces cerevisiae EBY100 as host (referred to as EBY100-pYD1-orf6-unm), yielding a specific xylanase activity of 137 U/g dry cells. The EBY100-pYD1-orf6-unm had greater xylanolytic activity and produced more xylose from beechwood xylan than the purified Orf6-unm overexpressed in Escherichia coli. The EBY100-pYD1-orf6-unm was evaluated for its effect on digestion of corn stover by in vitro rumen cultures. Both EBY100 and EBY100-pYD1-orf6-unm increased volatile fatty acid production, dry matter degradation, and total bacteria population, while shortening the lag time of gas production. However, EBY100-pYD1-orf6-unm increased both gas production and dry matter degradation, and shortened the lag time to greater magnitudes than EBY100. EBY100-pYD1-orf6-unm may be used to deliver both xylanase and live yeast to feed animals.