The industrial yeast Komagataella phaffii (formerly named Pichia pastoris) is commonly used to synthesize recombinant proteins, many of which are used as human therapeutics or in food. However, the basic strain, named NRRL Y-11430, from which all commercial hosts are derived, is not available without restrictions on its use. Comparative genome sequencing leaves little doubt that NRRL Y-11430 is derived from a K. phaffii type strain deposited in the UC Davis Phaff Yeast Strain Collection in 1954. We analysed four equivalent type strains in several culture collections and identified the NCYC 2543 strain, from which we started to develop an open-access Pichia chassis strain that anyone can use to produce recombinant proteins to industry standards. NRRL Y-11430 is readily transformable, which we found to be due to a HOC1 open-reading-frame truncation that alters cell-wall mannan. We introduced the HOC1 open-reading-frame truncation into NCYC 2543, which increased the transformability and improved secretion of some but not all of our tested proteins. We provide our genome-sequenced type strain, the hoc1^tr derivative that we named OPENPichia as well as a synthetic, modular expression vector toolkit under liberal end-user distribution licences as an unencumbered OPENPichia resource for the microbial biotechnology community.

工业酵母Komagataella phaffii（以前称为毕赤酵母）通常用于合成重组蛋白，其中许多用于人类治疗或食品中。然而，所有商业宿主均源自其的名为 NRRL Y-11430 的基本菌株，其使用受到限制。比较基因组测序毫无疑问地表明，NRRL Y-11430 源自1954 年保藏于加州大学戴维斯分校Phaff酵母菌株保藏中心的法菲酵母型菌株。我们分析了几个培养物保藏中心中的四种等效型菌株，并从其中鉴定出 NCYC 2543 菌株。我们开始开发一种开放获取的毕赤酵母底盘菌株，任何人都可以使用它来生产符合行业标准的重组蛋白。NRRL Y-11430 很容易转化，我们发现这是由于HOC1开放阅读框截断改变了细胞壁甘露聚糖。我们将HOC1开放阅读框截断引入 NCYC 2543，这增加了部分但不是全部测试蛋白质的可转化性并改善了分泌。我们提供基因组测序型菌株、我们命名为 OPENPichia 的hoc1 ^tr衍生物，以及在自由最终用户分发许可下的合成模块化表达载体工具包，作为微生物生物技术界不受阻碍的 OPENPichia 资源。