This memorial tribute honors Herman J. Phaff (1913–2001), a distinguished microbiologist who spent 40 years at the University of California at Davis before his retirement in 1983, continuing research for another 18 years. Born in the Netherlands, Phaff studied chemical engineering at Delft before pursuing advanced studies at UC Berkeley under H.A. Barker. His research initially focused on pectic enzymes in fungi and yeasts, but gradually shifted toward yeast systematics and ecology. He became renowned for collecting and identifying yeasts from natural habitats worldwide, establishing the world's largest yeast collection from natural sources. Phaff and his team described over 60 new yeast taxa and pioneered molecular approaches to yeast systematics in the mid-1960s, significantly improving species delineation criteria. He served as Associate Editor of the International Journal of Systematic Bacteriology for over 20 years and edited the Yeast Newsletter from 1953 to 1988. Phaff received numerous honors including the J. Roger Porter Award and served on multiple editorial boards. The Herman J. Phaff Culture Collection at UC Davis was officially dedicated in 1996. He died on August 24, 2001, from complications of a fall while vacationing in the Caribbean.

Key findings

• Phaff described over 60 new yeast taxa and established the world's largest collection of yeasts from natural habitats
• He pioneered molecular approaches to yeast systematics in the mid-1960s, improving criteria for natural species delineation
• Phaff served as Associate Editor of the International Journal of Systematic Bacteriology for over 20 years and on numerous other editorial boards
• His research initially focused on pectic enzymes before gradually shifting toward yeast ecology and systematics
• He remained a productive researcher for 58 years total, including 18 years after his official retirement from UC Davis in 1983