Alexander J. B. Zehnder

Alexander Jakob Boris Zehnder (born 21 February 1946) is a Swiss microbiologist. He spent most of his career as professor of microbiology at Wageningen University & Research (1982–1992) and later as professor of environmental biotechnology at ETH Zurich (1992–2004). Zehnder also was director of the Swiss Federal Institute of Aquatic Science and Technology during this latter period. From 2004 until 2008 he was President of the ETH Board.

Zehnder was born on 21 February 1946 in Goldach. He studied natural sciences at ETH Zurich where he graduated in 1971. Zehnder subsequently moved to Rabat, Morocco, where he worked as a consultant for the World Health Organization until 1973. Back in Switzerland Zehnder obtained his PhD in microbiology from ETH Zurich in 1976. During his PhD work Zehnder managed to discover and isolate Methanothrix soehngenii, which fellow microbiologist Willem Meindert de Vos described as a major discovery. He subsequently spent two years in the United States as a research associate in the bacteriology department at the University of Wisconsin–Madison. Zehnder then moved to Stanford University where he was employed as assistant professor in the department of civil engineering.

In 1982 Zehnder was appointed professor of microbiology at Wageningen University & Research in the Netherlands. He also became head of the Institute of Microbiology. During his period the research at the university became more focused on anaerobic and environmental microbiology. There was studies performed on microbial phosphate removal and biofilm formation. In 1992 he became both director of the Swiss Federal Institute of Aquatic Science and Technology and professor of environmental biotechnology at ETH Zurich. He held positions until 2004. In May 2008 Zehnder formally retired. From July 2004 until December 2008 he was president of the ETH Board. During this period he aimed to bolster the international reputation of the institution. He received critical reviews, being described as "a nice person in the wrong place". From 2008 until 2010 he also served as scientific director of the Alberta Water Research Institute. From 2011 he served as visiting professor to Nanyang Technological University in Singapore.

Zehnder's fields of expertise include water, in both qualitative and quantitative aspects and the relation between water and food security. Water shortages in relation to climate change has been a main topic for him. During his career he published more than 250 papers and supervised more than 80 PhD students.

Zehnder was elected a member of the Royal Netherlands Academy of Arts and Sciences in 1990. In 1999 he was elected a foreign member of the Russian Academy of Sciences. Zehnder also became member of the Swiss Academy of Engineering Sciences in 1999. Zehnder was awarded the Order of Merit of the Federal Republic of Germany (Cross of Merit 1st Class) in 2010. Singapore awarded Zehnder the Pingat Bakti Masyarakat in 2017. In 2019 he was elected a member of the Academia Europaea.