After working for 22 years with Apple’s CEO Steve Jobs, Mac operating system expert Bertrand Serlet is leaving the computer giant to pursue science. Apple made this announcement on Wednesday saying that the senior vice president of Mac Software Engineering will be leaving the company.

Craig Federighi, Apple’s vice president of Mac Software Engineering, will assume Serlet’s responsibilities and report to Jobs. Federighi is responsible for the development of Mac OS X and has been managing the Mac OS software engineering group for the past two years.

In a statement, said Serlet, “I’ve worked with Steve for 22 years and have had an incredible time developing products at both NeXT and Apple, but at this point, I want to focus less on products and more on science.”

Complimenting Federighi, Serlet added, “Craig has done a great job managing the Mac OS team for the past two years, Lion is a great release and the transition should be seamless.”

Lion is the next release of Mac OS X or version 10.7, and is expected to be launched around summer this year. On its website, Apple said that it is taking its best features from iPad and bringing it all to the Mac with Mac OS X Lion. In essence, it is a marriage of iOS and Mac OS X, as some in the media have called it.

Serlet joined Apple in 1997, and has been involved in the definition, development and creation of Mac OS X. However, before joining Apple, Serlet spent four years at Xerox PARC and then joined NeXT in 1989. Serlet holds a doctorate in computer science from the University of Orsay, France.

NeXT was founded in 1985 by Apple co-founder Jobs after his forced resignation from Apple. It was involved in making computer workstations for higher education. Apple purchased NeXT on December 20, 1996 for $429 million and 1.5 million shares of Apple stock. Much of the current Mac OS X system is built on NeXT’s programming environment OpenStep.

Federighi worked at NeXT, followed by Apple, and then spent a decade at Ariba where he held several roles including vice president of Internet services and chief technology officer. He returned to Apple in 2009 to lead Mac OS X engineering. Federighi holds a Master of Science degree in computer science and a Bachelor of science in electrical engineering and computer science from the University of California, Berkeley.