Hi Narendra Uttamrao Mokashe, below please find a link to a paper describing the enzymatic formation of olmesartan in human liver and intestine. Unfortunately I don't have access to the full text.
It's cheaper to make chemically when logistics is working properly. It's a dirt-cheap generic, so doing extra research to make it biosynthetically was never really needed before. Now with strained logistics it can be a useful technology as it would not depend on energy and large production sites, hence would be useful for distributed low-scale producion.