Arnold co-founded Gevo, Inc., a company focused on developing renewable chemicals and biofuels using engineered microorganisms. Gevo aims to produce sustainable alternatives to petroleum-based products.

Arnold co-founded Provivi, a company developing pheromone-based solutions for pest control in agriculture. Provivi's products offer a more sustainable and environmentally friendly alternative to traditional pesticides.

Arnold continues to be involved in various startups and entrepreneurial activities, providing her expertise and guidance to companies seeking to commercialize innovative technologies in biotechnology and sustainable chemistry.