In a move that expands its cleaning prowess, Ecolab Inc. has agreed to purchase the U.S. operations of Swisher Hygiene Inc. for $40 million in cash, officials said Thursday.

Swisher, based in North Carolina, is expected to broaden the restaurant-cleaning offerings of the St. Paul-based chemical giant Ecolab.

Swisher makes hygiene and sanitizing products for food service, hotel, retail and health care customers. Operations included in the purchase agreement generate $176 million in annual sales and boast 1,000 employees and 30,000 customers.

Ecolab generates about $14 billion a year in revenue from sanitizing chemicals and services provided to restaurants, hotels, food factories, hospitals, schools and oil and gas firms. As a result, analysts said the Swisher move should be a good fit.

The deal "will expand our institutional customer base and service coverage," Ecolab CEO Doug Baker said in a prepared statement. "The addition of Swisher Hygiene's U.S. portfolio of independent restaurants complements Ecolab's presence in national restaurant chains. We look forward to welcoming Swisher employees and customers to Ecolab."

Ecolab's stock rose 24 cents to $115.28 on Thursday.

Buying Swisher is the latest low-key acquisition for a company that completed two huge purchases in 2011 and 2013. It bought the filtration and oil and gas additive firm Nalco for $8.3 billion in December 2011 and Houston-based Champion Technologies in 2013 for $2.2 billion.

Those deals thrust Ecolab into the volatile energy business for the first time. Since then, Ecolab's acquisitions have been smaller and more in line with Ecolab's traditional cleaning, sanitizing and filtration businesses.

In June, Ecolab bought a controlling interest in Jianghai Environmental for an undisclosed sum. The industrial water treatment firm is based in Changzhou, China.

Last year, Ecolab bought a German pest control services firm and the Florida-based AKJ Industries Inc., a steel and refinery processing and specialty chemicals company. In 2013 it bought a Purate water treatment division that was based in Amsterdam.

Dee DePass • 612-673-7725