Lunch is not provided by the Midwest Enzyme Chemistry Conference.
On campus, buffet lunch is available for purchase at The Commons between 11:15 a.m. and 1:15 p.m. The cost is $14.00, payable by cash or credit card. A possible alternative is the coffee shop Global Grounds, which is open between 12 pm and 7 pm on Saturdays. Both The Commons and Global Grounds are in the McCormick Tribute Campus Center (a.k.a. MTCC), the building with a tunnel running over it, located directly across State Street east of Hermann Hall. Other campus restaurants are closed on Saturday. See a map of on-campus lunch options.
Close to campus, IIT's proximity to US Cellular Field means that there are a number of sports bars nearby. The White Sox are scheduled to play the Twins on September 12, but not until 6:10 pm, so it should not affect lunch. West of campus and across the 94 on 33rd street, you can find the sports bars Turtle's and Cork & Kerry. West of campus and across the 94 on 31st street, you can find Rocky's. You will also find Dragon Bowl (Chinese), Ferro's (Italian), and Husky Hog BBQ (Southern) along 31st street. Directly south of campus on 35th street, lunch options include Jimmy John's, Miller Pizza Company, and Starbucks. A few blocks east on 35th street, you will also find Subway, McDonald's, KFC, and Popeye's chicken.
A short ride away by the CTA green and red lines, additional lunch options are readily accessible. Chinatown is only one stop north on the red line.